Tuning the Flysurfer Boost v1 9m? Flutter issue.

[foilholio]

The 5kg is something carried over from paragliders to just try make measurement more scientific. It would be likely that flysurfer would use 5kg also for these bridles, 10 to 20kg is just not practical in a manufacturing setting I think. Of note 5Kg will partly restretch some line and you will get more elastic stretch the more force you use. I have found that to target to correct for shrink it is much better to measure bridles, well the thin foil kite bridles, with as little force as required to remove the sag, so maybe 100-200g.

a proof that all attachments are waaay off from the design

They are, but I would be 100% certain that they were exactly on spec when made.

OR the lines shrunk so badly (which I do not believe).

You don't believe lines shrink? Fortunately belief is not required for science, you have the proof in your hands. Maybe you would like to propose global warming had something to do with it?

the line a3 is shorter than designed that would fold the kite at the connection point.

I would think it would distort the LE slightly in such a way the the fabric at that area could be more likely to flap.

The question is how to measure ?

The flysurfer measurements I believe are from the very end of the bridle to the other very end.

We can't take the bridles off

Really? that does not seem likely. Are they sewn to the LE? But anyway it is not necessary to take them off to measure.

May I suggest you just post your measurements as numbers rather than pictures of measuring tapes.

You can just add pigtails to correct the bridles. Use lighter line than the bridle and make the loops with an 8 knot. The strength of the line used when doubled into a loop should be slightly stronger than the bridle. FS usually lists the bridle material, i.e. strength, they used in the line plans.

With foil kites it is often done to just correct the bridles so they are all shrunk the same amount and not to original length.

[downunder]

Mate,

I posted this on Thu Dec 07, 2017

Took you only two years?

The kite is long gone. Exploded. But, you missed that part.

[foilholio]

Well after two years have you realized your misconceptions?

[downunder]

Foil,

The misconception is that on 2m bridle the shrink is 4cm and on 6m bridle is 9cm. That's clear from photos.

Particularly on 1.1mm line FS is using for a back bridle. Sorry. That would mean how much shrinkage on 24m lines? Let's see, approx 4x9cm=36 cm? 6m x 4=24m right? So we multiply 9cm by 4.

Let me know when you find lines which changed length by 9cm, not to mention 36cm.

If they shrink, it is in single % digits. But what FOILS has to do with LEI bridles I do not know....

[Herman]

Interestingly I have recently been surprised a couple of times by the amount of shrinkage I have encountered. Oddly enough the most I found was a discrepancy of ~34cms where the brake lines on a blade had apparently shrunk more than the fronts. The kite had been loned to me by friend who is a good kiter so I expect it was originally in tune but the kite had been sitting in a shed unused for about 10 years.

It would be interesting to have tested line from different sections of a manufacturing run but I have never come across any test data on the subject! It would also be hard to compress the ageing and soiling process to make a quick test...........

Personally i would be happy to have a bit of a flutter and then go out with a bang kitesurfing!! Especially if it was still being talked about for years after!!

[evan]

Let me know when you find lines which changed length by 9cm, not to mention 36cm.

The worst cases I measured are indeed in the 30cm range for the steering lines when they are on the end of their life, abused a lot with almost all coating gone.

But often enough it is in the 10-20cm range for the back lines with normal use, luckily you can stretch them out again to get rid of the worst shrinkage.

[foilholio]

The misconception is that on 2m bridle the shrink is 4cm and on 6m bridle is 9cm. That's clear from photos

Bridles shrink at differing rates. It is possible that there is a production issue that caused differing shrink but you should see that as asymmetry.

Let me know when you find lines which changed length by 9cm, not to mention 36cm.

Most of my rear lines have shrunk by about that much. That is on quite a few kites over many years.

If they shrink, it is in single % digits.

Pulley lines can shrink even 20%.

But what FOILS has to do with LEI bridles I do not know

They use the same materials and are used for much the same function.

luckily you can stretch them out again to get rid of the worst shrinkage.

You can but then you need to keep doing it, better to just adjust and after a while you then need to make no more adjustments.

when they are on the end of their life, abused a lot with almost all coating gone.

Lines shrink in spite of wear and maybe not even because of it, they do it because of a lack of force applied to them. You can buy new lines that have already shrunk depending how long they have sat unused.