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.