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Andyjr1515

A Guitar Bouzouki (don't you know what one of THOSE is?)

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2 hours ago, Bizman62 said:

Who knows, maybe someday I'll copy that design to make an acoustic!

Please do - I'm pretty sure I copied that from someone else too ;)

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It's pretty much commonly accepted that we're standing atop the shoulders of giants. It does get to the point where one forgets who actually inspired you to do a certain thing, and it gets frustrating not being able to credit them. I've seen so many beautiful soundhole rosette designs - from the ornately involved and the superbly executed geometric types - that it's a complete mess upstairs!

Funny, because many of the things I like are more because of how they are done rather than just being about the finished product. Maybe that makes it feel like one is able to walk in the shoes of giants? Nice mixed metaphor. 🤨

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Well, still pacing up and down like the proverbial expectant father waiting for the remaining timber to arrive.

So modest progress this week.  Basically, thinned the back to 2mm and cut out the over-sized outline.

But every step, as they say...

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And the timber is here!

_MG_1443.thumb.JPG.8311f69660b768de89e832e70b51b069.JPG

 

And so to the top bracing.

This Bouzouki is based on an OM acoustic guitar and the bracing pattern will be identical. 

And it's all a bit precise.  My understanding is that legend has it that Martin in the thirties (?) did a bracing pattern that just, well, worked.  And from that point 90 odd percent of acoustic guitars have been, and still are, made with the exact same bracing pattern.  I probably have my facts completely wrong but my philosophy is that - like banging dustbin lids to keep the elephants away - it works and so that's what I'm going to continue to do! :)

 

So, for those who haven't seen an acoustic build before - a flat-topped acoustic generally isn't flat.  Most have a spheroidal shape of around 25 feet radius for the top and 15 feet radius for the back.  So you have to make (or buy) a 25' and 15' radius dish, you have to curve the bottoms of the braces and then you have to press the braces into the dish to force the flat top into the final spheroidal shape.

The process will become clear soon (probably tomorrow), but today I was cutting the braces blanks for the top.  This is a straight piece of spruce sitting across the 25' radius dish:

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It's subtle.  But the bottoms of the braces have to be planed and sanded into a curve - and because it's a sphere, the actual curve needed is different depending where each brace is going to fit.

First is the well known 'X' brace which is two pieces curved underneath and locked together:

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And here it is in position on my home-made MDF 25' radius dish.  Difficult to see, but both lengths are now completely gap free on the dish:

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The braces will have a LOT of work done on them, but it makes it a lot easier to remove some of the bulk by starting to cut them to side profile, especially in terms of the positions (again, very precise) of the peaks you can see below - the 'nodes'.  Here we now have all of the braces for the top, rough-profiled but finish-fitted on their under-sides to suit the radius dish at each of their respective positions:

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And tomorrow, these will be glued and pressed into the radius dish to form the basic top shape.  I might do some work on the cross-sectional profile of some the braces before they are glued in...I'll have a think about the best way round to make the access for the final shaping of the braces as easy as possible.

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I don't know why it's called a Go Bar Deck...but it is.  Basically, two pieces of chipboard held apart by some sturdy bolted treaded rods; the radius dish placed on the bottom; flexible rods (the Go Bars) pressing down the curve-bottomed braces into the radius dish while the glue dries:

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And here are all but the last four small braces.  

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This will be left overnight for the glue to fully cure and dry and then I'll add the last four braces.  And then we will have a subtly spheroidal top ready for the braces to be slimmed in cross section - and then the tap tuning can commence

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I'm not sure either. They're an elegant solution for a more civilised time though.

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And while the bracing is drying, there is time to start putting the linings around the edges of the body sides.  These held strengthen and stiffen the body but their main function is that the top and back will be glued onto these. 

While the edges are also glued, those joints will actually be routed away to fit the binding on the external edges.  The kerfing (the saw cuts) allow the linings to bend round the fairly tight bends of the sides.  The clothes pegs with stiff rubber bands wrapped round provide more than adequate clamping all the way round while the glue dries. 

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At this stage, the linings are set a mm or so proud of the sides because - on account of the top and back being spheroidal - they will be planed at an angle and sanded in the radius dishes to produce a good fit all the way round prior to gluing.

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As always, beautiful work and wonderfully exercised. Unfortunately, a great source of GAS or whatever the project equivalent is....!

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And the braces are on ready for fine tuning :)

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I've roughly profiled the cross sections to a more triangular/parabola shape.  Next steps will be to add the maple bridge plate and there is a small strengthener that goes across the X brace centre joint.  Both of these make a difference to the flex of the top and so need to be in place before I do the final tap-tuning.

