Grez Guitars & R.C. Allen Archtop Construction Part 2 of 2

[@dswitzer175]

Thanks for sharing your techniques. Very useful for my own builds.

[@lehacarpenter7773]

Very cool to learn about.

[@geemac7267]

Beautiful guitar. I'm definitely stealing the top clamping idea with all the bolts around the rim. Sure it beats wrestling with that many clamps.

[@GrezGuitars]

Greg McKnight Thanks Greg, And by clamping it in the form, the neck and tail block stay more square to each other so later when the neck and tailpiece go on, less drift compensation is required.

[@tadejverce5400]

How much pressure do you need to press together?

[@GrezGuitars]

Don't know the exact number but I'm using a 2 ton bottle jack maxed out and if you skimp on the pressure the veneers wont be totally flat but have some ripples. I'm told you can do this with a vacuum bag but I don't have personal experience with this.

[@jazzman1954]

I would love to know how the moulds were made. Both inside and out. What material are they made of? Thanks

[@GrezGuitars]

They are a wood frame with the center cut out and back filled with plaster or other pourable sandable material. A master shape is needed. You could carve an arch, or use an existing archtop to cast over. Then when you have one side cast, you can cast the other side from this. Very simple stuff. Now you could CNC both sides from a solid material instead, but these were made by R.C. years ago.

[@jazzman1954]

@@GrezGuitars Thanks very much. I think I understand. So are the final moulds made of plaster or resin? I would think plaster is too soft. Sorry to be so stupid.

[@GrezGuitars]

@@jazzman1954 The center is, I believe, plaster of Paris about 3/4" thick and when in use it's under uniform compression and in this orientation it's rather strong.

[@jazzman1954]

@@GrezGuitarsCheers! Really appreciate your time and help. I’m looking at building my first guitar here in England. I admire your skills.

[@edadpops1709]

How do you fine tune the top after glue up with .022 veneer??

[@GrezGuitars]

The top itself can't be tuned, the layers are too thin. The tone bars can be and you can play with the orientation of the layers of veneer to build a fixed tuning into the top. When I make a spruce top, it is 3 layers, each .06 and with this I can sand from the inside and the outside and tune the top, thicker in the center, thinner around the edges.