Wednesday, April 29, 2015

Bracing the 'cello

With the rosette completed, fitting the internal bracing is the next step for Jonathan’s mandocello. I’m using X-bracing as it’s simply the strongest and on a 10 string mandocello you have to be robust!
So, here is a number of days’ work compressed into a few photos.  Firstly, some accurate marking out is needed;  as the underside of the soundboard is hollow, it made sense to lay-out the angles on the same jig that I used for routing the sound hole and then transfer them to the edge of the top.

After making a number of templates, directly from the inside of the top, the braces are roughly cut on the bandsaw.
They’re then cleaned up with a flat file to a close-ish fit and then the fun starts……
Fitting the braces to the top, demands the utmost accuracy. I clamped a strip of angle aluminium to the top; this ensures that the brace is vertical and after checking, goes back into exactly the same position each time. A strip of abrasive paper then goes between the brace and the top, you then put a CD on and settle down to a couple of hours of painstaking sanding until the brace fits.

Once both braces have been shaped, the joint for the X has to be carefully marked-out and executed. I decided to glue the two braces to each other, before gluing to the top itself, this way they are self-supporting when you actually do glue them to the top.
I clamped them to the top whilst the glue set in order to ensure that they are in the correct alignment to each other.
As a belt and braces measure I’ve glued small fillets of spruce into the X, this should ensure that the joint never fails.
So, with X brace made and reinforced, another CD goes on to the player and some final fettling to the fit.
Last test; with clamps in place and a feeler gauge to check for gaps.
Then I made up a simple wood and foam clamping caul to support the weight of  the clamps and to help spread the pressure of them evenly along each brace.
The X is then glued into place………….

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