Author Topic: Wing aerodynamics question.  (Read 2138 times)

Badger

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Wing aerodynamics question.
« on: November 19, 2021, 02:37:09 PM »
Why aren't wings more wing shaped?

I keep thinking that wings might be more efficient and have better upwind ability if there was less turbulence behind the leading edge. It seems like a substantial amount of area behind the leading edge is just going to waste and the resultant turbulence interfering with performance.

Is the underside of the wing irrelevant to performance or is it only a matter of time before someone invents a way to fill that gap allowing the air to flow more smoothly across the underside of the wing?



Naish S26 Hover GS 125L - Axis BSC 1060/440 - Ozone Wasp V1 4m/5m
Sunova Flow  8'10 X 31"  119L
Me - 6'0" - 175lbs - 64yo

JohnnyTsunami

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Re: Wing aerodynamics question.
« Reply #1 on: November 19, 2021, 02:58:55 PM »
I'm curious about double skinned wings - think kitefoiling "foil" kites, but no need for the rammed air because we have an inflatable leading edge (and we need one since we have no bridles to maintain shape). It seems relatively easy to do, just put a thin canopy on the handle side of the wing as well, doesn't necessarily need to be connected at the trailing edge. Handles/boom can be where they are now, just come out through some reinforced holes the inner canopy, since it wouldn't be any further out that the main strut anyway.

Obviously would weight a bit more, but maybe you could get away with a lighter material and sill not have much flapping due to the double skins.

Tube-kite profile creates more lift than a Soft-kite profile in stationary flight conditions, but the drag is higher in low angles of attack. So upwind the double skin wins, but more grunt in the single skin.
https://www.ralfgroeseldesign.com/post/tube-vs-softkite-an-epic-battle

America's Cup Boats use this https://youtu.be/-M54CVWotvc?t=86

Also see the IWS inflatable sailboat sail, supposedly far more efficient that a similar sized regular sail and less heeling force compared to lift.
https://youtu.be/QGJ02kEDtXI?t=8

AKA "wing sail" https://en.wikipedia.org/wiki/Wingsail

Of course, kite foil racers use "foil" kites which are far more efficient than leading edge inflatable (LEI) kites, which are like our wings. Ozone seems to be the leader here. 

I'll give my shipping address to anyone and am happy to test!  ;D
« Last Edit: November 19, 2021, 03:55:10 PM by JohnnyTsunami »

Dwight (DW)

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Re: Wing aerodynamics question.
« Reply #2 on: November 19, 2021, 03:57:05 PM »
Weve been through this before with Windsurfing and Hang Gliding.

Back in about 1980 or 81 a brand introduced double surface. It performed worse. Why, because hang glider design wasnt good enough. There were way more design improvements that needed to be invented first.

Same with windsurfing. Double surface sails were not faster. Tip twist had not even been figured out yet.

Wings, way too early in the evolution of design.

Badger

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Re: Wing aerodynamics question.
« Reply #3 on: November 20, 2021, 04:42:48 AM »
All of those ideas attempt to bring the underside surface all the way to the trailing edge.

All I'm suggesting is to cover or fill the area directly behind the front tube of the wing where the air turbulence is. Beyond that, it's not needed. Then instead of being dead space, it would actually add to the usable sail area.

Foil wings have a gigantic leading edge which carries a tremendous amount of dead air behind it compared to any other type of sail.

It would be easy to take a 20-inch wide strip of cloth and attach it with adhesive velcro to cover the area of turbulence behind the tube just to see what would happen. Unfortunately, all my wings are new and I'm not ready to defile them yet

.
« Last Edit: November 20, 2021, 04:52:47 AM by Badger »
Naish S26 Hover GS 125L - Axis BSC 1060/440 - Ozone Wasp V1 4m/5m
Sunova Flow  8'10 X 31"  119L
Me - 6'0" - 175lbs - 64yo

Wetstuff

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Re: Wing aerodynamics question.
« Reply #4 on: November 20, 2021, 06:29:45 AM »
I don't know?!  But, these guyz never seemed to have drifted far from top-only surfaces, and they've been at it a bit longer... 

You can be sure someone will come along and add to the 'exotic' ...and the price. Pretty much anyone at the premium end of a market gains stature by default.

http://www.wikidelta.com/images/pdf/Hang-Glider-Design-and-Performance.pdf

Jim
Atlantis Mistress .. Blue Planet MultiTasker ..   Atlantis Venom

Dwight (DW)

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Re: Wing aerodynamics question.
« Reply #5 on: November 20, 2021, 08:48:07 AM »
The original GIANT leap in hang glider design was cross bar tension. It basically created massive canopy tension tip to tip.

Kind of like what Aluula is doing for winging. Holding onto more canopy tension.

PonoBill

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Re: Wing aerodynamics question.
« Reply #6 on: November 20, 2021, 09:15:34 AM »
Double skin is likely somewhere on the list of eventual improvements, but way down the page. We're more or less a little past the "it works!" stage. I don't expect any of the performance improvements we'll see over the years to be of any benefit to me except perhaps anything that makes wings lighter.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

Badger

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Re: Wing aerodynamics question.
« Reply #7 on: November 20, 2021, 10:24:17 AM »
One major drawback would be the extra time it would take to dry a wing like that.

