The new biax arrived. Putting it on was a repeat of the first layer, except that the core was now very stiff and hard. Since it had been more than a few days since the last epoxy work, I washed the CF layer thoroughly with water and a plastic scrubber to get rid of any blush before putting on the biax. After I applied the biax, I wrapped the mast in plastic packing film. This was not in the hopes of avoiding any sanding, but to evenly distribute the epoxy and to prevent any voids from forming.
The film is available at stores that carry mailing supplies and costs about $10.00 per 1000-ft roll. It is non-adhesive, stretchy, sticks to itself and does not bond to epoxy. It was very useful in this project.
Once the biax layer was cured and the plastic removed, the mast was structurally complete, but not ready for finishing. First, I wanted to plug the ends. The method I decided on was to make a fiberglass cone and plug it with epoxy mixed with filler.
First I prepared the mast end by sanding off the loose glass, CF, bits of epoxy, etc. The end was now square with the mast and was solid glass and CF. I wrapped adhesive packing tape about 1 inch back from the end completely around the mast. This was to limit the area where the cone would bond to the mast. Next, I made the cone from a scrap of biax sock about 2 inches long. I tied off one end, saturated the glass with epoxy, pushed the tied-off end into the mast with my finger and smoothed the open end down over the mast and onto the packing tape. Finally, I wrapped the whole thing with packing film to hold it in place and let it cure for 24 hours.
As you can see, the cone did not end up quite as thin or sharp as the schematic indicates. This was because of the pipe insulation foam that is not shown on the simplified schematic. The extra thickness is all to the good because it makes the end more solid, capable of taking greater impacts and allows for the possibility of adding an eyebolt or other mounting hardware. Note also how the packing film caused the cap to round over. This also helps with impact resistance.
The final step was to fill the cone with a mixture of epoxy and woodflour and wrap it all up with packing film to prevent the woodflour from falling out. This also formed a nice round end.
The mast is now ready for its final finish - some sanding, fairing and finally primer and paint. But that's a project for next Spring.