my new OM form

[Dan of SC]

This is my new OM size guitar form. It's made from 4 layers of 3/4" mdf, coated with 4 coats polyurethane. It has mahogany sides in it. I bent them by hand, set up the form(the white you see is thin foam), then I put them in the oven. Our stove has the lower heat element under the bottom of the oven so you can pour water in the bottom to steam clean it. I set the oven at 200 degrees, put about a quart of water in and put the sides on the top rack, left them for about 25 minutes, took them out and quickly put them in the form and tightened the inside form spreaders. I'm shooting for accuracy. Any thoughts anyone?

[belbein]

Im a Little conf used. Vitae bodied Octave mandolin or guitar?

[Grommet]

Nice looking form-

So you bent the guitar sides on a hot pipe first, and then steamed them in the oven before placing u the form? Would they have needed the steaming to take the bends? How thick were the finished sides? Thanks!

Scott

[Dan of SC]

It's a guitar, basically the size and shape of a Martin OM. The sides are .080". I bent them on a hot pipe first. Maybe it's just me but I can't seem to bend sides to fit a form perfectly. I got them as close as I could then put them in the oven to steam. When I took them out I put them in the form as quick as I could, then tighten the spreaders as fast as I can. From oven to form and spread snugly takes 1-2 minutes max. Hopefully they're still hot and moist enough to take the shape of the form and hold it after they cool. I'm planning on gluing in the end blocks tomorrow, then the kerfing on one side, then glue on the top, then remove the big spreaders and replace them with a small one at the waist. Then kerf the other side, glue on the back and remove the spreader through the soundhole. I'm still a novice, this is my eighth instrument if you count two ukes. If anyone has any advice here I'm all ears. Thanks, Danny

[sunburst]

It should work fine.
Normally, we over-bend sides a little because they always "relax" a little when they are released from the bend. Your form has bent them to their exact positions with no over-bend, so if you were to take them out of the form they would "relax" (un-bend) a little. In other words, they are slightly forced into the form as is. Once you glue the head and tail blocks, that would probably mean the waist would become wider if the glued rim was removed from the form. Once the top or back plate is glued, it will stabilize the rim, and eventually all the "stress" will equalize and it will all be as usual.

[belbein]

This is probably a stupid question, but it's Sunday and I expect charity. :-) Isn't the advantage of internal ("male") forms that you can put front and back--thus fixing the sides in place--before you remove the forms? I don't particularly find them easy to work with, but that is my impression.

On the external ("female") forms ... wouldn't it be possible to create a form that's, say, 63/64th the width of the sides at their narrowest point, with a hinge of some sort, so you can attach front and back--fixing the sides in place from top and bottom--before you remove the external form?

[Dan of SC]

belbein, It is Sunday, I had a little wine last night and guess what--you lost me. I'll try reading your post again later.
Danny

[Pete Jenner]

It's Monday here - expect no charity. ...just saying...

[sunburst]

belbein, It is Sunday, I had a little wine last night and guess what--you lost me. I'll try reading your post again later.

Same here, minus the wine.

[Pete Jenner]

that you can put front and back

Front and back of what? Where?

[Dan of SC]

I glued in the endblocks, removed the inner form, and the sides are hugging the form quite well. Hate to sound like I'm bragging, but when you've screwed up as much as I have, it just feels great to have something turn out good. I really think steaming the sides prior to clamping in the mold helped them to conform well. Danny

[Pete Jenner]

Good on you Dan.

[Bertram Henze]

This is probably a stupid question, but it's Sunday and I expect charity. :-) Isn't the advantage of internal ("male") forms that you can put front and back--thus fixing the sides in place--before you remove the forms?

with front, back and sides fixed, how do you get the male form out, on any day of the week?

[Jim Adwell]

with front, back and sides fixed, how do you get the male form out, on any day of the week?

Why, you suck it out the soundhole(s) with your shop vacuum, of course.

[Bertram Henze]

Why, you suck it out the soundhole(s) with your shop vacuum, of course.

...or the male form could be made of ice