Thinking of building an acoustic ---> It's done!

Misterg

Hi folks -  long time no post. 

While I've had a long-standing hankering to build a steel strung acoustic, this has now escalated to a burning desire.

I'm thinking of an OM size, according to the Grellier plans.

Nothing fancy* - spruce top, rosewood sides & back, ebony fingerboard & mahogany neck.

(* I'm toying with the idea of adding a Florentine cut-away, but the jury is out at the moment)

I think I understand the build process, but am still exploring. At the moment, I'd intend to make an outside mould, but not sure if I need to make radius bowls, or if I can manage without by pre-shaping the braces (space is a problem). I'm quite drawn to the 'masses of elastic bands' school of clamping.

I have hand tools and a router, etc. but no thickness sander or planer. I would probably order the back / sides & soundboard already thickness sanded from Keystone.

For bending the sides, I'm very tempted to try steaming them, otherwise it would be a hot pipe. I perceive this as the trickiest part...

It's the body / thin wood stuff that bothers me most - How worried do I need to be about humidity? Mostly the dusty work would be done in an un-heated shed, but stuff that only generated shavings could conceivably be done in the house, with the wood kept in the house in the meantime.

So, any words of advice? 

Cheers, 

Andy


Previous efforts #1 #2 #3 

WezV

Keep the project in the house when not working on it.

You can get away without a radius Dish the way you suggest, worth at least making some radius calls for shaping the braes and clamping up.  The top can even be flat without too many issues.

I would read some stew-mac kit instructions as they have some clever ways to assemble an acoustic with the minimum of extra jigs and molds.

markblack

I'm sure you've seen it, but this popped up on my yt feed today. Just incase you haven't. 

Misterg

Thank you both - I'll have a look at the Stew-Mac plans.

@markblack - I have that video on my 'watch later' list, but haven't seen it yet. I've been almost every other guitar build video on Youtube though - there are some gems and some horrors.

Incidentally - does anyone know what happened to Susan Gardener? I was really enjoying her guitar build a few years ago, then it all just stopped. I hope she's OK.

SteveF

Watching this thread with interest.  FYI, all your links in the original post need a colon after the https for them to work. 

Misterg

SteveF said:

Watching this thread with interest.  FYI, all your links in the original post need a colon after the https for them to work. 

Thank you! - I've edited the original post. Hopefully they'll work now. (I think my mistake was pasting in the url without clearing the 'http:\\' that appears in the box.)

ETA - links to the previous builds on my website without the photobucket mangled photos:

#1, #2, #3

SteveF

Working now Saved those plans for future reference!  

Misterg

A trip to the print shop this morning to get the pdf file printed at A0. The dimensions came out spot-on, which will be handy for making templates, etc.



  More significantly, I appear to have ordered some wood!

WezV said:

... worth at least making some radius calls for shaping the braces and clamping up....

Hi Wez - Do you mean a length of wood with the appropriate radius machined into one face something like this?


Or have I misunderstood?

Thanks.

WezV

yes, that's the one.  they can be used for sanding braces to shape, and clamping in place

Misterg

Blimey! That was quick.

I have wood:





The sides look absolutely gorgeous. The back has got a few worm holes near the edge which will need trimming off - possibly going beyond the patch of confused grain on the piece on the RHS of the photo



There are still a few saw marks on one of the back pieces that haven't sanded out - I haven't checked the thicknesses yet, but is that to be expected?

Next question is how best to store this until I'm ready to do something with it?

For the moment, I've just stacked it all back together on the backer boards used for posting, wrapped it loosely and put it in a spare bedroom. Does it need to be 'sticked' ?

Anyway, I'd best get on with my mould!.

Thanks,

Andy

ArchtopDave

Not advice as such, but I posted a Thread on here a few years back showing the Acoustic Build that I made under the guidance of Mark Bailey on one of his Build Your Own Guitar Courses. 

Here's the link if it is of interest    OM Acoustic Build (Mark Bailey Course)

Misterg

That looks fantastic - I'll have a proper read later.

Thanks

WezV

Misterg said:

There are still a few saw marks on one of the back pieces that haven't sanded out - I haven't checked the thicknesses yet, but is that to be expected?

Next question is how best to store this until I'm ready to do something with it?

