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by bohme
Mon Nov 13, 2023 11:21 am
Forum: Wingsurfing
Topic: YpraSurf. My experiences with some Gong foilwings
Replies: 89
Views: 13053

Re: My experiences with some Gong foilwings

I'm guessing the stabilizers can provide upward or downward lift depending on the AOA ... but surely the front wing always creates lift - without that the hydrofoil wouldn't work. You are wrong... ;) The Front wing lifts but the back wing always pushes down - "downward lift" as you called it. But t...
by bohme
Wed Jul 12, 2023 4:08 pm
Forum: Hydrofoil
Topic: Effects of Aspect Ratio on Performance
Replies: 11
Views: 2395

Re: Effects of Aspect Ratio on Performance

[/quote] So, why do almost all foils tend to be thin and have less camber? [/quote] I think your calculation is incorrect :-) There should not be much difference between 10 and 12% Each profile has an optimum 'design' Cl which is primarily driven by chamber. You should chose a profile with a camber ...
by bohme
Sat Jul 08, 2023 10:22 pm
Forum: Hydrofoil
Topic: Effects of Aspect Ratio on Performance
Replies: 11
Views: 2395

Re: Effects of Aspect Ratio on Performance

You can see the difference in profile drag in the XFOIL plots in XFLR. DAE51 has a lot of camber. AoA at -3° is not ideal. It will have high 'profile' drag at high speed (low Cl). Try run your simulation with a different section? Even a basic NACA2410 would be better? There should be a difference at...
by bohme
Fri Jan 06, 2023 1:13 pm
Forum: Hydrofoil
Topic: Ditch the trim strap?
Replies: 8
Views: 1628

Re: Ditch the trim strap?

I use my Peak4 underpowered. 3m in 20kn maximum. No need for depower. One wichard single line safety.
by bohme
Mon Mar 21, 2022 12:08 pm
Forum: Kitesurfing
Topic: Are thinner Kitelines a lot more performing?
Replies: 20
Views: 2458

Re: Are thinner Kitelines a lot more performing??

IKA Formula Kite rules specify minimum back 0.8mm and front 1.2mm lines.
by bohme
Tue Feb 22, 2022 1:39 pm
Forum: Hydrofoil
Topic: Stab shape effects
Replies: 19
Views: 1830

Re: Stab shape effects

Modern airplanes are optimised for saving fuel at a very specific cruising speed. Our hydrofoils need to work in a much wider range like takeoff, upwind, downwind etc., even working both ways (positive and negative lift) I guess the overall benefits are smaller. I like winglets because they are a bi...
by bohme
Thu Jan 27, 2022 12:45 pm
Forum: Hydrofoil
Topic: High modulus / Stiffer masts - gimmick or real?
Replies: 3
Views: 2203

Re: High modulus / Stiffer masts - gimmick or real?

Carbon fibre come in many different grades. Just stating High Modulus is NOT enough. Roughly speaking, the grades have similar strength, but VERY different stiffness and price. Stiffness is in the range 235GPa to 900GPa for the fibre only. The most cost effective is PAN based, with a stiffness of up...
by bohme
Mon Jan 24, 2022 5:42 pm
Forum: Foil Kites
Topic: Wich rope for 828 cleat?
Replies: 17
Views: 8897

Re: Wich rope for 828 cleat?

I have attached a photo of my CL828-68 setup :-) Keep it simple :-) Thanks for sharing Bohme! I wonder how you tied this pulley on a "no spliceable" rope https://i.ibb.co/cLLWNBK/Pulley-Large.jpg The rope has a dynema core suitable for splicing. The cover is removed at the cleat end (this end does ...
by bohme
Sun Jan 23, 2022 6:55 pm
Forum: Foil Kites
Topic: Wich rope for 828 cleat?
Replies: 17
Views: 8897

Re: Wich rope for 828 cleat?

I have attached a photo of my CL828-68 setup :-)
Keep it simple :-)
by bohme
Tue Jan 18, 2022 1:32 pm
Forum: Foil Kites
Topic: Single vs Double Skin
Replies: 26
Views: 12047

Re: Single vs Double Skin

PugetSoundKiter wrote:
Mon Jan 17, 2022 6:03 pm
:advise:
The lines are parallel to the total force (blue arrows) ??
Lift is probably around 10 times drag.

Anyway, single skin design sweet spot is at a higher 'angle of attack' than double skin.

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