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backstall on smaller kites

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neilhapgood
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backstall on smaller kites

Postby neilhapgood » Wed Sep 25, 2019 9:33 am

Hi all, since foiling and using smaller kites in less wind I find I really suffer from backstall when getting out the water and on the foil on a 5m and 7m, sometimes takes a few attempts to get going, if I pull on the bar at all they just stall, far more than my 9m. Am I on the wrong kites, bad technique or part of the fun!

using an old rebel 7m, 5m neo and 9m fone breeze.

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Re: backstall on smaller kites

Postby lederhosen » Wed Sep 25, 2019 9:48 am

I recognized the same on my 5m Cabrinha Radar from 2015. Since it is my smallest kite I often ride it a bit overpowered and so I guessed the small frame of the kite deforms more under the load.

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Peter_Frank
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Re: backstall on smaller kites

Postby Peter_Frank » Wed Sep 25, 2019 10:18 am

neilhapgood wrote:
Wed Sep 25, 2019 9:33 am
Hi all, since foiling and using smaller kites in less wind I find I really suffer from backstall when getting out the water and on the foil on a 5m and 7m, sometimes takes a few attempts to get going, if I pull on the bar at all they just stall, far more than my 9m. Am I on the wrong kites, bad technique or part of the fun!

using an old rebel 7m, 5m neo and 9m fone breeze.

It is normal, almost just part of the fun! Or challenge at least :roll:

It is the same with the big kites actually, just not as evident maybe?

Because most of us ride with a given kitesize in a lot less wind when on hydrofoils, they have to be flown at a lower aoa most of the time.
Just like you do on "other" boards in really light wind, you depower the kite to get it to fly and give power, instead of choking the kite and backstalling.


In light wind with a small kite on a hydrofoil, the depower stroke is extremely short, so two things happens:

1. You forget to use a different trim for hydrofoiling, meaning more depower trim/longer rear lines for the sweetspot.
2. Even if you get the right trim, the small kites will be extremely sensitive to oversheeting compared to the bigger ones, so with a short stroke and you not feeling feedback, you have to learn to fly your kite.

#1 above is one of the reasons I never use the same bar for hydrofoils and other boards, very different default trim (apart from different line lengths)

So no, it is not because it deforms under load IMO, on the contrary, there almost IS no load, when hydrofoiling, where you can use a much smaller kite with small kites than the equavalent power, because of their amazing peak power when looped, compared to bigger kites.

8) Peter
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neilhapgood
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Re: backstall on smaller kites

Postby neilhapgood » Wed Sep 25, 2019 10:37 am

thanks Peter, so does that mean that you have to slowly increase your AOA as you generate kite and board speed but worker harder initially to get to that point?

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Re: backstall on smaller kites

Postby slowboat » Wed Sep 25, 2019 11:09 am

How much back stall you have is often a matter of personal preference. Some people like to use back stall to "depower" their kites and then sheet out to get power back. Opposite of how we all learned but works very well for those who use it regularly.

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Re: backstall on smaller kites

Postby Peter_Frank » Wed Sep 25, 2019 1:03 pm

neilhapgood wrote:
Wed Sep 25, 2019 10:37 am
thanks Peter, so does that mean that you have to slowly increase your AOA as you generate kite and board speed but worker harder initially to get to that point?
Not really no...

Because, when no board speed you have so light wind that you need the depower, to get power, we agree.

But once up, the apparent wind kicks in, and it will mostly match spot on with the depower you got ("hydrofoil" trim setting) in my experience, so you can ride without changing trim really.

Of course, if you wanted to go max speed or jump or deep downwind, you should power up more (just not for going upwind, where you need the high L/D you get when depowered some).

But for normal riding where you dont want to get out of control, my experience is you will be fine with the kite depowered somewhat (compared to other "old" boards), all the time.

Especially because when carving downwind, you go a lot more with the wind than on other boards, so your apparent wind gets really low, thus you need even more depower for the kite to fly around in the carve, without backstalling.

If you are relatively new into foiling, you might also carve in really wide arcs, as tight carves comes later - thus with wide arcs you need even more depower, for the kite to fly.
So much it can often be difficult to keep it turning, and it might end in the drink when learning to carve the first times :naughty:

slowboat is right, backstall "level" is a personal preference, all my kites will backstall if I pull the bar all the way in, also when powered on a surfboard or other board - thats how I like the trim.
Others want their kites to behave so they just pull the bar fully for max power, without risking collapsing or backstalling kites, personal preferences only :D

8) Peter
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Re: backstall on smaller kites

Postby junebug » Wed Sep 25, 2019 2:02 pm

I trim the kites I use for foiling the same as Peter. I like being able to kill power, particularly when looping, and, because I use the same bar for all of my kites, the same technique results in more backstall for smaller kites, particularly 3m, 4m, and 5m. I like flying underpowered anyway (5m at 14kn, 4m at 17kn, 3m at 20kn), so the waterstart can be a challenge, particularly on a pocket board without rocker. I just have to focus on keeping the back lines long by keeping the bar pushed out during the waterstart and reaches where I need power.

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Re: backstall on smaller kites

Postby jakemoore » Wed Sep 25, 2019 5:01 pm

Smaller kite are more sensitive to bar movements and therefore short rear lines create a bigger backstall.

Consider also some small kites are designed for nuclear wind and I have had one in particular that flew like a turkey in hydeofoil or kid kitevoarding strength winds.

Finally some kites do well with backstall stunt kite style flying like Peaks and Clouds . Others not so much.

Boxer is a kite I particularly like in small sizes. But the lines still need to be tuned right. There are better choices for backstall stunt kiting and I trim Boxer for zero backstall.

Bigger kites tolerate detuned lines better.
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Re: backstall on smaller kites

Postby TomW » Wed Sep 25, 2019 9:12 pm

I'm totally new using 4,5 m foil kite. I figured out how to get up on it without looping.
I position kite in opposite direction of launch direction, fairly low , feet on board and keep kite powered, then direct kite aggressively in pivotal turn to zoom across wind window, direct kite up about 3/4 across window as I pop up, head more offwind than normal, then redirect kite into one sine to get moving.
I found I was trying to pinch upwind like I do on my 7m and kite is driving to wind window edge and loses power. By heading more off wind kite stays back more providing more room in window to sine.
Just learning, but think it helps to share the early experience before it becomes automatic.

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Re: backstall on smaller kites

Postby Regis-de-giens » Wed Sep 25, 2019 9:20 pm

I fully agree with Jakemoore explanations.
Just turned another way, with a bit of theory: on a small kite the chord (distance perpandicular to the span) is lower, so the same AoA angle variation needs less bar stroke centimeters on a smaller kite. As a consequence, when the middle of the stroke of the bar (say 30 cm.from chicken loop ) is set to you comfort position during the ride, then, when you sheet in 20 cm, the smaller kite will get more AoA so more prone to backstall. Solution is to force yourself moving with less amplitude with the bar, knowing that you will get higher AoA variation with only 15cm sheet in for example. Anoþher solution is to trim more and thus acccept to get your compfort zone closer to your body during the ride vs a larger kite.

You can add the fact that a smaller kite is generally heavier per square meter, so it will also give more backstall
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