Friday, February 12, 2010

Bending the Shears

The first step to the shears was getting the length down to about 18" longer than what I measured to be required. Since the fit of the shear to the breasthook is a set angle, I cut some scrap material on my mitre saw until I got it right and then cut an angle on the front of each piece to mate with the breasthook. The four shear pieces (two layers each) were then soaked in the stairwell soaking tube for a couple of days.

I worked on the one side of the boat where I had the most room between the boat and the wall. To support the shear while bending into place, I clamped long boards to the form or the frames over to the wall, just below the level where the shears would meet the frames. This provided a resting place for the shear while bending into place. I then wrapped a bath towel around the shear along the area of the stem and another in the area between the front and middle frame. I then poured hot tap water over the towels (buckets underneath).

To start the bend into the breasthook, a 24" Bessy bar clamp was clamped to the shear to provide leverage and the leading end was bent while the remaining length of the shear pushed up against the wall about 3' away from the boat. After shoving it into place and the breasthook clamp board squezzed tight, the rest of the bending took place at the rear end of the boat. A pipe clamp was put on the shear near the transom and used to gradually bring the shear towards the boat. After pouring another pitcher of hot tap water on the towels, the shears were gradually moved into place up against the frames and clamped in place. Towels were removed and the shear left to dry. After a day of drying, the first shear was removed and moved to the other side of the boat where I did not have as much room to work. I repeated the process for the next two shear pieces. Unfortunately I did not take any pictures during this process.

While pulling the third shear piece into place, I heard a loud crack and looked up to see a distinct sharp angle forming inside the towel, just aft of the breasthook. Another crack or two later and several expletives, the break was complete. I backed off on the bending process because this shear was toast. I removed the towels, the clamps, and put the shear aside for later analysis. I grabbed the last shear piece out of the soaking tube and bent it into place without incident. Analysis of the broken shear showed a severe grain run-out in the area. I thought I selected all pieces to put the staightest grain towards the front of the boat, but I got this piece backwards. I decided to make a scarf cut in the broken area and mend this piece back together putting the scarf joint at the back of the boat. After the piece dried, I made a jig for my chop saw and made about a 5" long scarf joint in the shear and epoxied that sucker back together. After curing, joint clean-up, soaking and bending, I was back on track with all four shears bent.

Prior to gluing the first layer of shears to the frames, I made a mid bow area temporary "spreader board" to ensure the contour was similar on both sides. One side measured wider from centerline and the curve did not look as smooth as the other. The way my stem support was made, I had a level surface to center and mount this board. The first layer of shears was glued to the breasthook and frames using clamps to the temporary spreader to force the curve in place on the one side. Then the second layer was epoxied to the first layer and clamped into place. Screws were only used in the breasthook.

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