In an earlier thread I recommended using Samson Amsteel for the 5th Element line that goes from the power strap to the ring halfway to the kite. Now I think Amsteel has too much elasticity for this application. According to the data sheet, 13.5m will stretch 9.5cm (3.7") under tension of 280 lbs. That is a huge amount of stretch and could screw up the length of the 5th line below the ring and it could reek havoc on trying to set your powerstrap.
Now that I think the Amsteel might suck for this application, I want to warn others about the potential elasticity problem. I haven't noticed a huge amount of stretch but it has been difficult to get the 5th line set right. If you already bought the stuff based on my recommendation, I am sorry unless it seems to be working for you. If it is or not, please let us know.
dt
Amsteel for 5th Element
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BigKahuna
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Re: Amsteel for 5th Element
Hi dt,dt wrote:In an earlier thread I recommended using Samson Amsteel for the 5th Element line that goes from the power strap to the ring halfway to the kite. Now I think Amsteel has too much elasticity for this application. According to the data sheet, 13.5m will stretch 9.5cm (3.7") under tension of 280 lbs. That is a huge amount of stretch and could screw up the length of the 5th line below the ring and it could reek havoc on trying to set your powerstrap.
Now that I think the Amsteel might suck for this application, I want to warn others about the potential elasticity problem. I haven't noticed a huge amount of stretch but it has been difficult to get the 5th line set right. If you already bought the stuff based on my recommendation, I am sorry unless it seems to be working for you. If it is or not, please let us know.
dt
You might want to double check the spec sheet or your math. As far as I know, Amsteel is Samson's brand of 100% Spectra. Although all Spectra line has a small amount of initial "creep", it's stretch characteristics is outstanding, far better than your estimate. The stretch you've estimated sounds like more than is typical for even 100% polyester (dacron).
I haven't checked Amsteel specifically, but it just doesn't sound right.
Any well made single braid of Spectra, Dyneema, or even Technora should work for your application.
All the best,
Paul
Paul,
Thanks for the input. I hope you are right but according to Samson's website http://www.samsonrope.com/home/general/ ... isting.cfm if you download the Adobe data sheet, it says that at 20% of breaking tension, Amsteel will stretch .7%. "Average strength" (They don't spec it as breaking tension.) is 1400lbs for the 7/64 line. The length used in a 5th Element is 13.5 Meters .7% of 13.5m is 9.45 centimeters (3.7").
The refer to it as elasticity, not stretch. So, apprently it springs back. It could have something to do with the weave. It seems a little elastic to me but since it is used as halyards I would think it must be less elastic. On the other hand, the halyard on a dingy can be fairly short making .7% less significant.
dt
Thanks for the input. I hope you are right but according to Samson's website http://www.samsonrope.com/home/general/ ... isting.cfm if you download the Adobe data sheet, it says that at 20% of breaking tension, Amsteel will stretch .7%. "Average strength" (They don't spec it as breaking tension.) is 1400lbs for the 7/64 line. The length used in a 5th Element is 13.5 Meters .7% of 13.5m is 9.45 centimeters (3.7").
The refer to it as elasticity, not stretch. So, apprently it springs back. It could have something to do with the weave. It seems a little elastic to me but since it is used as halyards I would think it must be less elastic. On the other hand, the halyard on a dingy can be fairly short making .7% less significant.
dt
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BigKahuna
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In the "yachting world" they refer to this initial stretch as "creep". Some kite flying lines are "pre-stretched" to eliminate this creep. If the lines you're using aren't pre-stretched, then as Dwight says, you need to pre-stretch them.Dwight wrote:It will stretch about 1 meter. You need to prestretch it, then it will stop.
Paul
I am talking about Amsteel ELASTICITY, not stretch. Stretch is permanent lengthening. Elasticity springs back. According to Samsons data sheet http://www.samsonrope.com/home/pdf/new/ ... msteel.pdf, this elasticity was measured after bringing the line to a percentage of its breaking strength 50 times. So, the elasticity doesn't go away after a good stretching. The Amsteel would be like have a bit of bungie between your front lines and your kite.
