Trapped line in Cuben seams
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Wild Exped
(bankse) - MLife

Locale: OZ
Trapped line in Cuben seams on 05/14/2011 17:55:40 MDT Print View

Ive been gleaning info on cuben seam and tie out bonds with in mind to eventually try something with a large group tarp. Not new to cheap poly tarps i was wondering about trapped cord in seam lines, something i have heard people mention though not much discussion.

Im guessing the weight would outweigh the benefit of spreading the stress loading? but imagine (especially with cat curves between tie-outs) the load would be very disperse?

I was thinking along the lines of running (say) 2mm dacron through seams between tie-outs (ie through an unglued 'pocket' in the bonded edge (or even up to the rigeline as well creating an equal 3 way tension on the tie out (ie knotted or attatched to a brass ring etc)

I had thoughts of abrasion and possibly running the lines through nylon tubing but at a rough guess i'm thinking this may add at least a couple of ounces (to a large tarp)...

Any thoughts? Has this been discussed somewhere previously?

Does it sound like i know what im on about : )

(I dont really, though I have done some sewing and do read a lot...)

Cheers

drowning in spam
(leaftye) - F

Locale: SoCal
Re: Trapped line in Cuben seams on 05/14/2011 19:12:12 MDT Print View

I would think that the stretch of dacron would be greater than the stretch of cuben fiber, which wouldn't change how the stress was loaded and only result in a heavier and unnecessarily complex tarp.

Also, changing from dacron to dyneema cord probably wouldn't help either because the braid of the cord should allow greater stretch than the straight spectra fibers in the fabric allows.

Edited by leaftye on 05/14/2011 19:13:51 MDT.

Wild Exped
(bankse) - MLife

Locale: OZ
hmmm on 05/14/2011 19:37:46 MDT Print View

I cant really grasp how that would matter; with a free running line (between peg points). With both the line and the cuben already under tension wouldnt any remaining stretch in the dacron/dyneema only assist?


BTW The tarps Im hoping to replace are 20' square.



Thanks for your reply, i'll think about that further.

Colin Krusor
(ckrusor)

Locale: Northwest US
Reinforced Cuben Seams on 05/15/2011 00:02:22 MDT Print View

I'm currently (gradually) doing something similar to what you describe. I posted about my plans a little while ago:

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=37663

I would agree that the stretch in the reinforcement is a concern. I don't think stretchy reinforcement would bear much of the load unless the tie-outs connected only to the reinforcement (and not direcly to the cuben panels). Running stretchy Dacron line through a tubelike seam might work if the guy lines are connected only to this line and not the cuben, but I wouldn't forsee any improvement in the performance (strength, durability) of the tarp.

I have concluded that reinforcement of a cuben shelter is only worthwhile if the reinforcement has very low stretch and is flat enough or small enough in diameter to be bonded to the cuben (in a seam or on the surface) without requiring too much extra glue.

One thing that has very low stretch and is very flat and is less complicated than my approach (Vectran tow) is cuben itself. I'd recommend just cutting out some cuben ribbon and bonding it onto/into the seams that you're concerned about.

Wild Exped
(bankse) - MLife

Locale: OZ
Yes on 05/15/2011 03:07:20 MDT Print View

I'm following your thread, great stuff,thanks very interesting.

Im approaching this more with thoughts of simply spreading tie out loading (on larger panels than ive seen anyone mention) rather than adding diagonals to also increase material strength in lighter applications.

I had envisaged (even free running) lines through the perimeter hem simply spreading the load much like an extension of the warbonnet corner. ie Im wondering whether bonding the hem reinforcement (at all) makes any difference when it is in tension. With nothing moving once the tension is in place wouldnt this eliminate the need to get your (bonded in) hem reinforcement under even tensions and pressures before bonding and the need to get the bond consistent along its length so that pressures dont vary on the reinforcement if the bonding itself isnt entirely consistent.. perhaps a simpler approach in which the reinforcement material (ie cord (or tow) resistance, bonding ability) isnt so crucial and can be chosen for durability/uv resistance instead.

hmmm... simple thoughts though difficult to explain perhaps?

I like the approach you are using. It will be interesting to see how you finish the corner ties and how you incorporate the diagonals. I imagine that you will need to have a design which allows tensions to equalize or very accurate even tensions when the corners are finished / reinforcements joined (even if incrporating your reinforcement with the tarp fabric itself..)

All the best!

Edited by bankse on 05/15/2011 05:07:16 MDT.