About 3 months ago I followed the directions on this thread to seal an asym and a hex tarp I put together. I've only used them a handful of times in rainy weather so while it is too early to speak on how durable these tarps are but they are definitely waterproof. The only times I've gotten wet was while using the asym in a windy storm but that was only on the ends and I believe that was more of a function of my tarp not providing adequate coverage. The hex has been set up in 2 storms with high winds and heavy rain and performed beautifully.

Quote Originally Posted by ge.jeffers View Post
ok, I just sat and read 45 pages of posts, replies, and comments. So just a few questions.
1. If you have the material, is it cheaper to do this vs. going out and buying silnylon?
For me it was cheaper in the sense that I had a large roll of fabric that I had sitting in my closet that I purchased from magna fabrics. I had ordered 50 yards at $1.25 a yard and had a good bit left from my DIY WBBB, IX underquilt, and climashield top quilt projects. Also I already had some clear silicon in the garage from an earlier home improvement job. So the only real expense I had was purchasing the mineral spirits and a few plastic D-rings from DIYGearSupply. Although I was risking wasting a few yards of fabric if it didn't turn out well I decided to give it a shot since I didn't have any other plans for the material.

Quote Originally Posted by ge.jeffers View Post
2. Do you sew the tarp, since I am wanting to do a winter or 4 season tarp, before you waterproof it?
Yes I sewed mine before hand. I made sure to add all my tie outs and grosgrain as well before attempting to seal the material.

Quote Originally Posted by ge.jeffers View Post
4. If you have to set it up, I assume it would be the same way that you would pitch the tarp, when they say they brushed both sides is that the left and right sides or is that the inside and the outside?
I only brushed the outside of mine after setting the tarp up as I normally would. I am unsure if this is the ideal way to apply the silicon but it worked for me. I made sure to apply several very thin layers until I felt it was adequately covered.

Quote Originally Posted by ge.jeffers View Post
5. Finally, I think, will the mineral spirits evaporate when it is cold outside?
Since I live in south Mississippi I have no idea how the cold would affect applying the silicon. Around here we start commenting on how cold the weather is as soon as it begins dropping below 45° F at night!

Overall if you’re having to buy all the materials I would recommend just buying the silnylon from Scott at DIYGearSupply. He has great prices and I’ve been very satisfied with all the orders I've placed with him. You won’t have to spend that much more and the quality will definitely be higher. Now on the other hand if you already have some left over fabric from another project or already have silicone then it is a fun project and I do think it’s a good learning experience. Now I feel comfortable applying silicone to my tarp and if I ever had to do repairs on a silnylon tarp I would feel more comfortable working with the materials.

I feel like this is the same debate that always goes on when considering going the DIY route or purchasing from the amazing cottage vendors that are present on this site. Overall their quality is top of the line and the prices are hard to beat. Now on the other hand assembling your own gear can be just as rewarding (and addicting) as actually using the gear!