Spectra Kite Line

An Informative Q'n'A Page

Spectra kite line is mainly used by sport- and power-kite enthusiasts. They fly everything from small two-line deltas right up to large traction kites used by surfers and landboard riders. This line material is so good for this purpose that it is also used for those experimental giant parafoils which help to tow large ships and thus cut down their fuel costs. Mind you, those lines are as wide as your thumb!

If you ever come across a single-line kite flyer using Spectra, you can bet they are up to something interesting—like setting altitude records! Or perhaps they just like the low weight of this material. Very large kites need quite a weighty and bulky spool of line otherwise.

Are you ready for some concentrated info on Spectra line? After digging around a little, some interesting facts popped up.

Just to be different, I've decided to use a Question / Answer format to present it all.

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Q: What's the difference between Spectra and Dyneema?

A: Not a lot! This is why you have probably heard both terms used in similar kiting contexts. Confusing.

The two materials have slightly different molecular structures, which explains why Dyneema tends to wear a bit less. More importantly for multi-line kite flyers though, is the fact that at 3%, Spectra has about half the stretch of Dyneema. For single-line flying, a bit of stretch can be handy for lessening the impact of sudden changes in line tension on the kite's frame.  

Dyneema (c) is a registered trade name of the Dutch company DSM Dyneema. This material is much more popular in Europe than in the rest of the world.

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Q: What is Spectra?

A: Spectra is a trade name for a very-high-molecular-density form of polyethylene. Like other synthetic materials, it is made in other forms besides long flexible line—like bullet-proof vests! Polyethylene, by the way, is the most widely used plastic on the planet. Most "plastic" bags are made from this material.

In Spectra, the very long chains of molecules are aligned which gives the material its very low stretch and high strength. In fact, the strength-to-weight ratio is more than 10 times better than steel.

Spectra kite line sold online is often of a length suited to sport kites (around 200 feet). The idea is to buy a sleeving kit as well and hence save some money. Putting knots in Spectra without sleeving that area first is not recommended! Many line sets now come with pre-sewn loops rather than requiring sleeving and knotting.

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Q: How does Spectra compare with other kite-line materials?

A: It is more expensive than most other line materials such as cotton and nylon. For a given strength, it is much thinner and lighter than the other commonly-used line materials. That explains why it has been used for altitude-record attempts! In fact, Spectra is about one third the diameter of nylon line of the same breaking strain.

On top of this, Spectra has very low stretch, which is important for flying steerable multi-line kites. In fact, it has roughly half the stretch of comparable Dyneema line. As for Dacron and nylon, there's no comparison :-)

You might have heard of Kevlar—a stronger line material than nylon or Dacron. However, Spectra is up to 40% stronger than Kevlar. Kevlar is quite abrasive and will rapidly saw through other types of material if lines are crossed. Hence, don't use this material for single-line flying if you value your friendships on the flying field :-|

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Q: When was Spectra invented?

A: Gel-spun polyethylene was invented by DSM High Performance Fibres of Holland in the 1990s. At that time, the company called the material Dyneema. It was later licensed to Allied Signal in the USA and Toyobo in Japan. Dyneema is very similar to Spectra and is used a lot with paragliders. Spectra is the trade name used by Allied for its version of the material.

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Q: How is Spectra kite line made?

A: Gel-spun, that's how. OK, I'd never heard of that either... While the hot polymer is still in a gel state, it's forced through a rotating spinneret to form individual strands which bond together as they cool. After this the strands pass through an air-drying and cooling stage before being cooled even more in a liquid bath.

It's no coincidence that spiders spin their incredibly strong web material the same way. Man copies nature.

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Q: Who makes Spectra kite line?

A:

Spectra is the trade name for polyethylene kite line coming from Allied Signal, a US manufacturer. Actually, the name "Spectra" is a registered trademark for the material, held by Honeywell International. This company was known as Honeywell Incorporated before being bought and renamed by Allied in 1999.

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Q: Does Spectra have any special properties?

A:

• It floats on water! That's more of interest to fishermen rather than kite flyers of course.
• It has a rather low melting point—147°C (297°F) to be precise—which is not a lot hotter than boiling water! For this reason, it must be kept well away from lines of other types while in the air. A back-and-forth sawing action by the other line will soon friction-heat the Spectra to the point of failure. Bye-bye kite!
• It is naturally very slippery, which multi-line flyers love since crossed lines don't inhibit the control of the kite.
• It is susceptible to "creep," meaning it will very slowly get longer if it is held under continuous heavy tension. Kite flyers would not notice this, I'm pretty sure, as far as flying lines go. Bridle lines could be another matter though, where relative lengths are important.

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I hope you found some of this info on Spectra kite line interesting, useful, or even both!

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