Carbon Fibre Vs Aluminum Wing

[Trevor D Michelson]

Hi All,

I was wondering if there was any data out there about the difference (if any) in speed of a boat with an aluminum wing vs a carbon fibre wing. If no data, any thoughts?

[andymck...@gmail.com]

On Wednesday, May 11, 2016 at 12:27:24 AM UTC+1, Trevor D Michelson wrote:
> Hi All,
>
> I was wondering if there was any data out there about the difference (if any) in speed of a boat with an aluminum wing vs a carbon fibre wing. If no data, any thoughts?

Well mainly from reading here, my thought is that the difference in speed attributable to the different material itself will be negligible. Where might the difference arise?

1. Aerodynamics - independent of material.
2. Stiffness - might affect the feel, but probably negligible in comparison to the elasticity in the blade itself.
3. Weight - with either material a boat can be built to 'minimum' weight, carbon rigger might be lighter, but does light = fast?

I think I'd worry more about robustness for mission. If I was elite (ha ha) and on a personal boat a carbon rigger might feel worth it for the psychological 'cool' factor. I might choose carbon on auditory grounds too, aluminium riggers can sound a bit 'clanky' which can disturb the tranquillity of a May evening's paddle. But for day to day club rowing I'd prefer aluminium for robustness.

Andy

[gsl...@gmail.com]

Robustness has as much to do with engineering design and manufacturing as with material. There are robust and week carbon fiber designs and aluminum designs.

[James HS]

So I would think whichever was the best at transferring the forces in the right way and was the most aerodynamic in the right way - which is kind of material independent!

[Adirondick]

Does anyone have a good way to quiet an aluminum wing rigger?

Andy wrote, "aluminium riggers can sound a bit 'clanky' which can disturb the tranquility of a May evening's paddle", and I agree. I've rowed with the wonderful carbon wing by Dreher and now am rowing a different boat that has the aluminum wing--a Hudson. When I called Hudson, the reps didn't offer a way to quiet the 'clanky' thing, but I'm tempted to remove a couple of the plastic plugs from the wing and inject some expanding foam. That is 'some' as in just a little bit; filling the tubing with foam seems like a good way to ruin the wing. (Can't you just see the jaw drop.) I'm dithering about just where to inject the foam, close to the oarlocks, or more toward the athwartships part. The idea is to reduce the area of the sounding chamber. String playing scullers, please advise.
Sorry if this is off topic, but it was a good opportunity for me to get some good advice.

[carl]

On 11/05/2016 15:58, James HS wrote:
> So I would think whichever was the best at transferring the forces in the right way and was the most aerodynamic in the right way - which is kind of material independent!
>

Let's be blunt about this.

Wonderful myths have been invented to give pseudo-scientific credibility
to this or that rigger design. All make bogus claims to a supposedly
"best path" by which the force applied to the pin reaches the boat, but
each displays only the technical ignorance or dishonesty of their
perpetrator & the gullibility of those who swallow such hokum.

The path through which an applied force connects to the boat is totally
irrelevant if the rigger is sufficiently stiff, for then that force will
reach the boat immediately & undiminished.

Even poorly-designed conventional riggers are stiff when compared to the
amount of flex we happily accept in a loaded oarshaft, in that the pin
easily maintains its position WRT to the boat. (Yes, some such riggers
may lack either torsional or vertical stiffness, but that's an
unnecessary & serious defect in their design.)

Any single-stay bow-mounted or stern-mounted wing will deflect
significantly more in the fore-aft direction than almost any 2-stay
rigger. That's because, weight for weight, a single stay - a simple
cantilever in which any off-axis applied force generates bending loads -
is always more flexible than the corresponding triangulated structure in
which all loads are either tensile or compressive. Put simply, if you
hang a weight on the outer end of a horizontally-projecting bar, that
end deflects far more than if you stand the same bar vertically with the
same weight trying either to extend (tension) or contract it (compression).

So if you really do imagine that a wing rigger is a divine gift to the
rower, then first test how much its outboard end moves under the bending
loads resulting when you load the pin perpendicular to the rigger stay's
axis.