Having said that, it already is returning a wide variety of notes and harmonics, which bodes well :)

 

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I got asked by some friends if I would ever attempt an acoustic build, and seeing threads like this, I'm fairly sure I won't :D 

Insane craftsmanship on display here, can't wait to see it done and hear it played. Very interesting instrument :)

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Talk to me about this flex Andy, how much flex should there be in the top? I understand this is a balance between freedom to vibrate and strength, it looks like there is almost no material at all at the end of those finger braces. Oh and I notice you haven't got any braces around the sound hole at the moment, are you planning not to bother with those given the shape of the sound hole on this one? 

I'm sat patiently waiting for my radius dishes to arrive so I can shape my back braces, according to tracking they are 15 miles away :D 

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That's it exactly. I think the amount of flex is determined by what sort of expected string tension will be applied and the feel of the builder. I was chatting with Andy on this project and acoustics in general, and one of my Washburns was used as an example of how overly-thick tops (mass manufacture, thick top for sake of avoiding failure in the field) need heavier string gauges to encourage them into motion. I'm far from being a guru on this one, but yeah, what you said right there.

So, your radius dishes have a 15 mile radius then? That's pretty flat. 

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Well, @ADFinlayson, to butcher an old phrase, this is probably a case of the blind leading the partially sighted (that way round intentionally).

But - here goes.

First - and by all means skip to the last 15mins or so when the guy starts actually working on the braces - but this is the best video I have come across where someone not only says what they do, but lets you hear the difference.:

And bear in mind that my 'where I finish' is closer to his 'before I start, this is what it sounds like' than once he's finished fettling it! :)

But never one to shy away from spouting about stuff I don't really understand...

- Yes - the main X braces and the top one in front of the soundhole go through the lining to be locked into the sides  (remembering that my top is slightly oversize.  Those 6 main brace ends will go fully into notches in the kerfed lining and butt up against the sides)

- but the smaller braces thin down to nothing shortly before they reach the side linings

- the tap tuning process is a process of changing the flexibility of top so it is capable of resonating - somewhere on the top - with every note that is going to be played on the instrument.

- so when you are tap tuning, you are tapping the top in various places listening out for the fundamental drum note but also the ringing harmonics.  In crude terms, the more different notes and harmonics you can hear, then the more even and clear the instrument will play.

- 'flexible', in my experience, is still pretty darn stiff.  But, say at the bass side of the top, the more flexible it is, then the lower the notes and harmonics should be.  At the treble side of the top, it ideally wants to be a little stiffer, which will vibrate in harmony to the higher notes.

- so - and here I really am spouting beyond my understanding and experience - with the two shorter braces angled up at the left and the two angles up at the right here...:

_MG_1469.thumb.JPG.8751b347bc8caf0c5e74916a316c1f50.JPG

 ...then I will be chiselling the righthand ones lower, and scooping deeper, the right hand ones that are on the bass side of the instrument.  On the last dreadnought, they were almost chiselled away!  The result is that the right hand waist will now be tangibly more flexible than the left hand waist.  My analysis is - the left hand ain't going to budge a gnats whisker and the right hand will tangibly move.  But it's a stretch on the term 'flexible'.

By the same reasoning, the two long braces coming off the X brace under the bridge area are already scooped in the middle, forming the 'nodes' but the thinner that becomes, the more the main area of the lower bout will flex and the more bass response you will get.

But you don't want to lose the upper harmonics.

What I SHOULD do, one of these days, is build two tops and carry on tweaking one of them until I have gone too far!  Because, I suppose, that's the only way of knowing when to stop.

I stop when my waters tell me to.  Which is probably usually a bit too soon... ;)

 

 

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Excellent reference material. I thought I'd seen that before, turns out that I hadn't. Thanks!

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So here you can probably see better, @ADFinlayson, the 6 places where the braces will be keying into the lining to the sides and the other 'tone-bars' fizzling out to varying degrees of nothing before they get there.

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Now whether I've fizzled out in the right places in anybody's guess but fizzled out I am and I think I'll be stopping tinkering with the braces round about now and turn my attention to the back :)

Oh - and yes - I will be putting some reinforcement under the soundhole, but - in that nothing from the X-brace join to the neck heel makes much difference to the variations in the tone - I won't need further tweaks of these main braces.

 

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That bridge plate seems a lot larger than others I've seen. You're not worried it will over-damp the top?

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1 hour ago, curtisa said:

That bridge plate seems a lot larger than others I've seen. You're not worried it will over-damp the top?

I thought that as well, but it could be due to the extra tension due to the additional strings. 

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2 hours ago, curtisa said:

That bridge plate seems a lot larger than others I've seen. You're not worried it will over-damp the top?

No - I'm pretty sure it will be fine.  I'll find a photo, but one of the very respected builders has a much larger one still!

The area so close to the X hardly flexes at all.  Same reason that most of the bit forward of the soundhole also doesn't.  But it also needs to be wider, because there will be two sets of staggered bridge pins and because the saddle is going to be significantly wider for the intonation.  And, finally, it is going to be fitted with some K&K Pure Mini transponders, which sit under that wide saddle on the bridge plate.

