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Trick to keep foil kite from stalling

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Kitemanmuc
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Trick to keep foil kite from stalling

Postby Kitemanmuc » Tue May 02, 2017 11:36 pm

Im new to foil kites and while I admit, both times I have been out with the kites, it was very low wind conditions, i cant seem to keep the kite from stalling at some point. I have however gotten really good at self rescue. Anyone have tips on how to keep a foil kite flying even in the lowest of wind. Pump kite i never have an issue, but foils is a new game.

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Re: Trick to keep foil kite from stalling

Postby overboard » Wed May 03, 2017 8:43 am

If you mean back stalling then just grab the front lines and pull them in.

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Re: Trick to keep foil kite from stalling

Postby gmb13 » Wed May 03, 2017 9:06 am

If the kite is not new, you might want to check your lines and brildes. A lot of times the back lines (steering lines) are too short. Also the mixer/speed system might have shrunk which will make the kite very backstally.

If the kite is new, then you might be chocking the kite by pulling in the bar before the kite has time to accelerate and build up speed for apparent wind. So make a foil kite pull you in those super light wind sessions you need to let it fly, eg. push the bar forward to let the kite accelerate and "grab" the wind.

--
Gunnar

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Re: Trick to keep foil kite from stalling

Postby Kamikuza » Wed May 03, 2017 9:09 am

And trim it so you can't back stall it at the bar. Yes, "depower" the kite for light wind power ;)

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Re: Trick to keep foil kite from stalling

Postby socommk23 » Wed May 03, 2017 10:54 am

As above. Depower the kite for light wind conditions....reduces aoa and allows it to fly quicker giving the power needed.

Otherwise just remember every kite has its limits. If the wind is not enough to give it the airspeed needed....its unlikily to fly well if at all.

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Re: Trick to keep foil kite from stalling

Postby Pump me up » Wed May 03, 2017 12:19 pm

Ram air kites are highly prone to stalling. Below are some of the reasons for this problem, along with helpful suggestions on how to deal with the stalling issue:
After several weeks of use, ram air bridles typically stretch and deform, further compromising aerodynamic performance: viewtopic.php?f=1&t=2358958&start=0
Kamikuza wrote:Have you done a mixer test and checked your SPL length? SPL = spare parts line = the bright yellow lines that go through the pulleys... they can shrink A LOT and bork up the handling…
joffaburger wrote:Moved to a foil kite 5 years ago (flysurfer pulse 10m)... I found after 6-9 months that the RAM started performing very poorly especially in gusty conditions I assume this was due to bridle stretching, I did manage to trim the bridle regularly to what I thought was intended spec however as already stated these are complicated bridles with many attachment points and I'm not sure if I did a perfect job! In the end I couldn't get the kite to feel anywhere near how it performed during the first 3 - 6 months of it's life. I think the kite and the bridles became quickly blown out...The kite was expensive and an attempt to resell the kite at half its purchase price failed...
gmb13 wrote:
plummet wrote:Hey bro's. I'd like to make my speed 3 less stally. Apart from resetting the mixer what else do you recommend?
Is it simply a matter of lengthening the rearlines or shortening the front?
Should I lengthen the Z line abit?
I am assuming a few things:
1) You have reset the mixer to 0
2) You have compensated for Back line shrinkage by shortening your front lines using the Black Line above the adjuster. Front and Back lines should be the same length when the Adjuster is fully open and the bar is pulled all the way down to the chicken loop. Best to tie up the end of the lines to a tree or other solid stationary object to test this.
So. If the kite is still to backstally, try lengthening C. B will adjust itself harmonically by itself. This will sacrifice a bit of stability, but will give you less backstall. Lengthing Z will just make the kite turn slower and will also reduce the Low end of the kite.
Gunnar
For the complete discussion on the diabolical problems associated with "resetting the mixer", "compensating for line shrinkage", "adjusting the adjuster", adjusting lines "C", "B", & "Z", & trying to stop RAM AIRS from back stalling, check out: viewtopic.php?f=1&t=2378918&p=778491#p778491

Alternatively, you could just trade-in your flying sleeping bag for an inflatable and save yourself the trouble.
:pump:

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Re: Trick to keep foil kite from stalling

