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Angles and Precision

I have experience in the housebuilding, construction world.  I used
to joke with my workers when they’d talk about measurement in
sixteenths.  “Sixteenths?  I didn’t know they made fractions smaller
than eighths.”  And in homebuilding, unless you are a finish carpenter,
there is seldom need to take such fine measurements.

Not
so much in building a boat.  I realized early that a sixteenth here and
a sixteenth there soon adds up to errors in real inches.  The tolerances
are small because it all has to fit together and somehow like voodoo, keep water out
My usual tolerances are not good enough because, it turns out, that
recent science has shown that water molecules are smaller than an eighth
inch.

The angles of the end cuts were not specified in
the plans.  In fact, I had to resurrect my long dormant high school
geometry knowledge in order to calculate the angles.  Working with the
plans a bit, I got the length and the height of the triangle that would
be the end of the boat.

Out comes the trigonometry
reference.  Looking at it and with some research on the interwebs, I
realized there was a magic word I remember being thrown about in high
school trig that I never did decipher: SOHCAHTOA.  This time
around it made sense.  Of course!  Sine, cosine, and tangent. 
Opposite, adjacent, and hypotenuse. So I had the opposite and adjacent
sides (TOA!), and so used tangent to calculate the angle.  Fucking
magic!

The angle was so frustratingly close to 45 degrees that it made
everything just a little bit more complicated.  43.5 degrees.  Looking
at a particular angle drawn on a board, it wasn’t easy to visualize whether the angle (or its complement) were correct for that cut.  Yet, the 3 degrees
difference between the two was maddeningly significant.

In fact, after all that work, while I managed to cut the long lateral pieces at the right angle (43.5 degrees, FYI), I managed to cut every end piece with the wrong angle (it should have been the complement at 46.5 degrees).

As I predicted, this tiny 3 degree error would make our lives slightly crazy as every stringer came together with a frustrating little gap or overhang at the ends.  Grrr.

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