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5 minutes ago, Andyjr1515 said:

No - I'm pretty sure it will be fine.  I'll find a photo, but one of the very respected builders has a much larger one still!

The area so close to the X hardly flexes at all.  Same reason that most of the bit forward of the soundhole also doesn't.  But it also needs to be wider, because there will be two sets of staggered bridge pins and because the saddle is going to be significantly wider for the intonation.  And, finally, it is going to be fitted with some K&K Pure Mini transponders, which sit under that wide saddle on the bridge plate.

This is good to know, I am planning to make my build slightly shorter scale at 25" instead of 25.4 or close to that as the plans say, instead of shifting the bridge enforcement forward, I was thinking of just making it a few mm longer to cover the area. 

Thanks for all the info Andy, a really useful read 

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There is one further major tweak I'm going to do on the braces.

The three dreadnoughts I have built all have a major cutout at the bridge side in the main X-brace:

Scoopdread.JPG.e28458a014bd6ef053ec80df06148997.JPG

While the first time I used this design I was nervous - surely that is the critical component in terms of strength??? - nevertheless, these three dreadnoughts have been outstanding in their bass response.  This one above is Matt Marriott's whose videos I have posted in the past.

But, I've never seen it done on an OM shape before - and I'm always a bit nervous with acoustics of bucking the trend too much.

But, in looking for an example of deeper bridge plates for @curtisa (and this one actually isn't a bad example), I came across this:

Scooped.thumb.jpg.35d400788e87376a787e8b792d57bcb3.jpg

I'm ignoring the cross brace behind the bridge plate - because that's a completely new one on me - but this is an OM shape and it has the same scoops in the X bracing as my dreadnoughts.  So I'm going to give it a go :)

I mean - what's the worst that could happen  ;)

 

 

 

 

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Oh yes...I suppose that could happen :)

 

 

 

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And to the back.  Once again, the braces are shaped to the radius dish - this one being more curved at 15 feet radius - and then pressed into the back in the radius dish while gluing:

_MG_1477.thumb.JPG.242be74af4f5eca1c8ec4a8288fe0d0f.JPG

 

Then, after initial shaping of the brace ends, a cross-grain backer is glued over the back join line:

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If you remember, the back had the splits in the grain.  Well, so far - and this is the time it will expose itself - there has been no tendency for the splits to lengthen.  And that is a very good sign.  It indicates that the splits were in the bulk timber before cutting and not a spreading stress crack.  I'm happy with that  :)

 

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OK - back in the cellar!

I was going to start on the neck, but decided there were still some necessary things to do with the body before doing that.

The reason is that, with an acoustic instrument, the neck angle is pretty much fixed at the initial build - and it has to be right.  And to do it you need the actual neck.  But you also need the mortised body.  And so you need (at least) the top on.

So back out came the 25 foot radius dish - and this time with some emery cloth double-side-taped to it.  This meant that I could sand the slightly proud linings to a gapless fit with the spherical top: 

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Then a double check inside and out that there is a good, tight and glue-able fit:

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Then likewise with the back - MUCH easier to do this before the top is glued on:

_MG_1541.thumb.JPG.3ce5c8f8cdbcd5cde6022b6abd2fe768.JPG

Note above the notches in the linings where the main X-brace and cross-brace will tie into the side/top joint.

And finally, after double and triple checking, the top is glued, using as many spindle clamps as I possess and clamping cauls to spread the load:

_MG_1555.thumb.JPG.c9f774b706f78ac073269ef37354df0a.JPG

 

For reasons I will explain later,  I will be breaking convention and NOT glue the back on at the moment.  Breaking this convention is something I tried on Matt's Dreadnought build last time and it gives distinct advantages.  So the back won't be glued for a while yet :)

 

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20 minutes ago, Andyjr1515 said:

OK - back in the cellar!

In trouble with the Missus are you?

That sounds suspiciously like us saying -well, back in the doghouse again.:D

Whatever the circumstances, you are getting some very nice work done while you're there.

SR

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This is how the figuring of the back will wrap round to the sides.  The lighter wood will come out more yellow and the darker areas will darken more:

_MG_1559.thumb.JPG.9c9765b9c256f5fc9f0aba33d1a2293c.JPG

The top glue job looks OK:

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Now - the traditional way of doing this is to glue the back on, do the corner bindings top and back and then do everything else (like bridge clamping, fitting pickups, etc, etc) reaching blind through the soundhole.

For Matt's Dreadnought, I proved to myself that you can do the top binding, rout the neck mortice slot, trial fit the neck, fit the internal pickup transducers and everything and THEN glue the back on.  And that is a lot, lot easier.  So that's also what I will do here.

I might do the top binding soonish, but the focus now will be neck and fretboard

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