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Hollowbody Oddball guitar build


argytar
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So hi, I was thinking of making a hollow guitar for the first time.

Looking to approximate the likes of the guitars Auerbach of the black keys uses.

Something of a cross between a Harmony and a Custom Kraft maybe.

I started by building a mold, bending the sides and making the kerf.

Then I bought some maple lams.

They are approxiamtely 2mm in thickness maybe a little thinner.

I made a carved top out of maple. And an mdf bracket. I will use a vacuum bag to merge the lams.

 

So I have a couple of questions...

 

Is it imperative that I use cross grain? Can I just kinda Combine two or three lams? Should use three lams or two are ok?

 

Thanks for any input!

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11 hours ago, argytar said:

Is it imperative that I use cross grain? Can I just kinda Combine two or three lams? Should use three lams or two are ok?

Cross laminated veneers is basically plywood and the method is used for adding strength. Take one veneer and you can bend it one way until it cracks neatly along the grain. The other way it won't bend as easily and it will crack into splinters. Two cross laminated veneers will be equally stiff when bent into either direction and won't crack that easy. Three ply cross laminated will bend more easily to one direction than to the other and again won't crack as easily as a piece of solid wood of the same thickness. -Was that the information you needed or did I just tell something that "everyone" knows?

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2 hours ago, Bizman62 said:

Cross laminated veneers is basically plywood and the method is used for adding strength. Take one veneer and you can bend it one way until it cracks neatly along the grain. The other way it won't bend as easily and it will crack into splinters. Two cross laminated veneers will be equally stiff when bent into either direction and won't crack that easy. Three ply cross laminated will bend more easily to one direction than to the other and again won't crack as easily as a piece of solid wood of the same thickness. -Was that the information you needed or did I just tell something that "everyone" knows?

Yes, that was very informative!!! Thanks a mil!! So , to get things even more clear, should I put the middle piece of wood with the grain perpendicularly to the grain of  the previous lam? 

Thanks again!!

 

 

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1 hour ago, argytar said:

should I put the middle piece of wood with the grain perpendicularly to the grain of  the previous lam? 

Basically yes. If you're making a laminated top or bottom, line the outermost (visible) layer with the neck just as you would do with a one piece top. That serves both the aesthetics and strength against string pull.

I've heard about boatmaking where the laminates can be glued at steeper angles for added directional flexibility. Several angles are also possible. If you want to bend the veneers to a shallow bowl a three dimensional laminate might work. A two dimensional would be strong enough for most uses, though.

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18 hours ago, Bizman62 said:

Basically yes. If you're making a laminated top or bottom, line the outermost (visible) layer with the neck just as you would do with a one piece top. That serves both the aesthetics and strength against string pull.

I've heard about boatmaking where the laminates can be glued at steeper angles for added directional flexibility. Several angles are also possible. If you want to bend the veneers to a shallow bowl a three dimensional laminate might work. A two dimensional would be strong enough for most uses, though.

No, I think bending the pieces on a maple carved top will count as a three dimentional, right?

So that is what I will do and hope for the best!!

I will put two radiator cover buckers in there to make it more oddball- esque.

A 6-in-line headstock and maybe some over the top switching options like out-of-phase and on-on-on switches with series-single-parallel options.

I also have a Duesnberg Les Trem that I would like to fit behind the bridge maybe using a sound post.

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So, I tried my top mold today with the vacuum bag, without the glue...

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Wow ! Seems to work quite nicely!! I will put and press a rim around to make sure the pressure is right and I will try to use hot hide glue... we shall see!!

 

I tried to find some cross-grain pieces but I couldn t find big ones in my inventory. I will use two piece lams for the middle, I hope that will be ok,  if I glue them tightly!

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How is that middle part’s grain? Am I moving on correctly, or do I have it all wrong?

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10 hours ago, argytar said:

How is that middle part’s grain? Am I moving on correctly, or do I have it all wrong?

That looks more like a piece of lathed veneer than cut. As it's in the middle it doesn't matter much. Plywood is usually made of rotary cut veneers and it's tough as can be. As long as you have the best looking veneer on top all is good.

