Air resistance of a rowing shell

Post by sander
Bill Atkinson posted this years ago: http://www.atkinsopht.com/row/airestnc.htm
Has anyone attempted to measure or estimate the air resistance of a rowing shell? Please point me to a source. Google doesn't seem to want to help me today.

Bill proposes a perfectly valid, necessarily basic, test protocol. And
it would be good if those who purport to be keen to win tried to
understand how much of the drag on themselves & their boat can come from
wind resistance.

However, once you get the boat moving there's a bunch of extra causes
and effects which contribute to overall drag in ways that are not much
appreciated.

Thus the oar-shafts generate more wind drag when you're rowing than when
static in a wind of the same effective velocity. Yet there are sound
ways to reduce oarshaft drag which rowers can't be bothered to
implement. And crucial amounts of speed are also lost in headwinds by
squaring small fractions of a second earlier than absolutely essential.

In crosswinds there are losses due to the boat being pushed sideways
(making leeway), even though the wind might be cross-tail over the water
& thus apparently only side-on when moving. Your shell is long & narrow
for a purpose as that gives the least drag when travelling directly
along its axis, but under side-forces the water flows increasingly
diagonally under the boat & this incurs big losses. Again, there are
ways to minimise the tendency to make leeway, & thus to incur leeway
drag, but it is a rare & bright coach who understands this & seeks our
help in the matter.

And there are steering losses, which also rise as the cox has to contend
with side forces which also render typical steering systems less
effective & costly on performance.

For the crew to row requires large openings in the upper plane of the
boat, & wind is whipped into vortices as it pours in & out of the
exposed open volumes, dissipating energy which the crew has to supply.
These losses can again be greatest under cross-wind conditions.

Bill is right to draw attention to issues of clothing. The funny thing
is that rowers tend to view end results as the only measure of the value
of having paid attention to a multitude of performance-affecting
details, so great ideas such as hooded, close-fitting all-in-ones become
causes for amusement unless the crew wearing this kit actually wins.

It is known that companies can have rather short memories compared to
the longevity of the equipment they use, which is why safety rules in
manufacturing process plant should not only be written down but there
should be easily accessed explanations for why each rule or practice
exists. Similarly, a wise club or rower will carefully maintain, review
& develop a science/engineering knowledge base on physical means of
performance enhancement, rather than blindly following the latest
gimmickry & fashions.

Rowing performance is not just about erg scores. While crew rowing may
seem like a form of voluntary galley-slavery, there is plenty of scope
for rowers & coaches to engage their brains not only it pulling
harder-for-longer but also in pursuing the means to minimise energy
dissipation.

Cheers -
Carl

--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories
Write: Harris Boatyard, Laleham Reach, Chertsey KT16 8RP, UK
Find: tinyurl.com/2tqujf
Email: ***@carldouglasrowing.com Tel: +44(0)1932-570946 Fax: -563682
URLs: carldouglasrowing.com & now on Facebook @ CarlDouglasRacingShells

Jake

2016-04-12 18:58:39 UTC

Post by carl
Thus the oar-shafts generate more wind drag when you're rowing than when
static in a wind of the same effective velocity. Yet there are sound
ways to reduce oarshaft drag which rowers can't be bothered to
implement. And crucial amounts of speed are also lost in headwinds by
squaring small fractions of a second earlier than absolutely essential.

I'd imagine it would not be too taxing to shroud the oar looms with a hollow NACA foil section that was connected to a pin at the gate, (so it remains at the optimum angle to the oncoming wind- does not rotate with the loom/ blade on squaring/ feathering). I reckon in single skin carbon/ epoxy it would weigh about 0.5 kg per side. The drag numbers provided by a cylinder (conventional oar loom) versus an optimised foil are really quite startling.

But would it be allowed? The FISA 'definitions of rowing' ban all sorts of things I'd love to see in rowing shells: a list including but not limited to:
Multihull (stabilised monohull/ trimaran or cat), sliding rigger, SWATH, Hydrofoil (particularly flapping tail type hydrofoil lift/ propulsion systems utilising the rowers pitching force for additional forward drive), underwater air injection.

Ok, I got a bit carried away with that list, after all, if there were no rules the oars would soon get ditched for pedals and propellers and we'd have HPVs. But the sliding rigger decision anoyed me. It was a useful idea that would have made everyone's boats a little faster and more plesant to row. I ought to get over it. It was 1983.

carl

2016-04-12 21:14:08 UTC

Post by Jake

I'd imagine it would not be too taxing to shroud the oar looms with a hollow NACA foil section that was connected to a pin at the gate, (so it remains at the optimum angle to the oncoming wind- does not rotate with the loom/ blade on squaring/ feathering). I reckon in single skin carbon/ epoxy it would weigh about 0.5 kg per side. The drag numbers provided by a cylinder (conventional oar loom) versus an optimised foil are really quite startling.
Multihull (stabilised monohull/ trimaran or cat), sliding rigger, SWATH, Hydrofoil (particularly flapping tail type hydrofoil lift/ propulsion systems utilising the rowers pitching force for additional forward drive), underwater air injection.
Ok, I got a bit carried away with that list, after all, if there were no rules the oars would soon get ditched for pedals and propellers and we'd have HPVs. But the sliding rigger decision anoyed me. It was a useful idea that would have made everyone's boats a little faster and more plesant to row. I ought to get over it. It was 1983.

Well, Jake -
If there was a shred of evidence from race timings of that period for
the sliding rigger giving a speed advantage, then it would definitely
show as a significant blip in times & I'd be right with you. To the
best of my knowledge such evidence is entirely lacking, & talk of
sliding riggers being unfairly banned seems just a modern myth,
unsupported by data but boosted by a touch of conspiracy theory.

We do have stabilised monohulls in adaptive classes, but even with
refined hulls I doubt they'd cut the mustard.

A Japanese crew in the Atlanta OG did use aerofoil envelopes over their
oarshafts, but they needed more help than that to win a medal. The
Sydney GBR HWt 8+ applied boundary layer trips to significantly reduce
the wind drag on their oarshafts (& made other intelligent changes to
their equipment) & then won gold.

I know no current rule that might ban a SWATH hull (entire hull
underwater, like a submarine, with rower above water on a pylon), & it
might work. Certainly there's nothing to stop anyone (you?) from
testing such a design .....

Oscillatory foils have been developed for recreational craft, & could be
adapted to rowing shells, but then you wouldn't be rowing.

Air injection? Might need a fair amount of pumping energy, or a
prodigious baked bean intake? Wouldn't want to be the person holding
the stern at the start. That said, air entrainment is worth considering
(e.g. via spray-rail features under the hull). I recall that, when I
rowed at school, we had a fine clinker eight which most of us reckoned
the equal of any shell, & some wondered even then if that was due to air
entrainment by the laps in the skin.

Cheers -
Carl

sander

2016-04-12 21:22:40 UTC

Some better googling revealed this from the famous Kleshnev: http://www.biorow.com/RBN_en_2009_files/2009RowBiomNews12.pdf

carl

2016-04-12 21:57:43 UTC

Post by sander
Some better googling revealed this from the famous Kleshnev: http://www.biorow.com/RBN_en_2009_files/2009RowBiomNews12.pdf

Yup. Now some back of envelope calcs:

And if a headwind reduces your boat speed by 10%, then the hydro drag
will fall to ~73% of what it was in still air.

If in still air the aero drag was 13% of total (aero + hydro) drag, then
that balance of 87% of the total drag attributable to still-air hydro
resistance must fall to .73 x 87% = 64% of total drag when the headwind
slows you by 10%

So in a headwind that slows you by 10% you use about 36% of your power
output just to overcome wind resistance.

This is the kind of argument I've spent some effort in conveying to
rowers, but the message seems too complex to be taken on board.

A parallel issue is: Why would anyone enter the Oxford/Cambridge Boat
Race in a boat with inadequate freeboard.

But rowers so easily fall back on the facile, foolish argument that all
you need to do is pull harder as all equipment is equal. Oh no it
ain't. In rowing we are nowhere even remotely near to the cyclist's
philosophy of the "aggregation of marginal gains".

Cheers -
Carl

m***@gmail.com

2016-04-25 13:19:39 UTC

Post by carl
And if a headwind reduces your boat speed by 10%, then the hydro drag
will fall to ~73% of what it was in still air.
If in still air the aero drag was 13% of total (aero + hydro) drag, then
that balance of 87% of the total drag attributable to still-air hydro
resistance must fall to .73 x 87% = 64% of total drag when the headwind
slows you by 10%
So in a headwind that slows you by 10% you use about 36% of your power
output just to overcome wind resistance.
This is the kind of argument I've spent some effort in conveying to
rowers, but the message seems too complex to be taken on board.
... In rowing we are nowhere even remotely near to the cyclist's
philosophy of the "aggregation of marginal gains".
Cheers -
Carl

Fascinating. I've never thought of the distribution of power between air and water resistance and how they change under different conditions in those terms, but I am not surprised. Unfortunately, I am also not surprised by the rowing community's collective stupidity: at best an indifference to, at worst a contempt of, those many "no-brainer" steps and modifications which more than a moment's thought ought to convince.
A case in point: I and three others own a 4x with Carl's AeroFin-plus-canard system. As I've stated several times on this forum, that combination allows us to make the most amazing course-changes with very little apparent loss of speed. We've been accused of doing our pushes on the bends, where we gain 1/2 a length every time when alongside another crew.
But another time, our boat was upside-down on trestles outside our boathouse when a fairly prominent member of the rowing community, an Olympic medallist, strolled past and scoffed at the canard: "what the hell d'you need that for?", with a contemptuous laugh.
These days I spend much more time training on 2 wheels than on the water and in the process come across many dedicated bike-racers, and I am fascinated by the difference in attitudes.
Cyclists are OBSESSED by, and prepared to spend vast sums on, the merest rumour of a performance benefit. Often the response to a poor performance is to buy an extra few seconds in the form of deeper-section wheels or a special stick-on TT number-pocket to replace the paper-and-pin attached to a skin-suit. A regular sight at TTs these days is air-flow trip-strips stuck directly to the skin of the legs. My own bike came with trip-strips along the down- and seat-tubes.

Magnus

James HS

2016-04-25 15:06:42 UTC

interesting - if you look up aerodynamic and rowing clothing you get nothing!

for years I have sculled with the number flapping on my back and never thought anything of it - but it is bound to have a drag attached to it!

This thread has certainly got me thinking - I am one rower who wants to eke every advantage possible out of the bits that just cause 'losses' and these have to add up to a few!

Time to get more technology in the sport and make the small gains!

t***@googlemail.com

2016-04-25 15:20:36 UTC

Post by James HS
interesting - if you look up aerodynamic and rowing clothing you get nothing!
for years I have sculled with the number flapping on my back and never thought anything of it - but it is bound to have a drag attached to it!
This thread has certainly got me thinking - I am one rower who wants to eke every advantage possible out of the bits that just cause 'losses' and these have to add up to a few!
Time to get more technology in the sport and make the small gains!

Same here, also want to eke every advantage that I can but the main issue I have is that the products just aren't available....

