Monday, April 26, 2010

Top Bracing, Rim, Back Bracing

In spite of a lack of posting, I have indeed been working. I've done much and work is keeping me very busy so I apologize in advance for my brevity. As (mostly) usual, clicking on the pics will enlarge the images.

Below you'll find a picture of the braced top with the braces mostly completely un-carved. The top already has a rosette installed which I'll take some pictures of later - it's a very basic design and I've gone over this before. The sticks coming from above are called "go bars" and make it very easy to clamp things down. One problem though is that I have to make the base of the "go bar deck" stronger as it was deflecting under the load of the go bars.

The bracing pattern is the same as my last Харків (Kharkiv) version. The only difference is that this time I didn't I-beam the braces. Even so, the top came in right at around 450 grams - perhaps I beam bracing isn't that necessary. Below is a shot of the braces in their final shape.

Next is a shot of the completed rim:

I'm finding this type of rim a bit more difficult to make because of the exact shapes required. Because the final model (remember that this is just a prototype) will be using a pre made "Шемсток" or Shemstok, the angles between the neck and the rim have to be perfect. As it is in this model, they're not but I've got some ideas on how to get it right next time. Mostly it involves building assembly fixtures to guarantee that things line up the way they're supposed to . Good thing I'm building this prototype!

What I'll do for this version is to cheat the angle a bit on the shemstok to get it right rather than "straighten" the frame because it's much easier. That's o.k. for this one but the next instrument will require it to be perfect out of the gates.

Below is a shot showing how I've got to fix up some wavy-ness in the rim. If you read in a prior post, I'm using a material called "compwood". One of the side effects are that heavy clamping can compress the wood. Here's a shot of me flattening the area where the shemstok will be glued on:

Finally, here's a shot of the back with it's rough bracing glued on. I'm bracing this top a little more as I had some warpage issues at Kobzarska Sich last year. I'll be trying to shave the braces down until the tap tone of the back is either about a semitone higher or lower than the top (haven't decided yet).