Revarnish - Sand it or Strip It?


I'm planning on revarnishing the interior of my 15 year-old Langford this winter. Any words of wisdom or rules of thumb regarding when its time to strip an interior before putting on another coat of varnish?

With the exception of some graying on the gunnels due to finish being worn through, the existing varnish looks pretty good, and I'm leaning towards some light sanding before putting on a couple of more coats over whats there now.

I lightly sanded and put on 2 coats maybe 7 years ago, so this would make it 4 or 5 coats total over the original finish.

Should I be thinking of stipping the existing varnish first, or going with my first gut reaction?
Stripping is nasty work and the chemicals aren't something you want soaking down into a canvas you're not replacing. Unless you have peeling or other signs of adhesion issues, I would sand and recoat.

If the interior varnish is intact, not peeling, etc. and its not too dark for you to accept, and you are NOT re-canvassing, then sand and re-varnish.

If it has lost its integrity and you're re-canvassing anyway, then strip and start from bare wood.
Thanks to you both, I'll stick to the light sanding option and avoid the mess. For what it's worth, this particular boat has clear fiberglass on the outside as opposed to canvas (it came that way from the manufacturer), so adversely affecting canvas is not really a consideration, for this canoe anyway.

Thanks again!
Adversely affecting the fiberglass then becomes the issue. Different strippers have varying effects (or amounts of the same effect) on fiberglass resins (softening and/or attacking it to some degree) but in general, keeping stripper away from them is a pretty good idea. It's well worth being pro-active about varnish maintenance on that boat and making sure that it never needs a major interior overhaul.
That's great advice, I never would have thought that stripper could harm the fiberglass. The boat will never be subjected to it while I'm still around.

Thanks a lot!