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Of hump-back whale tubercles, V1 Prandtl equasions and the long ignored V2 Prandtl equasions and birds wings.

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Matteo V
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Re: Of hump-back whale tubercles, V1 Prandtl equasions and the long ignored V2 Prandtl equasions and birds wings.

Postby Matteo V » Tue May 11, 2021 2:55 am

fluidity wrote:
Mon May 10, 2021 7:24 pm
I don't agree but that comes down not to the data, but to different ways we look at things. If you were to look up your own Myers Briggs type and compare it with mine of ENTP it would make perfect sense, we have skills and talents in quite different areas.
Rudders on aircraft are only designed for pointing the aircraft somewhere else, apart from that they are pretty much a waste of time except for compensating for the natural adverse yaw of a poor wing design. In air you can skip the rudder and fly with combo elevator/ailerons. Elevons we call them and I've slope soared gliders with them. On any delta shape they make a lot of sense.
Rudders are there to tackle adverse yaw of simple wings like the Wright brothers had and needed a fix for.
Since then, we've assumed we needed them so rudders are also used on landings to reduce side loads on wheels to (partially)compensate for cross winds.

So you can see I also have been guilty of judging Prandtl and other DELTA wings by a "need" to use a rudder to reduce cross wind landing side loads on wheels.

However it's actually a fallacy, "it's just the way things have always been done around here"

I think the advantages of a more efficient wing justify a modern reassessment of the landing carriage which is the real problem, not yaw of the aircraft.
And there's actually a solution!

I'll call it "Constrained castors for big stuff"

Let the wheels swivel for minimum rubber loss on landing and then deal with straightening the aircraft through steering as it slows down. Crabs walk sideways!

In current times we are a bit past the Wright brothers, we have computers, hydraulics, pnumatics, stepper motors, servo motors etc. If the Wright brothers had started with Prandtl wings this problem would have been solved too, it's just easier now.

Often what we "know" only holds us back. I see the Prandtl wiki is still out of date with it's subject, a new generation is coming through with the same half-story even now :lol:
The Prandtl based teachings and their missing components are going to go down in the history books, much like Luca Turin's brilliant overturning of the establishment to discover how scent really works and to use his discovery as a much more stable foundation for scent creation than previous beliefs.
K

Herman
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Re: Of hump-back whale tubercles, V1 Prandtl equasions and the long ignored V2 Prandtl equasions and birds wings.

Postby Herman » Tue May 11, 2021 11:32 am

Going back to adverse yaw, I am not current on this sort of thing but I didn’t think it was particularly speed related. I thought that was one of the Wright brothers problems in one of their crashes. Odd but I don’t think I have seen it discussed by the hydrofoilers as a design consideration.

For the unfamiliar:
Adverse yaw: roll left yaw right, need a bootfull of rudder to correct.........

Matteo V
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Re: Of hump-back whale tubercles, V1 Prandtl equasions and the long ignored V2 Prandtl equasions and birds wings.

Postby Matteo V » Tue May 11, 2021 1:46 pm

Herman wrote:
Tue May 11, 2021 11:32 am
Odd but I don’t think I have seen it discussed by the hydrofoilers as a design consideration.

For the unfamiliar:
Adverse yaw: roll left yaw right, need a bootfull of rudder to correct.........
On a hydrofoil, you have more than two bootfulls. You have an 80kg weight capable of varying the application of that weight over a lifting mechanism that easily fits inside of 1sq meter. All lifting and stabilizing surfaces are fixed because you have no need for any other inputs than shifting the riders weight.

Aircraft do not have "king kong" riding on thier back to vary control inputs like you do on a hydrofoil. So adverse yaw is actually a completely different thing in hydrofoiling that may be desirable instead of detrimental.

Herman
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Re: Of hump-back whale tubercles, V1 Prandtl equasions and the long ignored V2 Prandtl equasions and birds wings.

Postby Herman » Tue May 11, 2021 1:56 pm

Not the first time that I have been compared to a gorilla but it is torque more than weight that is required to correct yaw and a gorilla definitely has the feet for that. Not sure I can see much benefit in yawing away from the turn but probably above my pay grade.

