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stab design to match surf wing

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spiru
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stab design to match surf wing

Postby spiru » Mon Oct 22, 2018 5:18 pm

I am making a 1100-1200 cm2 wing with a 817 profile and dimensions quite similar to a LF impulse. Now it is time to design the rear stab and I have a lot of questions:

- Does it make any sense to put any kind of asymmetric profile in the rear stab? or just asymmetric shape works well? I think I have seen some foils with a inverse profile that pushes down.
- Will I obtain any practical benefit with anhedral or dihedral shapes vs flat? Of course making it flat is much easier. My goal is a stable foil to practice my footwork at low speeds and I like to carve and eventually want to play in small waves. Any special stab shape/profile to favor that style?
- Size: Is there any proportion rule between the size of the front wing and the rear stab? I guess it largely depends on the distance between them, so Initially I will be using the 78cm LF aluminum fuselage, which I now use with the stab at the most forward position (Rocket foil) to favor turnability.

Any recommendations are appreciated

Breze
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Re: stab design to match surf wing

Postby Breze » Mon Oct 22, 2018 6:36 pm

Your surf wing is for kitefoiling?
I have built a Eppler 817 64cm 800-850 qm. Fuse 74cm. The Stab is about 1/3 of the Fwing surface. Normaly a asymmetric profile is used. Mine came out pretty symmetric mustache style. Symmetric needs a bit more angle than the asymmetric. Dihedral gives you better yaw stability, or you use a TT fin.
Eppler 817 isn't easy to build bc the concave at the TE. Keep in mind what will be your aimed thikness.
For example the Levitaz cruizer is 15mm , Moses 633 30mm. Imho a big slow foil doesn't need a complex profile. Play at airfoiltools with the bottom flat profiles, much easier to build.

spiru
Rare Poster
Posts: 7
Joined: Thu Mar 01, 2018 3:57 pm
Kiting since: 2013
Local Beach: Laredo, Sopelana, Ereaga
Favorite Beaches: Laredo
Viana
Tarifa
Gear: Neo 6, 8, 10
Cloud 10.4
Edge 15
NOMAD WAVE
Mako
Fone surf
Brand Affiliation: None

Re: stab design to match surf wing

Postby spiru » Mon Oct 22, 2018 8:53 pm

Yes, I'll be kiteboarding.
So, must the asymmetric stab profile create upward or dowward "lift"? I know it can be a silly question, but I think I have seen both types.

When we say that dihedral stabs increase yaw stability, does that mean it affects turnability in a negative way? If turns and carves are a combination of yaw and roll and one of them gets affected...

Breze
Rare Poster
Posts: 23
Joined: Sun Sep 23, 2018 5:53 pm
Kiting since: 2003
Local Beach: Bavarian Lakes
Style: Freeride
Gear: Ram Air & Tubes, TT & Foil
Brand Affiliation: None

Re: stab design to match surf wing

Postby Breze » Tue Oct 23, 2018 5:35 am

Stab creates downforce, have a look here https://www.youtube.com/watch?v=q1abYwkEscE

Too much mustache or dihedral makes turning more difficult. A modern stab looks like this https://www.ketos-foil.com/fr/kite-foil ... 0-270.html


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