Finished! A Guitar Bouzouki - (no basses were harmed in the...)

[Andyjr1515]

And on to the bending.

A bit scary, because there is a very tight bend at the waist and, for bending, specifically Red Gum is a new variation for me - and some timbers bend great and some don't!  That said, it is a type of walnut and walnut usually bends well.

This is my bending iron:

 

And then this is most of the rest of the stuff:

A water spray bottle, the all essential thick gloves, the mould and - a bit of a brainwave which was a 'I don't know why I didn't think of that before' moment - the four body-shape cutouts from when I made the mould just clamped together in the vice.

First step is a very thorough soaking:

Then it's a case of pressing the sides firmly over the (very) hot pipe feeling for when the wood relaxes slightly and moving round a touch, re-wetting and repeating frequently and just easing the side round, checking often with the mould whether the curve is the correct radius.

Now - this is one of those times when 'he makes it sound so simple' is a bit misleading.  Because, if ever there was an experience element, it is here.  Press too hard or too fast, or have it too thick or too thin or too dry, and you can either start hearing the fibres start to fail  - or simply SNAP!  And if it's the latter, then it's a whole new back and sides set because they are always sold matched.  So, it's not for the faint-hearted.

For the main curve, I was happy this would be OK.  But that sharp bend at the waist...hmmm...

For that, I turned the iron round to be able to get to the tighter radius of the pipe:

 

Hand bending alone, I got to within around 15 degrees of the amount of bend that would be needed.  This is where those body-shaped offcuts came into their own.  I basically got it as far as I could round the pipe, then re-sprayed and popped a caul at the waist line and just slowly and evenly clamped it into the body shape - a bit like a manual and non-heated version of a Fox bender (an expensive but effective bit of kit that they use a lot in the US and a number of makers in the UK, particularly those who do repeat builds):

 

And it worked.  A very tight bend on each and no split grains to have to reinforce or re-orders to replace snapped sides necessary!

And here we are - this will dry in the mould and I will leave it here, clamped in place, until I am able to add the kerfing strip, tail block and neck block (don't worry, @Si600 - I will explain later) to both the top edge (running along the floor in this shot) and the back edge (uppermost in this shot).  The kerfing will stiffen the sides and enable the whole assembly to hold its shape, free-standing out of the mould:

 

 

Edited June 27, 2020 by Andyjr1515

[Andyjr1515]

All dry, so this morning I got to add the neck and tail blocks:

 

Although it will become much stiffer once the kerfed strips are put all the way round the edges top and bottom (these are the strips that the top and the back of the body will eventually glue onto), it's already holding its shape pretty well:

 

[Andyjr1515]

Well, still drumming my fingers waiting for a nice big parcel of wood to arrive.  So the only thing I've been able to do in the past couple of days is plane the back down to finished thickness (around 2mm) and cut out the oversize shape.  So a subtle change from the previous photo but, heck, progress is progress!

Workshop's a bit tidier too

 

[HazBeen]

Ooh, I consciously did not look at this thread for a bit. It looks lovely!

[Andyjr1515]

And we're back!  The rest of the wood has arrived

And based on the size of the bill...and our last Sainsbury's one too...I think that the Bank of England might be right about the economy heading towards a 'V' bounce back in a number of business sectors!!! 

 

[SpondonBassed]

Ready sawn kerfings?  Handy.

[Andyjr1515]

39 minutes ago, SpondonBassed said:

Ready sawn kerfings?  Handy.

Absolutely.  Life, as they say....

[Frank Blank]

1 hour ago, SpondonBassed said:

Ready sawn kerfings?  Handy.

I sawn kerflings, comin' out of the space ship yonder. I took one look and shot 'em in the a55.

Edited July 7, 2020 by Frank Blank

[SpondonBassed]

2 hours ago, Frank Blank said:

I sawn kerflings, comin' out of the space ship yonder. I took one look and shot 'em in the a55.

[Andyjr1515]

And so to the top bracing.

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

And it's all a bit precise.  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 may well have my facts wrong but my philosophy is that - like banging dustbin lids to keep the elephants away - it works 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:

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:

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:

 

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:

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.   

 

 

 

Edited July 7, 2020 by Andyjr1515

[SpondonBassed]

I'm thinking that this bit is where the cheaper guitar bodies tend to have skimped on.  It must take a significant portion of the overall labour time in the project.

