How do I seal the seams on a custom boat cover?

Question

I'm currently making a boat cover for my sailboat. I'm using canvas because I have the material readily available to me. I'm concerned that my seams may leak. I plan on coating the cover with waterproofing spray to help shed water and leaves. The seams will be under stress and I'm looking for something other than the waterproofing in a can in which to seal the joined pieces and still afford protection from leaks. If anyone has any ideas it would be greatly appreciated.

Answer 1

Seam Sealer works! you can buy it at a sporting store or maybe at a hardware store.

Answer 2

Triple stitched, flat felled seams in canvas should not leak without any sealant. I have a cover from the below link for  last NINE years in year-round  sun & it is still in good condition. Cover was 6 or so years old at least when I got it but was winter stored under cover.

http://thesailorstailor.com/  

They  may have example of the above. Also if the canvas is not UV protected you are wasting your time & energy.

Sell the canvas & buy the cover....