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Smaller lower aspect wing vs. bigger higher aspect

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noahsw
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Smaller lower aspect wing vs. bigger higher aspect

Postby noahsw » Tue May 26, 2020 5:51 am

I'm trying to understand how various foil attributes affect the ride. Typically, smaller surface area wings go faster than bigger ones and higher aspect wings go faster than lower aspect ones. And of course there are lots of other effects as well.

But what if these attributes were mixed and matched? How would the ride of a smaller lower aspect wing compare to a bigger higher aspect wing?

For example, the Lift 110 is a relatively small wing but has a lower aspect ratio than other bigger wings.

Thx!

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Re: Smaller lower aspect wing vs. bigger higher aspect

Postby Peter_Frank » Tue May 26, 2020 7:19 am

The small low AR wing would be faster than the bigger high AR one, in max speed going downwind or halfwind, as here you ride with really low lift/angle of attack, thus AR hardly has influence.

But the bigger higher AR wing would be faster (VMG) on upwind rides, where you go with higher lift, and here AR matters hugely, so the extra drag for more surface is by far reduced by the lower drag from less loss and less tip vortices (= less drag).

Roughly speeking :D

8) Peter
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Re: Smaller lower aspect wing vs. bigger higher aspect

Postby omg » Tue May 26, 2020 8:36 am

Good topic.

What if I look for the pumpability (to get better low end) from the foil, assuming the same area (cm2), what would be better; thinner higher AR wing or lower AR wing (they seem to be fatter)?

Also, from these above two options, which one would be more agile ie. better turning?

Thanks!

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Re: Smaller lower aspect wing vs. bigger higher aspect

Postby slowboat » Tue May 26, 2020 9:32 am

omg wrote:
Tue May 26, 2020 8:36 am
Good topic.

What if I look for the pumpability (to get better low end) from the foil, assuming the same area (cm2), what would be better; thinner higher AR wing or lower AR wing (they seem to be fatter)?

Also, from these above two options, which one would be more agile ie. better turning?

Thanks!
Higher AR will pump better.

Turning is a more difficult question. Higher AR should not turn as well but very skilled riders do well with them, so I think it is more dependent on rider skill and experience.

Bigger, super high AR wings are becoming very popular for wave riding (prone, SUP or wing) or down winding but I don't see much utility for them in kiting.

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Re: Smaller lower aspect wing vs. bigger higher aspect

Postby Peter_Frank » Tue May 26, 2020 9:36 am

Higher AR wings are better for pumping, a bit better than thinner higher AR wing of course, as even more lift.

Lower AR wings are thicker as wider chord, even if same percentage thickness, and you lose a lot of lift with lower AR, so the worst ones for pumping, more drag and less lift.

But the lower AR ones turns A LOT faster, and almost impossible to stall, so a lot more fun in waves and aggressive maneuvers :thumb:

Even skilled riders notice high AR ones dont turn well, no doubt at all, they are just good riders so others can not see this :rollgrin:

8) Peter

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Re: Smaller lower aspect wing vs. bigger higher aspect

Postby tkaraszewski » Tue May 26, 2020 3:34 pm

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).
Last edited by tkaraszewski on Tue May 26, 2020 6:43 pm, edited 1 time in total.
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Re: Smaller lower aspect wing vs. bigger higher aspect

Postby grigorib » Tue May 26, 2020 4:01 pm

From my experience:
- thicker wings reduce cruising speed
- you need sufficient wing area (depending on rider’s weight) to avoid stalling at low speed
- low aspect wings and stabilizers are not very roll stable nor efficient

So

More thickness = less speed
More area = lower possible speed
Higher aspect = efficiency and roll stability

That’s how Moses 720 (740 sq.cm) felt as fast/slow as 683s (1005 sq.cm) being as thick yet its higher aspect worked well to go almost as slow as 683s
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Re: Smaller lower aspect wing vs. bigger higher aspect

Postby slowboat » Tue May 26, 2020 4:50 pm

tkaraszewski wrote:
Tue May 26, 2020 3:34 pm
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 high 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).
This is a really nice, succinct summary of the important differences.

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Re: Smaller lower aspect wing vs. bigger higher aspect

Postby Whattheflock » Tue May 26, 2020 6:13 pm

tkaraszewski wrote:
Tue May 26, 2020 3:34 pm

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 high 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).
A low aspect wing stalls before a high aspect wing at low speeds? Thought it was the other way around?

edit: sorry makes sense thinking about sailplane wings vs eg: fighter jets wings..

Why are foils like the 633 so popular for lightwind vs a higher aspect foil of a smaller area? More playful maybe?

Wouldnt a high aspect foil serve better?

I'm learning bare with me :wink:
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Re: Smaller lower aspect wing vs. bigger higher aspect

Postby slowboat » Tue May 26, 2020 6:41 pm

Whattheflock wrote:
Tue May 26, 2020 6:13 pm
tkaraszewski wrote:
Tue May 26, 2020 3:34 pm

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 high 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).
A low aspect wing stalls before a high aspect wing at low speeds? Thought it was the other way around?

edit: sorry makes sense thinking about sailplane wings vs eg: fighter jets wings..

Why are foils like the 633 so popular for lightwind vs a higher aspect foil of a smaller area? More playful maybe?

Wouldnt a high aspect foil serve better?

I'm learning bare with me :wink:
It's the other way round. High aspect will stall before the low aspect as you slow down.


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