Seam Grip on silpoly PU4000 issue

**bmantheman** · 07-25-2016, 10:31

Hey guys,

Im doing some testing on a tarp I made.

and I applied the seam grip on the outside laye of the tarp.

I let it dry for over 24 hours but after setting it up once I saw the seam grip lifted up as some places and also sticked back on to itself.

any ideas why this would have happened . does the seam grip needs to absolutely be applied to the PU coated side ( I didn't want to it apply on that side since I didnt want the ridgline to rub against the sealant).

thanks for the input!

Bruno

**miyanc** · 07-25-2016, 10:56

I posted this a week ago. I was using seam grip on a similar tarp material and had the same results. My unscientific answer would be it isn't the right stuff to bond to the material. I have used permitex on everything prior and never had any issues. I was trying a newer material and checked the recommended sealing.

I would later reseal with permitex on the other side without incident. I have never used seal grim or any product by mcnalty. Maybe we missed a step, but either way I will stick with my windshield sealant.

**Tacblades** · 07-25-2016, 11:20

Seam grip will only work on polyurethane coating not on anything with silicone in it.

I use marine goop for uv resistance on pu coated fabric, and a silicone diluted for silicone fabric.

It does stick to itself contact adhesive. So just dust with talcum powder and blow the excess off, no more sticking to itself.

**Coheeba** · 07-26-2016, 07:15

Ripstop by the Roll recommends Sil-Net for the Membrane PU4000. Here's a link to an article about what works and what doesn't.

https://ripstopbytheroll.com/blogs/t...s-and-shelters

**Firesong** · 07-26-2016, 08:30

That's incorrect coheeba. Silnet for membrane silpoly only.
Here's the info for the PU4000:
*This fabric has distinct shiny (PU4000) and matte (sil/PU) sides. It is recommended to put the matte side facing out and shiny side facing inwards. If seam sealing, we recommend using a PU sealant such as Seam-Grip on the PU4000 side of the fabric.

**bmantheman** · 07-26-2016, 08:38

thanks for the input all,

as per the RBTR website, in the Silpoly PU4000 it says : *Note - shiny side is PU4000 and dull is sil/PU. If seam sealing this fabric, you will need a sealant intended for PU coated materials (e.g. Seam Grip).

so seam grip is suggested for that fabric.

**bmantheman** · 07-26-2016, 08:40

precisely! thanks Firesong!

Im just wondering if I should just try to apply seam grip on the inside of the seam... I worried it will mess it up again.
yeah pulling the seamgrip out is a ..... job.

**WalksIn2Trees** · 07-26-2016, 10:15

The inside is where it's easiest to be thorough as there's usually fewer loops sewn on the inside so you can seal most of the thread runs, especially the ridgeline. On the outside is mostly where things are sewn on, and you can't really seal between two pieces of fabric that are sewn together increasing the chance that water will find its way in along that route, even if you've sealed there. That said, I seal both sides, but I seal the inside first. Really sealing both sides is overkill

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**Mike7540** · 07-26-2016, 21:29

I purchased the winter tarp kit with this fabric and had great results sealing the inside of the ridge line with seam-grip. It also worked very well for repairing a small puncture from a falling tree limb. I just covered the outside with a patch from Gear-Aid and applied the seam-grip on the inside. Haven't had any leaks or problems.

**Boston** · 07-27-2016, 07:08

Originally Posted by bmantheman

and I applied the seam grip on the outside laye of the tarp.

any ideas why this would have happened . does the seam grip needs to absolutely be applied to the PU coated side ( I didn't want to it apply on that side since I didnt want the ridgline to rub against the sealant).

The pu4000 materal has a polyurethane coating on one side only. The other side is treated with a silicone/pu blend.

Seamgrip will only work on the PU only coated side (shiney side).

A silcone based sealer may work for the other side, but there has been problems in the past sealing RSBTR's silicon/pu blend. I think Kyle worked out the issue, but I can't confirm for this specific material.

Usually the inside of a tarp is sealed, as it's protected from anything that may damage the sealing on the outside of the tarp. Hang your tarp a bit higher if you're really worried about the ridgeline rubbing, but generally that wont be an issue.