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I’m in the process of finishing this jig up. I was unhappy with my last one although I did get decent- but not perfect results. Hopefully this one gets me to the place I want to be. Somagyi does something similar but has a snake like belt that fits over 2 pairs of the fingers and then takes one clamp per pair. I have 24 3” C clamps, a couple 4”clamps and a ton of Jorgensons. I can see where the benefit of pairing up a couple fingers in the upper bout will save clamping space but I think I can clamp the rest individually and have enough space for each one. If anyone has any suggestions to improve this jig please share.

That should work. I have tried various approaches over the years as well. Latest is making the cauls by using Durham’s Rock Hard. I made a little dam of binding tape around a block of wood to hold the putty and pushed it against the form. Sanded off the excess on a belt sander when dry. I think your approach will work well. As you see in the photo the lower caul has a little gap. I had to put a little more putty in that.





One trick to keep sides from shifting during clamping is to bend them together so they match perfectly and after glue is applied line them up on the form and tape the ends so they can’t shift then clamp up outward from the waist. That is what has worked best for me.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Just thinking here, not actually implemented. If you try to make an exact fit of rigid material, it will never really be tight everywhere. Make the cauls to accommodate some slightly compressible liner, such as very thick rubber.

Or just design in the proper sized gap to accommodate the veneers. That's what I have done.

I use kerfkore for the "blanket" part of the jig : https://www.google.com/search?q=kerf+ko ... sSmFS1CKwM:

I use the same block molds I use for bending with a heat blanket for the form. I have also thermoformed corian over the block mold to make another mold for laminating veneers (the kerfkore then goes on the inside of the mold).
I use waxed paper as a release agent and on occasion have laminated both sides on the same mold at the same time. The slight discrepancy in size is not too noticeable and seems to disappear when fitted in the building form.

Check out Tim McKnight's website. He has a picture of his jigs he uses for laminations.

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Guitar Building = Continuous Improvement Process

I had used cork on previous cauls and planned to use it on the molded ones but with a little minor tweaking it proved unnecessary.



I’ve used kerfkore too as well as an outside rather than an inside form and both work well but for some reason the cauls are easier for me. As mentioned,you can also use the inside form as your bending form.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

I do bend them together wrapped in paper and foil at another poster's suggestion. All the bending is done- just waiting on a few more clamps in the mail. I wouldn't have thought of the tape suggestion- thanks for the tip!

I haven't glued the top 2 cauls together yet. I bent the sides at around .055"-.065" depending on how stiff they felt. Curly Malaysian Ebony needed to be a little thinner than the coco side sets. I was planning to place the sides in the jig tonight and cover them with wax paper and then gluing up the top 2 cauls while the dimensioned sides are in place. I don't have any rubber handy unfortunately. I wonder if I'm not better off leaving the two masonite cauls unglued to allow more play when clamping?

I sometimes use 2 strips of scrap formica and place the veneer between them if the curves aren't too tight. The formica provides a nice smooth surface and keeps things fairly flat edge to edge (no cupping). If the mold is smooth enough they aren't needed.

I admit to being ignorant of the process but wouldn't a vacuum press be the simplest way to do this?

I gave up on using a vacuum bag to laminate sides after much experimentation. Just not enough clamping pressure.

My experience with the vacuum was that it would not press out minor wrinkles in the wood.

My problem was cutaways and the waist. Standard vacuum pressure is insufficient. You need something to concentrate the force in the deepest part of the bend.

I didn't have a problem with wrinkles probably because my top layer of wood was about .050" thick.

That is one the two major benefits that I'm looking for especially in figured woods and harder to bend figured ebonies/woods with interlocking grain. The other result I'm looking for is a more rigid side assembly that is resistant to cracking and more efficient at transferring energy between the top and back. Somagyi explains it a lot better than I'm doing here, but what he says does make sense to me.

It’s fun to try dissimilar woods too. You can use a lower grade lam on the inner side. One of my favorites was a Birds Eye Maple outer Indian Rosewood inner.

I think you’ll like what a double side does to the sound. Mine have been quite well received. I am a fan.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Hey guys thanks for the heads up about the vacuum system not working. well enough Saves some $$ . Was going to make one , I already have the vacuum system I have an older overholtzer alum heating jig which doubles as a bending form for a 3 layer side lamination for Cl gtrs.

Wow, Ernie, you go back a few years.

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formerly known around here as burbank
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http://www.patfosterguitars.com

I do Pat , It/s NOV 1 , my 70 th birthday today all saints day LOL

I have perfect results using vacuum, FWIW. I use a solid form, two .060" layers in a bag, and Unibond (which is specifically formulated for veneering).

This is a 20 second video of my process. I shot it in the back corner of a community workshop, so don't judge me by the setting.

I used a Joe Woodworker V2 in the video and have some of the V2 parts for sale in the classifieds in case anyone wants to put one together. I went to an EVS because my particular compressor is so loud (the EVS runs off of a vacuum pump).

I don't have any close-ups of my results, but you can get the idea here. No ripples, uneven sections, or spots that didn't quite laminate:

I am glad you had good results James. I still have concerns about sufficient clamping pressure in your waist though. You can see that the waist is the last place where the bag comes into contact with the wood and the bag has to stretch a bit in that area which also minimizes clamping pressure.

One approach that I think has merit is to keep the form outside of the vacuum bag. In other words, have a long narrow bag that you slip your wood into and then place that over the inside form. Then turn on the vacuum at the same time that you clamp it to your form.

Another possibility is to have a waist caul that goes into the bag that places additional pressure where needed.

I use a vac bag and a small Thomas vac pump. I only use an internal form made from hard foam. I tape the sides at the waist firmly to the form with 4 layers of masking tape. Tartan tape would work well too. So the waist is held down first. I work on the floor a lot, including vac bagging. Whilst the air is being pulled from the bag I squeeze the whole thing for a few seconds, with an elbow in the guitar waist and a knee in the top bout. Looks like something from a wrestling match. Or the karma-sutra. Not sure which. Either way, using me as a clamp whilst the air is pulled out works a treat. No issues. After a bit of practice.

I think the bottom line is, clamps work and vac bagging works. Both require experimentation, neither are without a learning curve or issues at the start. If you already have a lot of clamps, go with clamping. If you already have a vac pump, use that. If you have neither, decide which you might use more in the future - lots of clamps or a vac pump.

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nigel

http://www.theluthierblog.com

The bag actually slides down the side as it's pushed down into the waist thanks to the breather mesh. If you want to picture it, the breather layer is like window screen material, made of some kind of plastic material that the glue doesn't adhere to. It provides for both even air flow so that you have even vacuum pressure, and a sliding surface that the bag can glide along so that every area gets clamped with even pressure. Without it, the bag could definitely get choked at points.

Another thing that is helpful is that similar to Nigel's caul, I'm taping the waist down. My sides conform pretty well to the mold and to each other, and the little bit of pull from the tape keeps everything in place.

It's so easy to do in practice, too. Just brush on the Unibond, tape things down, slide it in the bag.

Here is a closeup of the waist. The dark sliver towards the notch for the X is a grain line.

I'm just getting around to laminating a bunch of side sets. Can't decide between epoxy and Titebond. I'm not a big fan of epoxy but the 30 minutes of time to get everything in place would be nice. What do you guys use?

Epoxy makes for a much more stable lamination. The water in Titebond will make the sides move around after removing from the form.