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Many have started using double side construction that utilizes two thin layers of wood laminated together. I have been intrigued with this construction method but decided to put my own twist on the concept.







It is too early to tell what effect this will have on the guitar but it has been interesting.

For the record...it is my understanding that this has been done but other builders but I have not see this design before. If you have used something similar please post your results.

Thanks for looking!

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Brad
Avon, OH

hey brad, that is a very interesting approach! i have no clue how it is going to work out, but i commend you for trying something different! the inside of that box looks incredibly clean. kinda strange to not see any linings in there. have you had any trouble leveling the sides? or have you gotten that far yet? it doesnt seem like you would have much wiggle room in getting them flat with that thin of an outer layer. looks cool. thanks for sharing and let us know how it turns out.

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sweat the small stuff.

My biggest concern is repairing damage to the sides.

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

I believe Sheldon Schwartz uses similar construction in his Oracle model.

Brad, Charles Fox does something similar with his current Ergo guitars. The backs are a thick sandwich as well, and have no braces.

I don't see the nomex in your photos and don't understand where it is. Can you elaborate on that?

Repair issues are also my concern with these thin-skinned sandwich constructions.

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

So far everything has been very level and square. I will know better in a few weeks but dont' expect any problems.


This has been mentioned by a few others I have talked with. With the two layers of wood with the nomex between the wood should have good resistance to cracking....HOWEVER....things happen and repair would be difficult.

Where was the picture you posted taken from?


This should help.

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Brad
Avon, OH

Beautiful and very innovative work Brad my friend!

What's the thesis? i.e. are you trying to get super-duper rigid sides, trim weight or what? (there needs to be a smily invented to convey that it's a genuine question and not a smart-aleck remark)

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

I`m with Andy,What are the advantages ,and do they out weigh some of the disadvantes, to warrant what seems to me to be a lot of extra effort ? Of course never having done this myself,maybe it isn`t any extra effort.
James

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James W Bolan
Nashville Tennessee

Andy...this is a fair question. My original goal was more process related than design related. I wanted to build a side set that had the advantage of double sides (stiffness) but eliminate the epoxy bleed through when laminating two thin sides together. I also wanted to use .024 inner side which would give the option of using 1/42 veneer rather than sanding sides down to a typical .030 thickness. So based on my goals I was able to eliminate the epoxy bleed and since no additional sanding is required after the lamination process the .024 inner side thickness worked fine. As for the extra work, with some process development I am not convinced it adds much work.

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Brad
Avon, OH

Thanks for the photo, Brad. I thought maybe that's how you did it, but I wasn't sure. In spite of my concerns about repairability, I think this is really cool and a very worthy pursuit. Thanks for sharing it here!

Charles Fox would probably love to see what you're doing, and some dialog between the two of you could prove very fruitful.

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

Too eliminate epoxy bleed through why not use something else ? The only time I have ever used epoxy for laminating is when it will be used out doors. Have you tried Uni-bond for laminating ? (Urea formaldehyde glue )
Very hard stiff glue, much more ridgid than epoxies.
Link

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Cut to size.....Beat to fit.....Paint to match.

I have heard of people using other types of glues for laminating besides epoxy. I considered trying this but just haven't yet.

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Brad
Avon, OH

Just a curious question.

What is the benefit over conventional laminated sides? It is a very innovative construction method and very nice work but I am not sure I see a practical gain

I was just at Vermont Instruments where we were taught about reversing the kerfed linings to create what I would imagine to be a very similar effect. I noticed after reversing the linings that my sides were much stiffer and there was no spring-back at all. I imagine it's probably the same concept, but just using the lining to reinforce the stiffness as opposed to an entire side.

the laminated sides are much stiffer by comparison. I use laminated sides with capped linings and I could literally build the guitar outside the mold after that point.


Brad, that is a great approach. Did you ever try that heat set epoxy? Did that stop any of the bleed?

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

Brock...I have not tried using heat set epoxies (yet). I still think there is much potential but it just comes down to trial and error.

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Brad
Avon, OH

So what about gluing with fishglue, or is epoxy the norm for double sides??

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Here is what a Parlor Guitar is for!
http://www.youtube.com/watch?v=oEa8PkjO6_I

http://www.frets.com/FRETSPages/Luthier/Technique/Guitar/Structural/Cracks/2TopCrunch/2topcrunch.html
Repair method for double wall construction. This happens to be a top.

Fishglue adds some moisture and the resulting warping is a problem. Epoxy is a much better shoice.

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"An adventure is only an inconvenience rightly considered. An inconvenience is an adventure wrongly considered." G. K. Chesterton.

Yeah, fish glue(as well as most other glues) don't hold the form/shape very well, when the epoxy dries you get a pretty rigid shape that is from that point on really easy to work with.

Cheers,
Greg

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Gwaltney Guitars

I don't believe that a fully cured fish glue will work noticeably better or worse than epoxy so far as strength goes. The reason a lamination holds its shape is based on the tension and shear load of the laminates and fish glue is certainly strong enough in shear for that.

The problems, as I see it, are related to the water content. Number one (already mentioned) is that fish glue adds water, which might induce warp. Number two is that it really needs to 'dry out' to cure, and it's really hard for it to do that under vacuum (which is the easiest and most consistent way to make laminates). You want an almost full cure before you take the laminates out of the mold to have them hold shape, and it'll be a -lot- of waiting for that with fish glue unless you're willing to invest in a complex setup. I, for one, would love to use fish or hide glue to do laminations but they just don't cure well under vacuum so I only use them in 'flat' laminations I can clamp between a couple aluminum plates for a day or two.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

So do you vacuum bag the laminates against the male mold that I see in one of the pics or do you have a female counterpart to the bottom mold? Any chance of some pics/description of the clamping arangement? Thanks, Peter

Here was my approach....

I started with the thin inner side and 2 reverse linings.


The linings are glued to the inner side in the flat condition. Note the lininings are actually installed backwards with the kerf mounted toward the inner side.

Once the linings are dry I send the side and linings through a drum sander to sand off the top part of the linings. This operation allows the side and linings to now bend by exposing the kerfings.


The nomex is laminated to the side in the flat condition. After this was dry I sent this back through the drum sander to sand the nomex even with the linings. This could be avoided if the linings and nomex were the same thickness when I started. (live and learn...maybe next time)


The inner side is thin enough that it does not require to be bent with heat. The entire inner side as this point is almost like a very large flexible kerfed lining with little rigidity of its own and can easily be bent around a form without risk of cracking. This picture just shows the inner side bent around the form held in place with wooden dowl and rubber bands.


The outer side is bend using traditional bending methods and laminated to the inner side subassembly using form as shown. I used a vacuum bag to clamp everything together but it could be clamped using other methods. This picture was taken after removed from the vacuum bag perfectly conformed to the form.


The sides after removed from the vacuum clamping process.


To connect the sides I used two thin pieces of birch ply glued between the inner and outer sides. The neck and tail block can then be installed.


As I mentioned earlier, the whole process isn't terrible complicated since most of the process is performed in the flat condition and doesn't require a tremendious about of precision. As a side note, since the sides were very ridid and had no spring back (and for a few other reasons) I did not use a mold for this project and question whether it is needed with this style of construction.

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Brad
Avon, OH

That's cool, Brad. Maybe you don't even need the tail block.

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/