Take the mentioned Aero trips, I understand the discussion around them and am sold on trying a set on blades/rigger, but AFAIK you can't buy them to fit to riggers/blades so the point is moot anyway, and you wouldn't suggest a DIY fit if you'd even seen my previous home DIY attempts....

Lucy

2016-04-25 20:48:35 UTC

Post by James HS
This thread has certainly got me thinking - I am one rower who wants to eke every advantage possible out of the bits that just cause 'losses' and these have to add up to a few!

Agreed - this needs to be a particular priority in Para rowing I think, given the "clunkyness" of much of our existing equipment and inability (for many of us) to rely on our bodies predictably responding to training. For instance, our very own Carl D once described the posts which allow my scullies to be mounted as "axle stands", a remarkably accurate assessment!

There often seems little point my putting in 8 or 9 sessions a week if you're still, as I am, stuck effectively rowing a trimaran, after all!

carl

2016-04-26 01:06:06 UTC

Post by t***@googlemail.com

Same here, also want to eke every advantage that I can but the main issue I have is that the products just aren't available....
Take the mentioned Aero trips, I understand the discussion around them and am sold on trying a set on blades/rigger, but AFAIK you can't buy them to fit to riggers/blades so the point is moot anyway, and you wouldn't suggest a DIY fit if you'd even seen my previous home DIY attempts....

Rowers don't take either aero or hydro-dynamic losses seriously. We are
coached to work harder, but no one considers the performance losses that
they incur, nor how to reduce them.

Further, rowers seem to have fear inculcated into their psyche from the
moment they approach a boat. No competitive water-craft could be more
stable than an eight with oars in place, & the skill set needed for
rowing is far more limited than for, say kayaking, yet we worry (or are
told to worry) about catching crabs & the supposed importance of getting
the blade out in a certain way.

Even the discussion of late squaring has evinced significant levels of
doubt as to the feasibility of a rower being able to walk & chew gum -
well, not that, but of their being able to perfect a late square and
combine that with a clean, hard entry. Would we have that sort of talk
if we were learning gymnastics?

Much is spent on kit that promises a second gained over 2K (that's about
0.25%!) yet, as Magnus notes, hydrodynamic losses of 1/2 length when
taking a modest bend (due to centrifugally-induced leeway) can be saved
by using the right equipment, yet this is not understood & never
discussed. And the leeway losses from course corrections on straight
tracks, not to mention the bigger losses from making leeway in
crosswinds, are not understood so not even considered as reducible. And
since a modest headwind can almost treble your aerodynamic losses, why
aren't you all seeking ways to reduce that penalty?

What's refreshing is that we have RSR contributors now discussing these
sources of performance loss. If we really are racers, then surely
losses on these scales should be of grave concern to us all?

I do take these losses seriously & have provided ways to diminish them.
Which is why we have invested a lot into developing foil control systems
as mentioned by Magnus (see "AeRowFin" & "HyperSteer"). In some cases a
very DIY approach is all you need to make some improvement, & in that
area it is not really so hard to apply appropriately-located wires, or
very narrow tapes, or otherwise to form ridges maybe 1mm high, running
along the oarshafts at about 70 degrees above and below what would be
the leading edge or stagnation point of the shaft when coming forward.

But there is more than can be done - if you care about aerodynamic drag.
After all, you wouldn't want to row a shell the form of which
resembled an inverted version of the normal shell with its seated crew &
oars, with all that's usually above the water now below the surface, &
vice-versa.

Cheers -
Carl

Kit Davies

2016-04-26 09:46:37 UTC

Post by carl
But there is more than can be done - if you care about aerodynamic drag.
After all, you wouldn't want to row a shell the form of which resembled
an inverted version of the normal shell with its seated crew & oars,
with all that's usually above the water now below the surface, &
vice-versa.
Cheers -
Carl

I have a vague recollection (from the early 1980s?) of somebody trying
out a design of single that looked like a missile, or maybe a fuel tank
of the kind carried under the wing of a fighter jet, ie cylindrical
tapering to fine points fore and aft. The sculler perched on top. There
wasn't a stateroom as such but dents inset into the cylinder where the
scullers feet went. Am I going mad? I can imagine that may tick quite a
few aerodynamic boxes, at least as far as the hull is concerned, and a
few buoyancy ones too.

My mind keeps going back to the SWATH hulls discussed earlier though.
There's another avenue to explore. At the least they would be good for
coaching launches in wake-restricted zones?

Kit

a***@gmail.com

2016-04-26 11:50:15 UTC

I have a vague recollection (from the early 1980s?) of somebody trying
out a design of single that looked like a missile, or maybe a fuel tank
of the kind carried under the wing of a fighter jet, ie cylindrical
tapering to fine points fore and aft. The sculler perched on top. There
wasn't a stateroom as such but dents inset into the cylinder where the
scullers feet went. Am I going mad? I can imagine that may tick quite a
few aerodynamic boxes, at least as far as the hull is concerned, and a
few buoyancy ones too.
My mind keeps going back to the SWATH hulls discussed earlier though.
There's another avenue to explore. At the least they would be good for
coaching launches in wake-restricted zones?
Kit

I have seen a boat like that, I think hanging in the ceiling at Marlow BC -(http://www.marlowrowingclub.org.uk/bar-and-social) but I thought it was from pre 1900.

Obviously the optimum rowing craft would look like an elongated flying saucer, both the rowers and the blades completely enclosed in an aerodynamic tear drop to minimise wind resistance. The cushion of air under the teardrop would act rather like a hovercraft skirt to provide stability, meaning that as there is no aerodynamic cost the blades can be rowed square, obviating much of the discussion around flip catches, and simplifying oar and rigger design (no collars, no gates). A simple autopilot guidance system from a drone, coupled with aerofoils and hydrofoils would control direction and enhance stability.

Suggestions that several low flying UFOs have been seen in the vicinity of Staines, with surfaces that look suspiciously like finely finished kevlar wood composites have been denied by the authorities.

Kit Davies

2016-04-26 12:44:16 UTC

I have a vague recollection (from the early 1980s?) of somebody trying
out a design of single that looked like a missile, or maybe a fuel tank
of the kind carried under the wing of a fighter jet, ie cylindrical
tapering to fine points fore and aft. The sculler perched on top. There
wasn't a stateroom as such but dents inset into the cylinder where the
scullers feet went. Am I going mad? I can imagine that may tick quite a
few aerodynamic boxes, at least as far as the hull is concerned, and a
few buoyancy ones too.
My mind keeps going back to the SWATH hulls discussed earlier though.
There's another avenue to explore. At the least they would be good for
coaching launches in wake-restricted zones?
Kit

I have seen a boat like that, I think hanging in the ceiling at Marlow BC -(http://www.marlowrowingclub.org.uk/bar-and-social) but I thought it was from pre 1900.
Obviously the optimum rowing craft would look like an elongated flying saucer, both the rowers and the blades completely enclosed in an aerodynamic tear drop to minimise wind resistance. The cushion of air under the teardrop would act rather like a hovercraft skirt to provide stability, meaning that as there is no aerodynamic cost the blades can be rowed square, obviating much of the discussion around flip catches, and simplifying oar and rigger design (no collars, no gates). A simple autopilot guidance system from a drone, coupled with aerofoils and hydrofoils would control direction and enhance stability.
Suggestions that several low flying UFOs have been seen in the vicinity of Staines, with surfaces that look suspiciously like finely finished kevlar wood composites have been denied by the authorities.

Well, that wasn't the one I was thinking of (ISTR it was bright orange),
but still "Nil novi sub sole" and all that.

My other train of thought has been on adapting technique, or at least
body shape, for better aerodynamics. Modern orthodoxy has one sitting
tall and opening the shoulders at the finish. Like a sail in a tail wind
but like a baffle in a head. I might have to try and compare that with a
low and rounded back, and see if I can see a measurable difference on
the GPS.

Kit

Henry Law

2016-04-26 13:42:30 UTC

sitting tall and opening the shoulders at the finish. Like a sail in a
tail wind but like a baffle in a head.

I've often been coached (by coach or cox) to "sit up tall in the head
wind"; always seemed a stupid thing to advocate.

--
Henry Law Manchester, England

a***@gmail.com

2016-04-26 13:54:09 UTC

I have a vague recollection (from the early 1980s?) of somebody trying
out a design of single that looked like a missile, or maybe a fuel tank
of the kind carried under the wing of a fighter jet, ie cylindrical
tapering to fine points fore and aft. The sculler perched on top. There
wasn't a stateroom as such but dents inset into the cylinder where the
scullers feet went. Am I going mad? I can imagine that may tick quite a
few aerodynamic boxes, at least as far as the hull is concerned, and a
few buoyancy ones too.
My mind keeps going back to the SWATH hulls discussed earlier though.
There's another avenue to explore. At the least they would be good for
coaching launches in wake-restricted zones?
Kit

I have seen a boat like that, I think hanging in the ceiling at Marlow BC -(http://www.marlowrowingclub.org.uk/bar-and-social) but I thought it was from pre 1900.
Obviously the optimum rowing craft would look like an elongated flying saucer, both the rowers and the blades completely enclosed in an aerodynamic tear drop to minimise wind resistance. The cushion of air under the teardrop would act rather like a hovercraft skirt to provide stability, meaning that as there is no aerodynamic cost the blades can be rowed square, obviating much of the discussion around flip catches, and simplifying oar and rigger design (no collars, no gates). A simple autopilot guidance system from a drone, coupled with aerofoils and hydrofoils would control direction and enhance stability.
Suggestions that several low flying UFOs have been seen in the vicinity of Staines, with surfaces that look suspiciously like finely finished kevlar wood composites have been denied by the authorities.

Well, that wasn't the one I was thinking of (ISTR it was bright orange),
but still "Nil novi sub sole" and all that.
My other train of thought has been on adapting technique, or at least
body shape, for better aerodynamics. Modern orthodoxy has one sitting
tall and opening the shoulders at the finish. Like a sail in a tail wind
but like a baffle in a head. I might have to try and compare that with a
low and rounded back, and see if I can see a measurable difference on
the GPS.
Kit

Kit,

Careful you don't hurt your back though - I doubt you go faster with a painful spine!

