Seam sealing RBTR silpoly

**Titaniumpyro** · 01-02-2015, 10:29

Have any of you guys got around to seam sealing or bonding to the Silpoly?
I used the Permatex flowable windshield Silicone to bond my reinforcements before
Sewing but after drying, even for 48 hours the overlap where the silicone got onto the single layer of Silpoly
Will rub off without much effort. I even tried thinning it down a bit with mineral spirits on a scrap and same result.
I am going to pick up some Silnet today and test to see if the bond is more permanent before I seal the ridgeline.

**squidbilly** · 01-04-2015, 20:54

Originally Posted by Titaniumpyro

Well mine is basically finished except for sealing the ridgeline and bonding the pullouts.
Quick pitch in the backyard in the rain just to see how it looks.
The color is the olive drab and does have more of a green hue than the pics suggest.
Attachment 99857
Attachment 99858
Attachment 99859
The darker patches are from hanging it in the rain last night and just folding it up while wet.
I have some small tests drying right now to test bond strength of Silnet and clear GE Silicone II
The Permatex I used to bond the reinforcements will rub off. I checked it on a scrap of Silnylon just to make sure it wasn't a bad batch and it bonds to it very well. So far it seams that Silnet in a not too thin or thick layer will be the most durable on this fabric but I will know more in 24 hrs.

So, did the Silnet work better? I discovered that I am having the same problem with the new Membrane sil. Permatex Flowable Silicone will barely stick, and peels off easily after curing. Silnet works a little better, but after packing it in and taking the tarp out of it's bag a couple of times, the Silnet starts to separate from the fabric. That ain't gonna work!

I tried a couple of other things on a scrap of Silpoly that I practiced seams on. I tried E6000: not flexible enough, but resisted peeling better than Permatex. I also tried Loctite Vinyl,Fabric & Plastic Flexible Adhesive. I didn't use either to bond the fabric together: only tried a few small spots to see how hard it is to remove them and see if they could be used as a seam sealer. The Loctite might work: it hasn't cured yet, but after a few hours it has dried nicely on the seam and has remained flexible.

**Freakin Farmer** · 01-04-2015, 21:17

Originally Posted by squidbilly

So, did the Silnet work better? I discovered that I am having the same problem with the new Membrane sil. Permatex Flowable Silicone will barely stick, and peels off easily after curing. Silnet works a little better, but after packing it in and taking the tarp out of it's bag a couple of times, the Silnet starts to separate from the fabric. That ain't gonna work!

I tried a couple of other things on a scrap of Silpoly that I practiced seams on. I tried E6000: not flexible enough, but resisted peeling better than Permatex. I also tried Loctite Vinyl,Fabric & Plastic Flexible Adhesive. I didn't use either to bond the fabric together: only tried a few small spots to see how hard it is to remove them and see if they could be used as a seam sealer. The Loctite might work: it hasn't cured yet, but after a few hours it has dried nicely on the seam and has remained flexible.

Will be waiting anxiously to hear your results. My Silpoly tarp is nearly complete and I am undecided on what to seal the seam with.

**Titaniumpyro** · 01-04-2015, 22:38

Originally Posted by squidbilly

So, did the Silnet work better? I discovered that I am having the same problem with the new Membrane sil. Permatex Flowable Silicone will barely stick, and peels off easily after curing. Silnet works a little better, but after packing it in and taking the tarp out of it's bag a couple of times, the Silnet starts to separate from the fabric. That ain't gonna work!.

My first set of tests were inconclusive. The Silnet does seem to bond better but could still be rubbed off somewhat.
I did another set that I will try in the morning. One area was cleaned thoroughly with rubbing alcohol and dried. Another area with odorless mineral spirits. The mineral spirits was just a whim and my thought is that bond strength would be less since it is somewhat greasy.
This is frustrating as the Permatex and Silnet test on Silnylon is stuck good. I cannot get it to come loose no matter how hard I rub or scrape at it.

**Titaniumpyro** · 01-05-2015, 10:07

Brewguy and corrumpu, those are both nice looking tarps!
So from my latest set of tests, both Permatex Flowable and GE Silicone II will still peel off silpoly
Even after the fabric has been wiped clean with rubbing alcohol or odorless mineral spirits.
The Silnet bonded much better this time. In the thicker applications I can scratch some of the silnet off but it does leave a thin layer behind on the fabric that I can't remove. So far this seems like the best option.
I am going to do a sample with Gen 1 silicone that is acetic acid cured and also try applying silnet to a sample that is wetted out with mineral spirits to see if that will allow it to bond any better.
Any other ideas? I want to figure this out today so I can seam seal this thing tomorrow if possible.

**corrumpu** · 01-05-2015, 11:02

Could you use a solvent that is stronger than mineral spirits? xylene? This might re-emulsify the sil within the poly and help to get a better bond? I am just talking out loud with no knowledge of the silpoly and how it's made.

**Brewguy** · 01-05-2015, 14:31

Originally Posted by Titaniumpyro

Brewguy and corrumpu, those are both nice looking tarps!
So from my latest set of tests, both Permatex Flowable and GE Silicone II will still peel off silpoly
Even after the fabric has been wiped clean with rubbing alcohol or odorless mineral spirits.
The Silnet bonded much better this time. In the thicker applications I can scratch some of the silnet off but it does leave a thin layer behind on the fabric that I can't remove. So far this seems like the best option.
I am going to do a sample with Gen 1 silicone that is acetic acid cured and also try applying silnet to a sample that is wetted out with mineral spirits to see if that will allow it to bond any better.
Any other ideas? I want to figure this out today so I can seam seal this thing tomorrow if possible.

I have not seam sealed mine yet. With the rolled or french hem do we know for sure if water will leak? It is right at the very top of the steep peak, won't it run off before it drips? I don't have much experinence in the rain, just a thought.

If none of these work perhaps the answer is to pinch the ridgeline in grossgrain and sew through so there are no holes in tarp at all?

**Titaniumpyro** · 01-05-2015, 14:47

Yes, I used the hybrid french or flat felled seam from the diygearsupply tarp plans and had it pitched for 1 day in a light to moderate rain and it leaked a good bit. Droplets form under the ridgeline and run down inside the tarp.

**Brewguy** · 01-05-2015, 16:01

Originally Posted by Titaniumpyro

Yes, I used the hybrid french or flat felled seam from the diygearsupply tarp plans and had it pitched for 1 day in a light to moderate rain and it leaked a good bit. Droplets form under the ridgeline and run down inside the tarp.

cool wasnt sure. What about some of the tapes out there like goretape for goretex or cuben tape?

Ok looks like zpacks says the cuben tape won't adhere to sil. Rockywoods has some Melco tape that is heat sealed, wonder if that works?

This is going to suck if everyone is buying this tarp material and can't seal it!!

**sandmaker** · 01-05-2015, 16:26

Originally Posted by Brewguy

This is going to suck if everyone is buying this tarp material and can't seal it!!

I plan on using my Silpoly to give my first go at making a tarp. Since that is the case, I plan on waiting a little bit longer while others are testing out what, if any sealants work on this material. If there doesn't seem to be a great solution for sealing, I will probably try my hand at a bound ridgeline instead of a flat-felled/french seam.