Molded Clamping Cauls
© Frank Ford, 3/19/98; Photos by FF, 3/16/98
Here's the job:
It's a 1910 Martin style 2 bowl-back mandolin that just happens to be in nearly mint condition. The owner's 9-month old son knocked it down and cracked the peghead loose. The joint did not fail; the wood underneath split. Clearly, this is a case for hide glue and good clamping pressure. The break flexes open very easily so there won't be any difficulty getting glue down in there, but clamping is another matter.
This neck is made of Spanish cedar, which is very delicate indeed. Just look at it hard and you'll dent it! Even a cork or rubber clamp pad will crush the fine detail of this carved "diamond" joint.
Time for a molded clamping caul to distribute the pressure.
I'll mix up a small batch of Quick-Carve:
And spread it on a one-inch square of scrap wood:
Here's the tricky part. This stuff is really gooey, and rather thin-bodied when first mixed, then it suddenly sets in 5 minutes or so. I'll hold the piece of wood with and keep testing the glop with my finger until I notice it just stiffening up. Then, as quickly as I can, I'll mash it down onto the broken peghead which I've protected with a piece of the thin plastic wrap:
If I'm making a large caul, or the surface doesn't have such fine detail, I'll just mix the glop and place it without waiting for the setting reaction to proceed. In this case, the Quick-Carve just doesn't weigh enough to make the plastic wrap conform to the carved contour I need to clamp.
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