Laminated Arch Back

Ukakuka

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Been working on an experimental project (laminated back and sides) tenor ukulele with an arch back. On the next one I’d like to use a heat press with male and female forms to press the shape I’m after using solid wood the way Bruko is doing themF25E80FD-8E99-468D-BFAE-5598321AE847.jpg and wonder if anyone has any experience in this group on how to do it?
 

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Looks great!
I've always wanted to try an (for a lack of a better and more descriptive term) a laminated quasi archtop back with a male/female mold (or for those easily offended, two non gender specific molds).

Can you show some pics of your molds?
 
If I remember correctly, something that is always iffy, Ken Timms did this some time ago and had posted his results here. But, I may not remember correctly
:rolleyes:
 
Looks great!
I've always wanted to try an (for a lack of a better and more descriptive term) a laminated quasi archtop back with a male/female mold (or for those easily offended, two non gender specific molds).

Can you show some pics of your molds?

Thanks Beau,

I’m calling it a parabolic convex arched dome with a 12’ outer radius and a 15’ mating radius...... Not! That sounds ridiculous.. Lol! Anyway, I’m still trying to figure a way to make the male/female molds you mentioned. I’d like to try cutting those molds out of aluminum and fit them to a heat press for solid or laminated builds.
388CBD4E-E4AD-4DD3-8498-C2DD262ACB01.jpgD7266A9B-487B-4D28-AB78-EC9DDD572301.jpg2EE5344F-3C05-4F9D-B29D-06EF87D6EA29.jpg021D2431-D006-4F39-B26D-83C42FBFE56B.jpg531C1EB7-DE82-42EB-B418-73742FCA0CB7.jpg
 
The easiest lofi way would be to carve an actual back (male) out of MDF, then cast it is resin (which gives you the female mold), then cast a working male mold from that cast female mold.

You would have to think about veneer thickness used too and their impact on the fitting etc.

Hand carving would give you much nicer curves then what you are getting, which looks rather abrupt (if you care about such things)
 
The easiest lofi way would be to carve an actual back (male) out of MDF, then cast it is resin (which gives you the female mold), then cast a working male mold from that cast female mold.

You would have to think about veneer thickness used too and their impact on the fitting etc.

Hand carving would give you much nicer curves then what you are getting, which looks rather abrupt (if you care about such things)


Thank for the response. I totally agree with your observations however, this build was all R&D and an experiment on a number firsts for me. Regarding your suggestion though, I wonder if the use of resin molds would hold up to the heat press application IÂ’m thinking of using which could be used for both glued laminate builds or, for solid wood. Aluminum comes to mind but, if resin can hold up and transfer heat, that might be the way to go.
 
Resin probably isn't good with heat.

However, you don't need heat to use epoxy.

Aluminum molds would be VERY expensive.

Therefore, you don't need aluminum molds.

I think your comparing apples to oranges here. I’m not talking about laminating. The aluminum forms would for bending solid wood in a heat press. And apologies if I wasn’t being clear.
 
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I think your comparing apples to oranges here. I’m not talking about laminating. The aluminum forms would for bending solid wood in a heat press. And apologies if I wasn’t being clear.

Argh- ok- that makes way more sense- I don't know anything about bending solid wood in so many directions with heat!
What wood thickness are you using?
 
Argh- ok- that makes way more sense- I don't know anything about bending solid wood in so many directions with heat!
What wood thickness are you using?

That makes two of us! Lol.. This is going to be a bit of trial and error regarding thickness. I did get a few tips from the folks at Bruko Ukuleles’s. Their process uses a heat press of some sort prior to gluing together the backs.

I didn’t push it with them for any further specifics but I’m thinking of try out using a simple t-shirt heat press @ about $100 (used) and machining a couple of either 5/8 or, 3/4 aluminum plates for forms and see what happens.
 
I've seen very few pressed backs, but the ones I have seen have all exhibited signs of asymmetry. I can't imagine that they left the factory like that, so I am assuming that something happened with acclimation or aging to encourage some areas of the wood to try to resume its unpressed state. This is not a scientific summation, just a casual observation … perhaps those few examples were atypical.
Pressed backs should provide a stellar strength to weight ratio, and likely a highly reflective shape, but I wonder if either of these features is worth the engineering effort over moderately arched braced backs.
If you have the tooling to make the presses, it should prove to be a very interesting process. Don't be discouraged … many of us will be very interested in your progress and results.
 
Lol! I’ll get some sheet metal tools from Harbor Freight!
 
If Bruko can do it, then maybe I can too? I’ll post along the way. Thanks for the encouragement.
 
This shows an interesting balance of specialist machinery and real-life lutherie skills.
I had to replay the fret slot cutting sequence multiple times to be sure of what I was seeing … unbelievable.

Yes I've seen that Guy at work in another video...He has a large rubber ink stamp that presses on the fretboard that marks the positions of the fret slots and MOP dots..then he cuts them out by eye with the handsaw and power drill...It takes great confidence and skill. :bowdown:
 
If you look closely when he's drilling the dots, you can see that he has not cut the fret slots on the marked line but about 1mm to the right hand side. (His Left)
 
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That slot cutting footage is the luthier's equivalent of the shower scene from 'Psycho' … a brutish coarse-toothed implement being wielded upon a cowering fret board … nightmare material. After my palpitations subsided, I thought 'Phew thank God it was only a bass'... but, before all the bassist brethren rush to ignite their flamethrowers, let me claim that my time fumbling up and down the bass neck qualifies me to joke about it.
More seriously though, by modern standards, my own fret slotting technique is primitive. I have only ever used a hand held saw (with depth stop), home-made aluminium fret scale rulers, a marking blade, and a true-squared wooden block for a guide (all applied with a healthy dose of trepidation).
 
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