I have this interest in the range of foil wings that keep appearing in the market promising to do this and that - do they really and what is the science behind the claims? I hope the ink works it makes for a really interesting read - well for the nerds like me !!
Aero Evo: Guest Post: Thin vs Thick Wings
Im beginning to doubt some of the designs given fluid dynamics - marketing or true advancement for the Sunday kite (etc) session?

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Lambie said..
I have this interest in the range of foil wings that keep appearing in the market promising to do this and that - do they really and what is the science behind the claims? I hope the ink works it makes for a really interesting read - well for the nerds like me !!
Aero Evo: Guest Post: Thin vs Thick Wings
Im beginning to doubt some of the designs given fluid dynamics - marketing or true advancement for the Sunday kite (etc) session?

I suppose it depends on what said claims are?

thin vs thick, theres some definite differences and advantages/disadvantages to each. No marketing BS.

I think the industry with its big installed base is starting to shake this all out. Thick, thin, high AR, low AR, stab angles, fuselage lengths, stiffness, strut lengths. You name it.

I am pretty sure the engineers are doing all (or most) of this empirically. Design, test on the water, re-design, test again, etc., without water tunnels for the most part. One water tunnel would cost the equivalent of years worth of sales for most companies.

By the way, the Reynolds number depends only on chord length and speed. Aspect ratio, thickness, and airfoil shape play only minor roles for R, but definitely play big roles for overall dynamic performance for users.

Matters little how it's supposed to work on paper.
Matters A LOT how it works in the world, on the water, for a human being.

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Lambie said..
I have this interest in the range of foil wings that keep appearing in the market promising to do this and that - do they really and what is the science behind the claims? I hope the ink works it makes for a really interesting read - well for the nerds like me !!
Aero Evo: Guest Post: Thin vs Thick Wings
Im beginning to doubt some of the designs given fluid dynamics - marketing or true advancement for the Sunday kite (etc) session?

You will not build an AC-70 without some serious math and engineering. But of course marketing is marketing and some will tell you almost anything to lure you into buying a new product, even when there is really little "scientific" behind the claim. Reality is that math and engineering can go just so far. Depending on the field they can be indispensable, but there is often a lot of experimentation and trial and error ... look at Space-X, and the time it takes to figure out the re-entry landing!

Thin vs Thick Wings? Who knows it will probably take a few undreds posts just to figure what that exactly means!

Yeah, perspective matters as much as real #'s.
Small area but thick?
Large surface area but paper thin?
Which is easier-faster-"better"?
For who?

R relates to AR when you have a fixed area or span in mind.

Not that difficult to crunch a few numbers then look through the existing airfoil catalog, there are ones specifically designed for hydrofoils. Usually they have a slightly reflexed trailing edge.
This is the feature that Slingshot claims adjusts pitch with speed, but in fact what it does is maintain a more consistent center of lift across various angles of attack at the expense of a little efficiency.

What DOES get complicated and requires experiential testing is winglet shape, anhedral and washout. Those effect handling rather than purely looking at L/D. There is definitely something to be said for downturned winglets improving tracking through turns.