Kitebuilder.com

[Al Hargus]

KEVLAR - Just the mention of this type of material used as kiteline seems to generate as much controversy and arguement as discussions about politics or religion!

I've read many of those comments both pro and con in this and many other forums and have heard the same sort of heated discussions out on the kite fields.

Sooooo, not being a "Man of few words" .................... Besdies when have I ever really written a short note. ..........

As I'm one of the Long Timers in kiteflying and often revert to posts of a Historical nature I'd like to share some info on tests I've performed in the past with Dacron, Nylon, Cotton and Kevlar line used for kiteflying! Some of those early tests concerned line stretch and strength, but in my testing I eventually learned some significant facts about Kevlar, and all other types of flying line!

Originally, Kite Line used in the late 70's and early 80's was mostly cotton or other natural fibers, and synthetics were not very common. As the synthetics industry evolved, so did Kite Line. With the popularity of polyester leisure suits lots of different companies produced line out of Dacron, Nylon and other man made materials.

For most kiteflying needs this synthetic line was Great The line was strong, usually a smaller diameter for it's strength and it had a stretch quality that was very helpful, especially in absorbing tugs and jerks a big, heavy pulling large kite could develop!

Then along comes the dual line controllable kite! Peter Powell produced his Famous Diamond in 1978! His famous Toy first came supplied with twisted nylon flying lines! This kept his kite package Toy inexpensive, but it also taught stunt kite fliers that twisted line stretched a lot. Peter eventually substituted braided line for his kite, which cured some of the stretch problem, but it didn't fix it!

In the early 80's serious dual line competitions start to pop up across the country and competitors find that this stretch and "Play in the steering wheel" is unacceptable for the serious competitiveness!

At about the same time, companies that produce line and accessories for sailboats begin to see the advantages of using a synthetic line called Kevlar in place of steel cables for the rigging of sail boats! Kevlar is very strong for it's diameter and is much lighter per foot then steel! Because Kevlar is so dense it also finds applications in armor, both for personal protection and in the production of military Tanks and other vechiles.

This new stuff called Kevlar is really appealing to Stunt Kite Fliers for two reasons 1.) Smaller diameter when compared to nylon or dacron 2.) It has virtually no stretch! So many if not all the competitors in the early 80's flew in competitions with Kevlar flying line!BUT Kevlar had some disadvantages! First and foremost was that it was more expensive (per foot) then any other flying line! And also that it had an abrasive quality that made Lots of Wraps in dual line flying very difficult, if not impossible.

In 1897 I was flying with the Chicago Fire. We first flew Ten Foot Flexifoils for competitions! (Flames 'foils, what else! ) We used 200# Kevlar for our competition lines. Because of this abrasiveness, we were limited in what we could actually accomplish in the air. (One serious team wrap and we would lose control) At the 1987 East Coast Stunt Kite Championships, Fran Gramkowski approached the team and offered us the use of a new flying line, called "Spectra" which his company "High Fly Kite Co." sold!

We accepted, and with frantic haste set up three pairs of this line to use in the competitions! (WE actually did this in the Pit area prior to our team competition) The line was indeed slippery then Kevlar, but we already had a "No wraps" routine so we never were able to benefit from this capability during the ECSKC Comps!

Lots of other companies began to offer Spectra flying line sets especially for dual line fliers! Spectra was pretty 'slippery' as it didn't have the abrasive quality of Kevlar. It also had a very low stretch factor and MOST IMPORTANTLY the line was Cheaper then Kevlar foot per foot. And the line got progressively cheaper as more manufacturers found uses for the material. (In replacing those before mentioned sailboat rigging, and bullet proof vests!)

One major disadvantage of Spectra is it's very low melting point Kitefliers were finding out that their Spectra line could easily be cut by most any other type of kite lines, even the twisted 30# test nylon line supplied with $0.99 kids kites! And because of that low melt point, you had to "sleeve' the line when you wanted to tie a knot in it.

The "Spectra Users" quickly learned to avoid ANY OTHER kiteflier and any other flying lines out on the field. AND because in the early 80's if you weren't using Spectra for you kite, you were using Kevlar, this meant that many of those first Line cuts for Spectra fliers came from Kevlar flying lines! At the time we did not have the attitude about Kevlar that fliers have today. Kevlar wasn't anymore 'dangerous' to Spectra line then ANY OTHER line!

