Be aware that re-varnishing a mast
can "generally" NOT be done while anchored out. It requires a helper on a windless, PERFECTLY calm day, in a protected basin, while tied to a dock
I've climbed masts hundreds of times, and the wake from a dinghy
can cause a concussion! If you have a brush in your right hand, and can of varnish
in your left, you have none to hang on with, (unless you have a prehensile tail). I learned this the hard way, and have a crushed sternum to live with.
You also can't tape, sand, or varnish
underway effectively, as there is too much spray & motion for good work.
When I had a Wharram
cat, I beached mine to renew the varnish, as I just couldn't do it anchored out. Perhaps on a monohull
in calm enough conditions you could?
Just another consideration...