I thought - this has to be something people have thought about so:

http://www.google.co.uk/patents/US5662062 - A crew shell fairing removably mountable to a crew shell includes an aerodynamic shell and a mounting member for mounting the aerodynamic shell on the crew shell

http://www.google.co.uk/patents/US6959958 - Designed to reduce drag on the back end of a truck - probably applicable to most rowers between Stroke and 3.....

https://patents.google.com/patent/CN101898033B/en?q=rowing&q=wind+resistance&page=2 - basically fairings for the body

https://patents.google.com/patent/US6609981B2/en?q=rowing&q=streamline&page=3 - trip fences on golf clubs (and oars!)

https://patents.google.com/patent/EP0113620A1/en?q=rowing&q=streamline&page=5 - a catamaran torpedo style hull

https://patents.google.com/patent/JPH1016885A/en?q=rowing&q=streamline&page=8 - fixed oar shaft fairings

Kit Davies

2016-04-26 14:58:24 UTC

Post by a***@gmail.com
https://patents.google.com/patent/EP0113620A1/en?q=rowing&q=streamline&page=5 - a catamaran torpedo style hull

This one reminds me of the Sea Sabre coastal single:
http://www.sea-sabre.com/the_seasabre_range/coastal/c1-single/

Kit

m***@gmail.com

2016-04-26 16:16:18 UTC

Just come across this, describing a study of how much fuel is wasted to drivers keeping their roof-bars on their cars.

http://phys.org/news/2016-04-roof-racks-fuel-economy.html

How silly of them to not realize that our sport has had the answer to this problem all this time - just use bigger engines!

a***@gmail.com

2016-04-28 01:43:39 UTC

I have a vague recollection (from the early 1980s?) of somebody trying
out a design of single that looked like a missile, or maybe a fuel tank
of the kind carried under the wing of a fighter jet, ie cylindrical
tapering to fine points fore and aft. The sculler perched on top. There
wasn't a stateroom as such but dents inset into the cylinder where the
scullers feet went. Am I going mad? I can imagine that may tick quite a
few aerodynamic boxes, at least as far as the hull is concerned, and a
few buoyancy ones too.
My mind keeps going back to the SWATH hulls discussed earlier though.
There's another avenue to explore. At the least they would be good for
coaching launches in wake-restricted zones?
Kit

I have seen a boat like that, I think hanging in the ceiling at Marlow BC -(http://www.marlowrowingclub.org.uk/bar-and-social) but I thought it was from pre 1900.
Obviously the optimum rowing craft would look like an elongated flying saucer, both the rowers and the blades completely enclosed in an aerodynamic tear drop to minimise wind resistance. The cushion of air under the teardrop would act rather like a hovercraft skirt to provide stability, meaning that as there is no aerodynamic cost the blades can be rowed square, obviating much of the discussion around flip catches, and simplifying oar and rigger design (no collars, no gates). A simple autopilot guidance system from a drone, coupled with aerofoils and hydrofoils would control direction and enhance stability.
Suggestions that several low flying UFOs have been seen in the vicinity of Staines, with surfaces that look suspiciously like finely finished kevlar wood composites have been denied by the authorities.

Well, that wasn't the one I was thinking of (ISTR it was bright orange),
but still "Nil novi sub sole" and all that.
My other train of thought has been on adapting technique, or at least
body shape, for better aerodynamics. Modern orthodoxy has one sitting
tall and opening the shoulders at the finish. Like a sail in a tail wind
but like a baffle in a head. I might have to try and compare that with a
low and rounded back, and see if I can see a measurable difference on
the GPS.
Kit

Kit,
Careful you don't hurt your back though - I doubt you go faster with a painful spine!
http://www.google.co.uk/patents/US5662062 - A crew shell fairing removably mountable to a crew shell includes an aerodynamic shell and a mounting member for mounting the aerodynamic shell on the crew shell
http://www.google.co.uk/patents/US6959958 - Designed to reduce drag on the back end of a truck - probably applicable to most rowers between Stroke and 3.....
https://patents.google.com/patent/CN101898033B/en?q=rowing&q=wind+resistance&page=2 - basically fairings for the body
https://patents.google.com/patent/US6609981B2/en?q=rowing&q=streamline&page=3 - trip fences on golf clubs (and oars!)
https://patents.google.com/patent/EP0113620A1/en?q=rowing&q=streamline&page=5 - a catamaran torpedo style hull
https://patents.google.com/patent/JPH1016885A/en?q=rowing&q=streamline&page=8 - fixed oar shaft fairings

Hi Kit:
Here a "truck" type fairing I designed several years ago for my recumbent bicycle:
<http://atkinsopht.com/atk/bicycles/bicycles.htm> See illustration.
It is worn like a garment. Saves a measurable few percent on bike speed.
Might be tough to arrange something similar for a sculler though.
Bill Atkinson

John Greenly

2016-04-27 14:32:02 UTC

Post by Kit Davies
I have a vague recollection (from the early 1980s?) of somebody trying
out a design of single that looked like a missile, or maybe a fuel tank
of the kind carried under the wing of a fighter jet, ie cylindrical
tapering to fine points fore and aft. The sculler perched on top. There
wasn't a stateroom as such but dents inset into the cylinder where the
scullers feet went. Am I going mad? I can imagine that may tick quite a
few aerodynamic boxes, at least as far as the hull is concerned, and a
few buoyancy ones too.

Kit,

I wonder if that might have been the Echo Ace- an open-water boat, intended to have a "wave-piercing" shape.

http://www.echorowing.com/ace.htm

Some people I know rowed that for a while but it doesn't seem to have caught on. I think people said it pierced the waves too well: it was hard to manage at an angle to the waves because the bow would bury and slew the boat off course.

In any case , it seems to me that at least in a straight headwind the oars, the riggers and the rower's body probably contribute more to resistance than the hull does- it's so close to the surface that the wind speed is diminished substantially.

John

t***@googlemail.com

2016-04-26 10:35:09 UTC

Post by carl
What's refreshing is that we have RSR contributors now discussing these
sources of performance loss. If we really are racers, then surely
losses on these scales should be of grave concern to us all?
I do take these losses seriously & have provided ways to diminish them.
Which is why we have invested a lot into developing foil control systems
as mentioned by Magnus (see "AeRowFin" & "HyperSteer"). In some cases a
very DIY approach is all you need to make some improvement, & in that
area it is not really so hard to apply appropriately-located wires, or
very narrow tapes, or otherwise to form ridges maybe 1mm high, running
along the oarshafts at about 70 degrees above and below what would be
the leading edge or stagnation point of the shaft when coming forward.

As a single sculler, unfortunately the AeRoFin and Hypersteer are I understand not things that are aimed at me - the DIY approach improvements are things that I could do but as mentioned I am not naturally DIY orientated - least not something that would be aerodynamic at the end!

It may be I am more or less unique in the rowing circles in my wanting to try and implement more modern/unorthadox techniques to save energy wastage but personally the main issue I have is not really knowing where to start, and not having a "guide"to follow to install aero modifications.

For example - Carl you have raised again the idea of adding wires/tape to the blade shafts - where would you get the parts needed for this and how would you install them? Would you use a glue? What glue could I use to not damage the shafts?

Like James mentioned earlier - my fluid has a "lip" cockpit protector (see in link) that is probably not the most aerodynamic - perhaps a shield that would lift the wind up and over the wing in the cockpit and past either side of me would also have a large aerodynamic benefits? epseiclally if the wings also had "trip" bands installed

Loading Image...

I'd even be happy to write up a detailed photo guide of myself installing these if it would help others, but first id need to know what I was doing myself :)

m***@gmail.com

2016-04-27 12:37:05 UTC

A bit of a defeatist view but there may be good reasons why so little is done:

In a very tech-phobic sport, any drag reduction may well get quickly banned quickly nullifying all the effort put into it

With the likely solutions implemented being technically simple, at international level other crews will copy and it is back to a level playing field

A tech obsessed sport like F1 can write off huge dev costs and effort to gain small advantages for a couple of races until other teams copy it or it is banned but rowing isn't one of those.

a***@gmail.com

2016-04-27 13:21:46 UTC

Post by m***@gmail.com
In a very tech-phobic sport, any drag reduction may well get quickly banned quickly nullifying all the effort put into it
With the likely solutions implemented being technically simple, at international level other crews will copy and it is back to a level playing field
A tech obsessed sport like F1 can write off huge dev costs and effort to gain small advantages for a couple of races until other teams copy it or it is banned but rowing isn't one of those.

While you may well be right, it's still bizarre that highly motivated, performance obsessed, teams, with substantial resources, don't seek to eke out any available 1/10 of second from their equipment and set up. These might be little things - clean and polished boats and seats that run freely, or things that might just cost time - rigging, blades and gearing optimised in every dimension for each individual rower, blades smooth and without chipped paint, or they might be things that need real money like logging force at the pin or aerofoil section blade shafts. But why, if you have invested 4 years of your life working towards one race and one medal, wouldn't you take every advantage you could?

Andy

Sarah Harbour

2016-04-26 12:25:02 UTC

Yes, but please can we not shout too loudly about it - I'd rather my opposition didn't know what I was doing!?

Sarah

A. Dumas

2016-04-26 13:20:40 UTC

Post by James HS
interesting - if you look up aerodynamic and rowing clothing you get nothing!

Dutch LM4- tested speedskating suits in early 2000. Wasn't allowed by
FISA for world cups/champs/olys just for the one crew because the whole
national team needs to be uniform. At least one of the rowers was glad
because he thought it was too hot (as in: temperature..). They lost in
Seville to the British M4- which got a sigh of relief from Redgrave
"otherwise I'd have to wear one."

http://archief.nlroei.nl/fotoalbums/sevilla-2000/fotos/1536

carl

2016-04-26 20:34:40 UTC

Post by A. Dumas

Post by James HS
interesting - if you look up aerodynamic and rowing clothing you get nothing!

Dutch LM4- tested speedskating suits in early 2000. Wasn't allowed by
FISA for world cups/champs/olys just for the one crew because the whole
national team needs to be uniform. At least one of the rowers was glad
because he thought it was too hot (as in: temperature..). They lost in
Seville to the British M4- which got a sigh of relief from Redgrave
"otherwise I'd have to wear one."
http://archief.nlroei.nl/fotoalbums/sevilla-2000/fotos/1536

(Thunderbird's buttons keep tripping me up, so I "Replied" a while back
to the Musketeer, rather than "Followed-up" to the group :( )

Not very joined-up thinking for that crew to invest in
hoody-all-in-ones, then row in a shell with the most draggy of all
rigger designs

For Karapiro '78 we fitted our 2x with a modest perspex (plexiglas, US)
cowling to smooth & fill the gap between the washboards & the bow
sculler's back (GBR W2x). We gave it to them, carefully explaining its
purpose. When they returned to the UK, a little disappointed, I sought
their views on the cowling. "Oh, we never took it out of the box!"

Rowers seem to often to think that when they are about to race they can
leave their intellects at home: "Let's go out & lose the same way as
last time." only 1 thing does seem to obsess crews about their
equipment, & that's the least rational of all: "Is my boat down to
minimum weight?" There is zero evidence that boat weight, within 10%,
has any measurable effect on performance. Rowers believe, as an act of
faith, that lighter = faster, & if you express any doubt on this belief
they're likely to reply, "Well, FISA wouldn't have imposed weight limits
if weight doesn't matter." Sad, innit?

Kit's excellent patent search proves there's not that much that's new on
wind drag reduction in our discussions. Yes, a bow cowling makes a lot
of sense. However, if doing wind tunnel tests on drag modification with
1/16-scale models you should still try for reasonable Reynolds number
similarity - in which case your tunnel should run at 16x the wind speed
experienced by the real life boat.

I was interested to see that the Japanese had patented the aerofoil
oar-sleeve system they took to Atlanta. And that boundary layer trips
had been studied in some detail for golf club shafts.

Yes, there's a lot we can do that is un-ostentatious but useful. At the
other extreme, how about personal cowlings to strap to our backs (I've a
hunch that might get banned)? And wearing reverse track-cycling helmets?

Cheers -
Carl

sander

2016-04-27 02:34:20 UTC

Great patent search. Of course not everything that is patented makes sense. Need to search for wind tunnel test results of shell/rower systems.

