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Double Bass Matthew's Double Bass Building Project

#62
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Really? why do you recommend a gouge with a profile that deep? Without any clue, I would have gone for a number 8 or 7 for carving a wide shallow curve like a bass top. Why would a deep gouge be better?

I have a Stanley 100 1/2 curved sole plane. I guess that's a bass-size finger plane. I have some violin-sized fingerplanes lent to me but they look awfully small for bass work! I'll get a gouge, wood comes off faster that way ...
 
#63
Well, Since I have a bag full of gouges it is hard to say which one is the most useful for this type of work. But for roughing the plate arching I would think a big nine woudl be most useful. A lot of makers put a big long handle on it for better control and leverage. I tend to use a mallet since I learned that way and have very good control. Plus when you get to scooping the inside your #9 will be a big help. I also have a big #5 35mm that I use a lot. And you are going to need a gouge to make your channel. A #7 is good for that.
 
#68
Thanks Luthiers

After fiddling with a smaller gouge on the lower bout edge, I now see exactly what you mean. A large gouge will be much quicker than any combination of planes. And better control over arching I think. The planes are good for big sweeps leaving a smooth finish.

I shall get a number 9 and a number 7 to start with.

My instinct is to gouge in a radial direction, starting at the edge taking the wood down to about 10mm to start, and then working my way back up to the middle. But I find that gouging across the grain on the flanks splits and tears the soft wood. Does it always do that? Is there a trick?
 
#70
I think I have found a supplier to give me the wood for the back and sides. I think he can get the wood close to size for me
as he is a guitar maker and has thickness sanders and special bandsaws etc. That's handy.

The bass is a flat-back. Chandlers plans make the back 6mm all over.

What I am now wondering is whether there is any benefit in graduating the plate thickness of a flatback, say 9mm in the centre gong to say 6mm at the edges? Keeping the inside flat, just shaping the outside?

Anyone have thoughts on this?
 
#72
Ken McKay said:
you will never know an answer to a question like that unless you build a series of instruments and compare them.
Click to expand...

Ken, thanks for you excellent advice as usual. But I was kind of hoping someone here with a series of instruments behind them might short-cut my quest for the perfect flat-back! I suppose I was wondering about the benefit of a 30% larger glue-line.

The large gouge is working out well, but its a bugger to sharpen ... a down-side of a big handle seems to be harder to manoeuver on the whetstone!

David Wiebe writes about large flames in the wood sucking up the glue out of the joint. Have you experienced this? Is is a good idea to size the wood before glueing in this case?
 
#73
Matthew Tucker said:
I think I have found a supplier to give me the wood for the back and sides. I think he can get the wood close to size for me
as he is a guitar maker and has thickness sanders and special bandsaws etc. That's handy.

The bass is a flat-back. Chandlers plans make the back 6mm all over.

What I am now wondering is whether there is any benefit in graduating the plate thickness of a flatback, say 9mm in the centre gong to say 6mm at the edges? Keeping the inside flat, just shaping the outside?

Anyone have thoughts on this?
Click to expand...

Firstly, I advise you to glue up the back halves while they are still thicker than the finished dimension. The parts will want to move around and if they are thin you will be forced to push them onto exactly the same plane, introducing tension. Also, this is not fun when everything is slippery and you only have seconds before the glue gels! After you glue them thick, you can true and thin them down with planes or perhaps your friend's thickness sander (if it is open-sided). Or you could even work it with a belt sander, across and then with the grain. Yes, graduating is a good idea, IMHO. I've seen it on many French basses and I do it myself. I would not go as radical as what you laid out, and I'd final-thickness the wood based on its flexibility. Having the center a little thicker is good for sound and durability, and allows you to use thinner bracing. I recently worked on a Jacquet which measured 7.5 in the center and 5.5 around the edge, but then had a 2mm raised bead around the rim. Now THAT was hard to do...
 
#74
Matthew,

I see you have made some progress on the top arching. Pretty fun, isn't it?

It is interesting following along with your build.

A couple of points and maybe some of Arnold and Nick and Jeff or some of the other great builders here on TB will help.

First, did Chandler's book recommend cutting the outline of the top from the template? Most of us don't do it that way. We first bend the ribs and when the garland is finished, then we trace it with a washer to get exactly the shape of the garland. This way if the bending of the ribs or linings causes a slight 1 or 2 mm variation, it won't show on the plate overhang as a small or wide area. You are going to have to be real careful when bending your sides and and linings to get it just right. You can do it though.

Second, I recommend a systematic approach to carving that top. Your approach is starting just fine. I can tell you the way I do it and it is based on all of the things that I have learned and perhaps you would want to follow your own road.
 
#75
I built the mould already, then because I didn't have rib wood yet and didn't have the patience to wait around doing nothing I cut out the top about 12mm oversize from the template to allow for any variation. Hope thats enough

Yes chandlers book did say build the rib garland first then trace the top. But he gives NO clues on how to carve the plates. Except to use a grinder chainsaw attachment to rough out the back of the plate.

As far as a systematic approach - well, any and all guidance is MOST welcome. I'd love to know how you do it! Already I'm down to about 10mm at the edges with the idea I'd need to leave about that in order to be able to carve a nice channel later. Then I feel like I need to carve a pretty flat edge to about 50-60mm in from the edges before bringing the arching up. Except in the C bouts where the arching starts pretty immediately. Today I'm going to make a better base-board to carve on, one that I can use real elbow grease on...
 
#77
yeah I have half-arching templates for top, centre and bottom bout and a longitudinal section. The chalk marks indicate 50% of full arching height and 90% of full arching height taken off the templates as a first guide. Not quite sure if there's a better way of using the templates - at the moment I hold them in approx position as a visual check, and just keep on carvin'.

I'm thinking that 10mm at the edge is perhaps too much, perhaps I should carve down to 8mm or so straight away?

I'm doing it the hard way ... so what's the easy way? :-)
 
#78
10 is good for now, don't get it too thin, You will need some thickness when you get the purfling in and final scraping. What is your final plate thickness?

"the hard way" I was just referring to the way you cut the plate out based on the template rather than the ribs on mold.

I don't much care for arching templates, but they are a good way to copy an arching.

Just use your templates and check often, that will get you there.
 
#80
You know, I just realised that my arching templates would be a lot more useful if I made them full width!

Call me stupid, but I made the arching templates exactly from the plans Chandler drew up ... but he only drew templates for one side of the bass. I now realise, I think, that he meant that the templates should be full-width.

Doh.
 

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