For the moment, I've just stacked it all back together on the backer boards used for posting, wrapped it loosely and put it in a spare bedroom. Does it need to be 'sticked' ?

it's not unusual to see some saw marks.  If you paid for them to be thickness sanded i would expect them to be gone to the point they will easily sand of scrape out easily. 

Most acoustic wood is not sold in final dimensions and will need some additional thickening even when apparently sold as thicknessed. it should be thicknessed to the point you can finish off with cabinet scrapers.

As an example,Thicknessed sides might come at 2.2-2.5mm, but you may need to take it down closer to 1.6-2mm before bending depending on the wood.  If you are building with a particularly curvy shape, cutaway or difficult wood then it will need to be closer to the lower end of that.



Air flow is key for storage, hence it best being stickered.

Misterg

Thanks @WezV ;

I had a proper look at the back plates today. These are the marks, held so that the light catches them (normally you need to look for them). I'm pretty sure that they're <0.1mm deep, so should sand / scrape out. The back plates are currently at 2.6 mm. The  plan says 2.5mm finished, so not unduly worried, but there's not *that* much to spare..



I'll get some sticks ripped up for storage / conditioning the wood to the house.

Getting there with the mould. I'd forgotten how much I hated MDF. 



It's all glued up; I just need to drill some bolt holes to keep the sides together and fit some alignment dowels. It'll probably be a few weeks before I pluck up the courage to try and do anything else with it.

Misterg

I'm still at the planning stage with this, and thinking about the neck joint:

I see that a dovetail joint would be a technical challenge, but I can't really see any advantage to the end result (YMMV), so I'm going to avoid it.

I have no qualms about a bolt-on neck (I noticed the current thread on this...).

I was originally thinking in terms of a mortice and tenon joint secured with bolts throught the head block into metal dowel(s) / threaded inserts in the neck heel. in this general manner:

(Picture from here )
 I have since found out that a number of builders use a 'flush' neck joint where the end of the neck is flat and bolts onto the body of the guitar without any other locating features. It is bolted on in a similar manner to the mortice and tenon joint. 

Obviously, this means that there is no need to cut/rout a slot in the guitar body - the only 'fitting' that needs to be done is to establish the correct neck angle (in both planes).

It almost seems too easy - is there any downside of this?

(In both cases, I would intend to glue the fingerboard overhang onto the top.)

Misterg

Well, some progress has been made, so a few updates:

First, a bit of tinkering around the edges.  I took a perfectly good spruce plank and split it into kindling (or at least, that's what it looked like).


   




I then spent some quality time planing each little stick back square again and to the thicknesses needed for the bracing. I had acquired a Stanley No. 4 plane that was really a bit poor. It took a couple of days work to get it flat, square and cutting nicely, but it's quite good now.

    

The aim was to get the grain vertical in each piece.



I made a simple template jig to cut a radius on them with the router (25' radius on the top and 15' radius on the back) and to reduce them to a little over their finished heights.

I did pick up on the fact that the upper transverse brace (T1) has a different radius to all the others to get the right height for the fretboard extension / neck angle. (It's slightly steeper than the back.)

 




I also cobbled together a bending iron (of sorts) - I had some 100mm diameter aluminium tube, but that would have been too big to fit into the curvature of the waist, so I squished it a bit and welded an end on it.



 



It seems to get plenty hot, but whether I have the skills to use it is another thing.

(Continued...)

Misterg

...continued)

I got the back plates out and trimmed off a few mm from each of them to get rid of the worm holes and get the figure properly symmetrical


I trued the edges using my (now nice) plane.

   

It took me a while to get the joint line perfectly tight, but it made all the time spent tuning up the plane worthwhile when I eventually got the plates to meet without even a hint of light between them when held against a window pane.

There's still quit a bit of light showing here -

    

I thought that I had better glue them while the surfaces were fresh - I clamped some blocks against the edges while the joint was raised on a batten, then pressed them flat to apply pressure which seemed to work very well.



Flushed with success, I jointed and glued the top plates, too.



This is them after a quick going over with a scraper, with my revised outline tentatively marked on them (if you can make it out) - I favour the higher placement of the two marked on the top as it makes the grain at the outside of the bouts more parallel to the guitar and avoids cutting the darker grain lines quite so abruptly.



