Soundboard Clamping Question

[Nahil.R]

I am using a go-bar deck and attached the back with the guitar face down, directly applying the go bars along the kerfed perimeter.

Now it's time to attach the top and was going to use the method Robbie O'Brien suggests which is to do it face down with the go bar pressure applied from the back of the guitar.

I've got 2 questions:

1) Is this a good method to use?

2) Since I have a radius dish for both the top and back, would it work to 'sandwich' the guitar between the two dishes and apply the go bars over the top radius dish?

Thanks in advance,

Nahil.

[Glen H]

I’m sure face down works , but I do it face up. I flatten the upper bout area and no longer matches the arch, assuming face down is into a dished form. I also want to see what I’m gluing and clamping when working with the top.

[Nahil.R]

Originally Posted by Glen H

I’m sure face down works , but I do it face up. I flatten the upper bout area and no longer matches the arch, assuming face down is into a dished form. I also want to see what I’m gluing and clamping when working with the top.

Yes being able to see the gluing surface was a concern of mine, but I tried out a dry run and with the mold I am using you can clearly see the top to ribs contact points.

I also am a bit weary of placing the go bar rods directly on the soft engelmann top.

[Glen H]

I use Engleman but never put go bars directly on the top. I have 1/4 inch thick pieces of pine about 1 x 2 I put under the bar to distribute the force. Do need to be careful though

[phavriluk]

OP: please assure yourself of a means to positively locate the top/back in position on the rim before clamping. Stuff moves around with a mind of its own when we try to hurry. And gluing top and back simultaneously is to me a very ambitious idea. For me, better one at a time. Lots to lose, little to gain, by hurrying.

[Talldad]

IF you have radius dishes for top and back then use them, you will keep the two surfaces very well protected and have a excellent even pressure.
The only thin you need to be weary of is keeping the shape firm in a mould. You don't want to risk having sides that are no longer parallel but splayed. This can be easily achieved by attaching blocks to the top radius dish to prevent splaying.

[Nahil.R]

Originally Posted by phavriluk

OP: please assure yourself of a means to positively locate the top/back in position on the rim before clamping. Stuff moves around with a mind of its own when we try to hurry. And gluing top and back simultaneously is to me a very ambitious idea. For me, better one at a time. Lots to lose, little to gain, by hurrying.

I am not gluing the simultaneously. The back is already attached my question was referring to the top.

Thanks.

[Nahil.R]

Originally Posted by Talldad

IF you have radius dishes for top and back then use them, you will keep the two surfaces very well protected and have a excellent even pressure.
The only thin you need to be weary of is keeping the shape firm in a mould. You don't want to risk having sides that are no longer parallel but splayed. This can be easily achieved by attaching blocks to the top radius dish to prevent splaying.

That was my thinking behind using the 'sandwich' approach. Thanks.

[bisco1]

I personally use cork padded spool clamps. That protects the soft top wood yet assures that the whole gluing surface has full pressure applied. I made my own clamps by gluing a sheet of cork to a piece of 3/4" birch plywood, then using a properly sized hole saw, cut the circles out. I then used long 1/4" bolts and wing nuts to apply the pressure. That works great for me. Bill

[Rudy4]

There are lots of ways to do it, part of the fun of luthiery is to find what works best for you. I've always liked clamping the sides against the inverted top or back plate. For me it provides a much better view of what's going on and the glue squeeze out is much more easily controlled. YMMV.

In the photo below each "finger" of the lower plywood support has 1/4" cork padding and is drawn upward to clamp the back plate against the sides using the heavy duty rubber bands.

[nikpearson]

And you can make your own out of rolling pins, threaded rod and cork pads.

[Neil K Walk]

I put the back on first for my first, the top first on my second (so that I could pay more attention to voicing) but I'm not one to rush and try and do both. There's too much potential for slippage. I lay the rims on the gobar deck gluing surface up with wooden cauls around the perimeter. I don't have radius dishes. I let the rim geometry and the brace radii determine the dome of the plate.

[Brad Howard]

I use a similar set up but with one "halo" cut from 3/16" plywood instead of individual cauls.

[Bruce Sexauer]

You are relatively close to Spain, and the Spanish method is based on North African traditions. The big advantage of top down construction is the ability to use hand placed peone (tentalones) to connect the top to the ribs. This means you don’t need a lining on that side nor do you need to shape the ribs to fit the top. This is directly from that tradition.

[Nahil.R]

Originally Posted by Bruce Sexauer

You are relatively close to Spain, and the Spanish method is based on North African traditions. The big advantage of top down construction is the ability to use hand placed peone (tentalones) to connect the top to the ribs. This means you don’t need a lining on that side nor do you need to shape the ribs to fit the top. This is directly from that tradition.

I hadn't really considered the Spanish top down method of construction. Based on my not so great experience gluing the top on second. With my next build I think I will try the top down method to get a better fitting top.

Thanks for the advice Bruce, and it would be interesting trying a more traditional (classical) method of attaching the top first (face down).

Cheers,
Nahil.