Radiused Workboard

[Parker135]

I'm just beginning to gather materials for my first mandolin build. I'm working from plans from Crystal Forest Mandolins for his flat top A style. I've also been studying Graham McDonald's book and I'm now curious about the need for a "radiused dished workboard." I understand the need for a something to clamp against while gluing the braces that will support the curved surface (making up a go-bar system following McDonald). The board described in McDonald's book looks like it would work best with a spherical surface. If the braces are all made to the same 10' radius of curvature, then the only place they match the workboard is when they go across the center. Is this cause for concern? It seems like a baking tin full of sand could be just as effective and the sand would more likely conform to the non-spherical shape of the plates.

....Or in practice does this not matter?

Thanks,
Parker

[Tom Haywood]

A dished work board is not necessary for the campfire style mandolin that I think you are talking about. The radius of the top and back are induced by clamping the plates to the radiused transverse braces. You can draw the radius on the bottom of the braces and sand that curve before gluing. You may want to put some thin flat bracing around the sound hole before installing the radiused braces. That will flatten the top in the sound hole area. That makes it easier to achieve a good neck angle. That's the way I do it. Others may have a different approach.

[Parker135]

Hi Tom. Caught me sitting here playing mandolin. Okay, that's consistent with what the Crystal Forest plans show. He uses a thin piece of plywood around the sound hole and his photos show him just clamping the top and bottom pieces directly to the radiused braces. I've already started on the dished work board, so I might as well follow through at this point just to see if it's useful. I'm waiting for wood from Old Standard Wood Supply. Meanwhile I'm getting my Wagner planer and sanding equipment set up; that sort of thing. Obviously I'm new at this. Thanks very much for your reply.

Parker

[chris scott]

greetings, i have built 3 mandos and the first pattern after the gibson A jr. I carved the top out of some sitka that I purchased from Old Stanard, I carved out a piece of rigid insulation, a bowl or dish simaler to my sound board, I used that to set the top in and used weights to hold the brace in place while being glued, actually uses a anchor, being round in shape as a tool to increase pressue on glue joint. ( thats a boat anchor).

[Parker135]

Whatever it takes, I guess! I'm working from plans for "flat" top and bottom, being slightly arched only after gluing in the braces. I'll have this dished surface ready to go and will just see what happens I guess. I built up a rig from two pieces of MDF and four pieces of all-thread to try "go-bars" made of oak dowels. I'm curious to see how they work out as clamps.

I'd love to try carving a top and back some time in the future.

[HoGo]

Radiused dishes are quite modern invention.
I read that all the prewar (and perhaps many years after) Martins were made without dishes.
What I read is that they stored tops in drier room (with elevated temperature, they didn't have any exact humidity control back then) before assembly to prevent cracking later in drier environment and after gluing top braces the arch induced itself. The back braces were just shaped and glued to back and they (together with preshaped rims) created the final shape.

[Parker135]

Fascinating story. So if one were to take one of these old Martins apart, the grain in the braces would indicate they bent into the arch rather than being cut?