"Free Form" Building Vs. The Mold.

[Gilbert Fredrickson]

I just finished a very nice side bending form and a assembly mold for a guitar that is very similar to the last guitar for which I built a a very nice side bending form and an assembly mold. Has anyone had good luck with the "free form" method?

[Chuck Morrison]

I've often built without a form. Usually when it's a "one off" that I don't expect to do again.It requires paying attention to things you take for granted when using a form, like the symmetry of the sides. Doing this without side bending forms requires some skill at hot pipe bending.

Did you have specific questions about doing it ?

[Michael Lewis]

It helps to make your instruments to fit into easily accessed cases, otherwise you will be special ordering custom cases or forcing your instruments into standard cases that don't fit all that well.

[Clay Schaeffer]

"I just finished a very nice side bending form and a assembly mold for a guitar that is very similar to the last guitar for which I built a a very nice side bending form and an assembly mold."

Rather than build a mold close to what I already have I will modify the shape of "mold bent" sides with a bending iron. This allows for some variation (cutaways) without doing all the work of making new molds or completely doing pipe bending.

[Rodger Knox]

I entered a challenge here some years back, along with some professional builders. Two of those builders, AC and MP, were building a one off and the first thing they did was build a mold. I've built molds for every one since then, it really is easier and maybe even quicker than building free form, for me anyway.

[Bob Gramann]

It takes me less than two hours to make a new mold of three layers of 3/4" plywood (I stopped using MDF because I hate the dust) using a bandsaw and a router. I've done it for one-offs and would do it again for another one-off. Why give up the ease and control when the mold is so easy to make? (I bend everything on a pipe, so I don't have to make bending forms.) The only problem this causes me is finding storage space for all of the molds.

[Alan Carruth]

I find that using a mold and bending form saves more time than it takes to make them, so it's worth it even for one-offs. Add in the ease of getting things 'right' (sides perpendicular, and so on) and it's almost a no-brainer.

That said, there are times when I build without a mold. One place this skill comes in handy is in making things like harp guitars. My designs have all used a separate soundboard for the harp, rather than having it as an extension of the normal guitar soundboard. I need to have some way of keeping the two soundboards aligned, so that the strings will come out in the same plane. A modified solera, with an auxiliary surface to attach the second soundboard to, does the trick.

You can, of course, use a 'horse collar' on a solera if you want. I've use pins and wedges around the outside of the sides to force them in against a top that has been trimmed to the exact shape. This comes out about as accurate as sides made in an outside mold, although, of course, the deviations are outward rather than inward. Each method has advantages and disadvantages, and you have to figure out what's important in the current case.

[Brad Heinzen]

Although I build mostly standard classicals, it sounds like I do what Clay does. I have several molds, but only one bending form. I just take the sides to the bending iron to tune them up so they fit the different outlines. I also think making a mold saves more time than it costs, even if you're only doing a couple of guitars. For me, the mold isn't so much a means to achieving a particular shape as it is a jig to hold the guitar while I'm working on it. Guitars are tough things to clamp, and molds can really hold them steady on the bench.

[Mario Proulx]

the mold isn't so much a means to achieving a particular shape as it is a jig to hold the guitar while I'm working on it. Guitars are tough things to clamp, and molds can really hold them steady on the bench.

Bingo!

[Michael Lewis]

I think the point is that you don't have to have a mold to make a guitar, but it makes the job easier and helps maintain symmetry and good form. You don't HAVE TO but it's better if you do.

[Lance Lawson]

I've haven't used a mold since 2003. I like the compactness of a bending pipe that can be clamped to a kitchen table if necessary. I do make a half profile from light styrofoam board to test the sides to. Free bending isn't all that difficult. My early efforts were 1/4" from form pattern. I can now get sides within 1/16" of pattern. Free form bending is a skill that can be learned just like anything else.

[Bryan Bear]

I have done both but find it much easier to make a mold. For a one off, I like to make a quick and dirty mold for assembly and skip the bending form. I like bending on the pipe better anyway. . .

I am right in the middle of making a new mold for my future guitars. I decided I wanted to be able to make a few sizes but have them "feel related." I decided to try keeping the curves constant and vary only the width by squeezing the tail. I drew up a shape that could "hinge at the heel center-line and by adding or subtracting part of the tail end the curves would fair into themselves. The result is (hopefully) OOO, OO and O sizes with identical curves but varying proportion of upper bout to lower bout. The added benefit is that if my adjustable mold design works, I only need one mold and bending form.

Here is a crudely done side by side of the shapes. It is all based on the 15" size which is inspired by elements of the OM and the L-00. The 13 1/2" version will likely never get the cutaway.

