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Author Topic: What level of spine/trailing edge reinforcement is reasonable?  (Read 772 times)
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arglebargle
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« on: October 09, 2018, 02:00 AM »

I'm building a sixth sense STD specifically, but I'm sure the topic is more general- what level of reinforcement is reasonable?

I see some people applying a 1" strip of mylar the complete length of the back of the spine, some including a full length strip of dacron on the front as well, and some doing neither as far as I can tell, all on the STD sixth sense.

Similarly, some use dacron on the trailing edge with leech lines, some just use spinnaker with two stitched seams, some use spinnaker but with what looks like a layer of dacron for several inches near where the standoffs connect, in addition to the specified mylar.

So is the extra weight of those sorts of reinforcements going to matter?  Would missing them mean a shorter lifetime for the kite?  Are there other factors beyond those two?  Maybe the answer to both is "Kind of, but it's hard to measure", but seeing multiple experienced kitebuilders making different decisions on the same design and the plans not really saying one way or another, I was hoping I could get some sort of a push or some background on what led to their decision so it was a bit less of a coin flip from my point of view.
« Last Edit: October 09, 2018, 10:05 AM by arglebargle » Logged
KaoS
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« Reply #1 on: October 09, 2018, 04:33 PM »

The spine is usually held under a fair amount of tension, so the strip of mylar down the spine area prevents that part of the sail from stretching over time.

When lying on its back, the trailing edge of a sport kite touches the ground at the standoffs.  If you get a wing wrap, or if you launch aggressively from that position, the trailing edge is dragged along the ground.  This will easily damage that part of the trailing edge and the leech line, especially on rough surfaces such as dirt or sand. Dacron reinforcing over the trailing edge tunnel prevents the trailing edge from wearing through.

I use 1.5 oz spinnaker tape for the trailing edge tunnel, a durable but flexible material for that purpose.

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Kevin Sanders

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Krijn
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« Reply #2 on: October 10, 2018, 12:12 AM »

Spine:
Some brands/builders use indeed a strip of mylar, and some (big ones) don't.
It looks neat.
I personally normally don't use it. Only for a kite that will take more beating than a "normal" kite, like a strong-version or a vented. Or also for a beginnerskite. (Or a speedkite, but I only build trickkites.)
If the designer himself uses it, I will almost ever also use it. Like the Return for example.
Hmm, Davide Equizzi did use it, right? I never do it on a Sixth Sense... So forget my last remark Smiley
I don't think the kite will fly any different.

Trailing Edge:
If you'll only use spinnaker here, it will definitely will wear out on a trickkite. Not only because - as Kevin said - it makes contact to the ground, but even more because of the yoyo's and multilazies!
I make the trailing edge of spinnaker tape and make a dacron strip of about 30-40cm from 5cm outside the outer standoff and the rest to the tail. That bit will be a bit longer, but there will the flyingline (or better: the leader) be when the kite is on its back.
On super ultra lights I make the dacron shorter, around 20cm.
I almost always put a leechline in a kite (an adjustable one with a bungie around the centre cross).


Good luck with the build!
Krijn
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arglebargle
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« Reply #3 on: October 11, 2018, 05:27 PM »

Great, thank you both, it's particularly useful to know that the extra trailing edge stuff is for wear and not for strength, since that means I can build on the light side there and watch for wear.  I'll do some introspection about whether I'd classify myself a beginner as far as the mylar on the spine goes, but I guess you can't undo stretching.
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Ca Ike
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« Reply #4 on: October 13, 2018, 09:09 AM »

When it comes to reinforcement a lot depends on the material and the direction of the bias in the cloth.  If I use nylon for a kite sail then the spine, trailing edge definitely get mylar backing even if the bias is positioned right because nylon stretches easily.  Icarex goes either way but usually gets mylar at the standoffs and dacron as well at any high wear spots.  As far as weight goes, unless its an SUL it doesn't make enough of a difference to matter.
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