Ash's acoustic rabbit hole

[Andyjr1515]

I made a 'roughly in the same ball park design-wise but made with bits I had in the shed' homemade version of this jig:

It actually works surprisingly well (there are other videos on his channel in use).  I think I remember that you can get hold of the plans to make one - I haven't looked at how much LMI charge but it's usually eye-watering!

Oh - and I fully agree that a high bridge and therefore steeper break angle can transform the tone of an acoustic. 

[Prostheta]

Exactly that sort of jig, yes. Given the right design, it shouldn't be too difficult to tune in the shoulders to tenths of a degree. How did yours turn out, Andy?

I know I shouldn't think about acoustics for more than a hot minute otherwise I lose focus on all the other silly things in my head and find a new one to roll over and over....

[ADFinlayson]

5 hours ago, Prostheta said:

No worries. I'm sure you've got a plan in hand. I was thinking of a jig to rout in the shoulders of the neck around the tenon at tenths of a degree. I've actually got mortise/tenon tasks in my head right now for basic CNC workholding and machining, so it made more sense with me already having pictures in my head!

Oh I see, I misunderstood what you meant. No I don't currently have anything like that and cut the tenon/shoulders on the neck be hand the last 3 times. I have just ordered the Elevate Lutherie mortice and tenon jig though. 

[ADFinlayson]

53 minutes ago, Andyjr1515 said:

I made a 'roughly in the same ball park design-wise but made with bits I had in the shed' homemade version of this jig:

It actually works surprisingly well (there are other videos on his channel in use).  I think I remember that you can get hold of the plans to make one - I haven't looked at how much LMI charge but it's usually eye-watering!

Oh - and I fully agree that a high bridge and therefore steeper break angle can transform the tone of an acoustic. 

I very nearly went down this route. A friend of mine made one so I got to see it in person. My gripe with it was the amount of space it needs in the workshop. Between the gobar deck, the form and the bending machine, it's all taking up a lot of room in the workshop so I ordered this from Elevate. This video is a really good explainer on it:

 

[Andyjr1515]

I used the principle but cobbled up a simpler, cruder version using a cheapo £15 folding workmate-type bench (ah, Maplin - where did you go to???) and some plywood.  It actually takes up very little room although, admittedly, doesn't have the elegance.  I haven't used it in a while and probably have cannibalized bits for other uses, but it did work pretty well. 

[ADFinlayson]

4 hours ago, Andyjr1515 said:

I used the principle but cobbled up a simpler, cruder version using a cheapo £15 folding workmate-type bench (ah, Maplin - where did you go to???) and some plywood.  It actually takes up very little room although, admittedly, doesn't have the elegance.  I haven't used it in a while and probably have cannibalized bits for other uses, but it did work pretty well. 

Yeah shame about Maplin, it was nice to be able to go into a shop and see the thing you needed, rather than play the lottery on Amazon. 

[ADFinlayson]

I made some more progress today. After rough shaping a bone blank for the nut, I was able to get the two outer strings on, then used a 105 bass string under them to get the correct intonation points. This is a quick and dirty method but it does work quite well. I make a pencil line at the front and back of the 105 string and use the centre point of those two lines for the top E intonation line, then I used the front of the 105 string on the bass side, that takes into account the compensation for the other strings.

 

Jumping forward a couple of hours and I have a practically finished bridge. After getting the saddle slot routed, I printed out a cross section of a 20" circle and made myself a 20" radius block out of an offcut, used that to sand a 20" radius into the top/centre of the bridge. Then I carved a bit of a taper so the height falls away behind the saddle to the back meaning the pins will sit a hair lower than the bridge. Sanded it up to 320 then just polished the bare wood on the buffer.

The centre of the bridge is curerntly sitting at 7.8mm off the soundboard.

I've got 4 strings off a 12 gauge set on there at the moment (I am planning to put 11s on it), action is currently sitting at 3mm bass side and 2.5mm treble side. 

But the saddle is currently sitting at 6.5mm off the top of the bridge so I am confident I can bring that action way down. I am not sure what is deemed as the "Correct" saddle height but I think I can get away with losing at least 3mm off the height of it before losing too much tension over the nut. I do also need to sand the bottom of the bridge to match the soundboard too, not that will take much material.

I'm surprised by how big it sounds, I thought being a mahogany top it might sound a bit thin. Unfortunately too many variables from previous OMs. Previously used ebony for bridge and fretboard, previously used spruce for tops, and kerfed linings.

