No paint job is any better than its foundation – surface preparation is critical. Painting over peeling paint is pointless – the old paint will continue peeling, taking the good paint with it. But if the old paint is basically sound, and/or if you scrape/sand off the loose paint, a fresh coat of paint can make a canoe look better, even if the new paint job is not perfect, and even if the old paint is a bit cracked.
Your photos, as I see them, show unusual cracking and peeling of the existing paint away from filler that appears to be sound -- do you know what kind of paint/primer was used. I suspect that paint was applied to a poor surface -- contaminated, poorly prepped, possibly water-based paint applied over filler that was not fully cured, or a very poor quality paint. Filler is usually integral with the canvas, having been rubbed right into the fabric’s weave when applied -- while it may crack, it does not usually crack and peel away as your pictures show; it is usually only paint that cracks and peels, as seems to be shown. Such peeling is caused by water getting between the paint and the filler and loosening the paint from the filler, which usually stays in place.
If in fact the filler is cracking and peeling away from the canvas for whatever reason, that process may well continue on into other parts of the canoe over time. And if this is the case, recanvasing is probably called for.
Have you actually tried to scrape away the damaged material?. You should do so over the entire affected area now to see just what your problem is -- if the problem is repairable, you will have to do this anyway. I’d like to see photos of the scraped areas to see what the canvas actually looks like -- the two bare spots showing in the photos above
If it is just paint that is peeling, you have some work to do. New paint will not keep old paint from flaking (especially if flaking and peeling is the result of poor paint), so it is important to scrape and sand to remove all suspect paint -- and filler, if the filler is actually separating from the canvas -- the sign of a poor canvasing job. If the problem is poor paint (as opposed to just old paint that is cracking from age and drying out), you may have to sand it all off, and you might as well do the whole hull now. In any event, fair the edges of any chipped areas by sanding, or by using spot putty then sanding fair, depending on the depth of the chip.
Sanding the flaking paint away may be sufficient, as long as what is under the old paint is compatible with the new paint to be applied, as it should be if ordinary oil- or water-based paint was used. Spot putty may fill in very minor scratches and dings. In any case a light sanding over all is called for to help new paint adhere. After sanding, at a minimum I would thoroughly wash the surface (soap and water, or TSP) and rinse completely, and let the canoe dry completely before applying new paint. Where the old surface may have been contaminated, as may be your case, it may also pay to use a primer (Zinsser or Kilz).
If the paint is tight, even if crackled, a coat or two of paint will prevent leaks and give you a serviceable canoe. But discretion being the better part of valor, it is wise to have a small roll of duct tape along if some of the old paint/filler under your newly-applied paint decides to flake off. Even without a duct tape repair, the resulting leak will likely be very slow and will likely not interfere with a day of paddling.
Here are some links to some discussions in these forums of painting over old cracked or chipped paint:
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.p...t-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
[URL='http://forums.wcha.org/showth...cha.org/showthread.php?8906-Repaint-Tips[/url]
Repainting canoes is done all the time with all kinds of paints. Most use an oil based paint, and many use “marine” paints. Some use various other paints intended for exterior use – house paint, porch and deck paint, etc. Oil-based gloss paints are most commonly used. Water-based paints can work well, as can semi-gloss paints. They are easier to apply, and may be easier to touch up in the future – the chief disadvantage I have found with semi-gloss is that it is not so easy to keep clean, a particular problem with a light color. Using one of the premium marine paint over an old paint job is likely a waste of money. A good exterior paint – house paint, porch paint, Rustoleum enamel, or something similar – should do the job.
I’m not sure what sort of “ flexible, reasonably resistant covering that will adhere to the canvas” there might be. If the problem is old peeling paint, applying new paint to a properly prepped surface should do the job. If the problem is failing filler, hiding the problem with another piece of canvas or other material will only add weight, be unattractive, and will not solve the problem -- your new covering will likely soon become detached from the flawed material it is covering.