Chuck: Do you try to get a water/air tight seal between your bottom board and the canvas or should it float just based on the buoyancy of the components?
Mike
Yes and yes...Yes, all decoys I have made to date, I try and get them water tight. I have used many different approaches, but lately have sealed/bonded the fabric to the wood with either a diluted wood glue(applied with a syringe after the final band of fabric) or caulk(applied under the band). With either method, when priming and painting, I goop the paint heavy over the seam to hopefully get extra protection. I had a few deeks a couple years back take on a little water, after I noted this I changed my methods to the above. The compromised deeks I positioned to let the water drip back out of the seam, then sealed with epoxy through a syringe.
With the exception of decoys weighted for competition, I try and keep them light and when done properly, the waterline is at or just below the top surface of the bottom board. If you can achieve this, you can make a 'self-bailer' with the canvas folded back under the tail, so any water that found it's way in through seams or shot holes would find it's way out too. When I get to making these, I will prime the inside of the canvas when I prime the outside by pouring the primer in, rolling it around, then pouring it back out and into the bucket. My thoughts would be to preserve the canvas from rot by priming from both sides.
Try some marine or (if not readily available) exterior caulk and see if you can get that sealed up...but odds are, it won't see much water. In my experience people who get decoys at such things rarely hunt them, if ever.
There are A LOT of methods and thoughts on how to make canvas decoys and how to seal them...just like making regular decoys, there is no one right way, these are my thoughts, but I am still learning more with each decoy I make.
Chuck