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Welcome to my blog on the building and sailing of a Goat Island Skiff (GIS). Join us on the Michael Storer Wooden Boat Plans forum or on Facebook, where the community of Storer Boat builders, owners, and admirers share their ideas, experiences, and watery hi-jinx.

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Sunday, May 8, 2011

How NOT to scarf a joint

Well, things did not go as smoothly as I had projected in my previous post.  I planed the mast staves for their scarf joints.  For some reason, I did each half of the joint separately, rather than stacking the two halves to plane them together.  The mating was questionable.  That is to say, a reasonable person might have questioned how well the halves mated, but I chose not to question myself.  I then proceeded to employ the “gravity clamp” method wherein one places a flat heavy object on the joint as it rests on a flat surface.  I have bricks and a garage floor... what could go wrong?

Well, gravity can decide not to pull very strongly on my bricks for one thing.  Basically all the joints on the pine staves were wack.  That’s not a nautical term, that’s a physics term.  A couple were so-so, which--in the big picture of things--is wack.  Here are just a couple examples of what wack looks like:

However, the four joints of the yard (Douglas Fir) came out good.  Good enough anyway.
So I proceeded to undo the wackness.  Thankfully, there’s enough excess length in these boards that I can afford to cut out the “joints” and start afresh.  The narrow staves are narrow enough to cut with my table saw (yay again).  I created a guide cut to a 10 degree angle and ran each stave through on either side of the joint.

After the first cut, I realized that I should orient the angle differently to prevent a wedge of pressure against the guide.  

10 degrees is very close to the 10:1 ratio I had previously used, both of which are overkill compared to the 8:1 often recommended.

In theory, two cuts from the same set-up should fit together nicely.  For the most part, the cuts went well.  Not quite as picture perfect as the sample above (which is why there are not any pictures...).
Sadly, the wide staves are too wide to fit through the saw blade on edge.  I thought about it pretty hard and was going to create a crazy scheme of rotating the blade to 45 degrees and feeding the staves through at another angle... none of that was feasible and I eventually realized that I should step away from the saw.
Belt sander to the rescue!  Being out doors, I was not afraid to create plenty of dust.  So I stacked the wide staves, marked the angle to achieve, loaded a coarse 80-grit belt, and wailed on it.

I’ve read and paid attention to the boat designer’s explanation of how epoxy bonds to wood.  HIs recommendation is to plane the mating surfaces whenever possible to cleanly cut the microscopic “tubules” into which the epoxy flows.  Sanding leaves the tubules ragged and epoxy doesn’t flow into them as well.  So I finished off the job with my plane.

I lied, there are pictures  of the not quite picture perfect cuts.  However, the slight gap will be filled easily by the epoxy goo.

Besides the weak gravitational pull on my bricks, another reason my joints were wack is that my garage floor is... you guessed it: wack.  So this time I'm elevating things to a new level.  Using two supports on the ends and a work table or two in the middle, my staves are clamped up and set to cure for the night.  THEN I’ll be able to taper, assemble, round, etc. like I said in the last post...

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