If you've ever wondered how the thin veneers are manufactured, here's how: https://gharpedia.com/blog/manufacturing-process-of-wood-veneer/

A fellow builder once brought rolls of 0.55 x 120 mm birch veneers to the workshop. I've used them cross grained to prevent control cavity covers from warping and splitting and also as accenting stripes. The seam is invisible when done carefully - which I know you can do! It's unbelievable how little material you need to counteract warping or in your case stabilizing a molded shape. Back in the day I visited a kitchen cabinet factory where they made laminated worktops out of chipboard. Now the laminate is watertight but the chipboard isn't which means that the bottom side could swell and warp with moisture. So to counteract that they laminate a single sheet of perforated paper on the bottom side, the holes being about 5 mm in diameter so it's rather a mesh than a sheet! And that works.

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1 hour ago, Bizman62 said:

That looks more like a piece of lathed veneer than cut. As it's in the middle it doesn't matter much. Plywood is usually made of rotary cut veneers and it's tough as can be. As long as you have the best looking veneer on top all is good.

If you've ever wondered how the thin veneers are manufactured, here's how: https://gharpedia.com/blog/manufacturing-process-of-wood-veneer/

A fellow builder once brought rolls of 0.55 x 120 mm birch veneers to the workshop. I've used them cross grained to prevent control cavity covers from warping and splitting and also as accenting stripes. The seam is invisible when done carefully - which I know you can do! It's unbelievable how little material you need to counteract warping or in your case stabilizing a molded shape. Back in the day I visited a kitchen cabinet factory where they made laminated worktops out of chipboard. Now the laminate is watertight but the chipboard isn't which means that the bottom side could swell and warp with moisture. So to counteract that they laminate a single sheet of perforated paper on the bottom side, the holes being about 5 mm in diameter so it's rather a mesh than a sheet! And that works.

Wow! Great info! Thanks!

My lumber provider told me that they are rotary cut- which is ok I guess. They will go in the middle, so no connection will show. (However I try for it to be as perfect as possible, I treat it as if I was glueing up a soundboard , which it technically is!).

I will ty to plane it thinner then to reach my goal of 5.5mm thickness.

Thank you so much for your info, big help! I appreciate it!!


 

 

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2 hours ago, Bizman62 said:

Goes to show that what's elementary for one can be new info to another hobbyist woodworker! And thinking that I was afraid to post all that in fear for underrating your knowledge...


No problem , I asked because I didn t know!

I only made solid body guitars up to this year, never had anything to do with laminates and I am just learning things as I go.

As far as I knew I would stack three laminated on one another without changing the direction of the grain. That would be interesting! ... not!

Again thanks for your help!

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So naturally I have another question!

A friend of mine tried titebond to glue the lams but they kind of cracked as if they were wet. I read Gibson used pressure heat and some kind of industrial glue on their 335s.

Any ideas on what non-hydrophylic (hydrophobic?) I could use?

 

Thank you!!!

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I might use regular Titebond but that's just me. If you're going to make sort of a laminated bowl you'd need a two piece mould. Moistening the veneers should prevent them from cracking, heat might help as well. Wood can be surprisingly flexible when it's properly steamed and it will stabilize when it's cooled down.

By the way, if you build a mould using sheets of plastic foam (the type used for packaging or even the yoga mat type) on either side will even the pressure, thus preventing bubbles between the veneers.

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2 hours ago, Bizman62 said:

I might use regular Titebond but that's just me. If you're going to make sort of a laminated bowl you'd need a two piece mould. Moistening the veneers should prevent them from cracking, heat might help as well. Wood can be surprisingly flexible when it's properly steamed and it will stabilize when it's cooled down.

By the way, if you build a mould using sheets of plastic foam (the type used for packaging or even the yoga mat type) on either side will even the pressure, thus preventing bubbles between the veneers.

Wow, that info is gold!

I have made a mold out of maple and not exactly a cap but a rim rather. I will use the vacuum bag and then press the rim at the edges. The yoga mat idea is really nice! I will see into that!

 

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  • 1 month later...

Hello again!

I have been planning this for a while now, so let us update the situation.

After some research and with the kind help of McKay guitars , I started looking for urea glue or kaskamite. It was a little difficult but I got me some.

 

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After that I found out that I needed a bleeder or breather cloth which I also found at a local store that sells vacuum application stuff for people that repair boats with epoxy resins and do vacuum infusion.

 

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So the time for the first test has come.

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I mixed the UF glue and applied it to scrap, then used vacuum to press it.

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I will let you know how that went in a couple of days!

They say that you need temperatures over 70 degrees for these glues to work. Fingers crossed!