I guess I'll leave it to the experts and be satisfied with what we have. There is a lot of money at stake for better wing designs. I'm sure they are working diligently on new concepts.
Naish S26 Hover GS 125L - Axis BSC 1060/440 - Ozone Wasp V1 4m/5m
Sunova Flow  8'10 X 31"  119L
Me - 6'0" - 175lbs - 64yo

tarquin

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Re: Wing aerodynamics question.
« Reply #8 on: November 20, 2021, 12:25:21 PM »
I am pretty sure kites went down the same path and they put out some with a second skin. I think too expensive and not that big a difference.
 What amazes me is its taken what, 3 generations of wings too make a big difference. I understand companies were reluctant at the start. How can companies that have been making kites for years go, oh we need a stiffer bladder. Version 2 has a stiffer bladder, version 3 has a even stiffer bladder and tighter canopy. Sounds exactly like what kites went through.
 I think some sort of carbon batten like the C tech furling batten could work. I emailed multiple companies for inflatable SUPs,kites and wings. Not one was interested. So maybe not?
 

tarquin

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Re: Wing aerodynamics question.
« Reply #9 on: November 20, 2021, 12:27:08 PM »

Badger

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Re: Wing aerodynamics question.
« Reply #10 on: November 21, 2021, 06:28:08 AM »
I can see full-length battens possibly being used at some point. I'm happy with the sport so far but it can't end here. There are more breakthroughs just around the corner.
Naish S26 Hover GS 125L - Axis BSC 1060/440 - Ozone Wasp V1 4m/5m
Sunova Flow  8'10 X 31"  119L
Me - 6'0" - 175lbs - 64yo

Wingfoil2001

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Re: Wing aerodynamics question.
« Reply #11 on: November 21, 2021, 11:50:11 AM »
We have been flying leading edge inflatable kites for years, very little has changed to the leading edge to canopy design. Double surface has been tried but of little benefit.
Now its all about weight saving, further relegating any thoughts of double surface and battens to the scrap heap.

JohnnyTsunami

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Re: Wing aerodynamics question.
« Reply #12 on: November 22, 2021, 11:35:38 AM »
Very interesting stuff. If there isn't much to be gained on double skin, then maybe the Aluula/Spectra/Dyneema material will lead to reductions in leading edge diameter and that will be the main performance gain? The smaller leading edge will result in less drag --> more efficiency?

My 6m Duotone Echo v2 goes upwind pretty poorly looking at my gps tracks. I'm a sit down sailboat racer who knows how to go upwind.
My 4.5m Duotone SLICK goes upwind much better. Maybe ~110 degrees on different tacks, hard to say without a protractor.

Do you think the difference is the smaller leading edge of the 4.5m? Or is it the wing outline or the draft or something like that?

I noticed a couple times people on a different brand 6m wing pointing higher than me - ozone I think. I was riding ART-999 and a Mike's Lab foil, so it's not what's under the water. Anyone on an Aluula wing and compare their upwind angles to a dacron wing of the same size?

PonoBill

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Re: Wing aerodynamics question.
« Reply #13 on: November 22, 2021, 08:28:53 PM »
I've quizzed a few wing designers on what makes a wing hold a better upwind angle. It's a topic that they seem unwilling to talk about--at least not to me. Mark Raaphorst has a couple of the Ocean Rodeo Alula wings. They seem quite good, I may spring for one, and they seem to go upwind very well. I've always considered my F-one Strikes to be particularly good upwind, and Mark holds a much line than I can. Part of that is undoubtedly rider, but I suspect both the extreme stiffness of the inflated bits (leading edge and strut) and the small diameter both help.

When I'm hanging off the board in strong wind going upwind as close hauled as I can, I know my Strikes get distorted--a bit taco-ed. That has to be spilling air off the wingtips if nothing else. The cloud wings (those light green and white things) seem to offer lots of power but can't seem to reach very well. the huge leading edge seems like it's gotta be a problem.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

Vancouver_foiler

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Re: Wing aerodynamics question.
« Reply #14 on: November 22, 2021, 10:32:02 PM »
I've quizzed a few wing designers on what makes a wing hold a better upwind angle. It's a topic that they seem unwilling to talk about--at least not to me. Mark Raaphorst has a couple of the Ocean Rodeo Alula wings. They seem quite good, I may spring for one, and they seem to go upwind very well. I've always considered my F-one Strikes to be particularly good upwind, and Mark holds a much line than I can. Part of that is undoubtedly rider, but I suspect both the extreme stiffness of the inflated bits (leading edge and strut) and the small diameter both help.

When I'm hanging off the board in strong wind going upwind as close hauled as I can, I know my Strikes get distorted--a bit taco-ed. That has to be spilling air off the wingtips if nothing else. The cloud wings (those light green and white things) seem to offer lots of power but can't seem to reach very well. the huge leading edge seems like it's gotta be a problem.

I was talking w Richard Myerscoff a bit back(trying out his all allula wing goodness me) and he felt winging just passed the c-kite phase. These designers have major improvements and innovations around the corner  they just can't get them tested and out fast enough. production with covid oversees saw them loose almost a year all in all.

Pono, not a surprise that the Glide felt so good. Ross Harington was a hangoglider pilot and designer before doing kites for OR. He's been designing wings for like 40 years lol.

 


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