Foil design details

[Peter_Frank]

Looks really good Hawaiis !

Peter

[ChristoffM]

Yes, that titanium wing does look nice!

Interesting that you say the bent wing makes it more stable. I think it confirms my theory as to why the front wings have anhedral. I do not think it is there for any of the reasons posted about induced drag or stalling. Induced drag is a very minor in the dense water and the types of loading angles I experience on the foil. Drag is mostly from parasitic (flow) drag (i.e. non smooth finishing) and vibrations.

A sudden stall is also of no concern, even on the elliptical flat wings that I have used.

I think the anhedral has to do with the roll and yaw interaction when riding. Providing a nice controllable feel to the foil, making it easier to ride, and would help to keep it stable as a whole.

I don't know if any of you saw my post on design issues here: http://kitehydrofoil.com/index.php/desi ... wings.html

Please give me some feedback what you guys think/experience.

[Peter_Frank]

I agree fully with you Christoff, that roll and dynamics could be the key factor why "bent" wings are used

Also agree that parasitic drag is a major contributor to drag and lower performance here, yes.

But whether the water is dense or not, does NOT change the induced drag principles

Of course, at high speeds and low AOA, induced drag is of minor concern - but it is still present !
And when going upwind, and the foil operates at a bit higher AOA (less speed), it becomes really evident.

This is the reason why high AR foils perform so much better upwind especially, besides from being faster.
Less induced drag


The wing, will typically perform better with higher AR, because of less induced drag.
Lots of disadvantages then, as structural weakness, and especially a MUCH HARDER stall

Low AR wings will stall very gentle, because the AOA changes towards the tips, so instead of a full stall of the whole wing, you will get a gentle stall, that can be recovered much easier.

A wing with some wash-out can be tuned to work okay at a certain high AOA, true.
The problem comes, when you try to go fast - as with low AOA, you can only have extremely low or no wash-out, otherwise it will only be drag

As with kites, you can not get it all, but have to decide and make many compromises.


All of above of course only "IMO" and knowledge/experience (R&D regarding glider design and competitions), not from tests nor facts regarding hydrofoils

Peter