arching height question

[Don Harris]

The plans for the Pallotta I'm copying call for a 42mm (1-5/8") arching height while my top wood would allow for about 59mm (2-1/4"). I'm not so much interested in making an exact copy, I just like the outline and the size. Should I stick with the plans or go a bit higher? On old basses I always wondered if the original arching would sink a bit over the years, so then I'm not starting where the original started anyway.

p.s. The top is sitka spruce if it matters.

-don

[1st Bass]

Paul Schuback told me I would have done well to go a little higher on my top plate arching, for the very reason you state. So my next one will be a little higher...not sure how much, just yet.

[ctregan]

How doe this effect the sound?

[Matthew Tucker]

Look at the side photo of the bass from the book and see if you see any sinking at all, like a dip in the long arch. If its arched still, or dead flat, that's probably pretty close. I scanned the photo in photoshop and zoomed in, easier to see.

I started out using Peter's templates but after a while the wood took over and I just finished the arching by feel. I didn't go as high as his templates said, as I didn't quite have enough thickness to start with. I didn't know about the long flat centreline, seemed a bit of a weak point, but I've seen plenty old basses have it. I used a gradual curve down from bridge position longways, made structural sense to me. David Weibe encouraged me to do it that way and it seems to have worked. Have a look at his cello pictorial - it really shows the "lofting" process well. I'm happy with the arching i ended up with. The bass "works".

CT - a higher arch is said to produce a more complex sound and to be structurally stronger at the expense, perhaps, of some volume. Some basses have hardly any arching at all, and still make sounds. Its been discussed plenty here, do a search.

[Silversorcerer]

This is a good question for Jeff Bollbach, who has built some Pallotta inspired basses. I'm not sure where to find him these days... He might be one place or the other.

If it was me, I'd be tempted to use the full available height, but I can't really explain why. One thing that is intuitive is if you change the arch height, then inevitably you have to look at adjusting the neck overstand and / or projection angle of the fingerboard as well. It's tough to change just one thing and not adjust other parameters to fit the change. I've never built a bass, but detailed drawings will point the way. Either the bridge will end up shorter than the plans call for, or you will need to increase the overstand as much as you increase the arch, or perhaps increase the angle of the projection of the fingerboard by decreasing the angle between the heel and the handle slightly. Which approach is the better one is hard to say. I would be tempted to go with more arch and split the difference between the overstand and projection angle. Like I said;- don't ask me why. It is just a hunch.

[Don Harris]

Good point that I hadn't really thought through. Everything affects everything...

[Silversorcerer]

Originally Posted by Don Harris

Good point that I hadn't really thought through. Everything affects everything...

"A bit more monitor .... and can we have everything louder than everything else?" - Ian Gillan on "Made in Japan"

[Don Harris]

I talked to Jeff Bolbach and he said that the 40mm arching height in the plans is plenty full. He said that anything more than 1-1/2 inches just didn't look good in his opinion. That some of the Italian basses had as little as 1" arching. This after spending all morning doing drawings to figure out the best way to adjust. My bridge is going to be less than 6" high, but then it's a pretty small bass. My neck angle is already at 78 degrees, which gives me some bridge height and will probably be good for thumb position, which is what I'm building the bass for (Bach). Jeff said he likes 83 degrees. If I did that, and kept the overstand where he likes it, my bridge would be at about 4 inches high! It's a little nerve wracking hoping it all works out after all the work. Like wondering if the crook of the neck is going to be in the right place... I'm going back and forth between my templates and my half scale drawing and so far the harmonic isn't in the right place for the crook of the neck. I'll keep working at it.

[arnoldschnitzer]

You cannot use neck angle as a reference point. Unlike violin, violas and cellos, bass neck sets vary tremendously. Many basses have "setback", where the neck block sits lower in the back than in the top. This helps with ergonomics. Some basses have a square neck block, and a few actually rise up in the back. Also, there is arching height and overstand to consider. And some makers cut the neck mortise deeper in the back than in the front. So when you say "My neck angle is 81 degrees" (or whatever) this is actually a meaningless statement. The only things that are important in planning and setting a neck are the overstand and the projection (and getting it on straight!). BTW, I agree with Jeff about arching height, but not just because of the look. I find high-arched basses to generally lack power and depth, unless carved very thinly.

