The
heavy demands for the gunwale rubber to bow and twist at the same time
made it difficult to achieve a good fit on the hull without it
snapping. One of the problems with the piece of Merbau I had been
using was the diagonal grain which allowed it to split along a fairly
short segment, ie. little resistance to splitting.
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But
another is the weakening effect of the screw hole bore. While I could
choose a piece with a straighter grain, I could not avoid the bore if I
were
to use the screw size specified in the plan.
An alternative would have been to have made up a laminated gunwale rubber of two thinner pieces, but as the lower rubbing strake was able to be fitted without snapping I felt that there must be a better way to do it. Steaming was problematic, as there were only two points at which the rubber could be clamped to the hull, and that is only after being screwed to the bow, so, by the time the piece was clamped into position, it would already be stiffening again. Even if it did take the curve there was no guarantee that it would not snap when drilled.
I could have tried shaping the piece before bending it. It was, after all, supposed to be a semicircular section. That would reduce its resistance. But it would also make it more difficult to locate the screw holes, because at this stage I was trying to drill them in the rubber to match the location of holes already in the sheer. Having a flat edge helped in that regard.
I decided to make one more try with a straight grained piece, but, if that were not successful I would build up a laminated gunwale like the stem.
After steaming the new piece at the section where the bend is tightest there was a little give in it, but not so much as to reassure me that the same fate would not be waiting. This time, instead of screwing all the holes I only did the alternate ones, to reduce the weakening effect. And I clamped the piece slowly towards the hull, taking a day or so to get it tightly approximated.
The beginning of the fourth attempt to get the rubber attached. Only alternate screws are used.
An alternative would have been to have made up a laminated gunwale rubber of two thinner pieces, but as the lower rubbing strake was able to be fitted without snapping I felt that there must be a better way to do it. Steaming was problematic, as there were only two points at which the rubber could be clamped to the hull, and that is only after being screwed to the bow, so, by the time the piece was clamped into position, it would already be stiffening again. Even if it did take the curve there was no guarantee that it would not snap when drilled.
I could have tried shaping the piece before bending it. It was, after all, supposed to be a semicircular section. That would reduce its resistance. But it would also make it more difficult to locate the screw holes, because at this stage I was trying to drill them in the rubber to match the location of holes already in the sheer. Having a flat edge helped in that regard.
I decided to make one more try with a straight grained piece, but, if that were not successful I would build up a laminated gunwale like the stem.
After steaming the new piece at the section where the bend is tightest there was a little give in it, but not so much as to reassure me that the same fate would not be waiting. This time, instead of screwing all the holes I only did the alternate ones, to reduce the weakening effect. And I clamped the piece slowly towards the hull, taking a day or so to get it tightly approximated.
The beginning of the fourth attempt to get the rubber attached. Only alternate screws are used.
As the
rubber had to be bent downwards to
follow the sheer, as well as inwards, there was a tendency for the
lower
edge to lift away from the hull side. No amount of tightening on the
two clamps could overcome that. Only the screws could do it. Otherwise
it
would have been tempting to glue the stick on with the alternate
screws, wait
a few weeks, and then put in the remaining ones. But, unless the lift
away from the hull can be prevented the rubber could not be glued down.
Shot from below, this shows the rubber lifting away from the hull.
Shot from below, this shows the rubber lifting away from the hull.
After
some further coaxing the rubber was clamped up against the hull, at
least on its top edge, but that is where I was when the third one
snapped. I was not rushing to screw this one down in case it split
again, and in fact I left it there for some weeks to adapt to the
shape before any more intervention.
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