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Speedbrake for going downwind

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rynhardt
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Speedbrake for going downwind

Postby rynhardt » Mon Mar 02, 2015 8:55 pm

Has anyone considered employing a retractable speedbrake for going downwind? :o

Something that remains streamlined on a reach but can be activated with a lever on the downwind run, and then returned back to streamlined.

I can think of various mechanisms, and have invested several minutes drawing one of them below.

Here we have a red line runninng through the mast and fuselage and attached to some kind of hinged flappy arrangement. The little flaps are returned to a streamlined shape by a spring of some kind. The line is activated with a lever - foot or hand operated.

This will hopefully provide a net zero lift but with appreciable drag. And positioned some distance behind the rear wing.

You could expand the flaps horizontally instead of vertically, or have 4,6,8 flaps.
You could use a springy material and forego the spring and hinges.
You could inflate/deflate a piece of rubber with one of those small CO2 canisters.
You could attach a pet blowfish and tickle it with a small electric current.
So many possibilities..

Worth investigating or mere mental masturbation?
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Re: Speedbrake for going downwind

Postby BWD » Mon Mar 02, 2015 10:38 pm

I thought of that idea a few years ago too, nobody seemed interested. Not sure if it's a good idea, but a simpler way to do it would be a line that trailed behind the fuse, or maybe some much smaller projections from the back of the fuse.
The illustration looks like something to use in air more than water, if considered roughly to scale.
If you are going to incorporate variable geometry though, might as well figure out how to make useful flaps on main wing or change AOA of the stab on the fly, instead of just a brake. Then you could do lots more, to judge by the foiling sailboats out there...

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Re: Speedbrake for going downwind

Postby edt » Mon Mar 02, 2015 10:44 pm

Don't you just make sure you don't point too far downwind? I must be missing something I always figured an anchor makes you go slower VMG.

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Re: Speedbrake for going downwind

Postby RedSky » Mon Mar 02, 2015 11:04 pm

This might sound a bit strange but have any of you kiteboarders tried flying directly downwind or as near to directly downwind with the kite flying in the other direction?
I rarely get to try it in the buggy and I discovered it by accident, but when the tide is far out and I have the space, I can ride back to camp at a fairly reasonable pace using this method. The trailing edge facing in the direction of travel.

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Re: Speedbrake for going downwind

Postby Peter_Frank » Mon Mar 02, 2015 11:33 pm

Interesting, but a bit confused about one thing, WHY ?

When you go downwind your speed diminishes, thus much easier to ride going very deep, and this is what you do if you feel you go too fast downwind, but still want to go downwind (home ?) as good as possible.

In fact, when you do this, you can, might even have to, sinus or loop the kite, as otherwise it will have no power and you might stall the hydrofoil because of lack of speed :o

If you go halfwind or on a broad reach, THEN you will get in trouble easy, if not used to it - indeed.

But you can easily avoid this by going deeper till the kitepower and speed goes "away" :D

Or, fly the kite up higher, slowly, to decrease speed, if on a reach going too fast for your liking.
(PS: One more reason why NOT to use non depower C kites that sits deep, as then this easy step becomes difficult almost impossible for some :( )

8) PF

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Re: Speedbrake for going downwind

Postby gmb13 » Mon Mar 02, 2015 11:44 pm

As Peter is asking: Why??

Why would we need a brake when going own a deep reach? Do you feel that you have a lack of control when reaching on your current foil?

I found that by having a wing with good L/D and a well tuned rear stabiliser its really easy to go downwind deep at any speed you want without too much of a risk of loss of control or stall.

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Re: Speedbrake for going downwind

Postby cglazier » Tue Mar 03, 2015 6:27 am

Peter and Gunnar have said it well.

When going downwind too fast you can reduce your speed by pointing even more downwind. Or you can bring your kite up slowly overhead. Do not try to go more upwind or your speed will increase.

Good hydrofoils go downwind very fast and in control. Others just misbehave. If you ride a simple recreational foil then that may be your limiting factor.

:wink: CG

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Re: Speedbrake for going downwind

Postby rynhardt » Tue Mar 03, 2015 7:57 pm

Yeah Gunnar - the problem is lack of control.

But if this is not an inherent issue with foiling then that's great news for me and I can work on my progression, i.e. a better foil and more practice..

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Re: Speedbrake for going downwind

Postby gmb13 » Tue Mar 03, 2015 9:54 pm

Can you be a bit more specific on what your problems are with control on your downwind legs? What is happening.

Pitch or Roll Stability? Nose Down?

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rynhardt
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Re: Speedbrake for going downwind

Postby rynhardt » Wed Mar 04, 2015 8:44 pm

The problem is not so much on a reach but mostly when running directly downwind.
I tend to overtake the kite, the lines go slack and it drops out of the sky - my kite does not drift very well.
I'm not sure if flying the kite higher will help, my gut feeling is it will hindenburg and cause all kinds of mischief if I overtake it when it's higher in the window.

So the problem is that I can't keep a downwind course without going too fast and I have no way of braking. I suppose I could turn upwind a bit to get tension back in the lines but that kinda defeats the purpose.

On my TT I'm used to just digging in an edge to put on the brakes and load up the lines, but I don't see how I can do that on the foil..


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