So if we are moving around 4 m/s average going up and down the slide at 1 m/s relative to the boat but the shaft / blade on recovery moves at 2 much faster, in wind still conditions we would look at (in terms of power)

Rower's back Area x K1 x 27
blade effective area x K2 x 512

And during the stroke

A1 x K1 x 125
Blade under water doing other stuff

My thinking being that average speed of blade = average speed of rower = average speed of shell

All horribly simplified of course. In a 2 m/s headwind this becomes

On recovery

A1 x K1 x 125
A2 x K2 x 1000

During drive

A1 x K1 x 343

Note to self: check this reply when it's not 4:30 Am. Trying to understand where the biggest gains are ... Do we focus on the body or the shaft/blade? Why didn't I buy skinny shafts?

Kit Davies

2016-04-27 07:28:42 UTC

Post by sander
Great patent search. Of course not everything that is patented makes sense. Need to search for wind tunnel test results of shell/rower systems.
So if we are moving around 4 m/s average going up and down the slide at 1 m/s relative to the boat but the shaft / blade on recovery moves at 2 much faster, in wind still conditions we would look at (in terms of power)
Rower's back Area x K1 x 27
blade effective area x K2 x 512
And during the stroke
A1 x K1 x 125
Blade under water doing other stuff
My thinking being that average speed of blade = average speed of rower = average speed of shell
All horribly simplified of course. In a 2 m/s headwind this becomes
On recovery
A1 x K1 x 125
A2 x K2 x 1000
During drive
A1 x K1 x 343
Note to self: check this reply when it's not 4:30 Am. Trying to understand where the biggest gains are ... Do we focus on the body or the shaft/blade? Why didn't I buy skinny shafts?

And just to be clear, Andy must take all credit for the patent search,
not me!

Kit

a***@gmail.com

2016-04-27 08:33:32 UTC

And just to be clear, Andy must take all credit for the patent search,
not me!
Kit

No problem!

Andy

sully

2016-04-27 19:30:17 UTC

Post by A. Dumas

Post by James HS
interesting - if you look up aerodynamic and rowing clothing you get nothing!

Dutch LM4- tested speedskating suits in early 2000. Wasn't allowed by
FISA for world cups/champs/olys just for the one crew because the whole
national team needs to be uniform. At least one of the rowers was glad
because he thought it was too hot (as in: temperature..). They lost in
Seville to the British M4- which got a sigh of relief from Redgrave
"otherwise I'd have to wear one."
http://archief.nlroei.nl/fotoalbums/sevilla-2000/fotos/1536

Been following thread w/ great interest.

back maybe a decade or more, many sprinters in track and field wore hoods for better aerodynamics.

That seems to have disappeared in recent Olys. I tried to google up this phenomenon to no avail. Anybody know why they went away?

No chance of overheating in a 100 or 200 meter sprint.

g***@gmail.com

2016-04-27 23:50:53 UTC

Some thoughts

Post by carl
And wearing reverse track-cycling helmets?

By far the biggest gains in cycling are from aero helmets and wheels. So this may be a good idea. But heat is always a concern but at least in cycling at 15 mps the cooling is better and areodynamics are much more important than in rowing at 5ms. One really needs to test this to see if it matters.

Post by carl
Why didn't I buy skinny shafts?

Or rather why didn't you buy aerofoil sction blade shafts? http://www.durhamboat.com/aero_sculls.php
I recently did a crude calculating and the skinny shafts would save me about .5 seconds for 1000m. For an Olympian with two or more times the power of me, it would be less. Should redo the cacluation to be sure. It is not a lot but enough to made a difference in about 3 out of my last 50 or so races. On the other hand steering (both good and bad on my part and on the part of competitiors) has made a difference in many times that number. For the vast majority of us who are not at the national level equipment is determining factor most of the time. Free time is nice but an extra hour or two of rowing per week would make more a difference for me than anything else.

Post by carl
These might be little things - clean and polished boats and seats that run freely, or things that might just cost time - rigging, blades and gearing optimised in every dimension for each individual rower, blades smooth and without chipped paint, or they might be things that need real money like logging force at the pin or aerofoil section blade shafts. But why, if you have invested 4 years of your life working towards one race and one medal, wouldn't you take every advantage you could?

I would expect everyone in international competition has new or almost new equipment (seats that run freely and non-chipped blades). I am highly skeptical that wet sanding or excessive polishing has any measurable effect at the speeds of rowing shells.

The bow cowling does make sense but you are dealing with human nature. It sounds like it was untested. It does not surprise me that someone would not try something that they hadn't practiced with. Handing someone a piece of equipment saying it will make you faster based on theory even if appears obvious to an engineer is very different than handing someone equipment and saying we found carefully tested it, and it saves 3 seconds in a head wind and 1 second with no wind. Rowers have a lot to think about at international competition. A new piece of equipment that no else uses or saw the need for may be just too much to think about at the last minute.

Even the aerofin plus canard only seems to have anecdotal evidence behind it. It may be obvious to those who try it but with out clear data it is not surprising that it hasn't caught on. Should I feel stupid for not buying one and putting it on our club quad? I've thought about it for years but never quite justified it to myself. Cost is not a big deal compared with a couple of years of entry fees, especially if it really means winning more races. But I very much doubt I'm the only one on this site who has been wondering about it for a long time and not tried it. If I had the time (i.e. was retired) I would love to try out many of these ideas but I'm not likely to spend the time until I retire.

Testing is often inconclusive and difficult. We still don't have a clear idea of which blade shape is fastest and under what circumstances. Maybe Fat2's are faster in a tailwind on flat water but maybe Macons are actually faster in rough water in a head wind.

It was suggested recently (I think in bio row), that crews should bring two boats to international regattas. One that is more stable for rough conditions and one that is faster in smooth. Professional cycling teams change equipment for different races but they have the money to do it.

If a few countries start doing these things and winning it will be perceived as necessary and will become common. Until then, or until there is a lot more money in rowing, the lack of innovation and lack of rigorous testing is to be expected.

t***@googlemail.com

2016-04-28 09:05:08 UTC

Post by g***@gmail.com
Some thoughts

Post by carl
And wearing reverse track-cycling helmets?

Post by carl
Why didn't I buy skinny shafts?

I would expect everyone in international competition has new or almost new equipment (seats that run freely and non-chipped blades). I am highly skeptical that wet sanding or excessive polishing has any measurable effect at the speeds of rowing shells.
The bow cowling does make sense but you are dealing with human nature. It sounds like it was untested. It does not surprise me that someone would not try something that they hadn't practiced with. Handing someone a piece of equipment saying it will make you faster based on theory even if appears obvious to an engineer is very different than handing someone equipment and saying we found carefully tested it, and it saves 3 seconds in a head wind and 1 second with no wind. Rowers have a lot to think about at international competition. A new piece of equipment that no else uses or saw the need for may be just too much to think about at the last minute.
Even the aerofin plus canard only seems to have anecdotal evidence behind it. It may be obvious to those who try it but with out clear data it is not surprising that it hasn't caught on. Should I feel stupid for not buying one and putting it on our club quad? I've thought about it for years but never quite justified it to myself. Cost is not a big deal compared with a couple of years of entry fees, especially if it really means winning more races. But I very much doubt I'm the only one on this site who has been wondering about it for a long time and not tried it. If I had the time (i.e. was retired) I would love to try out many of these ideas but I'm not likely to spend the time until I retire.
Testing is often inconclusive and difficult. We still don't have a clear idea of which blade shape is fastest and under what circumstances. Maybe Fat2's are faster in a tailwind on flat water but maybe Macons are actually faster in rough water in a head wind.
It was suggested recently (I think in bio row), that crews should bring two boats to international regattas. One that is more stable for rough conditions and one that is faster in smooth. Professional cycling teams change equipment for different races but they have the money to do it.
If a few countries start doing these things and winning it will be perceived as necessary and will become common. Until then, or until there is a lot more money in rowing, the lack of innovation and lack of rigorous testing is to be expected.

Great post, explained it more coherently than I was able to earlier in the thread! I agree, the lack of uptake/perceived interest in adopting things like aerodynamic improvements is a lack of both clear instructions on how to actually install/use such things (like aero trip wires) and also to a lesser extent a lack of testing results - more so I feel than a general lack of interest in making small gains - I feel that the quick adoption of skinny shaft blades is a good example that people are willing to accept/pay for aero benefits, as long as they understand the potential gains being made and if it is clear how their performance will benefit

m***@gmail.com

2016-04-28 11:50:04 UTC

Post by g***@gmail.com
I would expect everyone in international competition has new or almost new equipment (seats that run freely and non-chipped blades). I am highly skeptical that wet sanding or excessive polishing has any measurable effect at the speeds of rowing shells.

You might be surprised. Fairly extensive testing has been done in the dinghy sailing world with Frank Bethwaite concluding that even the traffic film from trailing a boat was enough to have a measurable impact. I'd expect an even greater impact on a rowing shell.

a***@gmail.com

2016-04-28 12:49:07 UTC

I don't know about Olympic and International standard, but you will definitely see scraggy blades on a few boats at Henley and junior international. Even at my rather pedestrian pace I can feel a difference between smooth and rough blades at the extraction (of course the question is which is faster?). We used to tease my son's coach that his obsessive polishing of their boat probably wasn't going to make more than 0.1 seconds difference, until they took a course record by 0.1 second!

Andy

m***@gmail.com

2016-04-28 15:18:23 UTC

The state of blades has always intrigued me seeing some very battered ones at Henley. While I'm not convinced vortex tips actually do much (too much separated flow) I'm confident bashed up ones at least cannot be beneficial.

Sarah Harbour

2016-04-28 17:40:30 UTC

Maybe not, but vortex edges do protect the edge of the blade from chipping...

Sarah

g***@gmail.com

2016-04-28 20:53:05 UTC

If you are talking about smoothing out scratches and nicks in the hull then yes, polishing will make a difference. But if you are talking about essentially new undamaged hulls, i don't think wet sanding and polishing will make any where near .1 sec at 5 m/s.

a***@gmail.com

2016-05-04 08:55:33 UTC

You might be right, and I can't even mentally get Reynolds numbers within 5 orders of magnitude, but if I understand it correctly we will have laminar flow under the bow portion of a boat, and at some point it breaks away and we get turbulent flow. A nice layer of river crud and dead flies presumably changes this transition point. If it shifts it a centimetre to the stern, would that increase drag? 0.1 seconds is about .03%. Hardly measurable, but worth having, and better in your boat than the boat in the next lane. Of course it might be that early transition is good - and at least that experiment doesn't require too much effort - I'll just stop shouting at crews to wash the things.