I couldn't find a spec of how much Amsteel stretches.
Hernan - I am not using the amsteel for the 5th line. I am using it from the ring where both front lines attach to the powerstrap. It has the full front line tension from both front lines of the kite.
Dwight - Spectra stretches 1 meter so you should prestretch it? Do you prestretch it 1 meter. A meter is longer than a yard. I would believe 10cm. I have alway used q-power lines but I don't think braided spectra stretches that much.
Well, thanks for all the encouragement and I hope I am wrong somewhere but I still think this elasticity could be a problem. I think I will switch from amsteel to two lengths of 600lb Q-power side by side. An advantage of this would be, if one breaks, the other could get me back to the beach. The disadavantage is another line to tangle.
dt
I couldn't find a spec of how much Amsteel stretches.
Hernan - I am not using the amsteel for the 5th line. I am using it from the ring where both front lines attach to the powerstrap. It has the full front line tension from both front lines of the kite.
Dwight - Spectra stretches 1 meter so you should prestretch it? Do you prestretch it 1 meter. A meter is longer than a yard. I would believe 10cm. I have alway used q-power lines but I don't think braided spectra stretches that much.
Well, thanks for all the encouragement and I hope I am wrong somewhere but I still think this elasticity could be a problem. I think I will switch from amsteel to two lengths of 600lb Q-power side by side. An advantage of this would be, if one breaks, the other could get me back to the beach. The disadavantage is another line to tangle.
dt
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kruzlifix
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amsteel 3 mm
@dt
One single line of 3 mm amsteel line has way better mechanical properties then 2 Q powerlines together (average breaking strenth of 953 kg!!!!!!. so in reality I am sure there will not be a problem.
when I was first using the 5th line and Y, I was also just using the 2 frontlines underneath the Y tighted together as one centerline. it works well but when you prepare the lines on the beach for launching it is not as clean as if one has only one centerline.
andreas
PS: but amsteel is not the most "hitech fiber" A twelve-strand braided rope of Parallay construction HMPE fiber, so it is made out of high molecular poly ethylen!
better would be the validator 12tm! this offers the assurance of "no creep" Vectran fiber, trhe 3 mm rope has an average breaking strength of 2700 lbs = 1200 kg! so you could easily lift off a VW beetle!
One single line of 3 mm amsteel line has way better mechanical properties then 2 Q powerlines together (average breaking strenth of 953 kg!!!!!!. so in reality I am sure there will not be a problem.
when I was first using the 5th line and Y, I was also just using the 2 frontlines underneath the Y tighted together as one centerline. it works well but when you prepare the lines on the beach for launching it is not as clean as if one has only one centerline.
andreas
PS: but amsteel is not the most "hitech fiber" A twelve-strand braided rope of Parallay construction HMPE fiber, so it is made out of high molecular poly ethylen!
better would be the validator 12tm! this offers the assurance of "no creep" Vectran fiber, trhe 3 mm rope has an average breaking strength of 2700 lbs = 1200 kg! so you could easily lift off a VW beetle!
Last edited by kruzlifix on Mon Jun 21, 2004 6:51 pm, edited 1 time in total.
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BigKahuna
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Maybe your "hi-tech" is different than my "hi-tech", but so far as I know, HMPE (Spectra, Dyneema) is still considered a "hi-tech" fiber. Yes, there are even stronger, newer fibers out there, and Spectra has become very commonly used in a wide variety of every-day uses (including kitesurfing), but I don't think that has downgraded it's classification.PS: but amsteel is not a "hitech fiber" A twelve-strand braided rope of Parallay construction HMPE fiber...
Keep in mind, Spectra has other qualities that make it a great fiber for kitesurfing: it floats, it is easily tied/knoted, and the fibers can be melted to "whip" the ends.
Sure you can use other fibers, but spectra is perfectly suited to kitesurfing.
As for the "elasticity" of Amsteel, that may be a factor of how the line is woven or how the product is manufactured. I know that Amsteel is also used on ships for mooring lines and towing hawsers, an application where a little bit of "elasticity" is desireable. Maybe an email to Samson is in order...
All the best,
Paul