Official Luthiers Forum!

Hi everyone -

I appreciated everyone's help on my recent question concerning making a
go-bar deck (I have my basic design for that now - just need to build it).
The next thing I want to do is make a body mold for assembling the body
of the guitar.

I want to have a custom shaped body (basically the Olson SJ shape). I
have seen some solid wood designs, and some semi-solid designs for the
building mold. How do you guys make your molds? If I want a 4 5/8"
depth, how deep should the actual mold be - in order to account for the
tapering depth of the guitar as you move towards the neck?

Thanks for your help!

I make mine 2 1/2 - 3"
2 layers of 3/4 plywood and spacers blocs about 1" in between.
You do not need the full thickness of the guitar, in fact it is better not to have the full thickness, so you can sand the rim, glue the kerfing, etc.. while the body is in the mold.

i just recently finished my first mold for an OM. after being unhappy with a first attempt with birch plywood (not the baltic birch, just regular old hardware store version, which isnt all that cheap by the way, about $40 for a 4x8 sheet), i decided to go with the less expensive 3/4" MDF. i didnt feel like the plywood was flat enough, but quite possible i was overthinking things. anyways, im making an OM and i made my mold 2 1/4" thick (3 layers of MDF). i believe in robbie o'brien's videos his mold is only 2 layers thick, although i could be wrong. you want it thick enough obviously to support the sides, but not so thick it makes installing the linings a pain in the rear.

to actually make the mold, i just made a template and used a bandsaw and a pattern cutting bit to shape the individual pieces, then glued them together. it helps to use some sort of nail or something to keep the pieces from sliding around until the glue sets up. then you have a small amount of sanding to do just get things right. this is obviously the abridged version and i think this will better explain. http://www.luthiersforum.com/forum/forum_posts.asp?TID=10884 &KW=tutorial#forumTop

the only thing i will say is that i used the "small" de-sta-co clamps at either end to hold the thing together, and while they are convenient, with the spreaders pushed against the sides, the mold starts to separate a bit at the top and bottom. you probably dont need much pressure pushing out to get things snug though. so you might want to consider what kind of fastener you use to hold the two halves together.

good luck and have fun. i think building this sort of stuff yourself is a great part of building. even though it has been a bit frustrating and i cant wait to actually get along to building a real guitar.

_________________
sweat the small stuff.

Thanks Heath and Alain!

I appreciate the help. That archived link was helpful.

i will also say one more thing about MDF. it really stinks at holding screws. if those screws are short in length or fine thread, it just stinks that much more. so i drilled some holes perpindicular to where the screws were going in (for the de-sta-co clamps) and glued some 3/8" dowels in so that the screws would pass through the long grain of the dowel. make sense? MDF will also split real easy like if you do not pre drill for screws.

_________________
sweat the small stuff.

Here is a good link to making a mold.
This is close to what I do, but I replace the inside layer with woods blocks.

And keep the cutted inside to make the Fox Bender form!

Good luck
making a mold

one has to be very careful when buying plywood these days...if it has China stamped on it AVOID IT AT ALL COSTS as it is at best wet as all **** and at worst still bleeding off nasty chemicals....in all reality the only plywood worth using for patterns is baltic birch which I hear is hard to get right now, I can't find anything thicker than 1/2" and am hording my 2 pieces of 3/4" for pattern use only...

Thank you for your thorough reply, Todd. I like that "ear" design and your
clamp use.

todd and others, im just curious about something. i tried to glue an outer sheet on either side of a master sheet and then pattern route both sides just as described above. what i found is that my flush cut bit (i believe it is porter cable) cuts the duplicate slightly larger than the master. its not a terrible amount, but its enough that i end up having to do some sanding. do all flush trim bits do this?

_________________
sweat the small stuff.

Is there an advantage to plywood over solid wood?  I happen to have some 12x2 redwood left over from a deck I built this summer which I was planning to use (doubled up for width).

 - Bill

Started to suspect something like that, once I thought about it.  Thanks for the answer - Bill