Simplistically Mg = lift in both aircraft and gorilla.
Last edited by Herman on Tue May 11, 2021 8:32 pm, edited 1 time in total.

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fluidity
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Re: Of hump-back whale tubercles, V1 Prandtl equasions and the long ignored V2 Prandtl equasions and birds wings.

Postby fluidity » Tue May 11, 2021 7:27 pm

Herman wrote:
Tue May 11, 2021 11:32 am
Going back to adverse yaw, I am not current on this sort of thing but I didn’t think it was particularly speed related. I thought that was one of the Wright brothers problems in one of their crashes. Odd but I don’t think I have seen it discussed by the hydrofoilers as a design consideration.

For the unfamiliar:
Adverse yaw: roll left yaw right, need a bootfull of rudder to correct.........
As Matio mentions there is a big rider to compensate.
I can't help wondering though, Wouldn't it ride more sweetly? We automatically compensate for things like adverse yaw through muscle memory and experience but an inherently ballanced design must feel nicer to ride with less compensation required. Most importantly though, the twist out close to the wing tip creates higher efficiency and moves the vorticies in to where birds have naturally co-evolved the Prandtl V2 solutions. If you google the Horton brothers and deltas you can see it more clearly than in Albion Bower's team's photos. I'm curious whether my "solution" which is closer to Humpback whale's fin tubercles will also work though.
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Herman (Tue May 11, 2021 7:39 pm)
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fluidity
Very Frequent Poster
Posts: 532
Joined: Sat Mar 19, 2016 11:20 pm
Kiting since: 2015
Weight: 104kg
Local Beach: Ngati Toa, Plimmerton, Titahi Bay, Waikanae, Petone, Seatoun, Lyall Bay, Eastbourne, Lake Wairarapa
Favorite Beaches: Plimmerton
Style: Wave, jump
Gear: Late model Switch kites element and nitros,
DIY CAD ultra-concave wave twintips 1500 and 130mm with my own fin designs. Easy upwind, awesome carving. Switch Nitro 10m V7, Naish 5.3m Wing.
Now focussing on Wingsurfing to rise to a new challenge. Building my own foils from my CAD design and 3D prints, built a CNC machine last year and now cutting designs with CNC as well as 3D printing.
Using my own software for foil design.
Location: Porirua New Zealand
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Re: Of hump-back whale tubercles, V1 Prandtl equasions and the long ignored V2 Prandtl equasions and birds wings.

Postby fluidity » Tue May 11, 2021 7:39 pm

Matteo V wrote:
Tue May 11, 2021 1:46 pm
On a hydrofoil, you have more than two bootfulls. You have an 80kg weight capable of varying the application of that weight over a lifting mechanism that easily fits inside of 1sq meter. All lifting and stabilizing surfaces are fixed because you have no need for any other inputs than shifting the riders weight.
Aircraft do not have "king kong" riding on thier back to vary control inputs like you do on a hydrofoil. So adverse yaw is actually a completely different thing in hydrofoiling that may be desirable instead of detrimental.
When you look closely at the eliptical vs the Prandtl V2 solutions it's actually the elevons that cause the adverse yaw in the non wing end twist solution and the proverse yaw in the wing end twist second solution. It's because of the net drag at the wing tips being side to side reversed on deflection when there is already up-flex on both sides in the same regions used for elevons. So I don't think it would be an issue on non America's cup level hydrofoils. (without elevons)

Matteo V
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Re: Of hump-back whale tubercles, V1 Prandtl equasions and the long ignored V2 Prandtl equasions and birds wings.

Postby Matteo V » Tue May 11, 2021 8:37 pm

fluidity wrote:
Tue May 11, 2021 7:39 pm
When you look closely at the eliptical vs the Prandtl V2 solutions it's actually the elevons that cause the adverse yaw in the non wing end twist solution and the proverse yaw in the wing end twist second solution. It's because of the net drag at the wing tips being side to side reversed on deflection when there is already up-flex on both sides in the same regions used for elevons. So I don't think it would be an issue on non America's cup level hydrofoils. (without elevons)
Yes, those are control surfaces. The point is we dont have those in kiting.


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