Mast repair - scarf question

Saturated screw holes don't work as well as you might think and isn't the same thing as a "bonded" fastener hole. It will help with some moisture invasion, past the fastener, but not all of it, mostly because the screw wipes most of it's coating off as it's driven into the hole. Even if you carefully fill the prebored hole with goo, the threads mash the epoxy too thin and not enough film thickness remains, to prevent moisture ingress. Also epoxy doesn't melt, but it does deform and plasticize with elevated temperatures. It's like a lot of plastics and goes from solid to a semi liquid, but never really melts, just deforms, until it reaches a temperature where it bursts into flame or vaporizes into a plasma state.

Varnish over epoxy is problematic, mostly because you need a lot of varnish to protect the epoxy. Polyurethane offers better UV protection, but at the cost of more difficult repair and upkeep. I love brightly finished spars, but you have to be prepared for what you've wished for.

One of the things you need to do when caring for a mast is keep it clean. The internal drains need to be kept clear and a wire is usually all you need. Bugs and other beasties like to live in these places and you've seen the results when their "homes" block the drains. A friend of mine, who I built a 35' stick for some years ago, uses compressed air. He has a Schrader valve installed on the mast head and he duct tapes the sheave and halyard exit points, then blasts the inside of the stick at the beginning and end of each season. Works pretty good, but maybe a bit much for most.

Back to your track hole issue. The usual choice is simply to move the track, so you have new wood to place the fasteners. Of course plugging the old holes too. If you absolutely need to reuse the holes, they should be restored. Again the best way is epoxying in some repairs (dowels), then bonding in the new fasteners. Lastly CA (cyanoacrylate) glues will harden up wood fibers quite well, but don't tolerate dynamic loading very good and the fibers tend to crack, break and split out of surround wood, if asked to accept these loads, which are very typical on a mast, especially if free standing.

 

I decided I could just slide the track and plugged the holes.

Laying out, cutting and fitting with hand tools I was concerned that I was going to hav to get creative with putty and wind up painting the mast, but I'm pretty happy with the end product. Now, even with stain pre-treat, let's see how the desperate pieces accept stain! I might wind up painting it after all, or maybe I'll just let the healed scars be a badge of honor