Double Bass Matthew's Double Bass Building Project

[jmpiwonka]

haha, that's a great picture there.
are you looking forward to cutting the ff-holes?
i bet that is tricky.

 

[Matthew Tucker]

It's all fun ... I look forward to everything on this project. Right now I'm blending in the channel with the arch and finalising that before hoofing out the back of the plate.

 

[Mudfuzz]

Are you going to copy the effs from the original or change them a bit?

 

[Matthew Tucker]

Well the huge Fs are what attracted me to this model so I'm going to try to copy them. That said, they will end up changed a bit, everything does. eg: My rib outline is not exactly symmetrical by several mm in places, as the bent wood is unpredictable, and my arching is only approximately that of the original. The original doesn't appear to have much of a channel cut inside the purfling, but I like that look and I think the thinned plate just inside the linings will help the top to sound nice. Just a hunch.

So, yes and no!

 

[arnoldschnitzer]

I think the thinned plate just inside the linings will help the top to sound nice. Just a hunch.

Good hunch. Tone is the reason for the channel, called the recurve. The thin zone helps to "uncouple" the vibrating top from the rib assembly.

 

[Matthew Tucker]

yeah what I thought ... otherwise too stiff. I have one of those indian tabla in my mind, thin at the edges and weighted in the middle to lower the tone and give ooomph.

 

[Matthew Tucker]

Last night after planing the joined back plates flat, I discovered that the blue chalk I used when fitting the plates together - although I thought I removed ALL the chalk with a wire brush and wet sponge - has left a dark mark all up the centre joint. Obviously the blue colouring has soaked into the wood a tiny bit.

What should I do? Steam the joint open and glue it up again?

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What do you guys use to remove the chalk when chalk-fitting patches etc? I read some article somewhere recently by a violin lluthier who refuses to use chalk, says it weakens the joints no matter how well you clean them. Now I'm beginning to wonder ...

 

[Matthew Tucker]

Does anyone put a recurve into the back of a flatback?

 

[Ken McKay]

Chalk can be a very evil thing, but necessary.

I don't think anyone puts a recurve in the back.

 

[1st Bass]

There is a chalk for children, sold as "sidewalk chalk" because it can be easily removed with water. It comes in a clear plastic package, looking like giant crayons...if you use the pink, it does not leave that dark line-- the problem is that the blue pigment turns green when it comes in contact with the yellowish glue, and is clearly seen. (I learned this one the hard way on a soundpost patch) The pink, if not all of it comes off, only makes a slightly orange line, which looks about like a normal line in the wood. The yellow and white, work fine, of course, but are hard to see against the wood.

The sidewalk chalk can be bought in department stores, usualy near school supplies. Pretty inexpensive stuff, and it works very well.

 

[Matthew Tucker]

There is a chalk for children, sold as "sidewalk chalk" because it can be easily removed with water. It comes in a clear plastic package, looking like giant crayons

yeah that's what I've got. I used the blue one ...

 

[arnoldschnitzer]

Your blue line will just about disappear under a few coats of brown varnish. In the future, try using white chalk. It's tricky, but leaves no visible line. As far as recurve on a flat back, I've seen this on several French basses, and also on a new Robert McIntosh bass. The backs are graduated, allowing the maker to leave a lip around the edge.

 

[Bob Branstetter]

Jeff Bollbach introduced me to a great shop tool a few years ago by sending me some white chalk that becomes fluorescent under black light. I don't think I could fit a bass bar without it now. It's not easy to find, but there are a few places on the internet that have it.

 

[Matthew Tucker]

I'm wondering whether my top arching is nearly finished?

What you reckon? remove more wood?

 

[PB+J]

This is a dumb question I bet, and I've never really thought about it before, but do you really want symmetry in a bass top? It looks beautiful, and I'm really impressed, but if you consider that one side has a bass bar and another a sound post, I'm not sure that symmetry is the highest priority. It's a db question--is symmetry in carving the goal for aesthetic reasons? For sonic reasons? Is it just customary?

 

[Matthew Tucker]

I'd say its purely aesthetic. That's why I'm not too worried about it, but since this is my first bass I don't want assymmetry to be confused with bad workmanship!

In fact, I believe that assymmetry in any instrument (except for maybe a drum!) is probably a good thing because it would reduce standing waves and thus even the resonance in the instrument. In any case, the rest of the instrument is not 100% symmetrical but its not easily visible, and the thicknesses of the plate will probably end up a bit left/right assymetrical, like thicker at the soundpost and under the bassbar.

But at the moment I just don't want someone taking one look at my bass and saying "amateur", even if that's what i am!

 

[Eric Rene Roy]

You can have symmetry in your arching (exterior) and achieve assymmetry in your graduations (interior).

 

[billyfalconer]

Matt, you haven't shown any pictures of the inside of your table, have you? I'm interested in that. I guess we'll see those when you attach the bass bar, though.

 

[.matthew e wengerd.]

I think that's because he hasn't done anything with it yet.

 

[Matthew Tucker]

I've been carving by eye so far. But I've just worked out that if I used true cycloid curves, THAT would flatten the FFs in the arch. I'm making up some cycloid templates using my plate width and arching heights just to see what that would do. Getting a bit muddled here ...

and no, I won't start on the back of the plate until I'm happy with the front