(for someone who understands the science ... http://lowcarbonshipping.co.uk/files/Ben_Howett/SCC2015/EXPERIMENTAL_DETERMINATION_OF_THE_ROUGHNESS_FUNCTIONS_OF_MARINE_COATINGS.pdf tests done of different paints - I think suggesting quite significant differences)

Andy

Kit Davies

2016-05-04 11:26:47 UTC

You might be right, and I can't even mentally get Reynolds numbers within 5 orders of magnitude, but if I understand it correctly we will have laminar flow under the bow portion of a boat, and at some point it breaks away and we get turbulent flow. A nice layer of river crud and dead flies presumably changes this transition point. If it shifts it a centimetre to the stern, would that increase drag? 0.1 seconds is about .03%. Hardly measurable, but worth having, and better in your boat than the boat in the next lane. Of course it might be that early transition is good - and at least that experiment doesn't require too much effort - I'll just stop shouting at crews to wash the things.
(for someone who understands the science ... http://lowcarbonshipping.co.uk/files/Ben_Howett/SCC2015/EXPERIMENTAL_DETERMINATION_OF_THE_ROUGHNESS_FUNCTIONS_OF_MARINE_COATINGS.pdf tests done of different paints - I think suggesting quite significant differences)
Andy

I'm somewhat surprised the rowing community (or at least that part of it
with the most to gain) haven't tested FISA's rules on surface finishes
more adventurously. IIRC the restriction is on "applying substances or
materials that affect the boundary layer" or words to that effect. The
main targets for these seem to be hydrophobic coatings and
dentricles/riblets, etc, but there must be a few loopholes in there
waiting to be jumped through.

Eg:
1. Are only external things banned, ie not part of the existing surface
of the hull, Ie waxes?
2. Am I allowed to alter the existing surface, ie suppose I had a
machines that could engraved riblet into the hull? Stricy=tly speaking,
that's not applying a substance, even if it is applying a finish.
3. Am I (somehow) allowed to shape the hull to affect the boundary layer?

And I'm sure there are plenty of others.

I realise that some of these may not actually provide benefits but
AFAICS no one is even exploring these kind of things.

Kit

m***@gmail.com

2016-05-04 19:37:11 UTC

You might be right, and I can't even mentally get Reynolds numbers within 5 orders of magnitude, but if I understand it correctly we will have laminar flow under the bow portion of a boat, and at some point it breaks away and we get turbulent flow. A nice layer of river crud and dead flies presumably changes this transition point. If it shifts it a centimetre to the stern, would that increase drag? 0.1 seconds is about .03%. Hardly measurable, but worth having, and better in your boat than the boat in the next lane. Of course it might be that early transition is good - and at least that experiment doesn't require too much effort - I'll just stop shouting at crews to wash the things.
(for someone who understands the science ... http://lowcarbonshipping.co.uk/files/Ben_Howett/SCC2015/EXPERIMENTAL_DETERMINATION_OF_THE_ROUGHNESS_FUNCTIONS_OF_MARINE_COATINGS.pdf tests done of different paints - I think suggesting quite significant differences)
Andy

Have a look at my post about tests in dinghy sailing where even traffic film from towing was measurable in full-scale tow testing. It definitely matters.

carl

2016-04-28 18:48:27 UTC

Post by g***@gmail.com
Some thoughts

Post by carl
And wearing reverse track-cycling helmets?

We should remember that the human back is scarcely designed for minimum
wind drag in headwinds.

Assume:
Exposed frontal area (WRT to wind direction when moving at 5m/s in still
air) is about .88 x .45 = 0.4m^2
It's moving at constant velocity (probably not too far off)
A drag coefficient of 1.2
Density of air =1.225kg/m^3

Then:
Drag force is = 0.5 x 1.2 x 0.4 x 1.225 x 5^2 = 7.35 Newtons
Power consumed to overcome this if moving at 5m/sec = 36.8 Watts.

That's a fair chunk (~10%) of a good sculler's useful power output!

Let's tabulate the effect of increased head-wind velocities, knowing
that power consumption is proportional to velocity cubed:
Wind Speed m/sec 0 5 10
Wind velocity WRT boat m/sec 5 10 15
Power consumed (Watts) 36.8 294.0 992.3

On that basis no sculler will ever achieve a 6:40 time for 2K into even
a 5m/sec head-wind"!

If the body's aerodynamic drag coefficient can be halved by a
well-designed fairing, that would also halve those power losses.

So I think we should eschew arm-chair punditry & do the maths before
dismissing the possible impact of any factor on race performance. My
own sums are, of course, open & open to challenge or correction but, if
correct, clear even in still airs we must lose a lot of performance to
bodily windage. Indeed, this suggests that wind drag on a rower's
torso, arms & head may, for a 1x, be the largest single cause of
aerodynamic drag & the most significant factor in impairing their race
performance.

Cheers -
Carl

g***@gmail.com

2016-04-28 19:57:36 UTC

Post by carl
We should remember that the human back is scarcely designed for minimum
wind drag in headwinds.
Exposed frontal area (WRT to wind direction when moving at 5m/s in still
air) is about .88 x .45 = 0.4m^2
It's moving at constant velocity (probably not too far off)
A drag coefficient of 1.2
Density of air =1.225kg/m^3
Drag force is = 0.5 x 1.2 x 0.4 x 1.225 x 5^2 = 7.35 Newtons
Power consumed to overcome this if moving at 5m/sec = 36.8 Watts.
That's a fair chunk (~10%) of a good sculler's useful power output!
Let's tabulate the effect of increased head-wind velocities, knowing
Wind Speed m/sec 0 5 10
Wind velocity WRT boat m/sec 5 10 15
Power consumed (Watts) 36.8 294.0 992.3
On that basis no sculler will ever achieve a 6:40 time for 2K into even
a 5m/sec head-wind"!
If the body's aerodynamic drag coefficient can be halved by a
well-designed fairing, that would also halve those power losses.
So I think we should eschew arm-chair punditry & do the maths before
dismissing the possible impact of any factor on race performance. My
own sums are, of course, open & open to challenge or correction but, if
correct, clear even in still airs we must lose a lot of performance to
bodily windage. Indeed, this suggests that wind drag on a rower's
torso, arms & head may, for a 1x, be the largest single cause of
aerodynamic drag & the most significant factor in impairing their race
performance.
Cheers -
Carl
--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories
Write: Harris Boatyard, Laleham Reach, Chertsey KT16 8RP, UK
Find: tinyurl.com/2tqujf

Perhaps my post was poorly worded, I hardly dismissed the possibility.

You need to test the helmet you make to see if it does what you think. In the famous Tour final TT where Greg Lemond beat Laurent Fingion, Lemond was wearing aero helmet. While the helmet was a big advantage when he was looking forward, but when he looked down as he did often the tail of the helmet stuck up resulting in more drag. He has said using the helmet was probably a wash in the end. So while you can design something that you think works you need to make sure it does what you think. Things that look aerodynamic aren't necessarily so.

A lot of money and a lot of time has gone into developing cycling helmets, and in refining many of the components of the bicycle for reduced drag. So maybe you can just put something on a rowers head without testing it but you may make things worse.

m***@gmail.com

2016-04-28 21:37:06 UTC

So while you can design something that you think works you need to make sure it >does what you think. Things that look aerodynamic aren't necessarily so.

Some interesting ones from Specialized's wind tunnel:

Time saved for a 40K time trial (note that it's fairly independent of speed, since slower riders experience less drag but experience it for longer):

Shave your legs: 70 seconds.
Hair in braid instead of ponytail, bun, or down: 14 seconds.
Switch from casual medium jersey to form-fitting size small: 91 seconds.
Move water bottle from seat post to down tube: 25 seconds.
Water bottle in back pocket or attached behind seat: 38 seconds.
Trade your 1980s steel bike for a modern aero bike: 50 seconds.

http://www.runnersworld.com/sweat-science/does-drag-matter-for-runners

carl

2016-04-29 01:20:24 UTC

So while you can design something that you think works you need to make sure it >does what you think. Things that look aerodynamic aren't necessarily so.

Shave your legs: 70 seconds.
Hair in braid instead of ponytail, bun, or down: 14 seconds.
Switch from casual medium jersey to form-fitting size small: 91 seconds.
Move water bottle from seat post to down tube: 25 seconds.
Water bottle in back pocket or attached behind seat: 38 seconds.
Trade your 1980s steel bike for a modern aero bike: 50 seconds.
http://www.runnersworld.com/sweat-science/does-drag-matter-for-runners

I've never understood why so many runners have their hair flopping
around behind them.

Carl

Sarah Harbour

2016-04-29 07:20:58 UTC

Post by carl

So while you can design something that you think works you need to make sure it >does what you think. Things that look aerodynamic aren't necessarily so.

I've never understood why so many runners have their hair flopping
around behind them.
Carl
--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories
Write: Harris Boatyard, Laleham Reach, Chertsey KT16 8RP, UK
Find: tinyurl.com/2tqujf

Oh blimey. I thought bun was better than ponytail. Does that mean I'm going to have to get Mel trained on how to braid my hair for me?

Sarah

A. Dumas

2016-04-29 09:31:16 UTC

Post by Sarah Harbour
Oh blimey. I thought bun was better than ponytail. Does that mean I'm
going to have to get Mel trained on how to braid my hair for me?

Irrespective of aero gains: yes, definitely.

m***@gmail.com

2016-04-29 10:21:16 UTC

My understanding is that the order of aero-benefits effect is something like: body position, helmet, legs-shaved, slippery skin-suit, foot-covering, wheels, frame

Of more import than choice of helmet between Lemond and Fignon in that final TT was the fact that Lemond was using aero-bars and Fignon wasn't. In other words his body-position would have had far more effect than his helmet.

Re: running, I find it anachronous that running records are allowed to be set with the help of pacemakers, somewhat akin to allowing Bradley Wiggins to do his Hour record with a series of pace-makers

I have a page of my cycling-related stuff here on my website for anyone who's interested http://www.slidingseat.net/cycling/cycling.html

g***@gmail.com

2016-04-29 18:01:51 UTC

Post by m***@gmail.com
My understanding is that the order of aero-benefits effect is something like: body position, helmet, legs-shaved, slippery skin-suit, foot-covering, wheels, frame

You may be right but I really thought wheels were more important than foot-covering and skin-suits. Must depend to some extent on what you are comparing since there is a big range in both wheels and clothing.

Post by m***@gmail.com
Of more import than choice of helmet between Lemond and Fignon in that final It was the fact that Lemond was using aero-bars and Fignon wasn't. In other words his body-position would have had far more effect than his helmet.

Yes of course. In rowing I don't think there is much you can do about body position where as an aero head covering is possible

Shaving legs in cycling is not done primarily for wind resistance but why don't cyclists sometimes shave their arms? If shaving legs make that much of a difference seems they should be.

Should we all be shaving our arms?

Kit Davies

2016-04-29 20:00:52 UTC

Post by m***@gmail.com
My understanding is that the order of aero-benefits effect is something like: body position, helmet, legs-shaved, slippery skin-suit, foot-covering, wheels, frame

Yes of course. In rowing I don't think there is much you can do about body position where as an aero head covering is possible
Shaving legs in cycling is not done primarily for wind resistance but why don't cyclists sometimes shave their arms? If shaving legs make that much of a difference seems they should be.
Should we all be shaving our arms?

