But I’ve been down enough rabbit holes already...
I was beginning to think this is reading more like a "how to build bend veneers" thread than "how to build guitars"
😆
But your experience is pushing me towards an approach of trying to use the CNC to carve a top, topside and underside, relying on careful measuring and CNC accuracy to make a reasonably thin top - maybe 2mm-3mm across most of it.
I'd still use the vacuum press and moulds for the sides though.
*thinks some more* Maybe laying a tea-towel down on the mould might reveal something?
Are you thinking something like an image of the face of Mark Bailey???
Online guitar making courses – guitarmaking.co.uk
Thinking out loud here: In 3D modelling, you usually build the shape and then wrap it in a texture - often a high res tiled photo of wood or bricks or whatever. You could probably use a 3D modelling app to ‘loft’ the guitar top, and then apply a striped material to the surface. The gaps between the stripes would be a simple indication of where the stress would lie.
I've got SolidWorks 3D software, I can give that a try if you want. Having said that, I've never had the need to do lofting in my line of work, but I'm sure the software has the capability.
Are you thinking something like an image of the face of Mark Bailey???
Hmmm... let’s see...
Nope. Well, that’s a little disappointing!
Jack of all trades and master of my own destiny. It’s only a small destiny.
Are you thinking something like an image of the face of Mark Bailey???
Hmmm... let’s see...
Nope. Well, that’s a little disappointing!
That's *more* disappointing than the split & bubbled veneers.
🙁
Are you sure you're actually in the right workshop?
Online guitar making courses – guitarmaking.co.uk
Turns out some of you have short attention spans and don’t like all this talk of veneers.
So, just for you, here’s some video of a vacuum pump.
Jack of all trades and master of my own destiny. It’s only a small destiny.
🗝️ "Life's what you make it"🗝️
So, just for you, here’s some video of a vacuum pump.
That looks like it might be successful this time, fingers crossed.
And some people (not me, obviously, but "some people") say that your videos aren't exciting!!
Particularly highlight for me was from 0:42 to 0:51 - great work!
What's the rationale for leaving the veneer tape in place in the vacuum? I'd have probably taken the tape off once the glue had set and before shaping. Would that have been wrong?
Online guitar making courses – guitarmaking.co.uk
@tv101 I’m making this up as I go along. It just seemed like a simple way to persuade the joined veneers not to split along my dodgy glue line.
As usual, I was wrong.
Jack of all trades and master of my own destiny. It’s only a small destiny.
By now, I had made two new moulds for back and front with 4 layers of 3mm MDF: i.e. an arch of around 12mm rather than 15mm as previously. And with gentler curves.
So, the back went into the vacuum press, this time glued with a slow cure urea resin, and you heard me say on the video there were a couple of creaks.
Sure enough, the next morning revealed that the face veneer (1.5mm thick) had opened up along the glue line.
Jack of all trades and master of my own destiny. It’s only a small destiny.
With some anxiety, I tackled the front lamination.
I was so concerned about the way the back had split that I cut apart the book-matched front face veneer and planed the edges again before joining (again). Just to be sure.
This time I also cut away the corners of all four veneers.
As with the back, I sprayed the face veneer with water, put it in a bag and left it to soak quietly for an hour in the Bailey moistening room.
The three knife-cut veneers were glued up and the face veneer added.
Then to the vacuum press.
This time, as the pump began to erm... pump, I pressed down on the two sides with my hands, just to try and prevent the join taking all the strain as the veneers bent and stretched. This was a last minute move, because I’d been thinking about the Gibson press and @rocknroller912 comments about concave and convex moulds. Or to express it in multi-lingual form:
I’ve no idea whether this was necessary or not, but please prepare yourself, Ladies and Gentlemen - my First Successful Pressing.
Jack of all trades and master of my own destiny. It’s only a small destiny.
Pleased you are getting somewhere at last, however you still need a foolproof method that works for teaching beginners.
Ive thought about this since we chatted last week. I would be inclined to start from the inside veneer, build up some layers and do the outside face last. This would give you a fairly solid structure to use as a convex mold.
Then I would use it to form the outside layer before gluing. Thinking logically the wood at top of the arch needs to stretch more, so a dry test fit before gluing would help.
Some people call me a tool, others are less complimentary. Tools being useful things.
I’ve no idea whether this was necessary or not, but please prepare yourself, Ladies and Gentlemen - my First Successful Pressing.
Congratulations!
This has proved to be a more troublesome task than I’d anticipated. Watching Darren’s videos, it all seemed fairly straightforward and error-proof. But I guess experts make things look that way.
I’ve pretty much decided that any carved-top that I attempt will be getting the CNC to carve out of a solid piece, rather than trying the veneers - I’ll probably waste less wood that way.
Should we call your newly proven method “the Bill’s finger technique”?
Online guitar making courses – guitarmaking.co.uk
So, the back went into the vacuum press, this time glued with a slow cure urea resin, and you heard me say on the video there were a couple of creaks.
Sure enough, the next morning revealed that the face veneer (1.5mm thick) had opened up along the glue line.
I'm glad that you've had success with the front.
I was thinking about the back and wondering if a convex mould might be better. That way, when the bag starts to press, the laminate will already be in contact with the mold. So I'm thinking that it won't have to move far. The bag will have clamped down most of the glue joint while the laminate gets pressed down towards the edges. It obviously has to end up the same shape, but maybe the stresses would be nearer the edges rather than the middle. (All theory of course)
With poor state of my fingers at the moment, calling anything after them is sure to end in failure.
For your carve top I would rough out the carving with a cnc but do the final finishing with hand tools. It’s what the top makers do, because you need to work with individual pieces of wood not a pre determined plan. Benedetto is the big name in carve tops and he does this.
if you don’t feel confident about F holes then use cnc
Some people call me a tool, others are less complimentary. Tools being useful things.
That way, when the bag starts to press, the laminate will already be in contact with the mold. So I'm thinking that it won't have to move far.
Exactly what I was beginning to think. However, the advantage of the concave mould is twofold:
- Darren (Bagpress) said it was better that way
- You can make the mould the same size as the front or back, without having to compensate for the thickness of the lamination.
I kept the waste I cut out of the 3mm layers of MDF. I could use those pieces to apply pressure down into the mould (more on that shortly).
The moulds might also come in handy when it comes to working on the body. Could the back mould double up as a work board?
Jack of all trades and master of my own destiny. It’s only a small destiny.
Having (relatively) successfully made two sides, a front and a back, I carted the whole lot home to rest in this old, cold, damp house.
Mr Bailey was surprisingly insistent that I keep the sides bound to their templates until I was ready to use them.
I didn’t think too much about this until I brought the back downstairs to wave in front of some pals on a video call. The house is unheated save for oil radiators in the studio and kitchen and a woodburner in the Duck Room (@TV101 will explain).
The temperature in the Duck Room was edging up to a nice toasty 24°C. Within 20 minutes the edges of the back lamination had started curling. Held upside down, it looked like a freakin’ manta ray!
To get it back into shape, it wasn’t going to be enough to lay it back in the mould. I needed pressure.
Cue the inverse blocks of the original mould.
Does it look like a plan is coming together?
Jack of all trades and master of my own destiny. It’s only a small destiny.