Postby socommk23 » Wed May 03, 2017 12:36 pm

Pump me up wrote:
Wed May 03, 2017 12:19 pm
Ram air kites are highly prone to stalling. Below are some of the reasons for this problem, along with helpful suggestions on how to deal with the stalling issue:
After several weeks of use, ram air bridles typically stretch and deform, further compromising aerodynamic performance: viewtopic.php?f=1&t=2358958&start=0
Kamikuza wrote:Have you done a mixer test and checked your SPL length? SPL = spare parts line = the bright yellow lines that go through the pulleys... they can shrink A LOT and bork up the handling…
joffaburger wrote:Moved to a foil kite 5 years ago (flysurfer pulse 10m)... I found after 6-9 months that the RAM started performing very poorly especially in gusty conditions I assume this was due to bridle stretching, I did manage to trim the bridle regularly to what I thought was intended spec however as already stated these are complicated bridles with many attachment points and I'm not sure if I did a perfect job! In the end I couldn't get the kite to feel anywhere near how it performed during the first 3 - 6 months of it's life. I think the kite and the bridles became quickly blown out...The kite was expensive and an attempt to resell the kite at half its purchase price failed...
gmb13 wrote:
plummet wrote:Hey bro's. I'd like to make my speed 3 less stally. Apart from resetting the mixer what else do you recommend?
Is it simply a matter of lengthening the rearlines or shortening the front?
Should I lengthen the Z line abit?
I am assuming a few things:
1) You have reset the mixer to 0
2) You have compensated for Back line shrinkage by shortening your front lines using the Black Line above the adjuster. Front and Back lines should be the same length when the Adjuster is fully open and the bar is pulled all the way down to the chicken loop. Best to tie up the end of the lines to a tree or other solid stationary object to test this.
So. If the kite is still to backstally, try lengthening C. B will adjust itself harmonically by itself. This will sacrifice a bit of stability, but will give you less backstall. Lengthing Z will just make the kite turn slower and will also reduce the Low end of the kite.
Gunnar
For the complete discussion on the diabolical problems associated with "resetting the mixer", "compensating for line shrinkage", "adjusting the adjuster", adjusting lines "C", "B", & "Z", & trying to stop RAM AIRS from back stalling, check out: viewtopic.php?f=1&t=2378918&p=778491#p778491

Alternatively, you could just trade-in your flying sleeping bag for an inflatable and save yourself the trouble.
:pump:
Can someone please do us all a favour and ban this waste of oxygen!
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joriws
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Re: Trick to keep foil kite from stalling

Postby joriws » Wed May 03, 2017 1:29 pm

With high performance foil kite best option in ultra-low-wind (single digit true wind in kn in my terms) would be active flying. "Let it breathe" like gmb13 states.

If you are just flying it with front-lines only below 10kn on window edge they are more affected by wind direction shifts and holes/turbulence in the air and experience poor behaviour of the kite. This depends a lot on kite model you are having.

When active flying you can also dive with more speed and continue to downloop if required for power impulse to get on board and accelerate to planing speed. On ultra-low-wind it is very important to know "sweet spot" of your foil kite. The bar depower range (without trim) is usually so large that with 40cm of travel (Flysurfer standard trim) you can have from no-power to max-power and to backstall. Kite rushing through air is apparent wind and effect on it for power level is much more than static flying in true wind only but with higher angle of attack (AoA).

Conceptually you need to understand this that you should fly at sweet spot of maximum lift which is determined by speed polar of your airfoil. So don't oversheet beyond that point because it will reduce the power output and slow the kite down until it stops in the air and backstalls.

You need to learn to control lift&drag co-efficients to your maximum benefit. As you see on example pic of polar of airfoil beyond 18 degrees AoA lift starts to reduce but drag still increases. Never fly in this zone (AoA > 18 on example pic) or you have the results described. Stall could happen on AoA 24deg because drag coefficient ends there.

So actually Kamikuza/Socommk23 tip of using trim strap to trim backstall out is in other terms taking bar travel away that you cannot enter >18 degrees AoA. But at absolute lift co-efficient top is no the best spot to run but little left from there as drag is increasing to right so little to left you have more flying speed with only little less lift co-efficient. So squared power from flying velocity wins linear increase of lift. "Let it breathe".

That is the theory in simple form. Then when riding with speed you get the wing loading which shifts the speed polar curves on velocity coordinates and you need to optimize that by direction of travel to gain best possible forces. But it is very complex and I don't know if anybody has done thesis level examination of this. So let's stick with simple theory.. :)

Image

With understanding above it is easy to outperform 17+ m LEI kites in ultra-low-wind with only 15m foil kite. On today the difference is even bigger with better L/D race foil kites. I've dropped my low end by 1kn with switching Flysurfer Speed4 (in below video) to Sonic. And I am 100kg+ / 240lbs+ where as LEI "flyers" were 20-30kg lighter.
https://www.youtube.com/watch?v=5CxSGhN4iPc
Last edited by joriws on Wed May 03, 2017 1:40 pm, edited 1 time in total.

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alexrider
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Re: Trick to keep foil kite from stalling

Postby alexrider » Wed May 03, 2017 1:37 pm

Pump me up wrote:
Wed May 03, 2017 12:19 pm
Ram air kites are highly prone to stalling......
bla bla bla bla
bla bla bla bla
bla bla bla bla

Can someone please do us all a favour and ban this waste of oxygen!

No way! PMU :dumbo: , who looks like the kite village idiot, is too precious to the community. He is actually an agent for major Ram Air kite manufacturers. He's doing all what is required to bring the attention to foil kites and nobody actually believes a word of what he says. But his work isn't necessary anymore, since foils have finally conquered the place they deserve in the kite market.

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Kamikuza
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Re: Trick to keep foil kite from stalling

Postby Kamikuza » Wed May 03, 2017 1:46 pm

joriws wrote:
Wed May 03, 2017 1:29 pm
So actually Kamikuza/Socommk23 tip of using trim strap to trim backstall out is in other terms taking bar travel away that you cannot enter >18 degrees AoA.
That's only the case in kites where the bar solely controls AoA though . . .


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