[Don Harris]

Thanks for the clarification Arnold. I was a little worried that I might be building an odd-ball bass, as looking at drawings, the angles from 78 (the plans) to 83 looked drastically different. plus I was having a hard time getting a bridge that would be up to 6-1/4" tall, again, thinking there might be something wrong. As it is, the bridge will be about 5-3/4" set up with a really low string height (4mm to 7mm). It's a small bass, which is what I want for solo stuff, so hopefully it's cool...

[Matthew Tucker]

Don,

Perhaps Arnold and others will have better suggestions, but I suggest you just make the neck, leaving an extra cm or so on the heel, and the neck block off the plans, carve your top to what feels right, then initially set the neck into the block with a shallower mortise than you think you'll need, then just adjust the mortise to suite the bridge height and string length and the overstand you want. If you allow extra overstand you can easily just trim away at the mortise to drop it back to where you want once the angle is more or less right. But everything affects everything, tis true.

I made a dummy bridge out of oversize piece of plywood attached to a stick that rests across the ribs, i can mark all my measurements on that, including approximate arching height, with a straightedge. don't forget to allow for the thickness of the plate and the overstand.

if you're bowing, you need to make sure there's enough clearance for the bow at the C's, which a low bridge may not give you.

You can adjust the D/Eb neck afterwards by carving the heel.

Matthew (currently stranded in Honololu)

[Matthew Tucker]

BTW where are you measuring your "78 degrees" on the plans, anyway? I didn't use an angle measurement anywhere on the bass. I don't own a protractor. But my bridge height (6.75") and overstand (32mm) is right where I wanted it.

[arnoldschnitzer]

Originally Posted by Don Harris

As it is, the bridge will be about 5-3/4" set up with a really low string height (4mm to 7mm). It's a small bass, which is what I want for solo stuff, so hopefully it's cool...

I hope so too. But that's a very low bridge, and you may run into the problem of your bow hitting the c-bouts. I suggest you kick up the angle and/or overstand to get your bridge closer to 6 1/2". That will also assure you of getting enough pressure down on the top to create power. As Matthew suggests above, rough out your neck heel and work it into place by trial and error. Don't get stuck on a plan or a theoretical angle. Good luck!

[Don Harris]

Thanks again for the input.

Matthew, there were no angles on my plan either, but in order to do a half scale drawing to mess with the possibility of doing a deeper arching I measured the angle built into the neck pattern with a device that I use for doing trim carpentry call a "True Angle". I guess the best way to explain the measurement would be to start with the bottom of the top plate as a horizontal starting point plane, then draw a line straight up at 90 degrees from the bottom of the neck/mortice. I then set one "arm" of the angle thingy on the 90 degree line and set the other "arm" to 78 degrees at the overstand height and that gives me the line for the front of the neck (looking from the side). Hope that made some sort of sense. It was interesting to do the drawing to get some sense of the geometry involved.

I wish Peter were still around to ask some questions about the bridge height on the bass he copied.

Matthew, did you not cut out your neck right on the lines from the plans? I mean, you left extra to carve the crook after the neck was fitted?

Here's a website with info about the model of bass I'm copying:
http://www.krattenmacher.com/publica..._pallotta.html

[Don Harris]

By the way, I'm with you all on fitting the neck to make sure the projection is right without getting too stuck on the "angle" or the plans.

[Silversorcerer]

Is anyone (besides me) using a CAD program to design a bass? I know for the experienced this is probably not a great help. But for a novice, it certainly helps give one a read on the consequences of minor changes and the minor adjustments necessary to bring things back to the proper match-ups.

This discussion and many of the bass building threads have resulted in me having a much greater respect for the tradtional builders of these instruments who didn't have the technology we have today to aid us. But they did have geometry, compasses, dividers, etc. Math is the same stuff as it was in 1650. It doesn't often appear that they were shooting from the hip;- when one can find the rare unaltered example of their original work.

