Well, I hate having to eat crow here, but anyway …
Was not able to repeat the successful bonding of silnylon to 2K Cuben with Permatex.
Have no idea why, and can only speculate. Maybe, because the original silnylon strip was glued to the edge of the Cuben, the Permatex glommed onto the Cuben fibers exposed at the edge. But that is only speculation.
Tried bonding Lightheart Gear "Cordura" silnylon strips to the face only of the 2K Cuben with Permatex, SilNet, Elmer's ProBond Urethane, and SeamGrip. Tried both sides of the Cuben with the Permatex, just in case there might be a difference (there wasn't).
The Elmer's and SeamGrip provided no bond to speak of. There was some resistance to peeling with the Permatex, and strong resistance with the SilNet. This was after 48 hours, without clamping, with over half the time at room temp. A thin bead of the Permatex does adhere well to the silnylon, however. No peeling, cracking, etc.
Did not use Hysol Urethane because it is quite expensive, and am saving it for when I actually want to use it for a project. Hope it does not turn out to be 'yellow' and partially cured when I take it out of the sealed foil envelope. Curing in the container is a big problem with urethanes.
Conclusions:
1. Use the Hysol or the tape to bond Cuben if it works for you.
2. I will use the SilNet to bond Cuben to itself and silicone treated fabrics when folding the edge over and bonding before sewing. Will use a hard rubber roller, but will not clamp – too much work on long tent seams.
3. Will use the Permatex, because it flows better, for sealing the finished seams which include Cuben and silicone treated fabrics.
4. Will continue to use the Elmer's for my footwear, especially where clamping is not doable. But not for Cuben or silicone fabrics.
About why to fold the edge over rather than simply bonding an extra strip on at the seam? If you are not stitching, and bonding only, I suppose that makes sense, as you will be bonding strips on anyway. However, for a sewn seam, I prefer to fold the material over at the edge and bond, because I believe the seam will be stronger.
It will have to remain a matter of 'belief' only until I've completed a shelter and seen how the seams hold under severe weather in the field.
Happy New Year!
