Ahoy Lee,
I use hand tools, no jig.
On what's possibly a half-baked theory, I like the male end pointed up - something about if the glue line fails at the surface, water will still roll off. And I prefer a 12:1 bevel, though I helped a friend put in an 8:1 for a new spot near the spreaders of his main mast and it seems to work fine.
I've made the male end in two different ways. One uses a sort of follow it by eye guide of two hinged V's apexes tacked diametrically opposed at the top of the male end and ends held in place by a couple of vertical bits tacked to the outside of the opposing legs. I like a japanese pull saw for ripping as it starts the oblique cut easily and I can follow the upper and lower legs by eye.
I've also started with graduated cuts across the grain, careful to keep the sets parallel to each other, and then knocking the excess off with a slick.
Once some wood is removed, I plane it carefully to exact fit. It helps to make what I call a parallel guage for this - simply a cross member a bit longer than mast diameter and two bits normal to it. Rather like a squared up U. Even though as you get more to the pointy end one leg must rest well down the bevel than the other, and you have to tick it back and forth, it gives a fast easy way to measure that you're planing the two surfaces in sync.
Once the male end in made and just right, it can be used to mark the female end. It is most handy to cut out the female end before you fully round the spar - better yet before you even eight-side it, as you are then cutting a V into a nice square chunk. Even so, it's likely too large and the stick too big to do in a band saw and no circular blade will get to the inside apex. So again, the japanese pull saw.
Small aside - I imagine you know how to make an eight-siding gauge with either 5-7-5 or 7-10-7 porportions but in case not, you could use the paralleling guide or something similar with shorter legs. The distance between the two legs is divided into either 17 or 24 segments. I make these for the job. If the spar's greatest diameter is let us say 10" I's space the legs 10-5/8" (17 5/8" units) apart allowing for convenient scribe points (chisel finished nail end) to be placed 3-1/8" from each leg and leaving the spacing (5)(5/8) - (7)(/5/8) -(5)(5/8). The porportions remain constant even though the gauge the gauge is slanted across the work and the gauge will accomodate any taper you want to put in. Whatever's convenient.
Most of the trim inside the V will be done with a set of rasps and files. I use carbon paper, blue side facing the female surfaces, and gently tap it against the male side to mark the parts that need to come down.
Before gluing I plane off a bit of the feather end of the male part of the V, leaving a roughly 1/8" flat. This gives a nice guide hole to bore for what looks like a stopwater, which is structurally pointless here. It really gives the space needed for just the right fit.
Not counting making the blank for the new part of the spar, this process takes me about 6 hours, perhaps a little less.
G'luck
Ian
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