I wish there was a clever software program to produce mitre templates for complex seat stay mitres. However it only recently occurred to me to reduce the time it takes to shape two by transferring the mitre from the first hand carved one to the second side. I like to do my seat stays in the “fast back” style for preference instead of using top eyes. With very narrow stays it is fairly easy to shape the mitre to the back of the seat tube, but so often the seat stays are 15mm or more in diameter and require quite a lot of shaping to wrap around the back and sides of the seat tube. It never ceases to amaze me how at first it looks like the tubes will never mate, then with perseverance they all at once seem to drop into place. It does however take a lot of patience to avoid over filing the mitres whilst continually offering up the seat stay to the seat tube.
Having managed to get one right I used tracing paper and glue to transfer the finished mitre to the opposite uncut seat stay. Simply find the centre line using an angled metal strip or in this case use reflected light as the seat stay was S bent, and mark it.
Remember that the opposite seat stay will be a mirror image. Draw a line transversley across the tube below the mitre to be copied and place a line on the uncut seat stay in the same place. This can be done by placing the tubes together but in the case of S bends it is better to measure the exact distance with a ruler as it is more accurate. Then wrap a piece of tracing paper around the mitre lined up with this line and transfer the centre line also, holding it in position with a LITTLE glue (Pritt stick or similar is good).
Draw around the mitre on the outside then cut away the excess tracing paper.
Now carefully remove the tracing paper mitre and glue it to the uncut seat stay to the previously drawn centre and base lines INSIDE OUT. With slotted dropouts you can also transfer the slots at the other end by the same method.
Cut the new mitre and fit. It seems to work.
