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Bridle Shrinkage

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kitexpert
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Re: Bridle Shrinkage

Postby kitexpert » Tue Mar 17, 2020 12:06 pm

I'm not sure why people want to bundle different things together like "long mixer test" does. Ok, it is simple and usually effective but if there is more difficult issues when this kind quick fixes don't help it is better to be more systematic. I mean to find out where issues really exist and to fix them where they are, so not to do some general adjustments which may correct (more or less) the original issue but also develop new issues.

Many new kites (Soul, Hyperlink, Sonic3) have similar line lengths in different parts of the bridle. This makes comparing and measuring those line very easy.

Systematic way to adjust a foil kite is:

1) Check and adjust flying lines. Front/backlines should be equal to a known manner

2) Check and adjust mixer. Pulley lines do shrink a lot. If you have adjustable mixer just adjust it to level. If pulley lines are worn out, replace, they can be 10% shrunk at this stage. If mixer is not adjustable replace pulley line(s) or make your own adjustment system. Mixers are quite simple things, nowadays 1:2:4 two-pulley mixer is a standard and it is not difficult to make one from dyneema line and some pulleys. Mixer length is not at all critical, it just have to be long enough and level.

3) Check the bridle. I always start from the most suspicious lines by comparing them to line plan. This means long thin lines which don't have much load on them, they have the biggest shrink. If differences are found it is best to measure more lines to find out how bad kite is in general and where issues are.

4) Correct shrinkage. There is different ways to do it: 1)to stretch 2)to make adjustments by knots or extensions 3)to replace lines. I suggest stretching for the bridle because it is fast and clean way to do it. With an assistant and doing it from both sides of the kite simultaneously its not that big job and symmetry is remained. After some pulling and referring to line plan you will find out how much force you need to restore original line length. You will also feel how stretching affects, shrunk line gives in and then becomes stiff. Replacing the whole bridle is for sure effective but there is quite a lot work and expenses and it is silly because lines themselves are not damaged.

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Re: Bridle Shrinkage

Postby Adventure Logs » Tue Mar 17, 2020 5:50 pm

kiteykitekite wrote:
Tue Mar 17, 2020 2:29 am
Adventure Logs wrote:What’s your method for the bridle restretch.
I know you didn't address me but a weight through a pulley. I don't usually do it anymore though, as it's quicker and much more permanent to adjust things.
Adventure Logs wrote: Only thing annoying about the long mixer test is you need someone to help you.
I have never done one, but having done much more complicated things I see no reason you couldn't do it solo. 2 ways is to use screw drivers likely 6 to secure ABCZ so black marks align at the kite and then pull against them securing your front and rear main. You adjust B and C as needed to have them right and AZ right. Another way is to secure both front and rear main with screwdrivers. Check and measure A to Z marks. Adjust the front and rear main with measurements. Check AZ marks align then measure BC marks. Adjust BC with measurements. Check and repeat anything you need to.

You do this all on some flat grass ideally under a tree with no wind and the screw drivers go in the ground. You can do it other ways and places.
tkaraszewski wrote: There's no other tuning to be done here, the kite should be tuned correctly, albeit with slightly short steering lines?
The other important thing you are missing is the mixer depower limit. While the LMT seems great it only accounts for the kite at one point in the span and not for other factors like your personal preference and the condition of the kites fabric etc. To account for all of these it is easier to one restore the mixer depower limit or maybe increase it 2 or more cm from standard, do a mixer test, and then adjust Z till you have a kite that flys how you like. You will most likely have to lengthen Z ~10cm, but maybe more or less. I have experimented with increasing the depower limit 5-7cm over standard and the results are very good. It is more important for very light wind. If you have a kite that will sit above you but ends up on the water and won't fly forward, it is because the mixer is not allowing it to depower enough or reduce it's AoA to fly forward. With such an increase you will get interesting effect when the kite approaches it's stall point in light wind, instead of just stalling it will start to drift back deeper into the window. You also get the benefit of more range, through more depower and a faster flying kite. When you increase the depower beyond standard you will notice more depower when flying through the window.
I can’t take advice from you, I don’t know you. Now if it was from my good old buddy foilholio, well that’d be different.

Thanks Tomlutz. I just haven’t done a long mixer yet so don’t know. It looked like I’d need help but I’ll try it out.

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Re: Bridle Shrinkage

Postby Tomlutz » Tue Mar 17, 2020 6:11 pm

Adventure Logs wrote:
Tue Mar 17, 2020 5:50 pm

...

Thanks Tomlutz. I just haven’t done a long mixer yet so don’t know. It looked like I’d need help but I’ll try it out.
It is essential to first align A and Z. You can attach the lines to two screwdrivers just likt Armin did in his video (1:25 - for the short mixer test, but it is the same for the long). I used the pins of a garden fence instead of the screwdrivers.

