Patching my Therm-a-rest pad

10:22 a.m. on May 29, 2009 (EDT)
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5,239 forum posts

On a hiking trip over Memorial Day weekend my Therm-a-Rest pad got stabbed by a tree limb. Now it has a 1/2 inch rip in it. How can I properly fix the hole so it will hold air again?

11:19 a.m. on May 29, 2009 (EDT)
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1,139 forum posts

I have a couple of pads I need to patch as well, but smaller holes, not an actual rip. Someone suggested to me putting a patch over the whole and cover the patched area with Seam Grip. I was going to try that and see what happens. Thermarest does make a patch kit with various patches and a sealant, but a piece of coated nylon and Seam Grip may do the same thing.

1:39 p.m. on May 29, 2009 (EDT)
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What is Seam Grip and would rubber cement do the same thing?

8:53 p.m. on May 29, 2009 (EDT)
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"Rubber cement" is a fairly generic term that covers a wide range of different compounds. Seam Grip and Seam Seal are both liquid polyurethane solutions that work well for sealing seams (obviously) and other edges. They are not particularly good as glues to hold a large patch in place. They are not really "rubber" cements, like you would use for repairing a flat tire. The Thermarest patch kit has a glue that is heated by putting the tube in boiling water until the glue is soft, at which point the softened glue is spread on their treated nylon patches. These interact to form a wide-area seal. Seam Seal or Seam Grip around the edges helps reduce the likelihood of the patch coming loose at some point (like a corner - you should make the "corners" rounded) and then peeling off. It doesn't take long for the softened glue plus prepared patch to tightly bind into a pretty permanent fix. I have never had any of my (or Barb's) Thermarests develop a leak, though I did replace the metal valves on our oldest ones with the newer plastic valves. But I have patched several inflatables in the field, the most exciting of which was on Denali. It is hard to locate a pinhole leak when you don't have a tub of water to immerse the whole pad! It took 4 of us using the "cheek and ear" search technique before we found that leak. Your rip is bigger than anything I have done, though, one being a crampon hole (easy to locate - on both sides of the pad!). Come to think of it, most of the repairs I have done have been in winter in the field, even though most were youth (basic rule - youth, especially adolescent males, will puncture their inflatable pads sooner or later, except that "it was my tentmate's fault!")

9:17 p.m. on May 29, 2009 (EDT)
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5,239 forum posts

Well, it wasn't my fault, the tree limb did it. I was minding my own business and the tree just jumped over and poked my thermarest pad. I am sure all the other trees had a good laugh on my account!

April 20, 2018
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