Wooden mast repair.

[Tatheelrod22]

The Copper sheathing on the mainmast of my gaff rigged schooner has started to come loose so I’ve removed it. this is my first boat with wood spars. I want to repair and replace properly, this looking for input. These are not solid spars. My thoughts are to
1. Make the tack holes slightly larger, then fill them with a slightly thickened epoxy (honey consistency?)& fair to smooth.
2. There was a very rubbery adhesive on the surface between the mast jand the Copper. What would be the best product to use upon reinstallation?
3. Replace the tacks holding the copper in place with new tacks given most were bent during removal.
4. Varnish
5. Reinstall sheathing

Pictures are below in case they help or prompt additional thoughts or questions.

Sent from my iPad

[Benz]

I would use a clear penetrating exopy sealer (like Smith's or Jamestown's version of Smith's) on the bare wood, using several coats and making sure it flows into the tack-holes.
Varnish--maybe. It's not like sun's gonna get past the copper.
I would bed the new copper with 5200 or Boatlife (boatlife will spread easier), and tack it with annular-ring bronze nails while the bedding is still gooey so it gets pulled into the nail holes. Those nails are....tough as nails to remove, and should hold the copper on pretty good.

[Tatheelrod22]

That’s exactly the kind of advice ai wanted. THANKS!

[Spot]

You might consider coating toothpicks or dowel pieces with epoxy and running them in and out of the tack holes wet and leaving them in to cure. Trim and sand and keep going.
I did something similar with 25 1/4" [6.4mm] holes in a fiberglass laminate using fiberglass rod. I was working overhead and it worked well.

PS The before and after pictures are impressive, nice job cleaning up behind the copper.

[Bowdrie]

Not germane to your questions; is the copper where the boom rides or is it up where the gaff rides?
Only asking because it was/is common to also have copper at the places where the gaff rides when the sail is reefed.
It's also common to surround the mast with vertical Teak strips spaced somewhat apart and let the boom jaws ride on them.
Such is also seen aloft for the gaff.
In many ways it's superior to copper, strips are easily installed/replaced and the hassle of working with the copper is eliminated, (especially aloft).
Ok, on to your particular job.
Don't know the age of the boat, but I have a suspicion that the black rubbery stuff was something like the old Detco-Grove deck compound, a two-part Polysulfide.
Should you wish to replicate that today you'd use the stuff from Boatlife.
Do not use a Polyurethane, (like 4000/4200/5200,) use a Polysulfide.
Their is absolutely nothing wrong with using the old standby Dolfinite either, it has been used for such jobs for longer than any of us have been alive and is a good choice.
Whatever product you use put some giant hose clamps around the copper sleeve to get a good squeeze-out and fit whilst you put in the tacks.
Yes, tacks, don't use ring-shank nails, should you or a future owner re-do the job the nails will probably either break off or pull-out little chunks of wood.
I agree with cleaning/plugging the holes with epoxy and little dowels, (1/8>3/16>1/4in.,) depending upon need.
You can buy ~3Ft long dowel rods and cut as needed.
Using Smiths CPES is good a good idea after the wood surface is cleaned up.
It appears from the pics that some wood has been "chunked out", try to glue some wood in if you can.