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Double Bass introduction and questions

D

Darren Molnar

Nov 6, 2007
152
0
55
saskatoon Saskatchewan Canada
www.darrenmolnarviolinstudio.com
Disclosures
humble instrument maker
#1
Hi all, I'm a violin maker ( making my first bass) from Canada.
After lurking for a while now, I thought I'd join the forum, and hopefully get some much needed advice from much more qualified luthiers than I.

Here's what I'm working on ( if pictures attach )

My question is on bass bar placement. I'm wondering how others determine things like length, distance of ends to plate edges, how much of an angle to place the bar, etc. Any help would be greatly appreciated. This bass is my own design and so I have no plans to follow ( hey, I'm stuborn ) Are there general rules to go by, as with violin bar placement?
 
#4
Nice to meet you Jimmy. I was looking for something a little more specific. For example, on violins, bars are placed 40 mm from the ends of the plate, violas are 45 mm, etc. To determine the angle, the widest parts of the top and bottom bout are divided in two ,and then that is divided into seven, and the bar edge is placed on the one-seventh mark.

I'm asking if d-bass luthiers have similar guidelines.
 
#7
Hey Chet, thanks for the welcome. Chet has been an enormous help to me already. I was starting to feel bad about bugging you off-line, as it were. Here's some random pics. You can see I haven't touched the back or the neck yet. I actually threw my back out last week carving the top! So I'm a little hesitant to tackle the back.
 
#10
Darren I think that's looking rather nice!

Well, same as on a fiddle, you want to get the bar running slightly diagonally to avoid a split in the top right next to it. You are limited by the upper eye of the FF in terms of how far you can go outward.

I don't think there are any rules for basses (someone correct me if I'm wrong) and this is why I love them so much. There may be rules of thumb, and the rest is from trial and error and experience.

I think a common approach is to measure say 1/7th lower bout width from the centreline and mark that, then 1/7th upper bout width from the centreline and mark that, and then join the marks with a pencil line. Then do the same for an 1/8th width, and a 1/9th width, and see which line gives you a position close to the upper eye of the FF but not right on it. That's the outer limit, and will probably be a good place to start.

Then, since you want your bass-side bridge foot centred on the bar you have to go back and check that will work, maybe you'll need to bring the bar in a bit. Ken Smith has written in another thread his thoughts on position of the bridge feet in relation to the upper eyes of the FFs, and I'm still deciding whether or not that analysis makes sense for me.

Most bass-bars I have seen are around 850mm long, around 20mm wide and around 40mm tall at the highest point. And the shape varies widely according to who's doing it and what the arching is like!
 
#11
Lay out the footprint of your bridge feet on the inside of the bass top, and use this to position the bass bar so it interacts with the bridge in the way you'd like. I like a bridge about the same width as the distance between upper f-hole eyes. And I like the meaty part of the bridge foot to lay directly on the bar. There is really no standard for length or height, but the average bass bar I see is 32-34" long and about 7/8" wide. The 1/7th rule does not work so well on bass because of the smallish upper bout on most (compared to a violin). Good luck!
 
#12
Thanks for the replies Matthew and Arnold, I think that helps confirm some things for me.

I was shooting for a 850 mm length and a 20 mm width so I guess I'm in the park. I tried for a 1/7 measure and it was close to where it looks right, but I wasn't sure. Then I moved the bar proportionally closer towards the f-hole a bit.

The distance between upper holes is 163 mm and I was planning for a 158 mm bridge. Where the bar is now, the outside of the bar will be 10 mm inside the bridge foot. So the bar will be just off center of the foot towards the outside. hope that's close.Sorry "bout the metric, Arnold, it's how us Canadian kids were taught when I was in school. :rollno:

I think too this is going to be a stiff top, so I am guessing for now that the bar will be a bit on the wee side, not very high.
 
#15
Arnold, so I'm guessing "Ken's thoughts" on bridge placement were actually your preferences relayed via him.

Which leads me to wonder ... when designing a model of bass, are the eyes of the FF holes so placed to "suit" an optimum bridge size and position for the top, or are the FFs so placed to optimise the top, with the bridge placement and size just following on from that? Which is more critical? Or am I wondering in a nonsensical direction?
 
#16
Hi Mattew, I am trying to make a strong top, for sure. I'm not crazy about mushy sounding basses. But since this is my first, I really don't know what I know, if you know what I mean.

But the top does feel stiff to me, it's about 48 mm high, sitka spruce and 8mm thick right now. for arching I'm using some c-cycloids and taking the low points fairly close to the purfling, i.e. not a lot of scoop at the edges.

There is a bass in my town that was made only a few years ago and it just seems that that top has sunken way too much for its age,and the arch looks like it was made flat and weak, so I'm trying to stack the deck in my favor ,by trying to plan a strong top that sounds great at the same time.

But if any of my measurements seem a little out of whack, please, don't hestate to give me a slap. I could take some arching pictures tomorrow if any one is interested. And I don't know how dense the spruce is, but sitka is much heavier and stiffer than what I'm used to using on the smaller instruments. (engleman)
 
#17
I don't have a huge experience here, but everything I've read and researched leads me to suggest that you might need to take it down to about 6mm at the recurve and leave it thick in the centre. But don't do that unless Arnold or someone else agrees with me :)

I think 48mm is quite high arching, too, even for a bass. It will have inherent strength because of the high arching shape. may not need to have such a thickness. Does it resonate nicely when you tap it or does it go thunk?

My first bass was 12mm at the soundpost, 10mm from top to bottom block (more or less) tapering to 6mm at the recurve, then back to 7mm edges. I used Cedar which needed to be a bit thicker.'

What does your long arch look like?

Of COURSE people are interested in pictures. On Talkbass, pictures 'R' us!
 
#20
Darren Molnar said:
And I don't know how dense the spruce is, but sitka is much heavier and stiffer than what I'm used to using on the smaller instruments. (engleman)
Click to expand...
The interesting thing about sitka is that it is quite flexible across the grain while being quite stiff with the grain. When I build with it I do a lot of cross-wise flexing to best get a feel for stiffness. Usually I end up graduating less than with Engelmann.
 

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