I cut the top and back roughly to size with my little bandsaw and got the  sides roughed out, following the template in the plan, but allowing an extra 3mm, top and back, for trimming to final shape:



I planed them down to 2.2mm per the plan. (I used a dial gauge mounted on the gantry of my CNC router to measure the thickness at various points).

The numbers on the sides is their deviation from target in 0.01mm. I think they're reasonably uniform (worst is one side that has an edge that is 0.1mm under - nothing is significantly over thickness):

   



The plans give 2.5mm as the back thickness, but some areas were below this already. I evened everything out at about 2.4mm, which (from what I can gather) is still a sensible thickness for a rosewood back.

 

 I'm glad that the wood came already thickness sanded and I only had to remove a few tenths of a mm. The rosewood certainly takes the edge off a plane iron quickly!

Andyjr1515

Some nice work here

Misterg

Thank you! 

I wanted to fit some sort of rosette before planing the top down to thickness. I had some ebony and maple offcuts from previous projects so thought I'd try and make a simple inlay design using my small CNC machine.


 


I cut out a load of identical segments that were a bit wider than the finished design




Then cut a groove in a scrap piece of plywood and glued the segments into it. The stack-up of tolerances meant that I had to trim one piece to get them to fit (bottom right in the photo)



I used the CNC again to level them off and then to cut around either side to release the ring with a bit of plywood stuck to the other side. This is the back of the design, so the pattern will go clockwise when it is inlaid into the top.

     

I used my CNC router again to cut a recess for the rosette into the top (not without a lot of trepidation, mind!).

    

I hogged the bulk out with a conventional spiral flute bit, then used a down-cutting bit to gradually machine away the OD and ID.

This photo shows the difference in the finish and amount of fuzz on the spruce (ID has been trimmed using the down-cutting bit, OD is still as cut with the conventional bit):

   

I kept going until the recess was wide enough to fit the rosette and a couple of pieces of BWB purflling in.

Having seen people struggle to get all the pieces in due to the wood swelling during glue-up, I went an extra 0.1mm - in hindsight, I don't think it was necessary.

   

I glued everything in and clamped it up while still on the machine.





After the glue had set for a few hours, I used the CNC to machine off the top of the rosette to within about 0.2mm of the surface.

   

 Next day I scraped it level by hand

   

With that done, I could thickness the top - the plates had been sanded with something of a wedge, and it took a while to get them to an even thickness.

This is the setup that I had been using to measure thickness - the CNC is just a convenient mounting frame; it isn't doing anything here.

   

 The shavings that came off the top were beautiful - thin enough to read through!

   



Not really knowing what I'm doing, I was aiming for the 2.8mm on the plan, but there was still some unevenness when I got there. Working this out, and a bit of sanding took the general thickness down to about 2.7mm (0.106").

At 2.8mm, the top still had a noticeable tone when held at the nodal point and tapped, but this had pretty much gone at 2.7mm. I have heard someone use the word 'flooffy' in the connection with top thicknessing - I would say that this is the perfect description of what happened to my top. It still very much has the 'sheet metal' sound when you hold it by the edges of the lower bout and shake it.

This is how the thickness ended up (the pencil numbers are the thickness deviation from 2.7mm in 0.01mm units) - there are a couple of very thin areas in the upper bout (roughly 2.6mm / 0.102") but I think this is near to areas that are braced, so I'm not unduly worried about that - the lower bout thickness seems to have come out quite uniform.

    

 I sanded it to 240 grit (front and back) and put it back on the CNC to cut out the sound hole.

     

 It seems to have come out OK cosmetically.



I quite like the rosette, even though it is very plain



Thanks for reading  

sev112

Didn’t think I’d like it, but that rosette looks ace!

PS does a rosette perform any function other than aesthetic ?

Misterg

sev112 said:

Didn’t think I’d like it, but that rosette looks ace!

PS does a rosette perform any function other than aesthetic ?

Thank you! 

I don't really know, but "I have heard it said that" the rosette also serves to stabilise the wood around the sound hole - to stop splits, etc. but I'm not really convinced, since the traditional rosettes are just stacks of endgrain wood anyway.