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Will a light weight rider be faster than a heavy weight?

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Will a light weight rider be faster than a heavy weight?

Postby Toby » Thu Mar 18, 2021 2:58 am

Friend of mine popped up that question I couldn’t answer.

Let me hear your thoughts!

Thanks

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Re: Will a light weight rider be faster than a heavy weight?

Postby PrfctChaos » Thu Mar 18, 2021 3:12 am

For slowish speeds the lighter rider will be faster on the same foil. Less lift induced drag.

Becomes less of a advantage at higher speeds and probably becomes more of a question how much kite power the rider can hold. Where a heavier rider (we assume stronger here), could be faster.

So good question. Probably comes down to strength/weight/skill for the racers Id assume.

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Re: Will a light weight rider be faster than a heavy weight?

Postby tegirinenashi » Thu Mar 18, 2021 3:21 am

Larger sail boats always outperform the smaller ones, at any wind conditions. It would be very counterintuitive if this won't carry over to kite foil races.

This is essentially the same phenomenon when free fallen smaller animals, such as cats, gain less velocity and can subsequently survive landing, while larger one like cows would be crushed to death. At the extreme, feathers fall extremely slowly, and even smaller object like pollen can float in the air for days. Yes, feathers do have enlarged surface area, but the effect is still valid even for objects of the same shape.
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Re: Will a light weight rider be faster than a heavy weight?

Postby Toby » Thu Mar 18, 2021 5:31 am

Does the foil have more drag with a heavy rider?

I assume the smaller kite of a less heavier rider also has less drag...

Maybe we can relate it to sailing...will a heavier rider be faster, since he can hold more power in the sail, but also might have more drag on the hull ?

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Re: Will a light weight rider be faster than a heavy weight?

Postby windmaker » Thu Mar 18, 2021 6:07 am

It's all about leverage. For pure speed, weight is important but so is height. Just as with Windsurfing a tall light rider can have the same leverage as a shorter heavier rider and have the same top speed.

In pure speed contests, riders wear weight jackets on their upper bodies, often up to 15kg in order to increase leverage.

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Re: Will a light weight rider be faster than a heavy weight?

Postby Kamikuza » Thu Mar 18, 2021 6:17 am

I know I ride faster on the TT than most people. Cos I sink otherwise :D

Can't compare on the foil, cos I'm cruising faster than the wing nuts and slower than the racers. Obviously.

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Re: Will a light weight rider be faster than a heavy weight?

Postby Skywalker7 » Thu Mar 18, 2021 6:46 am

Toby wrote:
Thu Mar 18, 2021 5:31 am
Does the foil have more drag with a heavy rider?

I assume the smaller kite of a less heavier rider also has less drag...

Maybe we can relate it to sailing...will a heavier rider be faster, since he can hold more power in the sail, but also might have more drag on the hull ?
Yes, a heavier rider has always more drag. So in lightwind with the same sized kite the lighter might win. However if both rider riding the same foil and board setup with right sized kites, than the heavier rider will be faster(if their riding skill is equal). Lets say the lighter rider is riding a 15meter race kite and the heavier rider riding the 18 meter race kite.
Larger wings has better performances than smaller wings. The 15 M kite will have a glide ratio of ca. 10.6 and the 18M kite will have 10.8 (I am just guessing the glide ratios, but competition paragliders with aspect ratios of 7.5 easily have best the glide ratio around 12 or even more but they are also roughly 25 meter is size.)

The reason is physics, where a larger wing of the same size will have better performance (glide ratio). Than another factor is added up to this that a smaller kite is never a perfect minimalization of a larger kite. While they might reduce the size of the kite and the lenght of the lines they not reduce the thickness of the lines, or the weight and thickness of the materials etc, so some part of the drag is more or less the same.

Also the lighter rider usually does not have a smaller foil or thinner mast or smaller board and the rider weight compared to the foil and board is also advantages the heavier rider.
Even if the perfect minimalization would happen that the smaller rider would ride a smaller foil, board, and perfectly minimalized kite the larger kites and foils (wings) would still perform better.

The only situation where a lighter rider can win is lightwind/underpowered condition where the heavier rider has to pull more bar=higher AOA what means worse glide ratios.

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Re: Will a light weight rider be faster than a heavy weight?

Postby Topaz » Thu Mar 18, 2021 1:13 pm

In my old days of Mistral One Design windsurf racing, it was well known than on light wind, light racers would go up and in strong winds heavier racers would make it to the top.
In the olimpic class, every body was in the same fleet, but there was another class called 'Raceboard', in which they would split the fleet in heavy riders and light riders just to make it more fun.

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Re: Will a light weight rider be faster than a heavy weight?

Postby Regis-de-giens » Thu Mar 18, 2021 9:01 pm

That really is an excellent question ! Not that obvious to answer from a theoretical and physical point of view IMO.

Underpowered is in advantage of light rider of course. Over power is in advantage of heavier rider.

Now if you consider that both can choose the perfect size of kite to be at sweet spot (i.e. smaller for the lighter) and foil and lines (smaller diameter and lenght for the lighter) , ect , this is not obvious, or at least i do not see which technical and physical argument could conclude this. Limit is often the leg muscle power to resist the pull kite low ... so may depend on the ratio leg power vs weight ...

For the material that is often standard (like mast thickness), it should be designed for all weights, so necessarily covers the heavier guys... hence less optimum for the lighter, so source of drag loss. But i think you can adapt in real, most of the material (kite, lines, wing, board, so ...

But still excellent question, thanks !

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Re: Will a light weight rider be faster than a heavy weight?

Postby Sceotend » Fri Mar 19, 2021 9:42 am

Agreed, excellent question!

I think in theory it comes down to the fact that the lift is relative to squared speed, while strength of the rider is more linear in terms of weight. That indicates a definite advantage for heavier riders. I think there is a lot of factors that reduce the difference. I'm sure there is a lot more to it and intuitively in light winds a lighter rider has an edge.

I don't have the data but I think racers are not particularly small or big guys, which likely means that weight is not particularly significant factor.
Last edited by Sceotend on Fri Mar 19, 2021 11:12 am, edited 1 time in total.


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