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: ca...@carldouglasrowing.com Tel: +44(0)1932-570946 Fax: -563682
URLs: carldouglasrowing.com & now on Facebook @ CarlDouglasRacingShells

[teap...@gmail.com]

Hey Carl

All agreed about the performance difference about the wing rigger - it's just a method for holding the pin in the right place like any other. However, the divine gift of the wing rigger (IMHO) is that it obviates the need for a bulkhead where the midstay of a conventional rigger would be. With no structural 'hot spot' there, the slide tracks can be further apart without the bulkhead. Then the athlete's legs can (usually) be straightened without much 'calf-bite' from the ends of the slides that is familiar to many scullers with the wrong ratio of leg length to calf-diameter (myself included, scars to prove it and tan line where my rugby socks reach to).

Certainly no performance gains from the wing directly, compared to a rock solid CD aerowing rigger (available at reasonable cost from the manufacturer direct, I gather...)
Now, if you made an aerowing wing rigger....

Teaplant

[gsl...@gmail.com]

On Thursday, May 12, 2016 at 12:53:12 AM UTC-7, teap...@gmail.com wrote:
> Hey Carl
>
> All agreed about the performance difference about the wing rigger - it's just a method for holding the pin in the right place like any other. However, the divine gift of the wing rigger (IMHO) is that it obviates the need for a bulkhead where the midstay of a conventional rigger would be. With no structural 'hot spot' there, the slide tracks can be further apart without the bulkhead. Then the athlete's legs can (usually) be straightened without much 'calf-bite' from the ends of the slides that is familiar to many scullers with the wrong ratio of leg length to calf-diameter (myself included, scars to prove it and tan line where my rugby socks reach to).

While certainly a problem in a 1x I'm not sure I've ever experienced this in a 2x or 4x, and certainly not in a 8+.

[carl]

The answer to the infamous track-bites problem is to use slides with
no-bite ends. We make them and many users recommend them.

on the personal hygiene issue, tracks which bite are a significant
health hazard. There could hardly be a better way to transmit
infections between otherwise fit rowers than by puncturing their skin
with a track end which, yesterday or earlier the same day, lifted the
scab off the back of another rower's leg. Indeed this form of
transmission became a problem among orienteers in Sweden and the focus
of well-reported medical studies
news.bbc.co.uk/2/hi/health/6404329.stm

[gsl...@gmail.com]

While your slides are certainly the best I've rowed with, We have an old vespoli where tracks do not cut the skin but anyone who is not tall ends up with bruised calves. It is not pleasant. Don't think your tracks would help much.

[carl]

On 12/05/2016 21:58, gsl...@gmail.com wrote:
> While your slides are certainly the best I've rowed with, We have an old vespoli where tracks do not cut the skin but anyone who is not tall ends up with bruised calves. It is not pleasant. Don't think your tracks would help much.
>

Fair enough, but better than being cut and possibly infected. One
remedy to that bruising problem could be to add a raised bar between the
slides at front-stops, to spread the contact area?

[gsl...@gmail.com]

On Thursday, May 12, 2016 at 3:15:17 PM UTC-7, carl wrote:

I think the solution is to raise the seat and foot stretchers, which of course has its own problems. Actually there is a bar across the front of the tracks already. It is an improvement but it is still bad.

[carl]

On 13/05/2016 03:24, gsl...@gmail.com wrote:
> On Thursday, May 12, 2016 at 3:15:17 PM UTC-7, carl wrote:
>> On 12/05/2016 21:58, gslewis wrote:
>>> While your slides are certainly the best I've rowed with, We have an old vespoli where tracks do not cut the skin but anyone who is not tall ends up with bruised calves. It is not pleasant. Don't think your tracks would help much.
>>>
>>
>> Fair enough, but better than being cut and possibly infected. One
>> remedy to that bruising problem could be to add a raised bar between the
>> slides at front-stops, to spread the contact area?
>>
>> Cheers -
>> Carl

>

> I think the solution is to raise the seat and foot stretchers, which of course has its own problems. Actually there is a bar across the front of the tracks already. It is an improvement but it is still bad.
>

The factor which most affects contact between the back of your leg & the
end of the track is not so much seat height as foot height. Raising the
feet by 1cm (vertically, not along the stretcher plane) has the same
sort of effect as raising the seat by 15mm.