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Re: Bridle Shrinkage

Postby kiteykitekite » Tue Mar 17, 2020 10:52 pm

If you replace pulley lines for shrink you would ideally be doing it every 10hrs.... Far better to adjust things than replace.

I forgot Armins aligning method it is good too, though it will affect B and C levels. If the pulley lines at not in a tight V they will be shorter, so the adjustments made will be longer.

Honestly though for all the messing around these things aren't worth it. Set the depower limit, and adjust Z a few times and it should be fine.

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Re: Bridle Shrinkage

Postby Ice101 » Tue Apr 07, 2020 5:59 pm

I did a long mixer today on my 9m soul as it’s been flying a little funny. Did the short mixer and all is fine. Did the long mixer and the A line on both sides was coming in about a cm longer on the bridle black marks at the kite.
How do you correct the A line length? Most of the stuff I read shows how to adjust b and c by using the grey loop adjusters on the mixer only. B and c were the same length as z.

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Re: Bridle Shrinkage

Postby jakemoore » Tue Apr 07, 2020 7:02 pm

Line up A and Z in the bridle and pull the mixer tight at the kite connection points. The kite connection points won't be even.

This will make B and C appear shorter.

Lengthen C then B if needed.

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Re: Bridle Shrinkage

Postby Adventure Logs » Tue Apr 07, 2020 8:09 pm

Ice101 wrote:
Tue Apr 07, 2020 5:59 pm
I did a long mixer today on my 9m soul as it’s been flying a little funny. Did the short mixer and all is fine. Did the long mixer and the A line on both sides was coming in about a cm longer on the bridle black marks at the kite.
How do you correct the A line length? Most of the stuff I read shows how to adjust b and c by using the grey loop adjusters on the mixer only. B and c were the same length as z.
You are doing it incorrectly. You need to line up first A with Z and then check B and C. I’d review Armin’s videos a couple more times.

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Re: Bridle Shrinkage

Postby hayes » Tue Apr 07, 2020 8:15 pm

Adventure Logs wrote:
Tue Mar 17, 2020 1:16 am

What’s your method for the bridle restretch.

Only thing annoying about the long mixer test is you need someone to help you.
sorry I missed this reply, bridle restretch involves tying the bridle ends (the metal loops) to a fixed object like a fence post
Spread your kite out with small tension in the bridle your kite should look similar to when it’s spread out waiting for a hot launch

You then grab each bridle attachment point at the LCL and compare it to the opposite side of the kite, I.e do row a first, compare a1 left to a1 right, then a2 and so on. You’ll find some crazy differences even from one side of the kite to the other.
To stretch the bridle put the hook of some luggage scales or a screwdriver through the LCl and pull to a tension of around 10kg, hold for a few seconds.
This will pull tension through the whole bridle as it is attached at the mainline attachment point. Always go through the LcL as if you snap an lcl you can replace instantly, if you hook and snap the bridle line you have to replace the actual bridle section if you have any spare bridle material. Then check this against the un stretched, you should find it’s stretched 10-40mm, obviously stretch the unstretched one to match

Do this for the entire kite, along all pairs of attachments on all rows
You’ll find the attachments at the tips and the Z row shrink most

I’ll get some photos tomorrow will make it a lot clearer
I did have a full run down on Foilzone before it disappeared off the internet

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Re: Bridle Shrinkage

Postby Ice101 » Tue Apr 07, 2020 8:53 pm

Adventure Logs wrote:
Tue Apr 07, 2020 8:09 pm
Ice101 wrote:
Tue Apr 07, 2020 5:59 pm
I did a long mixer today on my 9m soul as it’s been flying a little funny. Did the short mixer and all is fine. Did the long mixer and the A line on both sides was coming in about a cm longer on the bridle black marks at the kite.
How do you correct the A line length? Most of the stuff I read shows how to adjust b and c by using the grey loop adjusters on the mixer only. B and c were the same length as z.
You are doing it incorrectly. You need to line up first A with Z and then check B and C. I’d review Armin’s videos a couple more times.
We were watching Armin’s videos but they still aren’t that easy to follow. Will try again tomorrow and see if it needs adjusting. It was because when doing the short mixer it said to line up the knots at the start of the yellow lines so that is where we were putting tension on it and working from. I take from the other comment above to do the long mixer we should of be lining up the black marks at A and Z on the canopy end and then just tensioning them at the bottom of the bridle regardless of where the knots are now at the ends of the yellow ones then try B and C. Will try again tomorrow.

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Re: Bridle Shrinkage

Postby TomW » Tue Apr 07, 2020 11:01 pm

I have 200 + hours on my 9m foil kite. I have same bar and lines the whole time, and I've not adjusted anything, or done any maintenance except wash it 2 times after vacations in salty locations. It flys like new.


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