There is obviously confusion here. The canoe is 4 years old. There is nothing wrong with the epoxy. There was nothing wrong with the old varnish other than some scratches. I sanded lightly and applied 3 coats of varnish, sanding lightly between coats. The 4th coat of varnish was applied without sanding. I forgot. The varnish is now peeling like nobody’s business. Oh well, I guess I will use that old tried and true paint stripper: elbow grease and sandpaper.
Alsg, I followed all of that. I don’t envy you the stripping and sanding. Random orbital with 220 and a foam buffer pad, or all hand sanding?
I use Spar Urethane on all kinds of things atop epoxy coats, including a couple of ancient clear coat glass/nylon hulls that got sanded and had a full coat of epoxy rolled/tipped, then cured, wet sanded, washed and then spar urethaned. Those boats are still going strong.
I am really curious about what went wrong. Something is incompatible somewhere. I don’t sand between every coat of spar urethane, sometimes not even between every other coat, and urethane coats are often morning and evening 6 hours apart. I do always wet sand before the best-job-I-can-manage final urethane coat gets rolled/tipped.
Helmsman Spar Urethane does recommend at least 4 hours dry time and light sanding between coats, but that between coats sanding hasn’t proven necessary for me, or six-coat-a-day Memaquay (used to be six-pack-a-day). Based on that experience I don’t think it was the sanding omission between coats 3 and 4.
Best guess is that there is some incompatibility or contaminate between the epoxy surface and the urethane.
I have not used 207 hardener. The pump for that hardener is calibrated at 3/1, not 5/1 like the 205 and 206 pumps. There is a noticeable size difference between the pump chambers.
Improperly mixed epoxy can cause all kinds of problems, including amine blush with too much hardener hot-pots, even with epoxy that “doesn’t” blush. Too little 207 hardener with a 5/1 ratio pump would be reluctant to set up properly.
How that would get over the whole hull, I dunno, I guess it would be possible to drag the contaminate along with the roller or brush. Maybe check your pumps/calibrations?
The bigger question is, once everything is sanded, will you use spar urethane again, or real varnish? What was the original top coat, urethane or varnish? It’s harder to go wrong applying the same stuff over the same stuff.
). The more recent coats were not well bonded. All the varnish is off the bottom and the sides are rapidly getting there. So I will be working with a blank canvas. I still have an un-opened quart of the Helmsman, so I may go with it again, particularly since the original coats did well. On the other hand, I am feeling snake bit and may go with the Epifanes everyone likes.
