Friday, November 11, 2011

Kaiser Theorbo - Fitting and Gluing the Bridge and Belly

Today I am going to describe the techniques that I use for fitting the belly to the bowl, gluing the bridge on the belly and then finally, the belly to the bowl.

You will remember that in a previous post I paid a lot of attention  to fitting the temporary belly. This accuracy comes in handy again when I fit the top to the bowl. Before I glued the bars in place I drew the outline of the bowl on the underside of the belly. This line is clearly visible in the photo and it is the reference for fitting the belly to the bowl. After I have shaped the bars (in my previous post) I trim the bar ends so they terminate inside the reference line an amount equal to the thickness of the edge rib. If I have done the trimming correctly the belly will slide into place on the bowl with a slight amount of friction. The reference line will be visible just beyond the edge of the bowl. 

I won't describe the making of the bridge now. I will be starting another Kaiser this winter and I will describe those techniques at that time.

In this photo I have laid out the bridge position with painter's tape, a square and a center line drawn on the same tape. I found that it was difficult to balance clamps on the narrow top of the bridge so I make an insert that fits on the rear platform of the bridge. The top surface of the insert is level with the top of the bridge so the clamps have a wider surface to sit on.

The metal clamps are resting on the block part of the bridge while I use cam clamps with rubber pads on the bridge wings. I use just enough pressure to insure good contact between surfaces. Under the bridge area I fit wood cauls between the various bars. This assembly can then sit on the edge of my bench and the clamps can span the distance from the bridge top to under side of the bench top.

Once the bridge is glued I place the belly on the lute and using a length of sewing thread tied to the bridge like the first string I make sure that it aligns accurately with the edge of the fingerboard and that the height of the string at the neck joint is what I anticipated. Now I can glue the belly. I mark the location of each bar so when I start to apply the tape I secure those areas first. I apply a coat of thin hot hide glue to the edge of the bowl, the ends of the bars and the underside edge of the belly. Then, working quickly, I apply the tape over the entire edge of the lute, pulling the tape taunt and carefully pressing it in place.
Securely gluing the tongue area of the belly was a problem so I developed this technique that has worked well for me. I wrap elastic tape tightly over the upper part of the belly and under and around the neck. Then I insert opposing wooden wedges. This action presses down on the belly resulting in  good gluing contact.

John Edwards, theorboist and co-founder of Musicians in Ordinary dropped off his 1998 Kaiser theorbo this afternoon. It has a problem with loose braces. Sue, my wife, looking over my shoulder as I wrote this post commented on the jarring nature of the green tape. I agree, but it does the job. On the other hand, I am reminded of the technique described by Thomas Mace in Musik's Monument published in 1676 for repairing his lute belly that involves just what I have done here and what needs to be done to John's lute but using seventeenth century techniques and materials. Since I have to repair John's lute why not follow Mace's advice and really be a 17th century lute maker. It will take me about two weeks to get to this. I'll report on it here.

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