Welded over rivets .. Glued is best.. I had a duraboat that had no rivets or welds...it never leaked a drop...wish they made bigger boats..
Had one of them too, 15 footer. Good boat, but not as heavy duty as most any welded job, pretty thin material. Mine was beat to piss as the first owner left it at the dock through storms not tied well and it showed. Didn't leak tho.