[SpondonBassed]

5 minutes ago, Andyjr1515 said:

banging dustbin lids to keep the elephants away

 

Have they been nicking the bin liners for casual nookie again?  Tsk.  Pesky pachyderms.

[Andyjr1515]

7 minutes ago, SpondonBassed said:

I'm thinking that this bit is where the cheaper guitar bodies tend to have skimped on.  It must take a significant portion of the overall labour time in the project.

Actually, that is the next but one step after this - the dark art of tap-tuning...

[Andyjr1515]

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:

And here are all but the last four small braces. 

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

 

Edited July 8, 2020 by Andyjr1515

[Andyjr1515]

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. 

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.

[SpondonBassed]

For a long time I assumed that acoustic guitar tops were generally flat.  Now I suppose only some of them are if any at all.

What does making the top very slightly dished do for the instrument?  Is it a stiffer structure perhaps for the thickness of material?

[SpondonBassed]

6 minutes ago, Andyjr1515 said:

The clothes pegs

Does work stop if it's a good day for drying laundry or do you suffer an almighty scolding?

[Andyjr1515]

2 hours ago, SpondonBassed said:

For a long time I assumed that acoustic guitar tops were generally flat.  Now I suppose only some of them are if any at all.

What does making the top very slightly dished do for the instrument?  Is it a stiffer structure perhaps for the thickness of material?

I'm really not at all sure. 

The engineer in me says that it creates a tension in the top woods and that increases the harmonic potential (it is the harmonics from the top rather than the basic 'drum' pitch that seems to sort the men from the boys in terms of acoustic guitar quality).

But the pragmatist in me says that I'm just going to follow what the majority of the best builders do 

Edited July 8, 2020 by Andyjr1515

[Richard R]

On 07/07/2020 at 18:04, Andyjr1515 said:

And here it is in position on my home-made MDF 25' radius dish. 

I missed the significance of this sentence the first time round!

In order to build your acoustic guitars, you took a piece of MDF and made a spherical dish in it with a 25 foot radius. That is emphatically the most specialist bit of tooling to appear on BC

How did you make it? What are the tolerances? How long did it take? How often is it used? Where do you keep it???

[Andyjr1515]

48 minutes ago, Richard R said:

I missed the significance of this sentence the first time round!

In order to build your acoustic guitars, you took a piece of MDF and made a spherical dish in it with a 25 foot radius. That is emphatically the most specialist bit of tooling to appear on BC

How did you make it? What are the tolerances? How long did it take? How often is it used? Where do you keep it???

Hi Richard

Not too difficult.  Just some mathematics to work out the depths at a series of radii, a router on a radius bar to rout the contour depths and then a curved cabinet scraper to join up the contour lines.

The challenge was the dust.  I could not believe how much dust was created - and mdf dust is pretty dangerous stuff...

[Andyjr1515]

And the braces are on ready for fine tuning

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

 

[Andyjr1515]

And here we are with the braces as fettled as I dare.  Certainly there is a pleasing variety of tones across the various points and so I think this is the point to stop:

Note that the main cross braces and the horizontal one next to the heel block all will lock into notches that will be cut in the lining but that the ends of the slimmer 'tone bars' fizzle out into nothingness at various places.

There will be some thin reinforcement strips around the back of the soundhole but my attention will now be turning to the much more straightforward braces to go on the back.  And for that, out comes the 15 foot radius dish.  Yes - another radius dish!

There are some scary bits with acoustics (and most of them are still to come!) - but there is something deeply satisfying about the above

 

 

[Si600]

43 minutes ago, Andyjr1515 said:

And for that, out comes the 15 foot radius dish.  Yes - another radius dish!

I'm assuming that these radius dishes are not actually 50' and 30' across? Either that or you have a radio telescope array in the garden that double as luthier tools.

Edited July 9, 2020 by Si600

[Andyjr1515]

47 minutes ago, Si600 said:

I'm assuming that these radius dishes are not actually 50' and 30' across? Either that or you have a radio telescope array in the garden that double as luthier tools.

No - it's a 600mm wide slice off a 25 foot  50 foot sphere and so is a couple of mm deep

Edited July 9, 2020 by Andyjr1515

[SpondonBassed]

51 minutes ago, Si600 said:

I'm assuming that these radius dishes are not actually 50' and 30' across? Either that or you have a radio telescope array in the garden that double as luthier tools.

I wonder if Jodrell Bank would allow the use of their dish for my next guitar top?