Birdmouth - keeping scarf parallel each side of a pole?

zak99 · 27 Mar 2012

Need to do what I call a birdsmouth joint repair on the bottom of a small mast, ie two 12:1 scarfs on opposite sides meeting on a flat joint in the square section at the bottom. i.e. the damaged and rotten square section (80 x 80mm) at the bottom of the mast will be cut off and renewed in two flat halves (40 x 80mm) and will join to the round tapered mast via two scarfs.

The birdsmouth is necessary as there are wires runing up the inside of all but the bottom of the mast so I cant simply cut one scarf as I wont get enough length in it.

I'm used to doing scarf joints but have never done a birdsmouth. If jointing round I usually just mark the scarf beginning and end and then do the rest by eye, watching for an even (and flat) planed eliptical shape

I wondered if anyone had any tips for marking out, measuring, checking etc, so that I can keep the faces of the two scarfs flat and parallel to each other and the face of the square section joint.

rgds

Boatfixer · 28 Mar 2012

Last mast extension I did I made a 3 sided box jig out of mdf with tapered sides to suit the scarf angle. This clamped to the mast made a guide for the first side and with a block wedged in it a parallel guide for the opposite side.

Graham

Tony Spear · 28 Mar 2012

Dave R":2b94anws said:
I think I'd ask that question here.

Dave, that's not fair! I clicked on the link and found a thread about a Lady called Bernadette who's building a Yacht with the help of her 80 year old Dad, it's both technically interesting and a really inspiring story about life and I've spent the best part of 2 hours reading through it!

Sorry, can't find a suitable smiley for this.