Anyway, I think I'm safe to get the neck carved and get some lacquer on it.

[Bizman62]

7 hours ago, ADFinlayson said:

I am not sure what is deemed as the "Correct" saddle height but I think I can get away with losing at least 3mm off the height of it before losing too much tension over the nut.

One option is to lower the rear of the bridge, the hole area. I mean, make the bridge a bit slanted so you'll have lots of support for the saddle and a decent break angle.  Like so:

[ADFinlayson]

12 hours ago, Bizman62 said:

One option is to lower the rear of the bridge, the hole area. I mean, make the bridge a bit slanted so you'll have lots of support for the saddle and a decent break angle.  Like so:

Yeah I have a bit of a taper on the back of the bridge to lower the height of the saddles slightly, although it's not a concave curve like your diagram. That is an option if needs be but I think I've got more than enough tolerance in the saddle to get decent action. We'll soon find out.

[Andyjr1515]

The other thing you can do is file the 'v' grooves at the front of the peg holes so that the string at the rear of the saddle sits straighter and at a greater break angle over the saddle.   I'll try and find a photo to illustrate what I mean. 

[ADFinlayson]

1 minute ago, Andyjr1515 said:

The other thing you can do is file the 'v' grooves at the front of the peg holes so that the string at the rear of the saddle sits straighter and at a greater break angle over the saddle.   I'll try and find a photo to illustrate what I mean. 

I know what you mean, I was actually thinking I would try solid bridge pins on this one. Just need to make sure I've got the tools to properly notch the fronts of the slots. 

[Andyjr1515]

4 minutes ago, ADFinlayson said:

I know what you mean, I was actually thinking I would try solid bridge pins on this one. Just need to make sure I've got the tools to properly notch the fronts of the slots. 

I use a small triangular needle file to form the groove and exit point and then , on the thicker strings, a small round needle or the modded triangular needle which I have filed one edge smooth to use for rounding sharp edges off the fret ends.  

[ADFinlayson]

1 minute ago, Andyjr1515 said:

I use a small triangular needle file to form the groove and exit point and then , on the thicker strings, a small round needle or the modded triangular needle which I have filed one edge smooth to use for rounding sharp edges off the fret ends.  

Thanks Andy, sounds like I've got all the tools I need to make it happen

[Andyjr1515]

I've modded your pic to show the effect, @Bizman62.  It's not to scale but hopefully illustrates basically what happens:

As Ash says, you need to change to solid pins but I've had great success on two or three acoustics where the sound has been transformed and the owners think I'm some sort of magician!  Seems a shame to explain it's just physics and dispel the myth...so I don't   

 

[Andyjr1515]

I photo'd the last one I did with the tools I used @ADFinlayson but had a boot drive crash recently...and guess what drive the photos were on  

[Bizman62]

10 hours ago, Andyjr1515 said:

I've modded your pic to show the effect,

Yes, the groove method does exactly that. I was thinking about it when posting the image but at that point I considered it merely a fix. After giving the idea some more thought it actually can be even better than the slope as there will be more support to the saddle bone. And it can be done very decoratively!

10 hours ago, Andyjr1515 said:

had a boot drive crash recently.

Is it beyond recognition or just unbootable? In the latter case you may well be able to access your photos with a working system or even booting from a USB stick wit Linux. And even if the file system is irrepairable, files of a recognized disk can be saved with dedicated programs which I've been using a few.

[ADFinlayson]

Wow look at these tools. Luckily they arrived while the mrs was out.

I think I will rebind No2 and use it as a learner before I invest X hours into making another box

[ScottR]

1 hour ago, ADFinlayson said:

Wow look at these tools.

SR

[ADFinlayson]

Got the neck carved this evening. Rosewood stinger came out pretty cool, not as pointy as I would like but that seemingly is a lot easier to pull of with paint and masking tape than a 1mm veneer. Can you see I fecked up my tuner screw holes? Cocktail sticks came to the rescue

Went with a different heel shape this time, it's 20mm deep in the middle, 9mm at the edges and full width.

 

Here it is in situ, managed to get it all sanded to 220 without screwing up the joint. 

I need to sand the body now, see if I can scrape the scratches of the binding then it's ready for some grain filler.