What happened next did change that attitude about Kevlar! As mentioned many companies began offering Spectra line for kiteflying! Shanti Kite Company was in the 80's one of the largest supplier and manufacturer of Kite Line in the USA. Shanti wanted to sell their new Spectra product and I began to hear Rumors arriving mostly from west of the Rockies about the "Danger of using Kevlar as a flying line! Shanti Line Company carried an ad in a kite publication back then that touted the "superiority' of Spectra, that it was inexpensive (which it was) but it also added thatSpectra is safer then Kevlar

But being a smart company Shanti wanted to cover both sides of the fence. Due to the low melting point of Spectra line and the fact that you had to 'sleeve' the line to make a strong, break free loop, (and the fact that Shanti had miles of Kevlar in their warehouse) They came up with a line idea they called "Sky Bond"

Sky Bond line had a Kevlar core with a dacron outer covering throughout it's entire length. The inner core - Kevlar wasn't even twisted but was single small strands laid into a braided outer sleeve! (Similar to kernmantle rock climbing rope) This Sky Bond idea was a disaster! The inner and outer parts of the line stretched at different rates so after a day of flying in big winds parts of the Kevlar inner core would 'pop out' of the dacron cover to produce what we called, Sky Bumps Sky Bond went the way of the Dodo and Shanti renewed their campaign to sell Spectra! they had wasted all their Kevlar supply in the Sky Bond fiasco, so it was "Spectra Forever"

Lots of other companies began that advertising campaign for their own Spectra line products! They also picked up on the "Spectra Good/Kevlar Bad" concept! That legend still exists today! Kevlar is still more expensive, even more so now then in the past (the supply and demand thing) but like any other Tool like Spectra line, Kevlar has it's uses, it's advantages and disadvantages, AND in the hands of "unsafe" kitefliers Kevlar can be dangerous! BUT (and here comes that 'political/religious' arguing point)

There are only Dangerous Kitefliers, not Dangerous flying lines"

Now for the tests and the reason Kevlar isn't any more dangerous then any other type of flying line! In the 80's I had "Miles and Miles" of Kevlar dual line sets in my kite bag! I really wanted to find out about Kevlar properties and compare them to other types of kite lines! At the time I worked in a Print shop, and ran a "Roll Fed Web Press" in Chicago on third shift. And being at work at three in the morning with nothing to do (and no bosses around) I began a series of tests on flying line!

Web presses use large rolls of paper, in many cases weighing one ton or more. After we used a roll we'd weigh the left over "Stub" so we knew how much we had for later use! This gave me a warehouse of rolls with different accurate "weights" My "experiments" began with ideas to verify the published manufacturer claims of "Strength" For example I would choose a "Roll Stub" weighing 300# I created a harness that I could attach my test sample of line rated at 300# and using the Roll Hoist in the pressroom, I would attempt to lift that 300# roll with the Test line!

I'll not bore you with details and exact tables of my experiment results. (Which, by the way, I have no idea where those tables are) BUT as a rule manufacturer statements are wildly exaggerated. Many lines wouldn't even lift 1/2 the weight claimed! On the other hand in some cases I was able to lift more then the rated weights. (I once lifted 1000# with 400# test Spectra line) Now if you "jerked" the hoist when lifting the weighted rolls the line would sometimes break very quickly, which makes sense!

I tested a variety of "Claimed Properties" for all sorts of lines. Line strength, line stretch, and even the effect of knots in a line! I decided to employ another method to determine line stretch over the entire length of 150 feet of line (Common length of dual line sets used on the field) I found a hall in the print shops warehouse that had walls approximately 150 feet apart. I installed "Eye Bolts" in the walls and would string 150' of different lines through them. One end would be securely tied and at the other I would attach a different weights and measure the increase in line length.

Some of the claims of "No Stretch" were far from true. I did find as we all know today, that line of any kind will stretch initially, and then stop "expanding" after that first or second use. This was proved out in these tests. Also the "exaggerated" claims of many manufacturers were also proven to be just that, product advertising promotional exaggerations. (Exaggerated claims for Kite Line are more common, simply because, unlike strength claims for Climbing Rope, there is no risk of life, and only risk of a lost kite. Soooo, Product Liability isn't an big issue)

What I did learn when I compared Kevlar to Spectra was that those manufacturer claims were much more Correct and accurate when tests were applied to Kevlar. It did stretch noticably less then Spectra, both initially and over the 'long haul' Kevlar strength claims were much more accurate then any other line type. A simple 'overhand knot' tied in Spectra reduced line strength by 70 -80% while the same knot tied into the same strength of Kevlar reduced line strength by 40 - 50%. Kevlar came out as the "Winner" in these experiments!

