Monday, October 08, 2007

Making it Round

The mast is now finished, except for the final epoxy coating and sanding in preparation for paint.

It was fairly simple to take it from the square box-section after glue-up to the final round shape. I would have been done much sooner but had a lot of interruptions last week.

The first step in rounding the mast was to cut it down to 8 even sides. I did this by first laying out straight lines to divide it equally for the entire length of the mast. I then cut just outside the lines with a 7 1/4" circular saw set to a 45-degree angle. The final cut down to the 8-sided lines was done with a handheld power planer and then smoothed with a belt sander. The 8-sided spar is shown below:

After cutting the 8-sides, I first made and fitted the 4 hardwood rigging cleats, or "mast hounds" at the top of the mast. Then additional lines were drawn, laying out 16 even sides which were cut down the lines with the power plane. After this operation, the remaining 16 corners were flattened with the plane to 32 even sides, and from this stage the mast could be rounded by working these sides to round with a belt sander and the 6-inch orbital sander. I did all this on the bench where the mast was laminated, spending about a half a day on the shaping. The tools used are shown below: Power plane, belt sander, 6-inch random orbital sander, 5-inch random orbital sander, and block plane and sureform tool for areas where I couldn't use the power tools.

At the base of the mast I decided to leave the part where the mast is solid 8-sided. I like the way it transitions into round, and it will make it easier to install such hardware as the halyard rope clutches. The wiring conduit is shown where it exits the sidewall. There is one on each side.

Today I moved the finished mast out in the open and applied the first sealing coat of epoxy. The workbench is now free and I have the keel for the second hull scarfed and clamped on it now. When that cures, I will begin the process of wiring the second hull together, then suspend it from the rafters while I tear out the bench to make room for cradles to lower the hull in so I can begin construction.


tsunamichaser said...

Hey Scott,

Your mast looks great! Putting the hounds on early and leaving the bottom 8 sided is a smart move.

Dang I was hoping to see the next version of the 26 foot lathe. I guess we all can't be that insane.


Scott B. Williams said...

Hi Thomas,

I really liked your 26 foot lathe (AKA mast-maker/widow-maker). I figured my little DeWalt 1/2" drill motor couldn't handle the strain, so I decided to shape the mast the hard way. As it turned out, it went much faster than I expected. Careful layout to 16 even sides, then 32, makes it easy to round on out with a belt sander and 6" R.O. sander.

I pre-drilled and pre-installed the hounds, marked their footprint on the flat section, then removed them to make rounding easier, leaving the mounting area flat. Then they were remounted with epoxy and counter-sunk, bunged holes. These are teak, by the way, some of the cut-off scrap I brought back from the Florida job.