Of course, raising just the feet puts us at cross-purposes with who say
you need your feet low to get your weight over them at the catch, & we
can return to that discussion on another occasion. Raising the seat
increases the potential for balance problems.

Another contributory factor, flagged here only for later discussion, is
the insistence of some that you should finish with heels against the
stretcher.

[gsl...@gmail.com]

On Friday, May 13, 2016 at 4:19:15 AM UTC-7, carl wrote:
> Another contributory factor, flagged here only for later discussion, is
> the insistence of some that you should finish with heels against the
> stretcher.

That is easily solved too, just put wedges under the heals until they do :).

[madmar...@gmail.com]

On Thursday, 12 May 2016 21:58:09 UTC+1, gsl...@gmail.com wrote:
> While your slides are certainly the best I've rowed with, We have an old vespoli where tracks do not cut the skin but anyone who is not tall ends up with bruised calves. It is not pleasant. Don't think your tracks would help much.

I've got shortish legs and big calves - over the years I have donated quite a lot of blood to various boats! There is an early-90s Empacher at Mercantile RC in Melbourne that probably still has a lot of my DNA in it.

Lower cockpit deck and taller seats would suit me in a 1x. Now, if I could only find a boat builder to make me one...

[wmar...@gmail.com]

> Another contributory factor, flagged here only for later discussion, is
> the insistence of some that you should finish with heels against the
> stretcher.
>
> Cheers -
> Carl
>

Yeah... You don't see people jumping and trying to keep their heels on the ground, I don't see why you'd attempt to limit the contribution of the plantar flexors (VERY STRONG muscle group) to the stroke... Oh.. Sorry.. This is a discussion of wing riggers...

[teap...@gmail.com]

On this related note, does the arrival of the wing rigger presumable allows a 1x to be built narrower (smaller beam?) than is practically possible for a conventionally rigged single?

Would there be any benefit to this? narrower would presumably mean longer, or perhaps less tapered towards the pointy ends. does the need for a sachsboard wrapping around the cockpit, plus pesky bulkheads and the chunky thighs of an Olympic athlete, actually affect the design of a shell at present - or is a 1x already simply a perfect hull shape with a 'cockpit' bolted on top?

What constraints on boat design are imposed by 'the rules'? Which limitations arise from accommodating a human engine? Which are limitations of construction and materials?

Will the 1x Olympic champion in 2100 still be rowing in a shell that we would recognise - and will it still usually be yellow?

teaplant

[gsl...@gmail.com]

About the narrowest and least stable single I've rowed is a traditional Van Dusen with ribs. Without the ribs, you could make it even narrower but those boats are narrower than is common today, so I don't think you would want to do that. Without a lot of thought, I would guess you would end up with larger surface area and more drag, but maybe not.

I came close to buying on of the traditionals Van Dusen's two years ago. It was made for a lightweight women who raced the Pan Am team. She sold it to someone else because after she had a baby her hips widened and the rigger bolts kept ripping her shorts.
By the way some of the traditional Van Dusen's had the lightest riggers I've every seen. They were tubular carbon fiber two stay and they are extremely stiff.
There are a lot of those boats still around and are lovely to row if you have the technique to handle them.

[Brian Chapman]

On Wednesday, 11 May 2016 00:27:24 UTC+1, Trevor D Michelson wrote:
> Hi All,
>
> I was wondering if there was any data out there about the difference (if any) in speed of a boat with an aluminum wing vs a carbon fibre wing. If no data, any thoughts?

I have rowed with Carl's excellent riggers but then bought a second hand boat with a carbon wing. I can only say it is excellent with no flex. You do get some tilt in the boat in a strong crosswind as the aerofoil shape generates lift.

We have stable boats with aluminium wings and one recently showed how weak they are when a crew hit a landing stage. The side that hit sheared at the weld where the wing changes angle to go across the boat.

