Lining off and Spiling

So last weekend I cut myself a bunch of veneers at around about 100mm wide.

I then spent the last week doing in depth study into spiling, and discovered I had headed down the wrong track completely.

First thing I discovered was that I need to "line off" the hull.  This process is part science and part art if your to believe the multitude of posts on the web about it.

The science of it is that you decide how many strakes (boards) you want for a start.  Apparently the classic mahogany runabouts had 5.  Then at each frame to you divide the height by the number of strakes, and mark out these intervals. 

Then you take a "lining off" batten (just a long flexible batten) and join the marks.  That's the end of the science.  Then you "adjust" the batten until the line "pleases" the eye.

I gather that getting the perfect  line is more of a concern with lapstrake (clinker) built craft where the lines are more prominent in the finished boat.  With mine the lines will "soften" I think when the planks are sanded and varnished.

So then the trick is to make the planks fit the lines.  This is where I have screwed up a bit.  At its narrowest point my planks need to be about 120mm.  Plus due to the curves of the hull, after fitting your plank you end up with a plank that will be about 120mm wide but curved and so you need a wider plank to cut it out off.

So I am going to need planks at least 120mm wide and in some cases probably twice the width.

This is where the trick of spiling comes in, which is matching the curve of the previous plank in the next plank.  Spiling is an old art, however I have been advised of a newer cheat method.  This involves laying "Clear shelf paper" on the side of the boat and do the "lining" directly on to that.  when layed flat it will present a perfect pattern for the planks.

Another method, and this is the one I am going to try first is to secure the next board about 25mm below the last one, and then use a trim router with a modified fence to route a groove in the new board that follows the curve of the previous one.  Then use a block plane to clean up to the line.  I have practised this method on some scraps and it seems to work OK.

I have a couple of sheets of crappy ply that I am going to do some full size practice runs on.

In the meantime I have decided to use at least some of the 100mm wide planks to do the transom with.  So tonight I glued on the first piece.  This was also my first live run with using staples to secure the veneers on.  Despite my practice runs I have found the staples sink to deep.  I need to get longer staples so I have room to put scrap ply on top.

I'm now waiting for the glue to go "green" so that I can pull the staples.

I'll post some pictures of the above tomorrow.