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twin tip hydrofoil

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wil
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Re: twin tip hydrofoil

Postby wil » Mon Jan 19, 2015 7:21 am

Hi PF. Off topic. I was thinking the same. I will get in serious trouble because this is my daughter's board.

I have a Naish Venturi 2010. it is 58 wide and has a lot more volume than the North LTD. Would this board be ok with a foil????

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Peter_Frank
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Re: twin tip hydrofoil

Postby Peter_Frank » Mon Jan 19, 2015 9:17 am

wil wrote:Hi PF. Off topic. I was thinking the same. I will get in serious trouble because this is my daughter's board.

I have a Naish Venturi 2010. it is 58 wide and has a lot more volume than the North LTD. Would this board be ok with a foil????
It will be good to ride in low wind and especially suited and easy to do non-foiling tacks/jibes yes :thumb:

But the size and volume is maybe a bit over the top if you are average weight.
Maybe even for the North 2010 in my eyes, but it might work for marginal conditions - which was my plan :rollgrin:

8) PF

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Re: twin tip hydrofoil

Postby Tone » Mon Jan 19, 2015 11:45 am

Also, the footstraps will be way off.

They will be set up for riding flat and off the fins, the opposite to what you do with a foil.

Also, the Venturi is a directional, your foil is bidirectional.

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Peter_Frank
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Re: twin tip hydrofoil

Postby Peter_Frank » Mon Jan 19, 2015 3:22 pm

Tone wrote:Also, the footstraps will be way off.

They will be set up for riding flat and off the fins, the opposite to what you do with a foil.

Also, the Venturi is a directional, your foil is bidirectional.
The straps will fit just fine, as you can position the mast where you want to :thumb:

(And there is nothing opposite when you ride a hydrofoil BTW, you still use offset front foot strap for racing)

We are talking about using a directional hydrofoil of course - and as we said, Off Topic....

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davesails7
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Re: twin tip hydrofoil

Postby davesails7 » Mon Jan 19, 2015 7:04 pm

Peter_Frank wrote: The straps will fit just fine, as you can position the mast where you want to :thumb:
I think Tone is right on that. I think this is the board:
Image

The inboard screws of the front foot straps are pretty far off centerline. 3-strap setups for foils usually have the inboard screws less than an inch off centerline.

Also, this board has two rear straps that will need to be replaced with a single centerline rear strap.

There was a thread awhile back of someone converting a Cabrinha raceboard 178x53. He cut off the back of the board to shorten it up.
viewtopic.php?f=196&t=2384919&p=842111& ... ha#p842111

wil
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Re: twin tip hydrofoil

Postby wil » Thu Feb 19, 2015 8:19 pm

I went out in a light wind yesterday with my diy bi directional hydrofoil. It was gusty but enough wind to get on the board. The first time I got on the board the foil jumped up and bucked me off. From then on I tried to just ride the board on the water which was not that easy. A few times when I let the board slowly rise the foil would turn into the wind without me being able to correct and it threw me off every time. I had a good opportunity to get comfortable with the board and foil in the water. Very happy that it all stayed together. I hit the ground a few times at low speed.

Do I need to put some vertical fins on my front and back wings to be able to track straight when the foil lifts up? My front and back fin are straight and have no di hedral or winglets?

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Re: twin tip hydrofoil

Postby revhed » Thu Feb 19, 2015 8:58 pm

Wil,
I wonder how many people have learned to ride a unicycle before a bicycle?
I was not going to reply but that analogy seems perfect to me.
TT, bidi KBHFs at this time are just plain unstable in pitch,roll and yaw!
DIR KBHFs, well designed and built, are very possible to learn on and have fun flying.
Be careful.
R H

wil
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Re: twin tip hydrofoil

Postby wil » Thu Feb 19, 2015 9:10 pm

Revhed. My question was do I need to bolt some vertical fins to my front and back wing to tame down the yaw instability? Since you have experience with bi directional you may be able to suggest a solution. I had a good look at the Hawaiis video and he seems to be tracking straight. My foot straps were loose and I did not have any problems ejecting either windward or leeward.

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Re: twin tip hydrofoil

Postby revhed » Fri Feb 20, 2015 2:28 pm

wil wrote:Revhed. My question was do I need to bolt some vertical fins to my front and back wing to tame down the yaw instability? .
Maybe like this,
P1010003.JPG
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P1010005.JPG
P1010009.JPG
P1010007.JPG
Wil,
I would think it could not hurt.
I will be able to tell you in about 2 months when this TT,BD proto is finished and flown.
I do know from last summer that even more so that DR KBHF the wing mount AOAs and general hydrodynamics are far more sensitive.
This is why I have built the fuse with 4 outer wing mount postitions and used a square alu with a center line for alignment and flatness, 90° control.
The center wing felt to big in chord so I cut it and making 2 different ones and have MANY outer wing options as the hole spacing is standare tt fin so I can use any of my R wings to test.
The alu outer wings are 5mm alu and will be wing tip bent when I get back to my friens with the proper tool to do this.
The outer wings are sim profile and planform but the center is flat bottom, convex top.
Does it fly well or not? is it fun? time will tell....
And it may well turn out to be waste of time?
But I did some first time build systems just to test, like ulta thin tough plastic between the vac saced carbon strut to alu fuse so they do not come in contact but remain tight, strong and replaceable?
If this works then I will build a DR T bar with movable, changeable fuse to test many things.
I WIL mention again, it is mine and a few others feeling that these current design TT;BD KBHFs are very unstable and hard to fly!
RH

wil
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Re: twin tip hydrofoil

Postby wil » Sat Feb 21, 2015 11:05 pm

Revhed,

Thanks for the photo's. I had 2 spare old twin tip fins that I have cut down to fit on to the fuselage. I will put the little fins on the top of the outer wings to see whether that will give me a bit better straight line stability. They will be above the outer wings so I won't break them if I were to touch the ground.

Because I have bolts sticking right through my fuselage I could not put them right at the end. My next one I will not use a through bolt attachment.

At this stage I don't want to change the wing shape yet. I want to try and see whether I can get the board of the water and then start to experiment with different wings. The wings definitely provide upwards lift because if you push the board fast forward it lifts immediately.

As you probably have noticed I can very easily change my fuselage. Just get another piece of very cheap square alu box section and set up for a new trial. Can you explain why Hawaais bi directional looks very stable in all dimensions. He seems to be tracking straight without any huge yaw instability. I made my wings based on his recommendations.

Yes it is fun to try from scratch. I am already surprised the foil did not destroy itself the first time I took it out.

It would be great if some other clever clogs would also try the bi directional concept and start experimenting. I am convinced it is not impossible. If it works there maybe a new set of kiteboarder's taking on foiling and later on progressing to directional foiling.
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