Saturday, August 25, 2007


After some serious procrastination, I finally dived in and did something about the marks around the rosette created by rosewood dust from cutting groves for the rosette segments as well as some careless leveling of ditto. Somewhere in the back of my head some little persistent devil was sitting, insisting I should do this with a smoothing plane. Last night I couldn't take it any longer, and had to act against convention and advice from books and fellow builders, suggesting the use of sandpaper for this operation, first 150 grit then 220 grit. I figured I could always resort to sanding if the planing didn't work out.

OK, I'll be the first to admit it; I'm a stubborn bugger!

Off I went. I started by sharpening my 38º blade to the best of my ability and slit it into the Bevel-up smoother, adjusted it to the finest setting possible and secured the soundboard to the bench with a long MDF caul. With even pressure I slowly drove the plane through the spruce, up over the rosette, to the full length of the soundboard. My biggest concern was that the blade would bite into the rosette and tear it up and cause further damage, but it didn't. Instead I got whisper thin slivers of spruce and rosette. I slowly and methodically planed my way twice from one side soundboard to the other, with full strokes along the grain, until the marks and dust had gone.

Next came the thicknessing. I flipped the soundboard over clamped it to the bench with the MDF caul and started planing the back in a similar fashion: With full slightly overlapping strokes along the grain, slowly working my way across the soundboard. Once the first half was planed I unclamped and rotated it and continued on the other half. At the starting point the soundboard had an even thickness of 3.2mm all across.

After each complete cycle I measured the thickness and marked any area that would be a little thicker and leveled these first, before starting the next cycle. I also tapped the soundboard by holding it by the upper bout with one hand and gently tapping the bridge area with the end of my middle finger of the other. In the beginning the tapping produced a clear ring but as the thicknessing progressed the pitch slowly started to drop and became lower and lower. Supposedly you are striving to thin the top until you reach a pitch where the ring has 'dropped out' and been replaced by a low and indistinct tone, but as this was the first time for me it was hard to determine when that point was reached. Instead I resorted to measuring, tapping and listening along the way, ending up with a final thickness of 2.4mm in the middle, from the bridge area and up, and just under 2.0mm along the periphery of the lower bout.

It was interesting to follow the pitch drop as the soundboard got thinner. In the beginning the change was quite noticeable, but as I
got closer to the final thickness it became increasingly difficult for me to distinguish the change, which on one hand probably was due to the fact that I started to proceed in smaller and smaller increments, but also lack of experience. One thing I was quite aware of is the it is supposedly typical for the novice builder to overbuild. I just hope I didn't got too far in the other direction.






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