Building a Domed Back

[TallDad71]

I recently built this guitar, It's the first guitar I ever made that prioritised form over function. I knew I wanted a beautifully striped guitar and that was my main goal. Its sound was less important to me, hence I had no way of making the back live.

The only caveats I had was that I would finally put my Gore/Gillet books to use and make the top using Falcate Bracing, in addition I went through all my sets of tops and found the most musical I had, damn it was good!

The result is staggering, not necessarily visually as I can still only see the imperfections, but sonically it just sounds like the loudest, most evenly balanced guitar I have ever built.

So! Decorative is the way to go and here I need your advice please. Attached is a picture of Randy Parson's Red Queen acoustic and I've fallen in love with the fan tail. I want to make something very similar on a 3m domed dish.

His version is made from 15mm solid wood, laminated, and carved on the inside and out. I want to make mine out of 2mm sheet like I did for the one above. At the end of the glueing process I want the back to be arched like a lute which entails sanding the sides of every triangular strip until they meet with no light shining through.

How do I do this?

I was thinking of manufacturing a 3m domed clear perspex mould and using it as a light box to check the fit was correct, but truth be told I haven't got a clue how to do that!!!!

If you could put your thinking cap on and give any thoughts that would be greatly appreciated.

[Dave M]

Well that is very maradadi as we used to say in Kenya!

Can't possibly answer your question but I think you have just discovered how well Trevor's falcate bracing works, particularly, in my experience for steel strings

[TallDad71]

I love the smell of Swahili in the morning!

Very maridadi indeed.

Yes it's the first Falcate build and I am super Impressed. I didn't even both recording the acoustic frequencies yet as there was no need to find a way to optimise the sound. I am expecting all other builds to be identical

[WJ Guitars]

Excellent result and a great looking guitar build! Good to hear that the falcate bracing design worked well to achieve a great sounding guitar.

Wayne

[kiwigeo]

Nice work with that guitar..very interesting rosette.

If you're going for a full lute style bowl back you'd normally work with an internal mold. The process is akin to making a wine barrel using staves. Accuracy of the mold is critical as is fit of the ribs. Running a narrow black or white purfling strip between ribs can help. This is what I did with my lute build.

[TallDad71]

Thanks for the nice comments Wayne.

Martin, I think you've cracked it for me. If I build a dome using your method, it should have enough holes for the light to come though. That way I can ensure a tight fit. I used purling on the build above, very messy!!!!

The rosette wasn't my greatest idea but sometimes we have to do these things! I was fixated on having something different and in this case I wanted it to be raised above the level of the soundboard by 2mm.

The guitar is called "Stripey" so the rosette is made of 5 laminates and had to be finished separately from the guitar, then glued at the same time as the bridge. The time it stole from me means I'll not be doing that again anytime soon. It also necessitated a port hole being installed on the side of the guitar (more time) to keep the air flowing. We will and learn.

[kiwigeo]

Martin, I think you've cracked it for me. If I build a dome using your method, it should have enough holes for the light to come though. That way I can ensure a tight fit. I used purling on the build above, very messy!!!!

My "method" is as per David Van Edwards Lute Tutorial CD.

[Trevor Gore]

That's a striking guitar, Alan, and welcome to the falcate club!

A quick question if I may: How did you do the sides? If you glued before bending, what glue did you use?

My glue of choice for that application would be Aerodux 500 (which I used for boat building in the UK in the 80's and 90's). But it seems to be no longer available.

[TallDad71]

Trevor, the falcate bracing is a revelation!

As I mentioned, the balance is fantastic, which I assume is partly due to the bracing. The volume is also remarkable compared to the 14th fret guitars I’ve built in the past, I'm thinking that this has more to do with the bridge placement in the centre of the soundboard's active area.

How did I build the stripe ......... badly.

I didn't want to glue them first because of the heat treatment. Instead I routed out the channel in the sides for the strip and bent each separately, glueing them together as you would your linings or bindings. The thing I didn't factor in was that the 1mm deep channel in the sides is prone to changing shape under a bending iron both in width and depth! Consequently the strip didn't actually fit inside anymore.

That was a fun week!

If I was to do it again ...... I probably wouldn't!

[TallDad71]

I thought I should upload pictures of the insides of Stripey. In many ways I think a guitar is prettier on the inside.

I've taken to coating the insides with shellac, primarily I thought it might help them respond more slowly to humidity changes but also I couldn't think of a reason not too.

[Trevor Gore]

Thanks, Alan. Properly heat proof wood glues are hard to find...

[TallDad71]

Thanks, Alan. Properly heat proof wood glues are hard to find...

On a recent visit around the Jaguar F-Type factory I noticed that they glued their aluminium panels together to make a sold unibody. Although they used electric welds as bolt and braces the glue was the major component.

I wonder whether metal glue, which is heat resistant, would be a suitable alternative to the Aerodux 500 you used back in the day?

I might give it an experiment.

[Trevor Gore]

I wonder whether metal glue, which is heat resistant, would be a suitable alternative to the Aerodux 500 you used back in the day?

"Back in the day", when I was doing a lot of sailboat racing, the masts I used were made by a mob called Needlespar. They were constructed from tapered aluminium extruded tubes, glued together using internal sleeves and Araldite epoxy. I never heard of any glue failures. If a mast broke, it was never at a glued joint.

At one world champs I was at I wanted to dismantle the lower part of a mast with a glued on sleeve. It was impossible with the blow torch I had to hand, because aluminium is such a good heat conductor I could never get it locally hot enough. It would have taken an oxy torch.

Aluminium glues well with epoxy, but these days Jaguar might be using a polyurethane glue instead. If that stuff didn't foam (blowing parts apart) it would be a good glue!