Author Topic: Changing cord to thickness ratios from wing root to wing tip  (Read 2890 times)

SUPeter

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Changing cord to thickness ratios from wing root to wing tip
« on: January 21, 2019, 08:28:03 AM »
There has got to be someone out there who has information regarding this topic.   I am in the process of making a very large( 42" wide) downwind wing for my measly 155 lb body weight.   I also hope this wing will allow me to flatwater SUP start, eventually.  I have often wondered if decreasing the cord:thickeness ratio starting from wing root and decreasing towards wing tip would help with regards to increasing maneuverability of these XL wings.  Not sure if I want to go there.  For example, Wing root- NACA 4416 down to wing tip, NACA 4414.  Just a thought.  maybe it would lessen the outer wing torque against your feet?  Just wondereing.

Piros

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Re: Changing cord to thickness ratios from wing root to wing tip
« Reply #1 on: January 21, 2019, 10:00:11 AM »
The Signature Albatross Downwind foils have a very narrow cord. Might be a good starting point looking at these. Very efficient DW wing but I found it has a pretty small seeet spot balance wise.
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surfcowboy

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Re: Changing cord to thickness ratios from wing root to wing tip
« Reply #2 on: January 21, 2019, 05:21:36 PM »
It sounds like a logical plan. Although nothing about foiling seems logical.

SURFFOILS

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Re: Changing cord to thickness ratios from wing root to wing tip
« Reply #3 on: January 22, 2019, 01:12:58 AM »
The Signature Albatross Downwind foils have a very narrow chord...... but I found it has a pretty small seeet spot balance wise.
Whether foiling/surfing or just standing upright, the forces are vertically inline and aligned. When you lean, and despite the centripetal forces, there’s always the constant of gravity.
 As you lean further, the centre of balance moves further out to the side putting more pressure out to that side. You can check this by standing up and leaning to one side. One foot takes more weight despite the same contact area.
 On a foil it means that area across the span will dictate the balance when turning. If you reduce the fitting capabilities of the wing tip by changing the foil, area , AOA or chord and an/dihedral,  it will change the lift as you turn. This foil has a very small wingtip so it’s exactly as Piros said that it has a small sweet spot because there’s not a lot of lift out on the wingtip.
 
« Last Edit: January 22, 2019, 01:14:48 AM by SURFFOILS »

SUPeter

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Re: Changing cord to thickness ratios from wing root to wing tip
« Reply #4 on: January 22, 2019, 05:06:04 AM »
  Thanks everyone!
Funny!  This is the wing I have been looking at recently.  Their Stealth model actually has a little bit of Gull Wing (bottom concaves on either side of the mast.).  My new form incorporates a bit of Gull Wing which I hope provides greater lift and stability to the ride.  Then again I may not like it and will flush another $50 (and much time) down the crapper. Then again, $50 is a small amount to pay for the knowledge gained.  I di like the idea of having a wing with a higher aspect ratio and thinner cord to thickness ratio.   Just trying to decrease drag while maintaining lift.  Hope this will help in flatwater starts and downwind forays.  These Signature Albatross wings seem to be very thin from top to bottom as compared to GoFoils.  Then again, it appears GoFoils are thicker than most.  The wing pictured above is the smaller surface area wing in the Albatross line.  Their larger wing looks much more like the planshapes we are accustomed to seeing. 
« Last Edit: January 22, 2019, 05:10:51 AM by SUPeter »

PonoBill

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Re: Changing cord to thickness ratios from wing root to wing tip
« Reply #5 on: January 22, 2019, 09:55:25 AM »
It doesn't help that most of the useful knowledge about wing design relates to a medium that is 1000 times less dense. The idea of a wing 30 inches across moving 5 mph hoisting a 230-pound guy in the air is not easy to relate to airfoil design other than at the simplest level. Even in a basic lift equation some important modeling factors like Reynolds number and compression fall to 1x or 0 either by chance or because water is fundamentally incompressible. Refinements to the design based on things that work in the air are not reliably relatable. But that's about all I see. The knowledge of how wings work in air comes from a vast investment in R&D from governments and industry. And it doesn't really relate to water. With as much work as it takes to make a hydrofoil wing and as small as the market is I doubt there is any real development underway that measures the effects of small changes. It's all cut and try.

In other words, your guess is as good as theirs.
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.

Blackrat

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Re: Changing cord to thickness ratios from wing root to wing tip
« Reply #6 on: January 28, 2019, 06:54:21 PM »
The Signature Albatross Downwind foils have a very narrow chord...... but I found it has a pretty small seeet spot balance wise.
This foil has a very small wingtip so it’s exactly as Piros said that it has a small sweet spot because there’s not a lot of lift out on the wingtip.
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not quite , this foil is a race foil and thats why it has a small sweet spot , in the horizontal position the wing is sensitive (without banking), just about any high performance machine is tuned and becomes sensitive .... climb onto a small high performance board and it feels sensitive

The close coupled front and rear wing with very short chord's on both wings makes it sensitive however it also make highly efficient , a bigger (longer chord) rear stab will tame the beast at a cost of drag


 


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