 

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Utter and complete failure...

 

I don t know if it was the humidity ...

 

the non- consistent vacuum pressure...

 

or the mix ratio...

 

but after 24 hours the veneers came off just by pulling with my hand...

Not the entirety of them, that gives me some hope.

I obviously did something wrong...

maybe I should use titebond next time.

 

I will of course keep trying!

 

Thoughts? Anyone done this with urea glue? Your laminating experience will be highly appreciated!

 

 

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The existence and size of the glue lumps makes me think of too little pressure. As you know from top joints, the glue line should be invisible. That much glue would be very much visible.

You had a bottom mold, but no top mold. You'd need both, and some foam in between to fix any unmatching spots.

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nothing to contribute, but just wanted to say it's an interesting thread for sure.  experiments for me often end with a lot of effort and no result... but lack of experimentation in a build is boring.  this is def not boring!!  rock on.

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  • 4 weeks later...
On 2/7/2021 at 11:24 AM, Bizman62 said:

The existence and size of the glue lumps makes me think of too little pressure. As you know from top joints, the glue line should be invisible. That much glue would be very much visible.

You had a bottom mold, but no top mold. You'd need both, and some foam in between to fix any unmatching spots.

Thank you so much! I have bought some insulation hard foam and found a door press on a nearby woodsmith. He said we can give it a go in the near future. This time I will use scraps just to be sure!

I started refining the mold. I think having it in steps may have caused problems too! With three lams it didn t show , but when I put one maple lam in there, it assumed the shape of the steps so maybe some of the void was caused by this inacuracy.

 

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In the meantime, I made a scarf - joined Korina neck blank for the project and started making a compton-esque 7075 aluminum bridge for extra spanky tone!

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I will need to drill carefully, file- shape and polish!

 

 

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On 2/7/2021 at 5:44 PM, mistermikev said:

nothing to contribute, but just wanted to say it's an interesting thread for sure.  experiments for me often end with a lot of effort and no result... but lack of experimentation in a build is boring.  this is def not boring!!  rock on.

Exactly! Experimenting with new techniques makes this build even more exciting for me!!

Thank you!

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So, a few notes. I'm not there, of course, so I can only judge by the pics I see. But there are several pics that look very much to me like a temperature-related failed aliphatic glue joint. As in, those 'whitish marks' are very telltale signs of an aliphatic glue being applied too cold.

But with your urea glue, I don't know, I just know those whitish marks are a dead-giveaway of a cold glue joint failure.

It also seems you're not really doing a true veneer job (maybe I missed something) but actually making a laminated top. A lam top is not veneer, so I wouldn't use words generally associated with veneering, its confusing. For genuine veneer work, I use Better Bond Cold Press Veneer Adhesive. It comes in 2 tints, a light and a dark, and has wood fibers in it so the glue doesn't seep up into the veneer when applying great pressure to glue. But if you're not doing an actual veneer, then that information is invalid, see what I mean?

If it's an actual lam(inated) top, that changes things a bit, and the generally normal rules of veneer don't apply to a situation like that. If you're doing what I think you're doing (making a laminated top), you need heat as part of your recipe. And if those white marks are from cold-joint failure, you most certainly don't have nearly the heat you really need. You're looking more for nearly hot (or actually hot) temps to do lam work.

Looking at your first pic, I would imagine that you needed heat to bend your sides into form.

Think of a lam top in 'those terms', in 'that way' 'from that approach' and you'll be headed in the right direction.

When I was in my 20's, I had a job for a season in a custom plastics manufacturing plant. One side of the shop was artistic acrylic work (3" thick super-fancy artistic tabletops and other crazy artistic things). The other side of the shop was vacuum forming plastic parts. I worked with industrial-sized vacuum presses all day long. The exact same thing you're trying to do except with plastics on a much larger scale and for mass-production. We would bang out (for an example) 70-100 (plastic) guitar tops a day. We didn't actually make plastic guitar tops, of course, but that type and size of object was what we worked with.

And success all starts with the proper amount of heat. Just like forming a bent guitar side, exactly like that. Too cold, fail. Too hot, fail. Wrong (too delicate) type of wood, fail. The vacuum machines had huge electric heaters on top where you would slide the piece into place. The form (whatever you were making/forming) was down on the table. When the piece was heated to your satisfaction, you dropped (draped, really) the piece down over the form and the vacuum kicked in to form the piece. If the piece wasn't heated enough, total fail, it wouldn't shape and form properly onto the mold. If you overheated it, it would be too hot and form too thinly. It was all in getting the temps 'just right' so the vacuum process would work correctly.

