Filling Some Neck Gaps

Friday, June 12, 2009

Between work and some much-needed early summer-time chores, I did not get a lot done this week - but I did get a little.

After posting last Sunday, it dawned on me that I had made yet another mistake - while gluing the neck to the body, one of the things you need to do is to locate the neck at the proper depth with respect to the top of the head-block. Now this might seem pretty straight forward, but I can assure you it CAN be messed up. It’s not perfectly clear from my photos, but the head-block and top of the dovetail in the neck are in different planes - the neck plane is 6 degrees out from the top of the head-block. This means that, at best, only one edge of the two will line up while the other will be offset - no big deal provided that you align the correct edge. So which is the correct edge? The back one (closes to the tailblock - and even that is not EXACTLY the correct one) - and here is why.

The plane of the fretboard on the neck has already been established when it comes time to glue these two pieces together. The top of the head-block has not - it is flat with respect to the body. Once the glue in the dovetail joint dries the head-block needs to be sanded to match the fretboard plane. Now obviously (when your smart enough to think about it in advance) you need to align the neck so that all of the sanding is done to the head-block. I did not do this. I aligned it so that the top of the head-block was below the fretboard plane which, had I done nothing to correct it, would have meant creating a new plane for the fretboard. Not a good idea.

So what I did was to cut and add a thin shim (made from a left-over piece of maple side-wood) that matched the outline of the head-block. This, once glued to the head-block, I was able to sand it down to match the fretboard plane. Since this is located such that it is going to be almost completely hidden from view and then stained so dark that it will be almost impossible to detect, I feel pretty good about this fix.

Now, as I noted in my last post, I also needed a shim on the back of the neck. Just like the one I did on the front, I created a shim using another piece of maple side-wood and glued it to the neck. After sanding it to match the contour of the neck and the plane of the back, I think it looks pretty good, too.

I’m afraid I am not going to get to work on my mandolin next week at all (work, work, and more work), so (for all my followers) I apologize. I hope to post again in a couple of weeks.