Wave oriented hydrofoil

[ahmthai]

May I ask what profiles you are using for STRUT, F wing, R wing?
Any chance of a board photo with rails as well?
Strapless?
As I fly the Med sea, not waves very often but when there are sure fun, and as said lower AR 4ish thicker F wing seems to work better than my thin 6ish.
I have a feeling that if I lived near a wave spot that a 70 cm strut would be fun to have.
R H

I used a Eppler 817 for the wings. The stabilizer has the lifting surface on bottom and AOA is around zero. The strut is Eppler 836. I don't have molds, so the profiles are as good as I can get using templates.

Since high end speed is not important, I don't think the exact profile is that critical as long as the surface profiles are smooth and the training edges are thin. You just want something efficient and quiet through the water.

I will take a picture of the board over the weekend.

-Andrew

[ahmthai]

I have few comments on PF's first post:

Strut length: I don't think a mast of 80cm is short enough to take advantage of the maneuverability gains of short strut. I rode a foil with about a 80 cm mast and didn't feel much different than a 90-100cm strut. Wing and stabilizer design seem to have more impact on turning at these relatively long lengths.

Geometry dictates that a shorter strut takes a shorter path through a turn. As an example, the arc of 45cm strut is 140 cm through a 180 degree turn while a 1m strut 314 cm. It is much easier to do faster, tighter turns when the foil travels a shorter distance through the water between turns.

Turning and aspect ratio of front wings: Through trials of my own designs trying several production foil, the front wing aspect ratio has much less to do with turning than does the stabilizer size and amount of an anhedral/dihedral or the presence of a vertical stabilizer fin. I have made very low aspect wings which turn great if paired with a flat rear wing. Take the same front wing and add a vertical fin or stabilizer with dihedral and it feels really locked in and doesn't turn well. I recently rode the F-one foil which is relatively high aspect (less than racing foils), but has a large wide stabilizer with dihedral. The thing barely turns in comparison to my mid aspect wave foil with a flat rear wing.

We are still in early days of hydrofoil development, so it will be interesting to see how things develop as foils become more specialized just as kiteboards did. In 10 years time we will be looking back an wondering what we were thinking back then.

-Andrew

[fpvSB]

I think the idea is that he could turn at more of an angle without the blade leaving the water.

[revhed]

Through trials of my own designs trying several production foil, the front wing aspect ratio has much less to do with turning than does the stabilizer size and amount of an anhedral/dihedral or the presence of a vertical stabilizer fin. I have made very low aspect wings which turn great if paired with a flat rear wing. Take the same front wing and add a vertical fin or stabilizer with dihedral and it feels really locked in and doesn't turn well.
We are still in early days of hydrofoil development, so it will be interesting to see how things develop as foils become more specialized just as kiteboards did. In 10 years time we will be looking back an wondering what we were thinking back then.
-Andrew

Thanks for the profile info, I use the same although will make a few Speer H105s this winter.

h1051.gif (4.75 KiB) Viewed 1401 times

H105a.gif (1.87 KiB) Viewed 1401 times

To test this,
http://www.tspeer.com/Hydrofoils/h105/h105.htm
Because this is thicker will be stronger having a great moment of inertia as well.
I also will test at least for me a new way to make wings consisting of laminating 5mm of hard closed cell foam on each side of a 300g/m2 carbon center cord reference after vac saced on curved male mold.
Then will use thin plastic concave templates to profile shape foam on both top and bottom using the black carbon laminate as the LE and TE center.
After that 1,000 quadri (amazing stuff) will be layed up on top and bottom vac sacked if course!
Will test this also making a STRUT.
I look forward to see your board photos.
Nice to read that understanding the vital importance that the R wing, stabs, surface area, plan form, wing shape, A o A all play a HUGE role in overall flight performance!
rh

[Zeeko]

Hi

Here is the results of my tests in waves,
I'm very close to Peter's explanation. And like Peter, I dream about hydrofoil in waves (you will never slash a wave like a surfboard, but the feeling of riding waves with an hydrofoil is awesome)

