GWTW Forum

Kites! Kites! Kites! => Single Line Kites => Topic started by: thief on February 27, 2014, 07:36 AM



Title: might have to try this out for indoor kites...
Post by: thief on February 27, 2014, 07:36 AM
Over on kitebuilder there was a discussion on kevlar lines for big single line kites....and Twinline was suggested as a place to get kevlar and other material lines....
wandered around on the website for a bit and found that they have some 18# test kevlar line that might be good for indoor flying....getting a sample to check out...
http://estore.twinline-usa.com/collections/kevlar/products/kevlar-49-20-spools1-lb-lot (http://estore.twinline-usa.com/collections/kevlar/products/kevlar-49-20-spools1-lb-lot)
any tension would turn this into a garrotte and slice a finger off...but indoor flying on a iFlite, Hawk, etc would probably be just fine......


Title: Re: might have to try this out for indoor kites...
Post by: Allen Carter on February 27, 2014, 09:12 AM
What benefit would it provide over more mundane materials?


Title: Re: might have to try this out for indoor kites...
Post by: thief on February 27, 2014, 10:48 AM
i have been using just any old line that i have lying around (sometimes 150# was used ;) )...was thinking about actually getting some dedicated NEW line to have....
that stuff would cost about .006$/foot for the small roll......


Title: Re: might have to try this out for indoor kites...
Post by: Allen Carter on February 27, 2014, 11:36 AM
But does it have characteristics better suited than spectra/dacron/button thread/dental floss.....?

Seems like each person has their own likes when it comes to indoor line. I prefer how something feels in my hands to how tangle free it is, for instance. Some think weight is the only issue regardless of it being impossible to see/grip/tie, etc.

Not ever having handled kevlar line, I'm wondering what it does different than the alternatives. (my spool of button thread still has a ways to go...)


Title: Re: might have to try this out for indoor kites...
Post by: thief on February 27, 2014, 11:56 AM
yep...that is why i have samples coming...want to see what it is like.........let you konw!


Title: Re: might have to try this out for indoor kites...
Post by: Allen Carter on February 27, 2014, 02:54 PM
I'm sure I'd step on the line and cut the tip of my finger off or something.  ???


Title: Re: might have to try this out for indoor kites...
Post by: ae on February 27, 2014, 06:32 PM
You know, a spectra line cuts flesh better then kevlar, because for that application, the diameter to breaking strain ration is important. the thinner the line the easier it cuts flesh.  And spectra is thinner at the same breaking strain then kevlar.
Cutting other lines in flight is where kevlar excels because that is a matter of heat, not sharpness. And the kevlar line can withstand a lot more heat then other lines, therefore it will fail last.


Title: Re: might have to try this out for indoor kites...
Post by: damp_weather on February 27, 2014, 09:02 PM
ae,

I agree with what you write regarding melting points and the significance of line thickness.
However (and this is from articles and books rather than personal experience) kevlar has a reputation for cutting because of its surface roughness as well as for its tolerance of higher temperatures. 
A rather graphic cartoon sticks in my mind from: S. van der Horst and N.Velthuizen "Stunt kites to make and fly" Uigeverij Thoth, 1997 ISBN 90 6868 052 8.  It shows a small child asking to be lifted up to see the kites, but the adults around her are unable to respond as they have just been decapitated by the lines of a dual line kite that is flying at adult neck height across the picture.  If I recall correctly, the books authors' explain in the accompanying text that for safety reasons kevlar has been banned from sport kite flying in many competitions and festivals.  (I'll check the text's wording when I get home this weekend.)


...Addendum, Monday 3rd March.  The cartoon's caption was '2. You won't make many friends on your flying site with Kevlar lines.'  However, the text accompanying the cartoon did not talk of a kevlar line ban.  What it actually said was:
"Lines made of these fibres show a stretch just as low as Spectra lines, but they give a rougher feeling in normal use. Kevlar lines easily cut through someone else's lines, which seems to be an advantage over Spectra.  But this is only temporary.  When flying, these lines also fray themselves, which turns them even coarser.  Moreover, a Kevlar pilot clearly does not make many friends on his flying terrain."

Further down the page there is this on a Kevlar cored line:
"Skybond is something special.  This line consists of a Kevlar core with a Dacron coating, protecting the Kevlar, so that the line is somewhat safer to fly with on crowded sites.  It can be satisfactorily knotted, though you may count on some 30 percent loss in tension strength.  The line has the lowest stretch of all kite lines, because the Kevlar fibres in its core have hardly been twisted, hence run straight through.  But this line also has its disadvantages.  It is a relatively heavy and thick line, therefore unfit for low wind-forces.  Because of their relatively low stretch, the fibres are more often overloaded in gusts, causing a phenomenon comparable to metal fatigue.  The line will suddenly break below the breaking point given."
...In reading the above, please bear in mind that the book was published in 1997. Shanti's website says that 'Skybond' was withdrawn in 1985 when Speed line was launched.  Shanti says that the modern Skybond is a polymer coated Spectra line.


Title: Re: might have to try this out for indoor kites...
Post by: indigo_wolf on February 28, 2014, 12:21 PM
I agree with what you write regarding melting points and the significance of line thickness.
However (and this is from articles and books rather than personal experience) kevlar has a reputation for cutting because of its surface roughness as well as for its tolerance of higher temperatures. 

I expect that is part of the reason the Twinline Kevlar is actually a "KevlarŪ 49 base with a Black Polyurethane coating."

ATB,
Sam


Title: Re: might have to try this out for indoor kites...
Post by: mikenchico on February 28, 2014, 11:44 PM
I bought some very light braided Kevlar fishing line for use with fighters, not for cutting because we don't do that in the US but for the lightness and thinness, figuring it would increase speed and response. It tangled on the ground too easily because it was too flexible. I see the one you've posted has a Polyurethane coating though, if that provides a bit of stiffness so it lays in large loops without adding too much bulk it may work well.

Let us know for sure. My favorite, the old orange linen line, is over 25 years old and in bad need of re-waxing and I'm not sure that will bring it back to life.



Title: Re: might have to try this out for indoor kites...
Post by: thief on March 04, 2014, 09:51 AM
got my samples....the 20# stuff is thin.....nice though....comfortable on the fingers....
it does hold its curve from the spool it came off of well...so lays nicely...
i do wonder about the braiding and if that will cause trouble as it is a loose braid that opens easily (could make nice and clean knotless loops though...


Title: Re: might have to try this out for indoor kites...
Post by: mikenchico on March 05, 2014, 02:23 PM
The fishing line I bought was a loose braid too, that didn't seem to cause problems as it was still very responsive on a fighter as I recall. But a glider spends more time with the line slack then a fighter does, not being under tension may let the line loosen up. But a glider doesn't need the instant response that a fighter can use. 

Some gliders are balanced to include the weight of the line though, going too light could require a little tuning to compensate.