The Spar Taper Gauge

The mast has been a little tricky figuring out all of the tricks and tools.  The first 9′ of the mast is straight, but the top 6′ is tapered.  I read the portion in Dynamite Payson’s book about it, but I just could not seem to figure out what he was saying.  Finally with a random tip from Graham McKay at Lowell’s Boat Shop and some Internet research, it has all come to light and I am well on my way.

One tool that I’d like to talk about is the spar gauge.  While the mast was still square, I made some measurements according to the plans for the taper.  I used a thin strip of wood as a batten to trace the lines and cut the taper with a skill saw.  The next logical step is to cut the corners off with the skill saw to make the square into an octagon.  The problem there is how to lay out the lines to cut the corners off.  Enter the spar gauge.


No matter the size of the mast, this tool uses a ratio that will give you the correct lines for trimming off the corners of the box.  I setup mine with the following measurements.



I had a left over scrap of teak for the main body and I used wooden dowels for the 2 end posts and pencils for the markings.  I drilled all of the holes on the drill press to make sure they were straight and voila!







Provided the end posts are against the side of the mast, the pencils will draw the correct lines for trimming.  Questions?  Comments?


Thank you for reading!


2 Responses to The Spar Taper Gauge

  1. Just an update on this. Instead of using pencils, you should use some sort of sharp point to scribe the line. I used the pencils and the tip kept breaking forcing me to have to re-sharpen the pencil every couple of feet.

  2. I made my own spar guage years ago when building the sail version of the Bolger Nymph. They work like a charm, and while simple, are an amazingly helpful tool. I ended up putting fine point sharpies in mine!

    I read your blogs and visit your site to see updates and changes, Jed. You do nice work!

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