Design of flaps on a curved foil.

[Petros]

rather than putting a flap in the foil itself, why not use a separate smaller "trimming" foil near the trailing edge to alter the flow. It would be supported and hinged off of tabs or supports near the TE of the curved foil. Solves the problem of warping a curved foil.

[Doug Lord]

Originally Posted by Petros

rather than putting a flap in the foil itself, why not use a separate smaller "trimming" foil near the trailing edge to alter the flow. It would be supported and hinged off of tabs or supports near the TE of the curved foil. Solves the problem of warping a curved foil.

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Thanks, Petros. Sounds like it might prevent the foil from being retracted ,if I understand you correctly.

[Doug Lord]

Just discovered this picture which appears to show a curved foil with a flap:

click on image-then click on it again--

[Paul B]

Originally Posted by Doug Lord

Just discovered this picture which appears to show a curved foil with a flap:
-

Looks like something else to me.

[Doug Lord]

Originally Posted by Paul B

Looks like something else to me.

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I believe you!

[Paul B]

Originally Posted by Doug Lord

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I believe you!

Maybe if you spent a few minutes thinking about the mechanics of this type of system you would not have thought you were seeing a flap.

[Doug Lord]

Originally Posted by Paul B

Maybe if you spent a few minutes thinking about the mechanics of this type of system you would not have thought you were seeing a flap.

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I see your point. You're 100% right-thanks!

[Petros]

A flap like that could work if it was made of rubber or vinyl or a similar flexible material. you would not get a lot of range of movement out it but it would work for trimming.

for that matter if you make a stiff rubber trailing edge you would not need a hinge either (with its draggy gap), you could just "warp" the TE to get it to trim. That would be a nice clean set-up.

[sigurd]

jet flap.

[Manfred.pech]

If you are able to lengthen/shorten the forward beam telescopic and keep the rear one adjustable with a hinge (or flexible at a small multi) you do not need a flap for a bent board.

[Doug Lord]

Originally Posted by Manfred.pech

If you are able to lengthen/shorten the forward beam telescopic and keep the rear one adjustable with a hinge (or flexible at a small multi) you do not need a flap for a bent board.

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The idea,from my perspective, was to be able to connect the flap to a wand-based altitude control system and use in a similar way to a t-foil.

[ancient kayaker]

My thoughts:

An elastomeric flap may vibrate.

Are flaps required along the entire length of the foil or can a flap be used just on a straight portion?

If flaps must go on a curve, the simplest solution is several short flaps mounted on a single, flexible rod, with the ends of each flap beveled to prevent flap-to-flap interference.

As an alternative to a rotating flap pivoting from the trailing edge, have you considered a leading edge slotted flap with a linear movement? Viewed from astern as shown in your sketch attached to post # it would have the same curve and would move along the NW to SE diagonal, creating a variable slot along the entire length of the foil without need for flexible elements. The slot would not be the same along the entire length, this would need some thinking about from someone better informed on slot design than I am, ditto the control of lift.

[Doug Lord]

Originally Posted by ancient kayaker

My thoughts:

An elastomeric flap may vibrate.

Are flaps required along the entire length of the foil or can a flap be used just on a straight portion?

If flaps must go on a curve, the simplest solution is several short flaps mounted on a single, flexible rod, with the ends of each flap beveled to prevent flap-to-flap interference.

As an alternative to a rotating flap pivoting from the trailing edge, have you considered a leading edge slotted flap with a linear movement? Viewed from astern as shown in your sketch attached to post # it would have the same curve and would move along the NW to SE diagonal, creating a variable slot along the entire length of the foil without need for flexible elements. The slot would not be the same along the entire length, this would need some thinking about from someone better informed on slot design than I am, ditto the control of lift.

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Thanks, AK. In my application, approximately the lower third of the foil would use a flap. The slot might work but it would need the active participation of a Mark Drela or Tom Speer to consider the viability of that solution-I couldn't do it.

[Submarine Tom]

How about making the entire foil semi rigid and inducing a curve or contour to it on demand?

Somewhere I read it can be quite effective but perhaps ahead of it's time.

It makes sense to me...

-Tom

[Doug Lord]

Originally Posted by Submarine Tom

How about making the entire foil semi rigid and inducing a curve or contour to it on demand?

Somewhere I read it can be quite effective but perhaps ahead of it's time.

It makes sense to me...

-Tom

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Thanks, Tom-might work with some kind of shape/memory material, but its beyond me.....