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I am going to be building a semi hollow electric soon, it is still in the design phase in CAD. for the top I will be doing a carve based on the body shape, but for the back I was thinking just a 15' radius carve would be fine Ive had a few ideas on how to go about this. I am just wondering if anyone has done this and how you went about doing it.

thanks, mike

I would think it's the same method you would do on a full on acoustic. Either use a radius dish or whatever else you can come up with.

well as far as i know they radius the backs and tops by using braces with the radius carved into them and gluing those onto the back or top on the radius dish using those go bar decks so it forces the shape out of the back or top.

for this guitar it will be a carve out of the body blank so i would have to sand it use a radius dish ( if i had one) and that would take a long time the only thing i can think of is routing most of the wood away and shaping with hand planes so at that point i feel i should just copy the top carve just more mellow for the back.

I'll tell you how I have handled this in the past. Acoustic backs are usually domed, that is, radiused in all directions. What I have done instead is made a simple transverse radius, that is, the back is flat from heel to tail, and radiused only from side to side. You can make a simple sanding dish for this as follows:

Get a 3/4" piece of good flat plywood wider than the guitar and at least 6" longer. Get a piece of 1/4" ply just a hair wider than the 3/4". Get two long, narrow strips of wood, about 1/4" thick, and glue them down either side of the heavy plywood. Then lay the i/4" over the top, and force it down in the center so it touches the base plywood. You can glue/screw it in place. This creates a "fair curve", a parabolic curve. You can vary the radius by changing the height of the strips of wood on the sides. You can also adjust the curve by making the glued/screwed section in the middle just a little wider. After you have the curve the way you want it, just apply sandpaper to the curved inner surface (rubber cement or double-stick tape).

Then, after your body blank is hollowed out, just set in on the sanding dish and slide it back and forth along its center line, careful to keep the center line parallel with the axis of the curve. Since your body is hollow, this doesn't take long at all, just a few minutes.


I have opted for this way because on my instruments, the bodies all have a central core, just wider than the pickups, which remains solid all the way through. This means I've gotten by without internal bracing on the back, but if you want transverse bracing on the back you can use the sanding dish to sand the curves into your braces, and then as a clamping jig as well.

In any case, you can then rig up a system to apply even pressure on the back to curve it to meet the curved edges of the body blank. I use spool clamps, but others do it differently.

Hope this helps.