[Jason Rodgers]

This is cool, Bryan. I've played around with outline widths by doing this same process. It seemed, though, like I always needed to clean up that curve at the tail when expanding and contracting the width. You must have found the right curve to start with that works for all iterations. Even more clever to incorporate this into adjustable molds!

[Clay Schaeffer]

Hi Bryan,
I use the same mold for the "Martin inspired" 12 fret OO,OOO,OOOO bodies I build. I add a 1/2 inch piece at the head and a 3/4 inch piece at the tail to go from OO to OOO. The head and tail outline is pretty flat so adding the "shims" doesn't look too odd. I use clamps (sometimes screws) at the top and bottom to hold the mold and shims together. I use the same bending form for all three body sizes.
The O size I believe is a little shorter than the OO and Triple O and I haven't made any of that style ( I do the size 1 and the LG 3/4 size instead for small bodies.

Merry Christmas everybody!

[Bryan Bear]

Jason, I think the mold will work out well. There is, of course, a small amount of distortion at the heel surface where the mold hinges to the smaller shapes. It is very minor and I hand fit the heel mating surface to the body anyway. For someone who used a more automated method for making the neck joint might have to come up with a solution or two.

Clay, I did something similar when I made my mold for my guitar shaped mando; I used inserts to get the width I needed and still allow me to use it for my tenor uke design. That is what got me thinking about making molds for my new "guitar line" (tongue in cheek implication that I am a 'real' guitar maker) more versitle. Mine is optimized for the OOO and the OO seems to work well too, the O size has more compromises but still looks good IMHO (I probably won't make too many of those anyway). The length for all of my sizes has to stay constant (19 1/4"), but that seems within a reasonable range for guitars. I left the option open for a OOOO size but going bigger than the originally designed outline may have some problems. The heel side may not look right but, I can either try to add width to both the heel and the tail, just the tail, or varying amounts to both. The mold it 6 layers of 1/2" plywood with alternating layers left short or long to interlock with the other side and allow for spreading/squeezing the shape, so I should have room for playing with the OOOO size.

It just dawned on me that I am kinda hijacking this thread. That is not my intention! I just thought that a discussion of versatile molds fit well with the issue of having to make a bunch of molds, though technically not the question that was asked. In that spirit, I'll post a picture of my unfinished mold <G> :

The tail end has 3 holes that line up with the opposite half for the bolt that holds the shape. Push it all the way closed for the O shape, there is another hole off to the side for a dowel to provide a hard stop for the OO shape, I haven't figured out a good hard stop for the OOO so that one is a little finicky to get the bolt to line up.

[Jason Rodgers]

Hey, those articulated butt and heel joints are spiffy! You could make the heel slide like the butt and you'd have the upper bout dimension to play with, as well.

[Michael Lewis]

Bryan, I think your post is well placed and in good order for this thread. I like your idea for the adjustable ends of your body form. I have used a hinge at the heel seam and varying blocks at the tail with good results but I think your system is more versatile with the adjustable upper bout. Nicely done.

[Clay Schaeffer]

Hi Bryan,
I like your "adjustable mold". Very inventive and space saving.
To make a slightly shorter guitar I have on occasion added some shims at the head and tail. It holds the sides away from the mold slightly but can knock of a little length and help keep things in proportion.

[Bryan Bear]

That's a great tip Clay! I spent a lot of time thinking about designing m own shapes and fitting them into more versatile molds. With the new baby, I hadn't been able to get much time in the shop but I had plenty of time to ponder. . . It thought of shimming the length too, unfortunately I forgot the concept all together when I started doing my drawings. My thought was, as long as you aren't trying to take out a huge amount of length, the bent sides would find a natural curve of their own in the area where thew were unsupported by the mold. It is nice to hear you have had success with this.

I did something similar with my mandolin shape that uses inserts in the uke mold too. The mando has a Venetian cutaway on the treble side and a curved cutaway on the bass side. As a result, the heel block is much further south than the the mold. I used a shim (really a block) to take up that space. The sides just north of the waist are basically done free form. Someday, I may end up making an insert for that mold to complete the shape but it doesn't seem too necessary.

The only picture I have is when I was gluing in the linings. I had already removed the shim/block but people should get the idea:

For part-timers like me, space is a real issue. This is turning into a good discussion about mold options. Let's see some more pictures. I'm sure there are some great ideas out there.

[Jason Rodgers]

On the two molds I've built, I lined the inside walls with countertop laminate. It really does a great job of smoothing out any little lumps or imperfections in your mold construction, and you don't have to seal the mold, either. I haven't made any cutaway inserts, but I'll face those with laminate, as well.

Has anyone mentioned the adjustable dowel or pillar molds? Those seem like the way to go for experimental or one-off shapes.