And my humble shiny nitrocellulose Kremona;- what a work of contemporary art; with the heel of the neck giving the perfect placement of the 1/3 harmonic and again the overstand point perfectly matching A, D, g, c, f across all five strings. Precise internal resonances at "C". And no howling wolves. Definitely no accidents anywhere in the instrument.

Of course the credit must certainly be given to the Guild in Markneukirchen where the makers were trained, and perhaps to Josef Rubner, whose designs inspired the instruments' proportions. It is a complex business to design and build a well proportioned double bass. I don't think I would continue without a CAD program myself, given all the interacting variables. And I am certainly glad I bought an instrument made by a Guild trained maker to study before I started fooling around with the wood. It is one thing to follow a set of plans closely. It is another to create a variation on the theme that doesn't fall into the hotrod category.

[Matthew Tucker]

I use photoshop "paths" function to trace photos and make adjustments to actual size.

A half scale drawing would worry me, too many possibilities of forgetting to scale a measurement, bit like following a recipe and halving the quantities. There's always something you 'll forget.

Don, I made life hard for myself by leaving a good 1/4" oversize all around and extra at the crook. next time I'll cut closer to the line. The bottom of the mortise might start out perpendicular to the ribs but it doesn't need to stay that way and probably won't as you adjust things.

You can work out the D spot by dividing your string length by three and measuring from the nut line. Then if you want an Eb neck you'll have to carve another centimeter or so at the crook. Its not an exact science, its what the neck feels like that counts, too.

I think, just follow the plans, allow a bit extra at the crook and you'll be OK. Remember that you might have to plane the face of the neck again to get it really flat before fitting the FB. So allow for that, too.

[Bob Branstetter]

Originally Posted by Silversorcerer

Of course the credit must certainly be given to the Guild in Markneukirchen where the makers were trained, and perhaps to Josef Rubner, whose designs inspired the instruments' proportions. It is a complex business to design and build a well proportioned double bass. I don't think I would continue without a CAD program myself, given all the interacting variables. And I am certainly glad I bought an instrument made by a Guild trained maker to study before I started fooling around with the wood.

Silver - On a couple of occations you have referred to the German violin maker's guild as being an organization where violin makers were trained. In Germany, by law, you can not call yourself a violin maker or bow maker without being a member of the guild, nor can you claim to be a "Master Violin Maker" without being certified as such by the guild. However, the actual schooling is done at the German Violin making school in Mittenwald or in another approved school. Once you have graduated from the school you can join the guild as a Journeyman. This basically entitles you to work in a shop or to continue your studies under a Master maker in the Master's shop. After a few years of studying in one or more shops under a Master's supervision and training, you may apply to the Guild to take the master's examination. The applicant is tested on all facits of the trade and must present a violin or bow for appraisal by the Guild Master judges. If the applicant passes all the tests and his masterpiece violin or bow is judged to be up to the standards of a Master, he is presented his master's degree from the guild and may legally advertise himself as a master violin or bow maker and is permitted to teach students. So, in fact, the Guild is more of a state approved quality control organization than one that does training or teaching of violin makers. Perhaps this is a small point, but just being a member of the Guild does not mean you are an exceptional maker.

[Don Harris]

I found a couple reasons why my drawing was showing my bridge as too short. I was using the plan's "fingerboard edge thickness" measurement for the fingerboard thickness, not taking into account the FB radius. I also wasn't paying attention to a "FB extended height at bridge" measurement, which shows that Chandler intended the neck angle to change within the neck mortice during the neck set (otherwise his plans wouldn't give you the correct height). I feel better now. Arnold and Matthew were obviously right about adjusting during the neck set, not that there was ever any doubt... Now the bridge will be closer to 7".

[Don Harris]

I was re-reading Chandler's book last night and saw in the "How to copy an instrument" section that he chooses an arching height of 40-45mm for all the basses he copies regardless of the original arching because he assumes some sinkage on the old basses. That would explain why the Pallottas I've read about have a 30mm arch (very flat) and the Chandler plans call for 40mm (42 on the arching template). Time to remove some wood from the top!