Author Topic: Go Foil Advise  (Read 21519 times)

steamroller

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Re: Go Foil Advise
« Reply #15 on: August 29, 2019, 02:02:42 PM »
+1 on what jondrums and Beasho said...thats pretty much all of it right there

+1 on what pono said too AND once you get the new GL setup the whole discussion is moot cause you'll never want to run the old stuff again anyway...the GL stuff os too GOOD!

jondrums

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Re: Go Foil Advise
« Reply #16 on: August 29, 2019, 03:26:34 PM »
Would I get more lift out of the M200/M280 with the new 18Wide Tail instead of the Maliko tail?

I'm absolutely certain you will.  However it is a small factor and may not be detectable without back-to-back A/B testing.  You would likely be able to feel the reduced drag (and increased top speed).  I am also certain you would feel the difference in the "nose-up" pitching moment.  Some might mistake this feeling for lift because it "lifts" up the nose, but it isn't lift - it is pitching moment.

norcom

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Re: Go Foil Advise
« Reply #17 on: August 29, 2019, 07:08:20 PM »
Would I get more lift out of the M200/M280 with the new 18Wide Tail instead of the Maliko tail?

I'm absolutely certain you will.  However it is a small factor and may not be detectable without back-to-back A/B testing.  You would likely be able to feel the reduced drag (and increased top speed).  I am also certain you would feel the difference in the "nose-up" pitching moment.  Some might mistake this feeling for lift because it "lifts" up the nose, but it isn't lift - it is pitching moment.

I guess I should have asked if it would give me more lift in the absolute worst, ultra-tiny-small, wind chop generated "waves". Seems like everyone who loves the GL wings uses them to surf real swells the likes of California and Hawaii. I'm trying to ride stuff in the armpit of the Florida panhandle and find it impossible to even make the M280 fly. There's just never enough push from the "waves" to get going. When the waves actually get bigger, it's because the wind is nuking and I might as well be kiting or windsurfing because paddling into a 20mph head wind is futile.

Hdip

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Re: Go Foil Advise
« Reply #18 on: August 29, 2019, 11:17:41 PM »
Check out this guy. He has a good podcast about foiling too. Heís somewhere in Florida.

https://instagram.com/the.progression.project?igshid=1qwv25j5dop5y

PonoBill

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Re: Go Foil Advise
« Reply #19 on: August 30, 2019, 05:27:13 AM »
If you can't make an M280 work then a GL240 won't help. It's a little harder to get up on.
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Admin

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Re: Go Foil Advise
« Reply #20 on: August 30, 2019, 07:33:11 AM »
A big thing you have to understand is that the MALIKO tail creates DOWNFORCE! 

Hi John,

I was under the impression that they all were positive lift for the main foil and negative lift for the stabilizer.  It looks like both our Kai and Iwa tails are set up for negative lift and it looks like our Axis 500 tail is the same.  What alternate configurations are out there?

jondrums

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Re: Go Foil Advise
« Reply #21 on: August 30, 2019, 09:06:23 AM »
There is no rule that says the tail has to create down-force.  Can be neutral or lifting.  folks that have played with adjustable tails know more than I do about this (I haven't messed with the GL tail shimming - looks neutral out of the box).  KAI and MALIKO aren't adjustable of course, I'm not sure why they made them that way.  I was thinking that maybe doing that helps lower the stall speed for high angle of attack.

Admin

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Re: Go Foil Advise
« Reply #22 on: August 30, 2019, 09:22:54 AM »
I picture this differently.  I am seeing the front wing as "rightside up" and creating "up" lift.  On all of our tails the wing is inverted or upside down.  I would see that as always creating negative lift.  I had pictured shims to the tail to alter the angle of that negative lift.  Is that incorrect?

I think I have also heard of having both wings right side up and uplifting but is that done with these foils?



« Last Edit: August 30, 2019, 09:34:31 AM by Admin »

jondrums

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Re: Go Foil Advise
« Reply #23 on: August 30, 2019, 09:23:20 AM »
I think principles here are very similar to aircraft.

If the tail area is appropriately sized in ratio to the wing and the distance between them - then the best lift/drag ratio (lowest drag, best glide, etc) should be achieved when the tail is trimmed somewhere between neutral and slight lift.  In many planes, the tail is a lifting surface when the center of gravity is at the rearward end of the range (and vice-versa its a downforce surface when the CG is forward).  Maximum glide/least drag occurs when the CG is slightly aft and the tail can be trimmed to neutral or just above.  Big planes shuttle fuel around to optimize the CG and reduce drag / increase efficiency.

On a foil board, we can dynamically adjust fore-aft weight balance - so I see no reason why we should be using down-force rear wings.

Dwight (DW)

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Re: Go Foil Advise
« Reply #24 on: August 30, 2019, 09:55:06 AM »
Just FYI, some early kite foils did have lifting rear wings. Gong was one of those. They donít do this anymore.

jondrums

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Re: Go Foil Advise
« Reply #25 on: August 30, 2019, 09:58:34 PM »
has anyone experimented with shimming a tail to create uplift?  I guess I'll have to try it one of these days.  Might have to learn the hard way why everyone has designed downforce in the tail.

Beasho

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Re: Go Foil Advise
« Reply #26 on: August 31, 2019, 08:08:27 AM »
Theoretical No Dice on lifting tail:

"Yet the wing is invariably more efficient than the tail, producing its lift for a smaller relative drag penalty."

The most efficient wing is a long thin high aspect, glider wing, that would extend to infinity.  Every wing tip has a drag (vortice) penalty aka NO Tail is better.  Down force is also "Bad!"

This might be hard to build, and hard to control.  Any deviation from this produces LESS LIFT.

But your wing might breach, break . . . .
« Last Edit: August 31, 2019, 08:13:20 AM by Beasho »

Beasho

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Re: Go Foil Advise
« Reply #27 on: August 31, 2019, 08:33:50 AM »
Here is where the wings should be going.

I was setting up the GoPro and caught a loon flying overhead.  It is flying down screen note the leading edge of its wing is dead straight.

And NO or very little tail influence.  All a result of a few billion more test cycles (including the failures).
« Last Edit: August 31, 2019, 08:35:46 AM by Beasho »

jondrums

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Re: Go Foil Advise
« Reply #28 on: August 31, 2019, 11:13:09 AM »

The most efficient wing is a long thin high aspect, glider wing, that would extend to infinity.  Every wing tip has a drag (vortice) penalty aka NO Tail is better.  Down force is also "Bad!"


Thank you for this!  makes total sense.  This suggests that a perfectly neutral tail (no upforce or downforce) should be the best setup for maximum GLIDE. 

Admin

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Re: Go Foil Advise
« Reply #29 on: September 01, 2019, 02:04:27 AM »
has anyone experimented with shimming a tail to create uplift?  I guess I'll have to try it one of these days.  Might have to learn the hard way why everyone has designed downforce in the tail.

I think that you would need to de-invert the tail wing as well to create uplift.  As long as it is inverted (all of these these cambered tail wings) I don't think it can create uplift regardless of angle.
« Last Edit: September 01, 2019, 02:11:10 AM by Admin »