Applying G&G techniques to a kit guitar

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sleake
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Applying G&G techniques to a kit guitar

Post by sleake » Mon Apr 20, 2020 9:16 am

Hi everyone.

Not sure if this is the best place for the thread, perhaps the specific Gore/Gilet forum may be more suitable, guess ill let the mods decide (thanks)

So I've just closed the box of a stumac kit 000 I bought of the forum a few years ago. Ive pretty much followed the kit components and standard 000 bracing, aside from using a mould.

I had planned on building with radius dishes however i just had a run of awesome low humidity along with time off work so prioritised closing it up using clamping cauls and an angled sanding stick which has worked ok, but left a few small flatish spots on the back at the headblock, but i think only i notice them.

However, although the horse has bolted on the major design factors outlined in 'the books' was wondering what stratagies might be employed on the closed box to hopefully bring out the best in what ive done so far.

Key points im considering are doing a little edge thinning and building a lightweight CF reinforced bridge (though I was hoping to maintain a pyramid style - perhaps form over function?) Is there anything else? Im not really considering touching the braces without a really clear reason, and even then waiting till its strung up.

However, without any resonance or materials data, is there any point? I would consider the top to be currently a touch thick at 3.1 mm, but there is some tearout that will need to be sanded away so at a guess i reckon it will finish just under 3mm (yes i know i should have done this first, but humidity waits for no man!)

Would love to hear what others think.

Thanks, Steve.

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Re: Applying G&G techniques to a kit guitar

Post by sleake » Mon Apr 20, 2020 9:21 am

Might as well turn this into a build thread to keep me honest.

Back and sides - sorry I forgot I did follow G&G here with reversed kerfings and largish side splints.

And the top getting braced up. Just followed the 000 plans to a tee.
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sleake
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Re: Applying G&G techniques to a kit guitar

Post by sleake » Sat Mar 26, 2022 6:08 pm

After a wild 2 years, I finally got back into it this afternoon.

Binding and purfling channels routed with no epic disasters. All I could hope for!

Sorry the photos got a bit weird, I've put them in below as screenshots instead.

Ta, Steve
Last edited by sleake on Sat Mar 26, 2022 6:12 pm, edited 1 time in total.

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Re: Applying G&G techniques to a kit guitar

Post by sleake » Sat Mar 26, 2022 6:10 pm

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Re: Applying G&G techniques to a kit guitar

Post by sleake » Sat Mar 26, 2022 6:11 pm

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Mark McLean
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Re: Applying G&G techniques to a kit guitar

Post by Mark McLean » Sun Mar 27, 2022 10:36 am

Hi Steve
Looks like great progress, after a long break. One of the really good things about instrument building is that the project can just sit and wait until you have the time to get back to it. My projects certainly tend to be like that. The herringbone and bindings look really good.

If you are still keen to apply G&G methods as your original title stated you could do some top deflection testing to see whether your top thickness and bracing have you in the right ballpark. It is easy to do with a dial indicator (pretty cheap to buy if you don't have one already https://www.machineryhouse.com.au/M046). It gives an objective indication of one of the soundboard's key properties and could guide you in deciding about whether to thin it any more, or shave braces. I find it useful, but one problem of deflection testing is that there are no standardized ideal values because everybody's testing setup is different. You need to set up a simple deflection testing jig and then run some tests on a few other guitars to get some reference values, then test your box. It will probably have more deflection than a finished guitar with the bridge glued on but you will start to get a feel for things.

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peter.coombe
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Re: Applying G&G techniques to a kit guitar

Post by peter.coombe » Sun Mar 27, 2022 10:52 am

I have just done some modifications to a guitar I made just before reading the books, so your post is timely. I have been using it as a reference, but all my recent guitars beat it easily so it was not so useful as a reference any more. The first thing I would do is to add two blocks of wood with T nuts to the sides so you can add mass to the sides later. Since the box is closed, this is a little trickier than if it was not already closed because you can't clamp so you need to use a rub joint or maybe use epoxy. It is also difficult to get a good fit because you can't see the joint. However, it is not all that difficult because I have just done it. The bridge on my guitar was already there and I did not want to replace it so it stayed. It is really up to you what bridge you use, but you can of course use a laminated bridge with carbon fiber, but the important thing is not to use a heavy bridge (e.g. Ebony or rosewood). However, a bridge with carbon fiber lamination will work best with a bridge plate also laminated with carbon fiber. 3.1mm is a bit thick for the top, but without any measurements, you are flying blind. You can now make some measurements and get a rough idea of if you need to thin the top, but the horse has really already bolted.

Get it finished with the bridge glued on and strings on. Now measure. If you want to use the techniques in the Gore/Gilet books, you can't get out of having to make measurements. From the measurements you can determine what needs to be done, i.e. if mass needs to be added to the sides to drop the main top mode. With the traditional bracing on the back it is going to be difficult to change the back, so I would probably leave that alone. In my case, the main top mode was dead on G, so I added some mass to drop it 1/2 semitone. You can use spool clamps temporarily clamped to the sides to get an idea of the change in sound adding mass makes. I can assure you it does make a significant difference that you can hear easily. In my case the guitar sounded more even and with an added sparkle to the treble that is quite nice. Was well worth the effort. As a reference guitar it is now a bigger challenge to beat it in the sound department.

