Inside mold

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Walter Lay
Posts: 2
Joined: Thu Jan 12, 2012 3:11 pm

Inside mold

Post by Walter Lay »

Have any of built using an inside mold a la Ignacio Fleta?
Thanks for any info.
Walter Lay

Alan Carruth
Posts: 1048
Joined: Sun Jan 15, 2012 1:11 pm

Re: Inside mold

Post by Alan Carruth »

I use inside molds for violin family instruments. IIRC, Fleta started out as a violin maker, and probably got the idea from that. Fiddles have corners, and the corners have blocks in them (at least when you build on an inside mold), and those give you a good way to pull (or push) the waist in. I used to make 'peanut' shaped 5-string fiddles, aimed at the 'folk' market, and had to use flat crosswise 'blocks' on either side of the waist for the purpose, even though the outline had no corners. It's hard to fit corner blocks into a set of ribs built in an outside mold, as the French do, or without a mold in the Dutch and English method. Corner blocks add a lot of strength to the rib garland. It also makes it fairly easy to produce a uniform overhang on the plates. But there are no real advantages to working that way on a guitar, so far as I can see.

The Spanish tradition builds on a fixture called a 'solera', often defining the outline from the shape of the soundboard. The whole instrument is , in effect, built around the neck and top. The big advantage of this system, aside from the freedom it gives to vary the shape, is that the neck angle is defined by the fixture; if you're reasonably careful about lining up the center line of the neck it makes that whole process fairly simple once you've built the fixture. Fleta would have been used to setting a separate neck and getting all the alignments correct.

I've used both the solera and outside mold methods, and taught them both. Each has advantages and drawbacks. For many students the hardest part of making a guitar is fitting the neck; it's a matter of having sharp tools, taking fine cuts and checking often. Binding and finishing can be more complicated when the neck is part of the body, and there are other issues. IMO neither way is particularly 'better' from a work standpoint, and both methods can result in a fine guitar. But I see no advantage to working with an inside mold.

Clay Schaeffer
Posts: 1556
Joined: Fri Jan 06, 2012 12:04 pm

Re: Inside mold

Post by Clay Schaeffer »

Unless you want to screw the two halves together to also use it as a bending form (with heat blanket) I can't see where it would have any advantage over an outside mold. As Alan mentioned, Fleta was originally trained to build violin family instruments, so the inside mold may have been what he knew and prefered. Obviously Fleta made it work so there may not be any great disadvantages to using it either.

Ken Nagy
Posts: 48
Joined: Wed Jan 15, 2020 8:03 pm

Re: Inside mold

Post by Ken Nagy »

I made my first guitar last fall, an arch-top with a cutaway. I used an inside mold, because I've made violins, and a big, perfect, outside mold seemed impossible. It worked out, but I would NEVER do that again! I'm going to build on the belly in the Spanish style. It seems that many are kinda obsessed with having perfect symmetry and lines; I'm not; but many build on the belly and bend the ribs on a form. That should be close enough. If you want a certain shape, you could do something like Andrew Carruthers does here. I used a violin version on my last one, and it worked well.

https://www.andrewcarruthers.com/new-sm ... eton-mold/

You could still build on the belly, and even have a Spanish heel neck with the slots for the ribs. A center beam would keep the blocks on the centerline, and the cross sections would form the concave part. It seems that you would still need sliding blocks t-nutted to the solara, or SOMETHING to keep the ribs from spaying out, because there are no corners or blocks that are held in place. Then you just glue it to the belly, and glue on the little wedges, peones?

Or you could forget about the form completely, and use sliding blocks just to help keep the ribs in place while you glue them to the belly. To me, this option seems to be the only rational one. You could even use it with a dovetail, or bold on neck if you wanted to.

I really didn't like the inside mold.

Clay Schaeffer
Posts: 1556
Joined: Fri Jan 06, 2012 12:04 pm

Re: Inside mold

Post by Clay Schaeffer »

Hi Ken,
I sometimes use the solera method, but rather than make the plywood have the proper profile I add a built up cork and rubber composite layed on top of a flat plywood workboard. This allows me to change the arching according to the type of guitar I'm building. Originally I drilled holes and slots and used dowels and spool clamps positioned around the perimeter but later decided "L" blocks screwed directly in the plywood was easier and worked better. YMMV
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Walter Lay
Posts: 2
Joined: Thu Jan 12, 2012 3:11 pm

Re: Inside mold

Post by Walter Lay »

Thanks for the informative replies. I am nearing completion of my first classical guitar; based on the 37 Hauser (I took a few liberties). I am soon going to make a Fleta style. You guys have convinced me that there is no point in using the inside mold.
Thanks,
Walter Lay

Simon Magennis
Posts: 466
Joined: Sat Jan 07, 2012 7:51 am
Location: Menorca. Spain.

Re: Inside mold

Post by Simon Magennis »

The StewMac 000 and D kits come with a cardboard inside mould. I found them quite good so I have nothing against inside colds. However, for classicals I have only ever used a solera and I don't use any mold with it. Nowadays I use some wooden right angles at a few points around the perimeter but when I started I didn't even use those. Once you get used to doing things one way there isn't much incentive to change.

Ken Nagy
Posts: 48
Joined: Wed Jan 15, 2020 8:03 pm

Re: Inside mold

Post by Ken Nagy »

Clay, I like the idea altering the solara to use it for many different projects. I have 3 smaller guitars that I'd like to do, and others probably too. Two of them I'll probably do sort of like they were originally; though I might do the Voboam with a double X bracing, and not the transverse bars. It looked promising on the other I was doing, but I changed to 2 bars when the barn wood top split to pieces. The Stauffer I thought maybe using the oxidized copper plate that SnowManSnow showed on the other forum.

I like the over the top short, fat look of the vihuela, but MIGHT make it 21st century with a multi-scale, and twisted neck. I can see how both might make playing easier. Why not try it? I don't do much that is normal! If I did that, it would need a dedicated form of some kind. I might even do it with 13 strings, seven courses. Narrower spacing might be easier with the fan frets? I like the wider spacing I gave it, and the feel of the double strings on the Baroque. Short fat fingers, and the lighter tension per string.

Thanks for the idea
Ken
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