Smaller lower aspect wing vs. bigger higher aspect

[jaros]

my favorite wing at this moment, very low ar
a bit lower slow speed but super stable pitch in the waves, actually because wingspan 47cm only it's so easy to turn, easy to jump

Interesting! Could you share some more details, dimensions, photos from side and bottom? Thanks!

[jaros]

Double post, please delete.

[jaros]

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[jaros]

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[Peter_Frank]

Higher aspect wings are more efficient. They make more lift per a given amount of drag. This is why they are used on race foils, sailplanes, and the sails of racing yachts. But they fly at a lower range of angles of attack, which means they generally will not go as slow, nor will they tolerate mistakes as well.

If you size a low aspect wing and a high aspect wing so that they have the same amount of lift at a particular speed, the high aspect wing will be smaller, and make less drag, thus allowing it to accelerate further. However at low speeds it will stall before the low aspect wing and it will require a larger turning radius (because if you turn it in too tight a circle, you will exceed the angle of attack at which it stalls).

I wanted to revisit this because something is still not clear to me. Are we saying the lower aspect wing will be able to stay on foil at a lower speed than the high aspect wing (in the above scenario)?

Yes, the stall speed on a low aspect foil should be lower than the stall speed on a high aspect foil, all else being equal (i.e., both foils have the same total area). As you slow the foil down, you increase the foil's angle of attack. A foil with a longer path that the water travels over has more ability to smoothly redirect flow (i.e., prevent stalling) at high angles of attack. To illustrate, look at this graphic from the wikipedia page in "stall". You can see a wing flying at a very high angle of attack, but the flow over the top has stalled. Stretching the chord of the wing (i.e., making it longer from leading to trailing edge) will force more fluid to better follow the surface of the wing, resisting stall.

Here's the whole wikipedia article on stall.

True, but dont get fooled by the "low" stall speed, at a higher angle of attack, as it requires more power.

Of above two wings, the high AR wing can start a lot earlier than the low AR wing, when same area.
So low end much better with the high AR wing, and you dont need as much power to ride

Peter

[vol]

my favorite wing at this moment, very low ar
a bit lower slow speed but super stable pitch in the waves, actually because wingspan 47cm only it's so easy to turn, easy to jump

Interesting! Could you share some more details, dimensions, photos from side and bottom? Thanks!

foil length 67cm, wingspan 47, around 800cm2, press tech
this version is the prototype to check how it works, soon will build final ver with paulownia core and carbon-glass reinforcement, expecting all wing weight less than 1kg
the bottom now is flat, but in final ver wing and body will be profiled