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Trimming for riding style

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Moses 645/425 Foil
Diablo V2, Flysurfer Sonic2
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Trimming for riding style

Postby beebopbogo » Tue Dec 29, 2020 9:43 am

Hey all! I've been dialing in my "old" (2016) race kites and found that I have to adjust outside of the zero'd mixer setting to fly well again. (The long mixer test worked great.) But then I started experimenting. What if I increased camber or adjusted the brake line? Is there a point where the kite will fall out of the sky? (Yes, there is.) Here's a consolidation of what I THINK happens. I've only been riding foil kites for a year, and am no expert by any means.

Can anyone help fill in the blanks or fix a wrong statement? Mahalo!

Here's my quiver I've been experimenting on:
9m Flysurfer Sonic 2
12m F-One Diablo V1
13m Flysurfer Sonic 2
18m F-One Diablo V2

Start with the speed system all on the same level and bar lines perfectly equal in length.

Adjust B half of C when trimming. (i.e. Extend C 10mm and extend B 5mm.)
When trimming C, adjust Z to match A.

EXTEND B & C (More cambre)
More powerful
More lift
Better turning
Less backstall
Less stable
Worse upwind
Inflates faster?
The kite accelerates slower?
When extended too much the leading edge collapses. (Oh the humanity!)

SHORTEN B & C (Less cambre)
More stable
Better upwind performance
Increased backstall tendancy
Reduced power
Inflates slower?
The kite accelerates faster?
When shortened too much ______________ (What happens?)

Once your desired performance is dialed, try trimming the Z line.

Longer Z:
Less drag
Slower turning
Faster inflate
Kite accelerates quicker
When extended too much the trailing edge starts to luff and the kite won't turn.

Shorter Z:
Faster turning
More drag
Slower inflate
The kite accelerates slower
When shortened too much the tips won't inflate.

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Re: Trimming for riding style

Postby Herman » Tue Dec 29, 2020 11:46 am

Sadly I am not an expert either but your thoughts are pretty much the same as mine. There are a couple of minor semantic points, but these are inconsequential:

Longer Z - when too long the TE flaps or feathers. (Luffing is about air flow at the LÊ, imho.)

More camber - too much camber and the LÊ luffs. (Luffing is what causes the collapse, imho)

I think your post is a really helpful analysis and I don’t believe the above will change any understanding as it is just about terminology. From my limited experience, and has already been said, shrinkage of the lightly loaded bridle element is often the major factor and tweaking Z is often the first port of call.

PS If I was not restoring the bridle to drawing, I would factor the adjustment ratio between bridle elements to account for the different shrinkage rates at different load, but this would just be based on an eyeball guess.

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