twin tip hydrofoil

[davesails7]

Wouldn't anhedral be more effective on the two smaller wings than on the center, large wing? The point of the anhedral is to add directional stability in yaw, correct? I think it would be much more effective if it was further out from the center of rotation.

[ozchrisb]

Please inform FK24 that I have a provisional patent since 2013.]

On what? The wing arrangement, the profile, the idea of a TT hydrofoil?

[revhed]

H,
Thanks for the video, it does prove your TT KBHF flies, hard to tell if well or not?
Feel flattered if you want, even if your reason is false.
Good luck with your patent, you will be unable to use it offensively, due to prior art.
As for French innovation in KBHFs, there is plenty of history and for sure more to come.
R H

[Hawaiis]

Wouldn't anhedral be more effective on the two smaller wings than on the center, large wing? The point of the anhedral is to add directional stability in yaw, correct? I think it would be much more effective if it was further out from the center of rotation.

Anhedral adds both Roll and Yaw stability to the foil. If we put anhedral on all three wings, the prop wash will be closer, there will be more turbulence for the foils in the back. There are too many factors at play. Just have to pick the best compromise.

[wil]

Interesting discussion. Especially the concern of revhed for my safety. I would have thought that a high drag twin tip hydrofoil would be flying a lot slower than a super sleek directional hydrofoil.

Looking at the clip from HawaiiS on his twin tip it appears to move quite slowly through the water. If that is the case the chance of horrific accidents are probably no greater than flying a modern fast directional hydrofoil.

It is a pity that we don't have a clear video (from land) to see how the HawaiiS twin tip rides.

In regards to where to put anhedral - dihedral on centre wing or outer wings I am still a bit confused.

Looking at the photo that revhed attached it looks like anhedral on the centre wing and dihedral on the outer wings. Looking at the photo it appears that the rider is pretty confident. He must have been able to build up quite a bit of speed to lift out of the water.

HawaiiS do you think that that the tips on the wings can be rounded off so there are no actual sharp edges (similar to the photo attached by revhed) compared to your very sharp and square wings.

Cannot wait to get the call from the welders to have a go.

[Hawaiis]

Please inform FK24 that I have a provisional patent since 2013.]

On what? The wing arrangement, the profile, the idea of a TT hydrofoil?

The patent is still pending.

[Hawaiis]

Interesting discussion. Especially the concern of revhed for my safety. I would have thought that a high drag twin tip hydrofoil would be flying a lot slower than a super sleek directional hydrofoil.

Looking at the clip from HawaiiS on his twin tip it appears to move quite slowly through the water. If that is the case the chance of horrific accidents are probably no greater than flying a modern fast directional hydrofoil.

It is a pity that we don't have a clear video (from land) to see how the HawaiiS twin tip rides.

In regards to where to put anhedral - dihedral on centre wing or outer wings I am still a bit confused.

Looking at the photo that revhed attached it looks like anhedral on the centre wing and dihedral on the outer wings. Looking at the photo it appears that the rider is pretty confident. He must have been able to build up quite a bit of speed to lift out of the water.

HawaiiS do you think that that the tips on the wings can be rounded off so there are no actual sharp edges (similar to the photo attached by revhed) compared to your very sharp and square wings.

Cannot wait to get the call from the welders to have a go.

Diehedral on the two smaller wings will probably add more Kangaroo effect hence better for jumping.
I did round off the corners, FK24 just rounded off more. Titanium is very hard to cut, I did not cut it to optimum elliptical shape yet since it is only a prototype, I use the same wings for both directional and bi-directional testings.

[wil]

Got my mast and fuselage back from welders today. Not sure now whether to continue with the twin tip idea or to go to a directional. I am making a board 150 x 51 from Paulownia as well.

[Hawaiis]

looks really good, it can be used either as a twintip or surfboard.

[revhed]

Hi Wl,
You may have stumbled onto something interesting.
A sym strut is not the best profile but it will work, ala 1st gen caracrap, airchair copy.
Yours looks wider, I guess 11 cm or so? it will fly just not fast or well in the lowind.
And this is needed for a bi di design for sure.
Looking at your parts you should be able to configure a DIR fuse and a BD fuse using the same strut and by sliding it you can change wing locations relative to both the strut and each other.
Maybe the first BD, DR convertible KBHF!
Only because you asked repeatedly I did some ultra fast, crude not to scale specs for my next modded B D build. These will, have fllown, but as I told you good B D KBHF design is a way off.
These are in working with FK24 with a few mods.

strut 80- 90 cm
fuse 75-80 cm
board stance 65-70 cm
note aile c has flat bottom profile but maybe I will go sym here also so you can test tips up or down as well as fore aft ailes tips up or down just to feel the diference.
So far c wing tips curved down other 2 up.
Search NACA profiles to find a sym one that looks good for the fore ,aft ailes.My drawing is not good! Something with a nice progresive curve.
Fore,aft wing mounted AOAs extreamly critical, .5 neg, inside seems to be a starting point.
all L Es should be rounded more than most DIRs
For safty I will make 2 "side foot hooks" because B D crashes can be intense!
It also seems better to have a more Banana rockered TT board with very round rails?
Some other photos of oher surface piercing B Ds

foil_bidi1.jpg (142.13 KiB) Viewed 954 times

foil_bidi3.jpg (144.66 KiB) Viewed 954 times

foil_bidi_split.png (183.06 KiB) Viewed 954 times

I just hope to build something that flies better.
R H