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Problems with incorrectly set bridles

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Herman
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Re: Problems with incorrectly set bridles

Postby Herman » Sat Jun 15, 2019 6:29 pm

Normally I would describe the sections of a bridle as left main, right main, and brakes. The brakes are the lines at the trailing edge often called row Z. The brakes can be split left and right to 4 line handle control, or grouped to a 3rd line for bar control. The main bridles have rows of attachments, front is A , then B, C etc.

Each element of right main bridle is likely to be different in length but the same element of the left and right should be exactly the same length to within whatever tolerance the manufacturer can achieve in production. I don't have any data on manufacturers tolerances but I would think +/- 5mm would be generous.

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Re: Problems with incorrectly set bridles

Postby Herman » Sat Jun 15, 2019 6:39 pm

A 250mm difference means that the bridle element is entirely wrong. If you have flown kites you will know that 25mm of pull on the flying lines will cause sufficient asymmetry to make the kite turn. 1 element of a bridle effectively missing may well make this size of kite unflyable imho!

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Re: Problems with incorrectly set bridles

Postby Herman » Sat Jun 15, 2019 7:08 pm

One thing I would add is that when you lay the kite on the living room carpet and just lift the bridle I would have thought a 250 mm disparity should be reasonably obvious either as a cloth pyramid or sagging line.

Make it 2 things! When I referred to +/- 5mm as generous I was referring to each individual length of line that makes up the bridle elements. Given the difficulty in measuring a bridle accurately without disassembly your 20 mm differences may well not be a problem.

Are your flying lines the same length??
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knotwindy
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Re: Problems with incorrectly set bridles

Postby knotwindy » Sat Jun 15, 2019 11:38 pm

Yes

Herman
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Re: Problems with incorrectly set bridles

Postby Herman » Sun Jun 16, 2019 12:18 am

Knotwindy's answer is good too but I am killing time at the moment. Shorten the long one or put an extension in the short one, whichever makes it look right and test it if you don't want to just send it back.

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Re: Problems with incorrectly set bridles

Postby Herman » Sun Jun 16, 2019 8:39 am

In an ideal world manufacturers would publish their bridle drawings and amendment states on a website. Then you could easily check your bridle. Instead of relying on side to side comparison etc.

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Re: Problems with incorrectly set bridles

Postby Ittiandro » Thu Jul 04, 2019 2:03 am

The attachment IMG_0001.jpg is no longer available
IMG_0001.jpg
The attachment IMG_0001.jpg is no longer available
Herman wrote:
Sat Jun 15, 2019 6:39 pm
A 250mm difference means that the bridle element is entirely wrong. If you have flown kites you will know that 25mm of pull on the flying lines will cause sufficient asymmetry to make the kite turn. 1 element of a bridle effectively missing may well make this size of kite unflyable imho!
Thanks HERMAN

I attach the manufacturer's specs for the bridles' lengths. The hand-written lengths besides each bridle are the actual measured lengths .
I am pretty sure that b2 on the red side ( 1210 mm) is 250 mm shorter than the specs length of 1525 mm). Even on the blue side, b2 is still shorter, but only by. 65 mm
For the other bridles,too, differences in length do exist, both as compared to the specs and also between right and left sides. Depending on the bridles, these differences range between 20-60 mm. Aside from the b2, shouldn't 10-60 mm difference affect the kite?

Does the length of the bridles determine the angle of attack of the kite? I have a hunch it does, but I don't quite understand how. May be, if my measurements are correct, the angle of attack may be completely off, on account of this: either too steep ( stall) or too small, or( even negative ! Add to this the length differences between the two sides!

Any comments ?

Thanks

Ittiandro

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Re: Problems with incorrectly set bridles

Postby Ittiandro » Thu Jul 04, 2019 2:28 am

Herman wrote:
Sun Jun 16, 2019 8:39 am
In an ideal world manufacturers would publish their bridle drawings and amendment states on a website. Then you could easily check your bridle. Instead of relying on side to side comparison etc.


Ref my post a moment ago. I had problems with the 2nd attachment. Hre it is
Attachments
CS_BRIDLE HYDRA 2.pdf
(116.47 KiB) Downloaded 6 times

Herman
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Re: Problems with incorrectly set bridles

Postby Herman » Thu Jul 04, 2019 9:42 am

Simplistically :

I would expect asymmetric bridle variation to cause kite rotation. Isolated bridle element error to cause a bump or dip in the camber shape. Errors in the outer elements will effect the shape of the arc etc. Angle of attack is also critical and is controlled by the bridle by the difference in line length of each row. Fails in practice will have interrelated effects!

I do not have much experience measuring bridles but I would be asking the vendor to replace the bridle if your measurements are accurate. If second hand I would price up a replacement bridle. The bridle errors are considerably higher than I would expect them to be. If you research mixer tuning you will see how variable bridles control camber, arc, and angle of attack. You can then interpolate this info for your fixed bridle.

As an aside I will give you 2 examples of my experience:
Bought a cheap 2 line fixed bridle foil with simple 3 row bridle, virtually unusable as it kept hindenburging at window edge. Put a 15mm extension in the A group on both sides and it fly's ok.

2m Pansh legend 4 line on handles prone to hooking a single bridle element around flying line larks head effectively shortening it by ~150mm. Kite can be flown with compensation at the handles but performance is horrible and you know something is wrong.

From the photos your kite looks like it deserves a new bridle. I am new to this forum but you will encounter bridle experts if you research mixers and you may find it worth consulting one or more of them.

Afterthought, Also note that line shrinks particularly if left unused and minor shortness can be corrected by stretching. Good Luck.
Last edited by Herman on Thu Jul 04, 2019 3:29 pm, edited 2 times in total.
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Herman
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Re: Problems with incorrectly set bridles

Postby Herman » Thu Jul 04, 2019 3:12 pm

On further reflection regarding the variation from the design spec, if the red B2 was corrected I would expect the kite to fly ok-ish. Therefore, if it is second hand I would replace red B2 and fly it. Then attempt to retune the bridle by careful stretching if I thought its performance needed improvement. But please bear in mind that I have limited experience in tweaking bridles and so you might want to get a more experienced bridle tweaker to comment!

P.S. Don't load the canopy cloth when stretching the bridle!


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