After some brief experimentation in a headwind on Wed, I believe (but
may be wrong) there may be aerodynamic benefit in adapting the position
of the arms at the finish, eg tucking the elbows into the body further
than is orthodox

Kit

Lucy

2016-04-29 16:44:15 UTC

Post by Sarah Harbour
Oh blimey. I thought bun was better than ponytail. Does that mean I'm going to have to get Mel trained on how to braid my hair for me?
Sarah

So did I! Mine's long enough that even when I braid it, it still gets caught in the slide, so a bun's my only option...unless I get a very drastic cut? *winks*

Kit Davies

2016-04-29 07:42:00 UTC

So while you can design something that you think works you need to make sure it >does what you think. Things that look aerodynamic aren't necessarily so.

This article

http://www.cyclingweekly.co.uk/news/product-news/why-leaving-hair-on-your-legs-could-help-you-go-faster-186135

suggests cyclist Alex Dowsett shaves his legs but leaves unshaven trip
strips on each leg. Not sure how serious this is though.

Kit

A. Dumas

2016-04-29 09:29:21 UTC

Post by Kit Davies
http://www.cyclingweekly.co.uk/news/product-news/why-leaving-hair-on-your-legs-could-help-you-go-faster-186135
suggests cyclist Alex Dowsett shaves his legs but leaves unshaven trip
strips on each leg. Not sure how serious this is though.

He just missed a spot and decided it'd make a good IG joke.

carl

2016-04-29 00:31:09 UTC

Perhaps my post was poorly worded, I hardly dismissed the possibility.

I'm sorry if my comment, made in haste, was clumsily phrased. My
concern is over the general readiness of rowers to sweep science under
the carpet

Post by g***@gmail.com
You need to test the helmet you make to see if it does what you think. In the famous Tour final TT where Greg Lemond beat Laurent Fingion, Lemond was wearing aero helmet. While the helmet was a big advantage when he was looking forward, but when he looked down as he did often the tail of the helmet stuck up resulting in more drag. He has said using the helmet was probably a wash in the end. So while you can design something that you think works you need to make sure it does what you think. Things that look aerodynamic aren't necessarily so.

Yes, absolutely. Again it can be a matter of not having thought deeply
enough about how clever kit will be used & how it behaves in cases you
haven't considered, & in the hands of the real human. I believe, but
could be quite wrong, that the monocoque-framed Lotus bike used by Chris
Boardman in Barcelona (but actually created by Mike Burrows, which most
folk forget) did not show any real aerodynamic advantage but, while
evaluating bike + rider in a wind tunnel, a dip in drag was noted as he
moved between positions, encouraging a slightly different rider
positioning (but not to the Obree extent). But the popular view remains
that "it's the bike wot won".

Post by g***@gmail.com
A lot of money and a lot of time has gone into developing cycling helmets, and in refining many of the components of the bicycle for reduced drag. So maybe you can just put something on a rowers head without testing it but you may make things worse.

True again. Clever kit often needs intelligent users, so in a
cross-wind you might prefer not to have a bow cowling.

Cheers -
Carl

sander

2016-04-29 18:02:18 UTC

I think this is underestimating the effect. In my model, I took a drag coefficient of 1.1 (Carl: 1.2), and I needed to make the "area" for a single sculler equal to 2.0 to be able to reproduce Kleshnev's results.

Details here: http://blog.rowsandall.com/2016/04/14/windy-intervals-and-a-small-step-towards-quantitative-rowing/

Of course I am not sure about the reliability of Kleshnev's results.

Still, for example today I was doing 2km intervals on our lake. The wind was certainly below 2m/s (around 0.5 m/s according to close-by weather stations). There was fog, a slight ripple. My tailwind 2ks were 8:22 and 8:32. My headwind 2ks were 9:09. So more than thirty seconds, admittedly at a slow Master's rower's pace.

My model, with wind speed set at 0.5 m/s, was not able to predict such large differences. And I honestly worked as hard with headwind as with tailwind. The report is here: http://blog.rowsandall.com/2016/04/29/4x2km-in-interesting-conditions/

So in summary, wind is huge. At least, locally, on my lake.

a***@gmail.com

2016-04-30 14:06:25 UTC

Post by sander
I think this is underestimating the effect. In my model, I took a drag coefficient of 1.1 (Carl: 1.2), and I needed to make the "area" for a single sculler equal to 2.0 to be able to reproduce Kleshnev's results.
Details here: http://blog.rowsandall.com/2016/04/14/windy-intervals-and-a-small-step-towards-quantitative-rowing/
Of course I am not sure about the reliability of Kleshnev's results.
Still, for example today I was doing 2km intervals on our lake. The wind was certainly below 2m/s (around 0.5 m/s according to close-by weather stations). There was fog, a slight ripple. My tailwind 2ks were 8:22 and 8:32. My headwind 2ks were 9:09. So more than thirty seconds, admittedly at a slow Master's rower's pace.
My model, with wind speed set at 0.5 m/s, was not able to predict such large differences. And I honestly worked as hard with headwind as with tailwind. The report is here: http://blog.rowsandall.com/2016/04/29/4x2km-in-interesting-conditions/
So in summary, wind is huge. At least, locally, on my lake.

Hi Sander (and Carl):

Looking at result comparisons (Carl vs. Bill).

Carl very reasonably uses Cd=1.2 and A=0.4m^2 to get Fd=7.35N

I consider Ka=0.245N-s^2/m^2 at 5.0m/s (which is the result from the ROWING model) giving a resistance drag of only 6.13N -- at an effective Cd=1.00.
(See Fig.1 at <http://www.atkinsopht.com/row/airdrag.htm>).
We are clearly in the same region of space here (in the US we would be in the same "ballpark").

Cd for a flat plate of small L/d (around 1) and at high Re is indeed about 1.2, but for a cylinder (axis normal to air stream) it can be nearer to 0.6 giving a force of only 3.68N. The human torso is neither flat nor cylindrical but somewhere in between (Cd=0.8?). Welcome future empiricists!

Do not lose sight of the fact that the wind blows on boats, oars, and funny hats as well.

Soldier on me hearties -- thus advanceth science.

Bill

John Mulholland

2016-05-03 23:44:04 UTC

An aerodynamic helmet designed for a cyclist would have a fundamental problem; we face the other way. It would have to be round at the back of the head and taper to a point at the front. That might lead to problems with vision when turning round to check what was ahead; maybe not important on a 2k course, but in training on a crowded river!

m***@gmail.com

2016-07-31 14:41:59 UTC

Post by sully

Post by A. Dumas

Post by James HS
interesting - if you look up aerodynamic and rowing clothing you get nothing!

Dutch LM4- tested speedskating suits in early 2000. Wasn't allowed by
FISA for world cups/champs/olys just for the one crew because the whole
national team needs to be uniform. At least one of the rowers was glad
because he thought it was too hot (as in: temperature..). They lost in
Seville to the British M4- which got a sigh of relief from Redgrave
"otherwise I'd have to wear one."
http://archief.nlroei.nl/fotoalbums/sevilla-2000/fotos/1536

Been following thread w/ great interest.
back maybe a decade or more, many sprinters in track and field wore hoods for better aerodynamics.
That seems to have disappeared in recent Olys. I tried to google up this phenomenon to no avail. Anybody know why they went away?
No chance of overheating in a 100 or 200 meter sprint.

A thread bump because I found some info by accident on reddit if anyone is interested (https://www.reddit.com/r/Rowing/comments/4v4uuk/the_illusive_hooded_unisuit/)

"Dutch LM tested these in the early 2000s:
http://archief.nlroei.nl/fotoalbums/sevilla-2000/fotos/1536
They were speed skating suits, but they got ditched because they were too hot."

"The suit pictured was one of those tested by Rowing Canada Aviron in the run-up to the Athens Olympics. In what I understand was an ultimately failed partnership, Nike designed the hooded suits for RCA, and they were worn during some training sessions. They were sleeveless, unlike the Dutch suits /u/kitd mentioned, and were supposed to reduce drag by about 3%, if I recall correctly. Over a 2k race, the difference was significant, if not game-breaking (like those synthetic sharkskin swimsuits).

Ultimately, the partnership fell apart, and the Canadians raced with regular Nike unisuits. Here is a picture of the 2004 CAN M4- wearing them: Loading Image...

m***@gmail.com

2016-04-13 19:16:16 UTC

Post by carl
I know no current rule that might ban a SWATH hull (entire hull
underwater, like a submarine, with rower above water on a pylon), & it
might work. Certainly there's nothing to stop anyone (you?) from
testing such a design .....

At the first of derailing this discussion, if anyone is interested in this the Moth sailing class have tried it.

carl

2016-04-13 23:18:30 UTC

At the first of derailing this discussion, if anyone is interested in this the Moth sailing class have tried it.

Might you have this in mind:

?
Carl

m***@gmail.com

2016-04-14 12:31:15 UTC

Post by carl

At the first of derailing this discussion, if anyone is interested in this the Moth sailing class have tried it.

http://youtu.be/xW_UfYGO3Kg
?
Carl
--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories
Write: Harris Boatyard, Laleham Reach, Chertsey KT16 8RP, UK
Find: tinyurl.com/2tqujf

It was pre-foiling. The entire hull other than a small strut was shaped like a submarine and was underwater. It was a long time back but I'm sure you'll be unsurprised to know it had some problems as was abandoned especially as foiling became more promising.

Lucy

2016-04-14 10:46:55 UTC

Question for the stupid...

What's actually the difference between SWATH hulls and hydrofoiling?

From what I already know (precious little) and what's been posted here, it seems that SWATH is a big underwater hull with a small crew "pod" on top that is permanently raised out of the water, whereas hydrofoiling is a small foil under the water then a larger hull on the surface which lifts once a certain speed is reached....is that right?

There's some great footage of a prototype foiling 4x somewhere, but I'll have to dig it out later as I should currently being ringing up truck lubricants companies rather than procrastinating and reading rowing sites...*blushes*

carl

2016-04-14 11:35:28 UTC

Post by Lucy
Question for the stupid...
What's actually the difference between SWATH hulls and hydrofoiling?
From what I already know (precious little) and what's been posted here, it seems that SWATH is a big underwater hull with a small crew "pod" on top that is permanently raised out of the water, whereas hydrofoiling is a small foil under the water then a larger hull on the surface which lifts once a certain speed is reached....is that right?
There's some great footage of a prototype foiling 4x somewhere, but I'll have to dig it out later as I should currently being ringing up truck lubricants companies rather than procrastinating and reading rowing sites...*blushes*

SWATH = small water-plane twin hull. It's a displacement craft in the
fully Archimedean sense (a single-hull SWATH would be unusual & tricky).
Often dependent on foils to maintain trim & ride height as a given
SWATH's pitching stability & rate of change in displacement with depth
of immersion is rather small (most of its displacing volume being
already below the surface).

Hydrofoil = water craft supported largely or (usually) entirely above
water by hydrodynamic lift generated on submerged foils (wings mounted
on pylons & running below the surface). The foils "fly" through the
water & are trimmed just as wings are to achieve the desired lift &
hence desired rid height of hull above water.

The swath's hull, being fully submerged, does not generate the wave
train that you get with all surface craft. It can be optimised for
proportion whereas surface vessels' speed may be limited by having
inadequate length, so they tend to be made longer & thinner which
minimises wave drag at the cost of increase wetted surface & hence skin
drag.

