Time I got this thread going again, and thank you for the compliments.
Moving on to the control cavity. The template for this was made by sticking a drawing to a piece of MDF and cutting the shape out by hand.
The control cavity cover was made from an off-cut of the alder back.
To make a routing template for it I wrapped the curved side of it in painterís tape; both sides and the edge. Three sides of it are straight so strips of wood were butted up to them and screwed down. A fourth strip was profiled to the same approximate curve and then spread with a layer of polyester mastic used for car-body repairs (Bondo?). This was then pushed up against the curved surface, screwed down and left to harden. When it became rubbery and started to harden I trimmed off the surplus that squeezed out.
When the mastic was hard I took off the straight strip and pulled out the control cover, and screwed the straight strip back in place.
Then I routed the template on the router table. As you can see, the MDF template has already served in trials for other routing operations.
Fixed the template to the body (still using the dowels) and routed the recess for the cover.
The cover will be held in place by small magnets so I stuck the cover to a piece of MDF using double sided tape and routed round it to make another template. I marked out the positions of the magnet holes and drilled them through the template and into the cover.
Then I took the template off the cover, turned it over, fitted it into the recess in the body and drilled the holes through the template and into the recess. (Youíll notice that Iíd also gone round part of the back of the body with the ĹĒ round-over cutter.)
I fitted the magnets in the cavity cover and the recess. They were quite a tight fit so I pushed them just below the surface and then wicked a drop of thin CA around each one.
I covered the inside face of the cover with copper shielding foil and stuck some temporary strips of copper foil onto the ledge where the cover sits.
So now when the cavity cover is in place, it sits slightly proud of the back.
So I sent it through the sander a few times until it was flush. The cover turned out to be quite a good fit.