And in basic approach, laminate-thicknessed wood works basically the same way, it needs the right amount of heat to cooperate. So if those whitish marks are from a cold joint glue failure, you can see why it failed, the variable of heat was completely off the mark for success.

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2 hours ago, Drak said:

So, a few notes. I'm not there, of course, so I can only judge by the pics I see. But there are several pics that look very much to me like a temperature-related failed aliphatic glue joint. As in, those 'whitish marks' are very telltale signs of an aliphatic glue being applied too cold.

But with your urea glue, I don't know, I just know those whitish marks are a dead-giveaway of a cold glue joint failure.

It also seems you're not really doing a true veneer job (maybe I missed something) but actually making a laminated top. A lam top is not veneer, so I wouldn't use words generally associated with veneering, its confusing. For genuine veneer work, I use Better Bond Cold Press Veneer Adhesive. It comes in 2 tints, a light and a dark, and has wood fibers in it so the glue doesn't seep up into the veneer when applying great pressure to glue. But if you're not doing an actual veneer, then that information is invalid, see what I mean?

If it's an actual lam(inated) top, that changes things a bit, and the generally normal rules of veneer don't apply to a situation like that. If you're doing what I think you're doing (making a laminated top), you need heat as part of your recipe. And if those white marks are from cold-joint failure, you most certainly don't have nearly the heat you really need. You're looking more for nearly hot (or actually hot) temps to do lam work.

Looking at your first pic, I would imagine that you needed heat to bend your sides into form.

Think of a lam top in 'those terms', in 'that way' 'from that approach' and you'll be headed in the right direction.

When I was in my 20's, I had a job for a season in a custom plastics manufacturing plant. One side of the shop was artistic acrylic work (3" thick super-fancy artistic tabletops and other crazy artistic things). The other side of the shop was vacuum forming plastic parts. I worked with industrial-sized vacuum presses all day long. The exact same thing you're trying to do except with plastics on a much larger scale and for mass-production. We would bang out (for an example) 70-100 (plastic) guitar tops a day. We didn't actually make plastic guitar tops, of course, but that type and size of object was what we worked with.

And success all starts with the proper amount of heat. Just like forming a bent guitar side, exactly like that. Too cold, fail. Too hot, fail. Wrong (too delicate) type of wood, fail. The vacuum machines had huge electric heaters on top where you would slide the piece into place. The form (whatever you were making/forming) was down on the table. When the piece was heated to your satisfaction, you dropped (draped, really) the piece down over the form and the vacuum kicked in to form the piece. If the piece wasn't heated enough, total fail, it wouldn't shape and form properly onto the mold. If you overheated it, it would be too hot and form too thinly. It was all in getting the temps 'just right' so the vacuum process would work correctly.

And in basic approach, laminate-thicknessed wood works basically the same way, it needs the right amount of heat to cooperate. So if those whitish marks are from a cold joint glue failure, you can see why it failed, the variable of heat was completely off the mark for success.


Wow, thanks so much for the info!

The process I want to follow is to make a laminated top, sorry for the confusion.

I want to use 1.5mm thick lams to achieve a cross - grained laminated top. The problem is that the temperatures in my “workshop” at this time of year range between 12-16 degrees centigrade. That said, I most definately agree that there was a temperature failure. 
 

I found a door press and I might try laminating again with titebond this time. I hope I will be more successful! I will leave urea glue to use in the summer, maybe that would be better.

Thank you all so much for contributing!!

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If it were me doing that, I would probably thin the Titebond with some water.

Not a lot, but some.

Either that, or sometimes I'll take a spritzer bottle with water in it and spritz the pieces before glue-up.

Very careful with spritzing, its really easy to over-wet, but some additional water helps in a lot of glue-up situations.

Either by thinning the glue w/ water, or spritzing (super-light misting) the pieces first.

...Which you would never do when doing a veneer glue-up, haha!...

Veneer glue is supposed to be thick and viscous so it doesn't permeate the veneer and come up through it.

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@Drak just yesterday I was thinking about this project and remembered how we carved moulds for acrylic sheets which we heated in a regular electric oven.

At around 0:50 you'll see how much pressure they use for a Höfner bass laminate:

 

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