Posted 25 June 2009 - 10:01 AM
You can use the original mount as a template for the new one. After roughly cutting each part to size clamp each panel to a panel from the old base and trim to exact shape and size with a router fitted with a trimming bit. They have a ball-bearing guide along the top or bottom of the bit that guides the router and enables you to get exact duplicates. A circle cutting jig will then make cutting out the ground board and rocker bottom quick and easy. If you don't have these tools, see if you can borrow them. They're not too difficult to learn how to use and they are a must for many other kinds of wood working projects too. I would use yellow carpenter's glue such as Titebond II or III and biscuits to join your base, there will be no screw holes to hide and driving screws edgewise into plywood could wedge the plies apart too. That is avoided with biscuits and the joints are strong too when properly made. Finish with three or even four thin coats of exterior polyurethane. I don't recommend staining Baltic Birch because it does not stain all that well but several coats leaves a nice amber like patina on the plywood when sanded correctly. Get all traces of glue off first before varnishing, because even without stain stray traces of glue will show up and look awful.