1- I prefer to ride long mast (at least 90cm). For 2 main reasons:
Long mast allows to ride in shallow water with the wings can be deeper in the water
Long mast allows to prevent the board touching the water. When the board touches the water during turns, it stop your turn (as the board starts to be flatter on the water)

2- I love front wing with no anhedral.
Anhedral seems to be good but it is not (except constant anhedral). If you use anhedral only on tips of the wing (with flat part in the center, like the zeeko race wing for exemple, cerbon freeride wing have a constant anhedral) when you turns, the tip of the wing can ventilates more easily when it is close to the surface of the water. Flat wings prevent this

3- I love front wing with thin profil and medium AR
In fact in waves, you have a lot of acceleration and you need to control this increase of power. With a thin profil and medium AR, the power increase is smoother, then you can be concentrated to your turn.

4- I love small back vertical fin. You know there is 2 different back wings: ones with anhedral or dihedral, and the other fully flat. When I use flat wings, for waves I add a 2.5cm height back vertical fin on the back of the fuselage for waves (specially if my front wing is without anhedral). When I ride for freeride, I keep my 4.0cm vertical fin (in order to prevent yaw effect).

When you use small vertical fin + flat back wing and flat front wing, the rotation point of the foil is between the mast and the back wing, which is perfect for turns (the foil turns like a surfboard)

If you use: Front wing with anhedral, back wing flat with no vertical fin, the rotation point is between the front wing and the mast (tacks are easier, but jibes and front turns more difficult, then surf more difficult)

5- I love mast with a smaller cord.
Smaller is the cord of the mast and shorter turn the hydrofoil. 115mm is a maximum for waves (for example, I prefer my carbon mast with a 99mm cord, than my alloy mast with 115mm of cord).

6- I love to ride strapless: when you ride in small waves, usually the water is not deep enough. Then when you turns with speed, you can touch the ground and break something if you keep straps. If you ride strapless, the stress on the hydrofoil is close to nothing because when you touch the ground you fall immediately.

7- I love to ride very small board.
In Waves, I love to ride my 108cmX46cm board (we are in production now). The fact that the board have no nose makes the turns closer. This is due to the fact that the board have no inertia (in fact the inertia center is close to the foil inertia center).
Here below is the green board I use in waves

ride easy
Nicolas

[Peter_Frank]

I think the idea is that he could turn at more of an angle without the blade leaving the water.

Spot on

PF

[philippe 13]

Hi there!

Great brain storming here on what I consider as an amazing feeling : surfing on kitefoil. I mean, true surfing

The Horue H13 is the only foil that has been develloped especially for strapless freestyling and wave. Very light (<1.4kg), short turn, 90cm mast etc..

[Starsky]

The Horue H13 is the only foil that has been develloped especially for strapless freestyling and wave. Very light (<1.4kg), short turn, 90cm mast etc..

I want!

So far ahead of the pack.

[jespin4845]

Hi


In Waves, I love to ride my 108cmX46cm board (we are in production now). The fact that the board have no nose makes the turns closer. This is due to the fact that the board have no inertia (in fact the inertia center is close to the foil inertia center).

When is this board going to be available? I was looking at getting the slingshot dwarfcraft but i feel like my zeeko foil needs that board

will it be completely be padded on top?

Keep up the good work Nicolas

[tegirinenashi]

Is it really wave surfing? Let's compare it with surfboard. When riding a wave we have water surface inclined which provides gravitational force pushing the board forward. Pretty much like ski or snowboard is pulled down/pushed forward the hill slope. Compare it with hydrofoil which dynamics is defined by the forces below water surface, so I can't visualize what is that pushes it forward. Remove the kite power, and it would sink?

Let's examine the issue little more closely. A surfboard on the wave slope is not horizontal. The angle provides a fraction of gravitational force pushing the board forward. Please note that the board is inclined, yet its movement is horizontal. The steeper the angle, the more the force.

Now, the hydrofoil movement has to be horizontal as well, but then the board&wings orientation has to be horizontal too, because hydrofoil dynamics is defined by the lift force of the wing gliding below the water surface. So there is no gravitational force involved altogether. What I see on the video confirms this little theory, as it is essentially a hydrofoil riding in front of the wave.