Mast Partner

The mast partner was made from a lamination of two pieces of 3/4″ yellow pine. I put a layer of 6oz fiberglass in between but I’m not sure how much that helps the strength, if any. The cloth is along the neutral axis, so it won’t help with bending strength, but it should help keep the fibers of the wood from splitting.

To glue it in place, I first clamped a batten along the underside to locate it at the right height. Then I carefully measured so the center of the notch was on the centerline of the boat. Then I dry fit four big stainless screws through the bulkhead and into the mast partner, but avoided the glue line. Then I glued it in place with thickened epoxy and healthy sized fillets. The 3/4″ holes will have some 3/4″ x 6″ long bronze rods epoxied in place to use as belaying pins.

After a few trips I decided another pair of belaying pins would be handy since I have two halyards, a snotter, downhaul, and brail line to tie off. Here’s how I did it.

Unfortunately the original mast partner cracked when my wife and I took the boat down to Hatteras in 2020. It rained every day we were there and I think the moisture caused the wood to swell around the bronze belaying pins and crack. This is the second time this has happened, so clearly a better solution is needed. Since I do metal work for a living, I decided to make a new partner out of aluminum.

I CNC plasma cut out a new mast partner from 1/4″ aluminum plate and bent up the sides from 1/4″ flat bar with a press brake. The circular part is a piece of pipe I split and flattened out a bit. All of the side pieces were annealed with a cutting torch prior to bending, otherwise they’d probably crack. Coat the pieces with soot from the acetylene flame, then turn the oxygen on and heat until the soot burns off.

Next I TIG welded the seams around the outside and also the seam between the circular part and the flat bar. I plan to have four belaying pins in the same positions as the original. The 5th hole next to the notch for the mast is for a piece of pipe so I can lead the snotter line back to the cockpit.

After trimming the sides to size I worked on the rear plate which will attach the whole thing to the boat. I went back and forth between whether the bolts should be welded to the mast partner or if the bolts should thread into the partner… but eventually decided this way would be easier to repair in the future. Also you can see the piece of pipe that forms the passage for the snotter line through the partner.

I smoothed out all the welds with a flap disc in an angle grinder and then gave it a good sanding with a random orbital sander. I used my mill to smooth out the welds inside the notch for the mast.

Next I cut some 3/4″ round bar to 6″ long and chamfered the ends for the belaying pins.

After welding them on I ran a ball endmill around the threaded holes to about .020″ deep to make a slight groove to give the butyl tape somewhere to go.

All ready for the next time I have some stuff ready to powder coat at work. I think I’m going to have it coated green to match the coaming and shear stripe on the boat.

I had it powder coated Battlefield Green, although it’s a little bit lighter than the Equestrian Green that’s on the coaming. It’s pretty good though. I’m using four 1/2-13 aluminum bolts through a 1/4″ backing plate to hold it onto the bulkhead. I know they’re weaker than steel, but I wanted to minimize any galvanic corrosion.

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