Here's a glam shot. That's the closest I could get to the tortoise shell on the binding (both were labelled as dark brown tortoise shell), not  huge fan of all the gold in it but I don't have the option of picking one out unfortunately,

In other news - I'm going to have a change round and put some more bench space in around the edges of the workshop. It's occurred to me that I am not using the space well at all and I could probably fit a dedicated acoustic or setup/repair bench so I cut up a couple of sheets of 8x4 ply and have some 2x2 to frame it out, though I have a feeling I don't have anywhere near enough 2x2s 

[Andyjr1515]

The guitar is looking great.  That neck joint looks neat.

[ADFinlayson]

19 hours ago, Andyjr1515 said:

The guitar is looking great.  That neck joint looks neat.

Thanks Andy, it's definitely tidier than the previous 2 efforts,

Made a bit more progress this evening - Firstly got the the body and neck sanded up to 240 grit, forgot just how damn loud taking an orbital sander to an acoustic guitar body is. Then I sanded the bottom of the bridge to match the top, that takes forever! Started with 60 grit and tidied up with 120.

I taped off the bridge area by bolting the bridge down on top of the painters tape then VERY carefully scored round it with the fresh scalpel blade. 

With everything taped off, I made myself some grain-filler from pumice powder mixed in to boiled linseed oil and some brown and black alcohol based dye mixed into it. Once I was happy with the colour and consistency I added a glug of lacquer to the mix which helps the filler cure much more quickly. Then applied the filler with some hessian fabric. 

I really like this type of filler the only ingredient that I need to buy especially is the pumice and a bag of pumice lasts for ages. I like that it works as a bit of a shader too, it's done a really nice job of darkening up the rosewood.

I'm hoping I'll manage to get a few coats of lacquer on it over the weekend. I am thinking I will do a few coats of Morrells pre-cat cellulose on it as a base coat, get that fairly level and do a cherry shader and top coats with Dartfords lacquer over the top so it will check.

[Bizman62]

6 hours ago, ADFinlayson said:

forgot just how damn loud taking an orbital sander to an acoustic guitar body is.

Bwaahhhahah!!!

On the positive side, that serves at least two purposes aside the actual sanding: First, you'll soon notice if any of the braces has been poorly glued. Second, the noise proves that the guitar will reproduce sound.

6 hours ago, ADFinlayson said:

I made myself some grain-filler from pumice powder mixed in to boiled linseed oil

Have you tried using wood dust instead of pumice and if, is there any noticeable difference? I once saw someone use ebony dust mixed with something to enhance the grain figuration of an ash body and it looked pretty nice.

6 hours ago, ADFinlayson said:

I added a glug of lacquer to the mix which helps the filler cure much more quickly.

I don't know if I've been using the "wrong" types of BLO and lacquer since they both seem to cure well. Both versions of BLO seem to include siccative and both that and the lacquer are very fluid and thin so they don't seem to make much of a filler. That said, the consistence of mixing them with some turpentine looks and feels very much like Crimson Guitar Finishing Oil... But I still wonder what type of lacquer we used in primary school back in early 70's. That stuff was thick! I made a cutting board and slabbed on one single layer. It has been used at our summer cottage since then and all the knife strokes still haven't been able to totally destroy the finish. The sides are fully intact, no crackles or other damage despite the cottage having been freezing cold during winters. That stuff is what I'd like to get for thickening the BLO!

[ADFinlayson]

Yeah I thought that would be testament to it's amplification ability. 

That would involve me making some ebony dust. I watched a series on That Pedal Show Youtute channel recently where Luthier Jonny Kinkead makes a guitar and he sprinkles plain pumice powder onto the rosewood headstock veneer that he is coating with Shellac.While he was doing it he said that it was a traditional method for grainfilling and that the oils from the rosewood dyes that pumice powder brown to work as a coloured grainfiller. So I thought the method I'm using is a cool nod to the traditional way of doing things, also I like that the dye in filler helps to dye the wood rather than just colour the grain.

 

[henrim]

Nice guitar coming up. Looks like top craftsmanship!

10 minutes ago, Bizman62 said:

But I still wonder what type of lacquer we used in primary school back in early 70's. That stuff was thick!

Must have been too good or seriously poisonous since in the beginning of 80’s we got to use that milky white water based stuff.

[ADFinlayson]

The lacquer doesn't have a filling properties, at least that's not the intention, it is simply in the mix because it makes the grain filler go off much faster. Doing any kind of gap filling with lacquer is fraught with disaster IMO, because it's always going to shrink down into whatever you're filling.