The hydrofoil, once running as intended with hull above water & foils
below, has only the frictional & form drag of its foils & their
supporting structures. But to start foiling it must be able to overcome
the drag on its hitherto immersed hull.

HTH?
Carl

don Vickers

2016-04-14 12:07:16 UTC

I recall seeing a video of the quad with hydrofoils being posted here a year or more back. Unfortunately, I couldn't find it in a short search.

An interweb search did find this video,

which shows a single with hydrofoils. In addition to hydrofoils the shell has a sliding rigger which is probably required to minimize changes in the center of gravity. The boat seems to rise out of the water rather easily. The rowers don't seem to have trouble with oarlock height even with the boat being well above the surface. There is a frame on the rigger at the oarlock that looks like it may adjust but I don't see the oarlock adjusting in the video.

This was published in 2009 and the text indicates the project was continuing. It gives a URL at Yale for more information but that page seems to have gone off to web page heaven or maybe the other place. It would be nice to learn more about what the Yale engineers learned from this project. It is virtually certain that such shells would be outlawed, of course.

Don Vickers

Jake

2016-04-14 19:31:34 UTC

Post by don Vickers

I recall seeing a video of the quad with hydrofoils being posted here a year or more back. Unfortunately, I couldn't find it in a short search.
An interweb search did find this video, http://youtu.be/9BXxL9gztO8 which shows a single with hydrofoils. In addition to hydrofoils the shell has a sliding rigger which is probably required to minimize changes in the center of gravity. The boat seems to rise out of the water rather easily. The rowers don't seem to have trouble with oarlock height even with the boat being well above the surface. There is a frame on the rigger at the oarlock that looks like it may adjust but I don't see the oarlock adjusting in the video.
This was published in 2009 and the text indicates the project was continuing. It gives a URL at Yale for more information but that page seems to have gone off to web page heaven or maybe the other place. It would be nice to learn more about what the Yale engineers learned from this project. It is virtually certain that such shells would be outlawed, of course.
Don Vickers

Somebody needs to tell Yale uni to put a small LE fence, or series of fences on each one of those pylons! Look at that great sheen of water climbing up both pylons- wasted energy.

Kit Davies

2016-04-14 13:40:00 UTC

Post by Lucy
There's some great footage of a prototype foiling 4x somewhere,

You may be thinking of the RISE Delft project?

Kit

Lucy

2016-04-14 18:44:46 UTC

Post by Lucy
There's some great footage of a prototype foiling 4x somewhere,

You may be thinking of the RISE Delft project?
http://youtu.be/6Mb_U-ne89A
Kit

I was indeed, thanks Kit!

Jake

2016-04-14 19:13:05 UTC

Couple of points:
First a point on the acronyms. SWATH hulls denote a catamaran (small waterplane area twin hull)
A single submerged hull with a rower (somehow balancing!!) above on a pylon connected rowing station is a SWASH hull. They also exist and are usually stabilised by flat, planing surface hulls on outriggers.

What I am interested in now is SWATH-stabilised hulls.

As an aside, I have already done plenty of experimentation with rowing shells stabilised by surface amas- rather similar (with a cursory glance) to the adaptive boats but rather more carefully considered. This creates a much more conventional trimaran rather than a SWATH. I've tried both planing hulls and displacement hull forms for these amas. Interestingly (or not- read on if you like this sort of stuuff!) My on-water tests and a need to have a fast single scull that I could commute to work in year round, in nasty open water and flat water alike brought up an interesting early development: The stabilising hulls can plane! At 6 or 7 knots you need a pair of, and I choose my phrase carefully, 'buoyant slappers'. As flat bottomed slappers they hit the wave and the boat is slapped back upright. At standstill or when you get hit by a big wave and stopped and are in survival mode, the buoyancy of the floats (only about 15 litres a side at the end of the riggers) is needed to prevent capsize- and it does so very effectively. At rowing speed, when a float hits the water, its flat bottom, and moderate nose rocker provides ample righting moment to prevent a capsize. Just because at 6-7 knots the main hull is in displacement mode, it does not mean the stabiliser hulls need to be! I don't understand why people don't understand this. A 2 foot long ama that is brought, usually fairly lightly into contact with stationary water at anything over about 2 knots will want to plane, just like a 2 foot long toy boat at your local pond- so optimise it for planing!
Clearly, for a compromise of flat water performance (both amas out of the water all the time), and rough water safety there is a sweet spot in ama height. With extensive trial and error, I found that adjusting the amas to be about 4 inches above the water (with boat sculled flat) is a good compromise for me. The better the sculler, the higher you want the floats, because you don't want them constantly hitting the wave tops and slowing you down when you are in conditions where you are perfectly able to balance the boat by yourself.

Going out with this kit in very very rough conditions that would be completely unrowable in a monohull scull improved my open water rowing skills greatly. I believe more than any other teaching aid could have.
Similarly, the same could be said for safely teaching youngsters to row. When I, some time in the future teach my son to scull, (he's 2.5 yrs old, but already over a metre tall and his Daddy used to pull a 6:06- so he might be worth putting in a boat at some point), He won't be messing about with Virus boats and the like. He'll be going straight into a custom, fine single scull with proportionately correctly sized oars and riggers for his height. It will have my buoyant slappers on it, but set way down by the water for confidence (making it more stable than any monohull including Virus etc.) (I know that's only INITIAL stability by the way before anyone pipes up) Then as he gets better the amas get moved up. Right up to the point (probably about a day later) when he can balance in flat water without them.

At one point I wanted to make and sell these things as a junior coaching aid but the market size in rowing is too small to bother with and the audience (as mentioned elsewhere here) too technically uneducated/ uninterested to make them anything else but an expensive (for me) flop. Bit of a shame, because any country that started training their youngsters in proper fine boats instead of yellow HDPE tubs could get a leg over all the others at international regattas a few years later. It could also mean fewer rowers, particularly single scullers who go out alone, would die.

I got sidetracked there, my apologies. As Carl has mentioned in an earlier post the fact that SWATH hulls are already partially sunk (they do not have a reserve of extra buoyancy above the water to provide vastly more lift as they are pushed (further) under, means they are not going to provide as much roll resisting force as my buyoyant slappers. However, I plan to put some small buoyant slappers above them to provide safety at standstill and will play if necessary with small electronic stabilising foils to keep the craft horizontal while moving. The SWATHS will also provide significant lift to the main hull- so where the athlete (note I'm not saying rower or sculler as this is not a rowing boat) would typically sit a 100 kg boat, he will be able to sit a 75 or 85 kg boat- so some of the additional skin drag cost of the SWATH hulls and pylons will be made up for by this main hull's lower wavemaking and skin drag.

If you were going to do a SWATH rowing boat it would almost certainly be a catamaran, (mine's only a trimaran because it needs a surface central hull to mount the drive, make it cheaper to make etc.), it would be illegal to race due to more than one hull, and it would be sensitive to pitching due to the lack of reserve buoyancy in air. Perhaps, then there might finally be a need for a sliding rigger:)

Ps. For those not up on their Tamil, amas= a multihull's floats (as in cat ama ran). The other useful word for describing a multihull's component parts is 'akas'- these are the crossbeams that join the amas together. Amas and akas.
As Captain Cook and various others discovered some time ago, swathes of the rest of the world and many Pacific cultures which are now considered backward or even 'third world' have been thinking about such technologies rather longer than we have, so I feel it is only fair to use some of their terminology.

Don't get me onto yulohs, flaping tail propulsion, whale tail propulsion etc.!

Jake

2016-04-14 19:26:01 UTC

Post by Lucy
There's some great footage of a prototype foiling 4x somewhere,

You may be thinking of the RISE Delft project?
http://youtu.be/6Mb_U-ne89A
Kit

I saw the TU Deft 4x at Europort last year and chatted to the team at length. Quite a shock to come across a 4x in the middle of a commercial marine exhibition full of ships' azimuthing propulsion units etc.!

It's a great academic exercise for them. But I thought it a bit of a waste of good foils and good brains. It will of course get up on them, but won't stay there for long. The somewhat awkward sawtooth output profile of a rowing boat's propulsion system means that hydrofoils are probably not the best option.

Many years ago I built a hydrofoling single scull which failed to get up on its foils at all. An achievement I'm sure I share with many!

There is an interesting parallel in the Flyak. If you are a world class canoeist you can get a flyak up onto its foils. For about 100m.

a***@gmail.com

2016-04-16 17:06:28 UTC

Hi Sander:
Last fall I had a query from a young rower from a Club in Oz (Sydney area). She needed a lysee science project and, because she is a sculler, hoped to find one rowing related. I suggested the air resistance problem--absurdly simple in concept, but not without practical hurdles. In the end she decided that it would be too difficult even with the help of her Club. One of the dodgy problems is finding a reasonable way to make use of the prevailing wind.
My best regards,
Bill

m***@gmail.com

2016-04-16 21:43:02 UTC

Last fall I had a query from a young rower from a Club in Oz (Sydney area). She needed a lysee science project and, because she is a sculler, hoped to find one rowing related. I suggested the air resistance problem--absurdly simple in concept, but not without practical hurdles. In the end she decided that it would be too difficult even with the help of her Club. One of the dodgy problems is finding a reasonable way to make use of the prevailing wind.
My best regards,
Bill

I imagine a low-speed wind tunnel and a boat mockup is what is needed. Low-speed wind tunnels seem to be quite within cycling budgets but not rowing!

carl

2016-04-16 22:24:52 UTC

I imagine a low-speed wind tunnel and a boat mockup is what is needed. Low-speed wind tunnels seem to be quite within cycling budgets but not rowing!

I was interested to see no reaction to my comments & back-of-envelope
calcs on the possible scale of the real aerodynamic drag component for
crewed rowing shells. Do rowers really think that aero drag is, or needs
immutably to be, the same for all, with nothing to be done to reduce it?
Seems a rather flaccid attitude.

None of this is too difficult to do, but the simplistic mindset of our
sport sees it as far too much bother. When one talks about taking time
& effort first to plan, then to measure & finally to analyse, rowers'
eyes glaze over & their attention seems to wander.

Aerodynamic drag can certainly be tackled with a wide range of
techniques, including experiments with models in low-speed wind-tunnels,
at full-size with dummies and with live crews (including towing in still
air), & by analytical & computational approaches including CFD - as here
(for example only):
www.hanleyinnovations.com/stallion3d.html

It's strange that such such defeatist attitudes permeate this highly
mechanical competitive sport of ours.

Cheers -
Carl

sander

2016-04-19 20:49:37 UTC

Not defeatist here. Your calculations seem ok. Just not replying until I have something substantial to contribute.

For intermediate results, check blog.rowsandall.com

carl

2016-04-19 21:45:56 UTC

Post by sander
Not defeatist here. Your calculations seem ok. Just not replying until I have something substantial to contribute.
For intermediate results, check blog.rowsandall.com

Sander -

I don't doubt your continuing interest, but I am somewhat surprised that
the simple numbers which I generated regarding the effect of wind
resistance on speed have generated not even a ripple of comments.

Is that because greater minds than mine are still chewing it over or, as
I suspect, that it's too disturbing a concept for a rower to engage
with? Are we so conditioned to focus on rower/boat/water interactions
that we have no capacity to consider the likely influence of design &
technique on wind resistance?

