would i use silicone sealant for a xpac-silnylon seam? thanks

good question. in the one instance where I have had such a seam on a pack (extension collar to main body), i used silicone on the silnylon side and seam grip on the xpac side. good results so far.

on the flip side, i can say definitively that silicone sealer will not stick well to a PU coated fabric (from firsthand experience before I knew you needed the right sealer for the right fabric). I've never tried seam grip on silnylon though, so I don't know for sure that it won't work, but I doubt it would.

hope that helps. cheers,
andy

Don't use seamgrip on silnylon, won't stick

Diluted silcone 10:1 with mineral spirits soaks into the threads and thus makes the seam much more waterproof even if it's PU fabric

thanks for your replies. what about seam tape, if i design a flat felled seam with the xpac on the inside of the pack (i too am using silnylon collar on xpac body) can i just iron this stuff on and be good?
i realize seam sealing a pack is somewhat futile but i figure if it was reasonably easy why not?

I don't know about seam tape but

I try to make my packs waterproof. I use silnylon. Coat the entire inside surface after it's all done with silicone : mineral spirits. Stuff inside stays dry when the outside gets wet from rain.