Some of us obsessive compulsives like to remove the vinyl skin when patching, so we can work directly on the ABS structural layer. Vinyl can be sanded off, or scraped off, but it turns out there is an easier way. It can be skinned off easily with a sharp 1/2" chisel. The tool must be held at the lowest possible angle, with the handle right against the hull. The vinyl will let go right at its bond with the ABS. It is better to undercut with the chisel head at an angle rather than push straight ahead.
This works best on flat surfaces. If the Royalex is very grooved and dented, you may have to use smaller chisels or go to scraping. But once you get a leathery leaf of vinyl raised, you may be able to grab it and peel it off cleanly like skinning a peach. One comes to appreciate the genius of covering ABS with vinyl, the latter being very sun resistant and tough.
How well does a glass and epoxy patch stick to vinyl or ABS? I’ll let you know in some months or years. The patch went right under the seat area of my MR Synergy, where 10 years of use led to the vinyl wearing away. What we really could use is something thickish to paint over worn vinyl to build it up again.
A possible chisel technique
When you said the chisel handle must be right down tight against the work surface, it reminded me of a trick that might help. Since the handle of the chisel prevents you from getting the bottom of the blade flush with a flat work surface, try turning the chisel around so the beveled side of the blade is down, rather than up. Now the beveled side can be positioned perfectly parallel to the work surface and the non-beveled edge acts as the wedge which peels the material up.
This is an old woodworker’s trick for getting a flatter cutting angle than can be achieved with the beveled side of the blade facing up. This method would not be needed when working on convex curves, but if the handle of your chisel contacts the hull while you are working, try flipping the blade over and see how much better it works.
My problem with that method was that
I had more difficulty controlling the forward force and keeping the blade angle constant. Also, the peeling goes better if done, not straight ahead, but peeling under from the side.
I thing the approach you describe could be done with shorter chisels, or with certain specialty planes, some of which I have. My wood chisels are about 10" long, and are a little hard to keep on the bevel.
if you
use an old fashioned hand planer, work becomes easier and less dangerous (for hull and hands).
Have some OLD hand planes. But
there is no danger using the chisel as long as one points it away from all parts of one’s body. And, this is a low-power, finess operation where being able to see the blade is important.
I thought about using my little bull-nosed plane, or even a carefully set spokeshave. But an ordinary, sharp chisel does just fine.
Plus, once you bet a peel of vinyl started, a lot of the rest just pulls off by hand.