Cheers -
Carl

sander

2016-04-20 04:08:17 UTC

Actually small, lightweight anemometers are easy to install on a boat. Could be part of the kit that fisa puts on boats during world cups. We could then see the average headwind during a race live in the broadcast. But that may be too disturbing. It would reveal lane differences.

As a lake dweller I am very much aware of the effect of wind. The weather stations around the lake reported 0-1 m/s but out on the lake it is a wind that creates a 15 second difference in steady state pace between going up or down the lake. So at least 2m/s in my rough estimate.

Yes, reducing wind drag can be a race-winning move.

James HS

2016-04-20 08:13:46 UTC

I am waiting with anticipation to hear the drag reduction strategies.

Kit - hmm, probably not a lot I can do with the boat, blades etc except look for the most aerodynamic version? (or are there).

Body - I can try to get thinner.

I wear a headsweat cap and understand that might not be a good idea - better replaced with a simple sweatband?

Tight fitting top - tick

I remember reading that a double (or more) have an advantage over a single as you increase the power plant, but the air drag remains roughly similar to a single ??

Where (please) can I make the gains - as on a tideway head race, wind is definitely a large and long lasting effect :)

James

a***@gmail.com

2016-04-20 08:47:35 UTC

Post by James HS
I am waiting with anticipation to hear the drag reduction strategies.
Kit - hmm, probably not a lot I can do with the boat, blades etc except look for the most aerodynamic version? (or are there).
Body - I can try to get thinner.
I wear a headsweat cap and understand that might not be a good idea - better replaced with a simple sweatband?
Tight fitting top - tick
I remember reading that a double (or more) have an advantage over a single as you increase the power plant, but the air drag remains roughly similar to a single ??
Where (please) can I make the gains - as on a tideway head race, wind is definitely a large and long lasting effect :)
James

And what about when the wind is blowing the other way? How baggy can my shirt get before someone notices that I'm wearing a sail?

Andy

sander

2016-04-20 20:05:19 UTC

Headwind will slow you down more than tailwind will speed you up.

I took a wind meter in my single today. There was a stiff 3 m/s wind with gusts up to 6 m/s. I rowed a leisurely steady state. In tailwind conditions, I did a 2:20 /500m average pace, except in the parts where the chop was so heavy that that slowed me down. In headwind conditions this changed to 2:45 min/500m.

On the Beaufort scale, that was "gentle breeze" (3 Bft) to "moderate breeze" (4 Bft). I wouldn't let the kids go on the lake in these conditions, though. Which proves that the body of water is as important as the wind speed. On the Brno lake, a moderate breeze will produce heavy chop and whitecaps. I remember that when I learned to row, in Naarden, The Netherlands, we were allowed to go out up to 7 Bft. We used to listen to the reports for shipping on the radio.

Henry Law

2016-04-25 18:22:01 UTC

Post by a***@gmail.com
How baggy can my shirt get before someone notices that I'm wearing a sail?

That made me laugh. I have this mental image of Andy barrelling down
the course at Dorney with a strangely-configured shirt billowing from
his back. It would, of course, be made of bright material (along these
lines, maybe:
Loading Image...

. There could even be halyards attached to the outer ends of the riggers.

It'd make looking ahead a bit difficult, though.

--
Henry Law Manchester, England

g***@gmail.com

2016-04-20 20:37:38 UTC

Post by carl

Post by sander
Not defeatist here. Your calculations seem ok. Just not replying until I have something substantial to contribute.
For intermediate results, check blog.rowsandall.com

Sander -
I don't doubt your continuing interest, but I am somewhat surprised that
the simple numbers which I generated regarding the effect of wind
resistance on speed have generated not even a ripple of comments.
Is that because greater minds than mine are still chewing it over or, as
I suspect, that it's too disturbing a concept for a rower to engage
with? Are we so conditioned to focus on rower/boat/water interactions
that we have no capacity to consider the likely influence of design &
technique on wind resistance?
Cheers -
Carl
--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories
Write: Harris Boatyard, Laleham Reach, Chertsey KT16 8RP, UK
Find: tinyurl.com/2tqujf

C2 advertises the lower wind resistance of it's Skinny shaft and Dreher does for their elliptical oars. Van Dusen advertises the lower wind resistance of the advantage's splash guard vs their traditional shell, (they even give some number I don't recall). The air foil shape of some wing riggers is also often mentioned as a selling point. So wind resistance is not ignored (when trying to sell equipment).

One only needs to sit single in a single in a head wind and feel the differences with blades feathered and squared to realize that wind drag is significant. At some point the larger surface area of modern blades has to be a serious liability over smaller blades.

Various boat manufactures claim they have put a lot of effort into testing and modeling the hydrodynamics of their shells, it would seem that it is not much of a stretch to spend some effort on the aerodynamics also. There has to be some low hanging fruit there. But maybe there it is easier and more profitable to spend that money on advertising.

James HS

2016-04-21 12:55:34 UTC

Interesting - from their website .....

Some important factors

Hydrodynamic Drag - The Van Dusen Advantage produces up to 5% less hydrodynamic drag than other leading racing shells.

Extensive full-size towing tests sponsored by the US Olympic Committee and theoretical and practical analyses of hull shape help us hold frictional drag and wave drag at minimum. Tank tests conducted between 1986 and 1992 proved that the traditional Van Dusen hull reduced hydrodynamic drag by three to four percent over other leading boats. We reduced hydrodynamic drag by an additional few tenths of a percent on the Advantage singles and more than one percent on the Advantage doubles and pairs.
Aerodynamic Drag - Recent wind-tunnel tests show that Van Dusen aerofoil wing riggers can reduce the total drag on a racing shell by 1% over conventional tubular riggers.

In addition to the wing rigger, the design of the Van Dusen Advantage reduces the frontal area of the rower by lowering the seat deck, further reducing aerodynamic drag.
This combination of drag reduction can give you a six meter advantage over a 2,000 meter course.

I can see the argument about small percentage gains as Carl's analysis shows that it multiplies quite considerably. My Splash Deck is /_____, so would there be merit in me filling in the V so that it was more like /\____ - i.e. more aerodynamic - yes it would not have the wave repelling nature of the original, but by the time the water is that high they have normally cancelled the race, whereas I race constantly with some headwind. As long as the material was light weight enough (and probably buoyant!)there might be a marginal gain?

Mine is an old simms with a wing rigger build out of 40mm aluminimum 'scaffold' - so should I skin over that with a lighweight fabric and put trailing edge aerofoil shape?

Close fitting clothing.

Splashdeck? (welly storage cover)

Different (tighter fitting) headgear

Oh - and practice squaring 'just in time'.

Small gains, but when they multiplied could be good - I have beaten colleagues by 5 seconds over the head races and would happily increase that to 15 with no additional 'effort' and just some smart thinking!

James

g***@gmail.com

2016-04-21 18:10:41 UTC

Post by James HS
Interesting - from their website .....
Some important factors
Hydrodynamic Drag - The Van Dusen Advantage produces up to 5% less hydrodynamic drag than other leading racing shells.
Extensive full-size towing tests sponsored by the US Olympic Committee and theoretical and practical analyses of hull shape help us hold frictional drag and wave drag at minimum. Tank tests conducted between 1986 and 1992 proved that the traditional Van Dusen hull reduced hydrodynamic drag by three to four percent over other leading boats. We reduced hydrodynamic drag by an additional few tenths of a percent on the Advantage singles and more than one percent on the Advantage doubles and pairs.
Aerodynamic Drag - Recent wind-tunnel tests show that Van Dusen aerofoil wing riggers can reduce the total drag on a racing shell by 1% over conventional tubular riggers.
In addition to the wing rigger, the design of the Van Dusen Advantage reduces the frontal area of the rower by lowering the seat deck, further reducing aerodynamic drag.
This combination of drag reduction can give you a six meter advantage over a 2,000 meter course.
I can see the argument about small percentage gains as Carl's analysis shows that it multiplies quite considerably. My Splash Deck is /_____, so would there be merit in me filling in the V so that it was more like /\____ - i.e. more aerodynamic - yes it would not have the wave repelling nature of the original, but by the time the water is that high they have normally cancelled the race, whereas I race constantly with some headwind. As long as the material was light weight enough (and probably buoyant!)there might be a marginal gain?
Mine is an old simms with a wing rigger build out of 40mm aluminimum 'scaffold' - so should I skin over that with a lighweight fabric and put trailing edge aerofoil shape?
Close fitting clothing.
Splashdeck? (welly storage cover)
Different (tighter fitting) headgear
Oh - and practice squaring 'just in time'.
Small gains, but when they multiplied could be good - I have beaten colleagues by 5 seconds over the head races and would happily increase that to 15 with no additional 'effort' and just some smart thinking!
James

Things doesn't always work as expected (e.g. the late square may screw mean you are not really prepared for the catch and cause you to over reach) and aerodynamics can be counter intuitive. But the answer to all those things is most likely yes but it is always best if you can test.

John Greenly

2016-04-20 03:52:02 UTC

Post by carl
I was interested to see no reaction to my comments & back-of-envelope
calcs on the possible scale of the real aerodynamic drag component for
crewed rowing shells. Do rowers really think that aero drag is, or needs
immutably to be, the same for all, with nothing to be done to reduce it?
Seems a rather flaccid attitude.
None of this is too difficult to do, but the simplistic mindset of our
sport sees it as far too much bother. When one talks about taking time
& effort first to plan, then to measure & finally to analyse, rowers'
eyes glaze over & their attention seems to wander.
Aerodynamic drag can certainly be tackled with a wide range of
techniques, including experiments with models in low-speed wind-tunnels,
at full-size with dummies and with live crews (including towing in still
air), & by analytical & computational approaches including CFD - as here
www.hanleyinnovations.com/stallion3d.html
It's strange that such such defeatist attitudes permeate this highly
mechanical competitive sport of ours.
Cheers -
Carl

Hi Carl, your back-of-envelope calcs look right to me. All too true, in fact. As an old, feeble, fairly tall (high-windage) very lighweight sculler, I absolutely hate headwinds. It feels to me as if a 5 m/s headwind about doubles the effort I need to go at a good speed. I remember one horrible race on Long Island Sound when it was blowing well over 10 m/s and I found myself stopping completely on the recovery before I could get the blades back in the water, and even going backward in the most ferocious blasts.

I would be interested to know what proportion of my total windage is me versus the boat and oars. By feel, I'd say me most, then oars, then boat least. Those round oar shafts are definitely an area of possible improvement. However, the best air resistance reduction for me would probably be to remove my head, which seems to be an impediment to good sculling in other ways sometimes anyway.

Cheers,
John

Lucy

2016-04-20 20:10:39 UTC

As a Para who has to use scullies/floats, albeit at the top of their posts so they don't touch the water 99.9% of the time, I can assure wind resistance is a VERY big deal! *sobs*

a***@gmail.com

2016-04-22 15:38:53 UTC

I have just completed a ROWING model run showing the effect of air drag on Shell speed and on course time.
http://www.atkinsopht.com/row/airdrag.htm

A. Dumas

2016-04-26 10:30:21 UTC