[pct-l] seam sealing a taped-seam sil-nylon tarp/fly?

[Matt Thyer]

Ron, 

Why shouldn't a urethane sealant be reapplied to the nylon tape?  Perhaps
I'm missing something here, but wouldn't the solvent found in the new,
applied sealant simply dissolve the old sealant until it evaporates?  The
seam tape is most likely nylon of some sort and should be chemically
permeable with a polyurethane sealant.   The outer seams, if its exposed,
are a most likely a nylon thread binding the two sheets of silicon
impregnated nylon fabric together.  Shouldn't the outside seam side be
re-impregnated with silicone sealant if the tape leaks?  I suppose the
stitching and tape arrangement probably has a lot to do with this.

BTW, thanks for the gear pages.  Wow!  You've Six Moon has some neat stuff.
I'm super interested in the Gatewood Cape.  Have you proto-typed it using
Cuben Fiber yet?  

Matt

-----Original Message-----
From: pct-l-bounces at backcountry.net [mailto:pct-l-bounces at backcountry.net]
On Behalf Of Ron Moak
Sent: Friday, September 04, 2009 1:17 PM
To: 'linda.hungerford'; pct-l at backcountry.net
Subject: Re: [pct-l] seam sealing a taped-seam sil-nylon tarp/fly?

Linda,

You should note that silicone coated nylon tent fly that has been seemed
taped is not the same as a pure silicone coated fly. The taped side of the
material is coated with polyurethane. This is because seam tape will not
stick to silicone. The non taped side will be the silicone coated side. 

My suggestion is to ignore the side with the seam tape. And apply a thin
coat of silicone seam sealer to the other side. Make sure to thoroughly
clean and dry the seam before applying the sealer. The silicone on silicone
sealing should create a bond that will last the life of your fly. 

Detailed directions on making and applying silicone sealer can be found at
(http://www.sixmoondesigns.com/support/seam.asp). 

Because of the nature of polyurethane, you cannot create a permanent bond.
As a result any efforts at sealing that side will need to be repeated at
some point. Nor can effectively you apply silicone to the polyurethane as it
will not adhere correctly.

Hope this helps.

Ron



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