[Kit Davies]

On 18/05/2016 12:48, Brian Chapman wrote:
> We have stable boats with aluminium wings and one recently showed how weak they are when a crew hit a landing stage. The side that hit sheared at the weld where the wing changes angle to go across the boat.

There have been 2 similar incidents posted to the Reddit rowing sub in
the past couple of weeks, one was in a single mid-race!

Kit

[carl]

The problem there, from examples we've seen of similar aluminium wing
failures, is when a rather thin extrusion is welded to a thicker part.
The weld pool contracts by up to 10% as it cools, generating yield-level
stresses in the adjacent thinner metal. Aluminium is vulnerable to
fatigue failure & the combination of this high residual stress with the
much lower cyclic loads of the rowing stroke is sufficient to initiate a
hard-to-detect crack at the most vulnerable location. That crack then
propagates rapidly, with the result you describe.

Even where 2 similar sections of extrusion are being welded together,
the greater thickness of the weldment & the resulting residual stresses
in the adjacent thinner material can again lead to premature
fatigue-induced failures.

If, in addition, you row in brackish or saline water then, even if the
rigger has been anodised, you will get the more rapid process of
stress-corrosion cracking accelerating this fatigue failure. Chloride
ions in the water will attack the stressed metallic grain boundaries at
any weak point in the coating &, thereafter, will drive on the crack
formation. This can often start from the inside of the rigger
extrusions since it is very hard to weld a tube which does not have a
small vent hole to atmosphere, so water easily gets into the unprotected
inside of the tube, where the damage it starts can't be seen.

Unless welded aluminium riggers are stress-relieved (the heating of
which process will soften & distort the rest of the rigger) or in other
ways treated to hold off weld-induced fatigue failure, they will
eventually fail through that combination of weld stress and cyclic loading.

Carbon riggers have a different problem: they won't corrode, but carbon
has poor impact resistance compared to metal. It will take a knock up
to a certain level without apparent injury, but at any higher load it
will fracture, not bend or deform. And, if the impact was enough to
start a fracture you may be unable to detect a defect which may then
continue to grow. It is for that reason that elaborate systems for
crack detection in aerospace carbon structures are required.

HTH

[marko....@gmail.com]

On Wednesday, 18 May 2016 14:24:42 UTC+1, carl wrote:
> Carbon riggers have a different problem: they won't corrode, but carbon
> has poor impact resistance compared to metal. It will take a knock up
> to a certain level without apparent injury, but at any higher load it
> will fracture, not bend or deform. And, if the impact was enough to
> start a fracture you may be unable to detect a defect which may then
> continue to grow. It is for that reason that elaborate systems for
> crack detection in aerospace carbon structures are required.

The cycling industry who has reasonable amount of experience with CF compared to many sports has had some disasters related to this with carbon mountain bike frames in particular.

[gsl...@gmail.com]

On Wednesday, May 18, 2016 at 10:57:31 AM UTC-7, marko....@gmail.com wrote:
> The cycling industry who has reasonable amount of experience with CF compared to many sports has had some disasters related to this with carbon mountain bike frames in particular.

There have also been some disasters with steel and aluminum bikes. Sure there are some products that are not well designed or manufactured, (i.e. some supper light parts that never should have been designed such as handlebars), but CF has been successfully used in bikes for a long time and has proven itself to be strong and reliable. It has different failure modes than steel or aluminum but there is much more freedom to reinforce it where necessary and to eliminate stress points. There are very good reasons that the top bikes are all Carbon Fiber.

Again you can design and make good riggers and bad riggers out both Aluminum and Carbon Fiber.

[Chip Johannessen]

This discussion of the shortcomings of aluminum wings has me nodding my head, having sheared one off a Pocock 2x during a collision with a large rowing dinghy. Until the rigger broke open, I had no idea the material was that thin.

Question, re: Fluidesign. Does anyone have an opinion about the old style vs new "modular" riggers? My double is back at the factory at the moment, and I was considering upgrading, but this talk about stress-corrosion fatigue has me worried. I row in salt water and presumably, this failure mode would be sped up with the new thinner-metal riggers. I've already had a rigger mounting bolt fail during a race due to just this effect and would rather not have a similar thing happen with the whole rigger.

Chip