Making a birdsmouth hollow mast for Gwragedd Annwn
Now that I have done my test sails and found that Gwragedd Annwn is a good sailer, I am going to make a new mast for her…a birdsmouth hollow mast. The old mast is about 2′ too short, the new mast will be over 16’4″ long.
There are a lot of formulas for determining the size of your strips. My mast will be 2½” at the base tapering to about 2″ at the top. I used the one on the Duckworks site. My strips will be a little bigger than ½” by 1⅛”. I will try to get the most out of my Douglas Fir beam. Depending on the test sailing results, I may make a boom for the rig.
The first step is to rip up the strips for the birdsmouth mast.
I will first rip it into 3 planks. I want to get 6 strips out of each plank, for a total of 18 strips. I need 8 for the mast and 8 for the boom, if I find that Gwragedd Annwn needs a boom to sail well downwind.
My 10″ Shopsmith table saw will not cut through the beam in one pass and trying to line-up in and out feed tables does not work…I decide to use my circular saw and the edge guide. I spend a lot of time setting up the saw and the guide…the saw adjustments are not very precise, but, I do my best.
The routine was to make a cut, turn around and make another cut on the opposite side, then roll the beam over and make the two cuts on the bottom side.
My son, Paul (of Paul’s Canoe) helps me rip the strips. I set up the Shopsmith to rip the boards into an even number of equally sized strips.
Fortunately, I only need 8 strips for the birdsmouth mast.
I end up with a ⅜+” taper, from about 2½” to 2+”.
A little string (not shown) aligns the forms on the 2 by 4s.
The shop temperature is about 10° Celsius. That is why I am using Cold-Cure Epoxy. I will have a lot of working time at this temperature.
I ended up with some sort of clamp every 4″ or so.
I turn on the shop heater and warm up the mast. The overnight temperature is predicted to be -2° Celsius. The shop will stay at about 10° Celsius tonight.
The mast looks pretty straight. I should be able to fair the mast to be straight to the eye. I think the glue-up has been a success. The next day I strip off all of the clamps and get the mast ready for final shaping.
I use my shop scale to weigh the mast…a little less than 14lbs!
The weather is predicted to warm up. It will get to 8°C today and will stay about that warm overnight. I will continue to work on the mast in a few days.
A few days have passed and the epoxy is cured enough to work with. The first step is to knock off the biggest lumps so I can use my power planer.
The mast blank seems to have a few “bends” in it. I will see what they look like after I begin to plane off the sharp edges.
I will again let the epoxy cure for a few days. Next step will be to sand, this time with the grain to get the mast smooth for varnishing. I will then make a plug for the bottom and a masthead insert piece with a sheave in it, glue them in, let the epoxy cure. Then, more sanding.
The mast diameters have ended up being 2½” at the base, 2⅝” between 18″ and 24″ from the base and 2¼” at the top of the mast.