Last summer we faced a dilemma; how best to go about ensuring Hawila’s main mast was fit for purpose. Unfortunately, rot had developed in the top of the mast, and it would therefore be incapable of withstanding the huge pressures and strains that it would be subjected to when undersail. We had to decide whether to repair or replace, and ultimately we chose to repair. We found it was better to make an extensive repair as we were able to preserve a part of Hawila, keep costs down, and save a tree.
We first cut into the mast in little sections to investigate how far the rot has spread. From this we saw how much of the mast had to be replaced and we calculated the length of the scarf required.
A scarf joint is effectively a wedge which has a long gradient which allows for a greater surface area for glueing. This distributes the loads over a greater amount of glue and keeps the loads safely within the manufacturer’s specification of the glue’s capabilities.
It was necessary to cut into the mast on two planes, making it ready to marry up with the new section. We cut the two planes into the mast with a chainsaw by means of a carefully constructed jig, and then planed it to its final dimensions.
To produce the material for the new section of the mast we made two lengths of stock with a gradient on one side, roughly corresponding with the required ratio of the scarf, by laminating together lengths of pine with epoxy glue . These formed the basis of the two opposing sides of the repair, and we then cut and planed the scarfs to correspond perfectly with those prepared on the old section of the mast.
The two sections of the repair and the original mast were then bonded together with epoxy and clamped with custom made clamps: This part of the process had to be done during the night as it was too warm in the daytime for the epoxy to cure properly.
The new section of the mast then had to be rounded to join the shape of the old section of the mast. This is achieved by first planing four new faces into the new section to produce an octagonal or 8 sided object, and then this is repeated to produce a 16 sided object. These 16 sides are then blended into the required cylindrical shape of the mast by sanding.
The mast now awaits its return to the ship, and meanwhile it is being well looked after. Our dedicated volunteer Johanna has spent the last few days making sure the mast and its new repair is well oiled and tarred and looking its best.