Pattern Making

A large part of today will be spent waiting for the epoxy in the rudder blank to cure. It is "dry" to the touch, but I want to wait at least 24 hours before I remove the clamps.

The waiting time has been put to good use - I made the pattern to be followed while shaping the foil.

The boat plans include a "Sample Only" drawing of the foil template. That page of the plans has a straight line with the instructions to resize the image so the straight line measures 120 mm. I played with the Adobe sizing tool and printed out two test efforts. On my third try the page printed to the correct size: the line measured 120 mm, which made the foil template drawing the correct size.

I cut the paper template out, taped it to a piece of left over 3/4" x 1-3/4" western red cedar. I drew a second outline -inside the correct line - to be a cut-to line. The piece was clamped into the WorkMate and I got out the Japanese saw. Cutting a series of kerfs down to the cut-to line, I then used a chisel to remove the wood between the kerfs...





...until I had a rough cut pattern for the foil shape. I plugged in the Dremel fitted with a used sanding drum. The western red cedar is pretty soft and I didn't want to risk sanding away too much material or gouging the pattern with a new drum. Being careful to stay within the lines, I was able to smooth out the roughness of the chiseled pattern. A few more minutes of careful power sanding made the pattern ready for hand sanding.

A strip of 80 grit sandpaper was wrapped around a wooden paint stir stick and served as a mini-rasp to smooth the pattern and take it to the original shape outline. Some 120 grit paper finished the sanding job. I put the paper template over my wooden one - and I am satisfied with the result. If I try to fine-tune it any more I will probably take too much and have to start over.



The one last finishing step is to cut the pattern in half. The drawing - even the resized one - was drawn to fit on the page and is not as wide as either the rudder or centerboard. Since the foils are shaped on the leading and trailing edges and flat in the middle, the width of the foils doesn't matter. Once the pattern is cut in half it can be used as shown below (pic borrowed from the MSD Forum).



Shaping of the rudder will begin tomorrow.