No paint job is any better than its foundation – a good sub-surface is critical. Painting over peeling paint is pointless – the old paint will continue peeling, taking the new paint with it. New paint will not keep old paint from flaking, but will simply come off as the old paint keeps failing. Painting where old paint has peeled away without finding and eliminating the cause is just asking for more peeled paint.
In some cases, with sufficient surface preparation, cracked and crackled paint can be repainted to get you a couple of extra years of use before a new canvas and paint must be applied.
But from your pictures, I think this canoe needs a new canvas, not just new paint. Besides the tears in the canvas (which might be adequately repaired functionally, but will be difficult to repair esthetically), you have two serious problems with your paint.
The first and lesser problem is that there is quite a bit of what I call crackling -- seen in your pictures 4 and 6. The raised edges of the cracks, which appear to be in the underlying coat(s) of paint and perhaps also the canvas filler, can be sanded down to be more-or-less smooth, but the cracks will remain after sanding, and are almost impossible to remove completely. If this were the only problem, repainting might get this canoe a couple more years of use before recanvassing.
A much greater problem, in my opinion, is that much of your paint has, as you note, pulled away in sheets, as shown in your pictures 1, 3, and 8. Paint peeling off in sheets indicates that the new paint did not bond to the substrate. It could mean that the new paint is simply not compatible with the light substrate, notwithstanding the use of expensive marine primer and paint. It could mean that the substrate was contaminated, or that it was not sanded appropriately. (Query -- what is the light substrate -- paint, some other coating, or the material used to fill the weave of the canvas? Was the substrate, whatever it is, ever treated with a silicone-based wax, polish, or sealant, or some other chemical? Silicone virtually impossible to remove, and is very difficult to paint over.) The way the subsurface shows through the “spider web” of numerous small cracks in the dark paint, adjacent to the places where the paint has sheeted off, in pictures 1 and 8, suggest to me that the dark paint is ready to all come off, perhaps not in sheets, but in thin strips. It looks as though the film of the dark paint has maybe shrunk, but stuck a bit more to the substrate in the webbed areas than in did where separated so readily and completely that it came off in large sheets. And even where the paint is crackled and the dark paint has not yet separated from the substrate, it is likely that the dark paint will come loose in the not-too-distant future.
Repainting canoes is done all the time -- but it is effective only when done on a sound and well-prepared surface. I don’t think this canoe has a sound surface that is amenable to proper preparation, and therefore I don’t think a new coat of paint will be worth the effort.
Recanvassing a canoe is also done all the time, although not as frequently as repainting. Is considered routine maintenance, and is not a particularly difficult job (although the sponsons on this canoe do make the job a bit more complex). The 60+ years this canvas has lasted (if it is the original canvas) is a good long life for a canoe canvas.
Below are some links on repainting over old paint -- as you will see from them, I am far from opposed to using paint to get a few more years out of an old canvas with ratty paint. But the way the paint is coming off this canoe after only three years, I think repainting would be a waste of time, effort, and money.
(As an aside, it looks like the paint failure is mostly on one side of the canoe, and I wonder why? How was it stored? Did one side get more heat, or sunlight, or dampness, or ?? than the other? Was something spilled on one side of the canoe? Whatever you do, I think this issue deserves some thought.)
http://forums.wcha.org/showthread.php?t=5790 see pp. 2-3 of this thread
http://forums.wcha.org/showthread.php?7769-Painting-over-existing-paint&p=41339#post41339
http://forums.wcha.org/showthread.php?5933-quot-Minor-quot-Restoration-advice-please&p=32358#post32358
http://forums.wcha.org/showthread.php?7775-Temp-repair-to-bare-spot-on-canvas&p=41357#post41357
http://forums.wcha.org/showthread.php?7619-time-is-not-on-my-side!&p=40689#post40689
http://forums.wcha.org/showthread.php?8564-Smoothing-Canvas/page2 starting at post 12, on bondo spot putty
http://forums.wcha.org/showthread.php?6607-sanding-or-not&p=35286#post35286
Good luck, and let us know what you decide to do.
Greg
