SPILING AN OUTER CLAMP

Comment

Comment by bob mitchell on January 13, 2012 at 3:10am

       Our search for an answer as to why I had to spile my outer clamp when the original outer clamp was not spiled led Clyde to an interesting hypothesis, and then a further discussion about "Scantlings" in general. (SCANTLINGS are the dimensional elements of the lumber used to build a boat - as in a "Table of Scantlings" for a particular boat telling the dimensions of the parts - for instance the outer clamp)

From Clyde " But by increasing the size of the outside clamp you probably used a size that wouldn’t bend naturally into the notches in the frames.  Scantlings should be what they should be; too small and the boat will come to pieces, too big and you can’t make the wood do what it should.  Those kinds of things are what makes the designing and building of boats so interesting.  Before the scantling rules boats were built by using the ways it used to be done, and that way was what developed by trial and error; the errors sunk so the boats that didn’t sink became the models to build from.  Therefore, the boats were usually built heavy, so as to make sure they last through at least the first few storms.  Scantling rules came into being as a result of racing; designers were starting to design boats to be built with smaller dimensioned lumber so they came up with the rules to keep them from going too small.  At least that seems like what probably happened—I only have my sense of how things could have developed (guess) but it sounds good, since I have no data to come up with a better statement."

Comment by bob mitchell on January 11, 2012 at 7:25pm

Clyde and I had a sort of running spar on spiling the outer clamp, because originally it was just "set" without spiling. One of his relevant comments was about how a board has a natural curve when bent on to fit a slanted surface  -  maybe matching what you need.   From Clyde: "

Take any size board, lean it over a little, pull the ends the same direction, and you have your curved board applied to a slanting surface—without spiling.  Of course, the natural curve of that kind of “construction” may not be the same curve as your outside clamp. It may have to be pulled up or down to make it fit. So, spiling may be the way to go to relieve the tension.  A lot of small craft are built by taking a couple of planks with straight parallel sides, fastening the forward ends to a stem and wrapping them around a central form (wide at the top, narrower at the bottom) and fastening the after ends to a transom that is generally the same shape as the central form but narrower.  The “boat” at this point has no bottom, but the the bottom of the planks show a good rocker (curved up) shape and the gunwales will show a shapely shear, producing a good looking boat.  This gives good looking curves put together with slanting surfaces without “spiling.”  That’s a quick way to build a boat, but don’t forget the bottom!"

      However I did not find that the case in my situation of applying a bigger outer clamp. One of the main reason I used greater dimensions, which Clyde appreciated, was that the notch surface wood was worn out, so by cutting new over size notches I created a fresh glue surface.