Now I'm sure at this point your all asking yourselves, "What the heck did this guy do at work, besides play with Kite Line?" Well I did work (occasionally) but my shift supervisor was also a pretty easy going guy, and as long as jobs got printed, and the press maintained, he didn't care what we did! Eddie (my boss) got kind of interested in my "experiments" and occasionally helped me with them! While I was doing the 150 foot stretch experiment I explained to him, what results I was trying to find. Strength, stretch, etc. I also mentioned the abrasiveness of lines and mentioned the current belief that Kevlar was Dangerous BUT I also said that I couldn't figure out any way to actually test that, Possibility of Danger"

The next day Eddie arrived at work with a package which contained what he said was, " .... the solution to my danger tests ..." Eddie opened the package and it contained several "Pigs Feet" that he had bought at the local butcher shop! Eddie said, "These look and feel just like human skin, so lets run these pigs feet up and down those lines you stretching across the pressroom, and measure how deep the cuts are"

Ekkkkkkk, Kinda gross, but Eddie was the boss, and I wanted to make him happy (and continue my work time experiments) So what we did was rigged flying line across the pressroom! We then made a weighted harness that would hold these raw pigs feet balanced on the test flying line! We would then with a "leash" pull the pig foot down the test flying line under tension and after a measured distance we'd take the "Test Foot" and measure the depth of the cut! TRUST ME it was definitely a gross test! And because of the fact that the pigs feet really did resemble human flesh, I had many sleepless nights with the Willey's after sticking a rulers into those "Test Feet" cuts. The tests weren't definitive and it was kinda hard to actually measure depth!

BUT ............ BUT............. BUT

I did learn one VERY important fact in these slightly weird tests. Types of line materials are NOT a factor in the lines ability to cut and injure! BUT ............ BUT............. BUT
Line Diameter is a factor in the lines ability to cut and injure

For example 50# Spectra has much more cutting ability then 300# Kevlar. 30# monoflilment is More Dangerous to flesh then 150# Spectra. So although 100# Kevlar is Sharper the 300# Spectra, 100# Kevlar produced nearly identical results in the "Pigs Feet Test" that 100# Spectra did!

Fighter Kite fliers are always talking about how 'cut up' their hands get when they use very thin flying line. And believe me, that "Danger in Diameter" of line was driven into my head when 50# Spectra line cut Too the Bone in 1/4 the distance, needed to make the same cut with 150# Kevlar during the "Slightly Weird" Pigs Feet Tests!

I'm not trying to persuade anyone to switch their lines to Kevlar. Both Spectra and Kevlar have advantages and disadvantages! BUT I do think you should know the Real advantages and disadvantages of your flying lines!

I just get a little irritated when someone approaches me on the flying field when I'm fly my kite train on Kevlar and they launch into a diatribe about the Dangers of Kevlar line.

In my experience over the years I've found that Danger on the kite fields comes from the participants and not the, line, kites or equipment used!


P.S. Sorry if I grossed anyone out with the description of the "Pigs Feet Tests" It really didn't produce "quantitative data" BUT it did make me VERY paranoid out on the flying fields when the winds are up and lots of fliers are zipping around the field with that VERY Thin 80# Spectra flying line, MUCH more paranoid then when those fliers were using 300# Kevlar.

I am always paranoid in conditions where a flier is being Dangerous regardless of what Kite Line their using!


_________________
GOOD WINDS

AL
Columbus, Ohio
USA

[KiteSquid]

Al,

You never know who's kite line will get cut when flying if kites cross paths, but if you are flying on Kevlar you probally will not make many friends... as you can tell I am in the anti-Arimid camp.

Simular but diffrent line: We had a guy very close to going to jail one day because a person flying a fighter kite on Manjah cut the line of one of his friends who was flying on braided Dacron... The park police on the National Mall are serious about their job.

[kiteguy]

I have a spool of 200# Kevlar line that I sometimes use. Actually, only one Kite Line has been cut, so I guess it is not really much of a problem. I try not to fly with that line when in a crowded field. In fact, I usually pull down and become a spectator.
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Dave Ellis
Kites + Kids = Education

[Al Hargus]

[Progcraft]

Al, wow, thanks for that. Alot of what you said seems to be just common sense. But, sometimes there is need to actually state it. I'm glad you did so in such a complete posting.

Hey, I have a question. Do you call you pigs feet test, "Swine on the Line"?

P
_________________
There is no box.

[Al Hargus]

[Dorsal]

Excellent report Al, including the unorthodox method of testing the cutting ability!
You presented the materials tested, the methods and setup used to perform the tests, the (remembered) data, and a conclusion that seems to be borne out by the data produced.
And it was interesting, to boot!

Bravo!

[Grant L]

[Doug LaRock]

Thanks for the good post Al. I like to see people test things instead just accepting what "everybody" says.

Doug

[KiteSquid]

Actually the only place Kevlar line does not work well is in a Rokkaku battle, as it cannot be cut by anybodyelses line.

I can see it's uses elsewhere and I may start packing some in my bag....

I will NOT use is on multi-line kites as Spectra is sooooooo much slicker!!!!
_________________
VR/
KiteSquid
AKA TakoIka
AKA Harold
King George VA


P.S. Yet another post by the Squid..... Doesent he ever shut up???

P.P.S. The wind is like the air, only pushier.