On mandolins I have found blu tack to be very useful. Sticking on blu tack adds mass, and because you can stick it on or take it off in a second, it is easy to hear the differences adding mass makes. Stick some blu tack to the bridge of a guitar and you will soon learn that adding mass to the bridge is a really bad idea. I usually stick some blu tack to the back of a mandolin and if the sound improves I know I need to shave some wood off the center back brace. No improvement, or no change, then leave it alone. It does correlate with the measurements, but is super easy and quick to do. On guitars you will need to use more blu tack, and experiment on how much is needed to match up with the measurements.
Peter Coombe - mandolin, mandola and guitar maker
http://www.petercoombe.com

sleake
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Re: Applying G&G techniques to a kit guitar

Post by sleake » Sun Mar 27, 2022 8:36 pm

Thanks for such detailed and considered replies.

I must apologise for my brief post, I wrote it 3 times waxing lyrically about the joy of coming back to a project after a long hiatus, mainly due to more pressing joinery, building and landscaping work on my place. But it was deleted into cyberspace 3 times so kept it sort and sweet on the 4 try 😄

The deflection testing is an intereesting idea, and I already have the dial indicator for my machinery set ups, just need to convince some of my friends to borrow their best guitars for the weekend!

Peter, thanks for the idea of side mass, I am considering a side port as this will be a lounge room guitar, which could assist the installation of the required hardware etc.

The light bridge is my next focus...... I really want to keep the all rosewood theme, but perhaps ebonised walnut might work........ no cf in the bridge plate though.... next time!

Thanks again, will update once bindings are on. Hopefully not in 2 years time!

Steve

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56nortondomy
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Re: Applying G&G techniques to a kit guitar

Post by 56nortondomy » Mon Mar 28, 2022 4:29 pm

I use EIRW for my bridges, they weigh around 22grams so not that heavy. Wayne

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WJ Guitars
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Re: Applying G&G techniques to a kit guitar

Post by WJ Guitars » Mon Mar 28, 2022 7:19 pm

I also use EIRW for my bridges on my SS guitar builds and I am very happy with the results. IO also agree that the weight is not heavy. I have not tried alternatives such as Blackwood that would be lighter. The natural finish with oil on an EIRW bridge ties in nicely a Macassar Ebony fretboard.

Wayne

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Re: Applying G&G techniques to a kit guitar

Post by sleake » Tue Mar 29, 2022 7:30 pm

Well thanks to the confidence you've inspired in my desire for old school aesthetics, I rummaged under my house and found my 'special' scrap milk crate among the 20 other crates of offcuts I've hoarded, from which I found a nice 30 x 35 chunk of quarter sawn rosewood.
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I departed Gore and Gilet's recommendations for hand tools, turned on my jointer and panel saw and 5 minutes later had a rosewood blank 25x10 mm dead square and dressed, along with a few spare scrap blanks to test my machining setups.
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Off to deep dive into the long history of Martin's pyramid bridges for some inspiration!

A question to the brains trust, to rout the saddle slot now, or wait till it's been glued on? I can see merit in both ways....... not sure which way I'll go.

Cheers, Steve

sleake
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Re: Applying G&G techniques to a kit guitar

Post by sleake » Tue Mar 29, 2022 10:18 pm

More good ideas from the books!

I've always struggled with accurate marking out and drilling etc, so instead tried to make a drill guide from 25mm bar steel.

Wow, so much easier than working with timber! Highly recommended strategy for bridge pin layout and drilling, even without the need for avoiding braces etc as described for the more modern bracing designs.

Thanks!
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Mark McLean
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Re: Applying G&G techniques to a kit guitar

Post by Mark McLean » Fri Apr 01, 2022 7:52 am

“A question to the brains trust, to rout the saddle slot now, or wait till it's been glued on? I can see merit in both ways....... not sure which way I'll go.”

I find it easier to rout the slot now, rather than try to work with the router on the top of the assembled guitar. But I know some folks do it the other way. People who do a lot of repair work have often gone to the trouble of making up a fancy jig for routing slots on bridges in-situ, but I don’t have one.

When it comes to gluing the bridge on with a pre-routed saddle slot your task is to carefully place the front edge of the slot at the requires scale length (plus intended compensation)

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Trevor Gore
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Re: Applying G&G techniques to a kit guitar

Post by Trevor Gore » Fri Apr 01, 2022 8:29 am

The main reason for routing the saddle slot after gluing down the bridge is because the bridge is pre-positioned by the bridge pin holes on falcate braced designs, as there is little latitude for error due to the proximity of braces if the pin holes are drilled in the closed box. If you have the right sort of jig (I still use the one pictured in the book) you know you can get a flat bottomed saddle slot in exactly the right place.

If you prefer to slot the bridge before gluing, dowel the bridge to the soundboard through the bridge pin holes in the "correct" position, then make any micro-adjustments by shifting the fretboard before you glue that down to the fully fitted neck. This latter procedure only really works for bolt-on, bolt off necks, though.

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Mark McLean
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Re: Applying G&G techniques to a kit guitar

Post by Mark McLean » Fri Apr 01, 2022 9:34 am

Yep, good point Trevor. The approach that I described is OK for a X-brace or similar design where you have some wriggle room for the bridge placement in order to get the saddle to locate where it needs to be. But I forgot that doesn’t work for a falcate design where you need to place the bridge according to the relationship of the pin holes to the braces.

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