Making a double bass

[Christopher Jacoby]

Again, thank you so much for all your work putting this up! I remember the nightmares I had trying to shape my button and heel cleanly on my first cello, gluing without doing any of the finish work.

I am getting into a B Form cello right now, and I wondered if there was a ratio you use, Roger, for the over-high edge you leave in order to implement your channeling and edgework steps. How high over the finished edge thickness, is what I mean. I am looking forward to giving your methods a try.

[Robert MacPherson]

With the angle thus calculated he routed a line across the back with a tiny V shaped cutter to within about 1.25 mm. (Better him than me.) The back was then turned, clamped on a flat board with the upper portion suspended over the edge, and steam was applied with wet cloths and an iron until Rene felt that it wanted to go. Actually by this point I was also wanting to go. Then while heating it with an iron, downward pressure was applied until the required angle was reached. Once the angle was reached it was cramped in position overnight. The following day the studs (see photographs) were fitted to hold the whole thing in position. And not a crack in sight. Actually this construction remained very fragile and it required careful handling while I worked on the purfling, the edge-work, and above all the scrapping work to accentuate the flame, (mentioned earlier). This was a totally new experience for me. I don’t recall ever having  worked on anything quite so large and so fragile. It really required constant concentration. Turning it and finding ways to hold it while rounding the edge was genuinely nerve wracking.

 

Roger,

 

I did not see any mention of glue here.  Is it the case that the bend is secured only by the studs (and, of course, the ribs) with no glue in the bend itself?

 

Mac

[Carl Stross]

Roger, I didn't quite understand how are you shaping the neck using a single template. Is a d/bass neck very different from a violin neck ?

[Roger Hargrave]

I am loosing track of what has been covered already. Some of the stuff I wanted to include is elsewhere on this site, but I will try and catch up.

 

Unlike the probable Cremonese method, for this bass Rene and I used a more conventional modern approach. There was for example no need to remove the ribs from the mould and attach the neck before finalizing the outline. The outlines of both the back and the belly were finalized while the ribs were still on the mould. Inevitably this had the effect of producing an instrument that is considerably more symmetrical than a genuine Cremonese instrument would be. Asymmetry is especially noticeable on this original Amati bass. In spite of the remarkable symmetry of its center bout ribs, overall the ribs are quite distorted. As a consequence the back and belly outlines do not match each other exactly either. In contrast the back and belly outlines of our bass match the ribs and each other very well. This became even more obvious as the ribs were removed from the mould and the finished back and belly plates were glued on.

 

But I am running off again. The back outline purfling and edge-work were completed almost up to the bend. It was now time for ribs to be removed from the mould and for the back to be fixed to the rib structure so that the upper portion of the back (outline edge and purfling) could be completed. Some minor adjustments were made to the angle with a block plane and the fit was perfect. As was seen earlier I had cut a chamfer on the underside of the back in the classical Cremonese manner. I then rounded the edge. In Cremona the purfling would have been inserted and the edge rounded only after the back had been fixed in place. In Cremona this chamfer was applied before the back was attached, so that it would be easier to round the edge without damaging the ribs.

 

The mould that Rene made for this bass is beautiful, if almost a little too exact for our purposes. It is collapsible. It allows the top and bottom linings to be glued in place on both sides. This system also allows the ribs to be sprung from the mould without the need for the squared Cremonese block shapes. (See my web site for more Cremonese details.)  Firstly the blocks were split off the mould. A strip of paper between the blocks and the mould helped make this process relatively easy. With the corner blocks free, the ribs could open and expand, and with the help of a little alcohol in a syringe the two end blocks could also be split away.The screws that hold the mould together were then removed and one half was eased over the linings and out of the rib structure.        

[Roger Hargrave]

The back was now glued permanently onto the ribs. I am in the dark about exactly how the Cremonese made basses and I am getting too old to be bothered. The important thing for us was that we still needed to finish the outline of the bent area, insert the remaining purfling and round the edge. Effectively this meant finalizing the outline and rolling the edge with the ribs in place. The final outline was completed with a knife and a rasp. This was relatively easy. However, cutting the chamfer with the ribs in the way made me realize why the Cremonese masters cut this chamfer before they attached their backs and bellies.

 

Before rounding the edge completely I cut the purfling channel, this time by hand. And, as can be seen from the photograph I made a scarf joint (also described recently in the Strad magazine) and inlayed the remaining purfling. To give more stability, the strip running across the button was not set in quite as deep as the rest.    

[Roger Hargrave]

Roger, I didn't quite understand how are you shaping the neck using a single template. Is a d/bass neck very different from a violin neck ?

No its the same. It is all about getting those chamfers absolutely perfect and checking their widths and flatness constantly. Twenty five templates won't help if you don't have these factors right. 

[Roger Hargrave]

About this edge-purfling question, I don't see strad using a completely different method than Amati did.

On some (many?) strads you can see the purfling tool mark following the corner shape before deviation ( see Sacconi Soil corner pic)

And it seems a lot of work to do the outline twice! I can't imagine these guys doing more steps than absolutely necessary.

But that's just me.

sorry Roger for spamming up your post...

Paul

 

They more or less all did the same thing. The lines in the corners are the remains of the cutter not a marker They did not use a marker as such. I think that the main difference is that the corner flutes were finished shallower (hence the raising channel and thicker edges) and unlike most Amati instruments, Strad chose to deviate from a more central miter. 

[Roger Hargrave]

Again, thank you so much for all your work putting this up! I remember the nightmares I had trying to shape my button and heel cleanly on my first cello, gluing without doing any of the finish work.

I am getting into a B Form cello right now, and I wondered if there was a ratio you use, Roger, for the over-high edge you leave in order to implement your channeling and edgework steps. How high over the finished edge thickness, is what I mean. I am looking forward to giving your methods a try.

 

I can't help you much. It depends on so many factors. The overall depth of your flute. The distance of the purfling from the edge. If the inside or the outside of the purfling channel is deeper. (For example some Amati's and Andrea Guarnieri's are deeper on the inside)  And of course, how thick do you want the final edge to be. You need to experiment with a couple of gouges with different curves. You may even need different curves for the C bouts. On a new model I often make a short mock-up. 

[Roger Hargrave]

Roger,

 

I did not see any mention of glue here.  Is it the case that the bend is secured only by the studs (and, of course, the ribs) with no glue in the bend itself?

 

Mac

 

Yes, a little high quality hide glue was applied, but thick rather than thin. Too thin might penetrate through the thin joint. Otherwise the ribs and studs do the trick. 

[Robert MacPherson]

Thank you, Roger!

 

Mac

[Christopher Jacoby]

I can't help you much. It depends on so many factors. The overall depth of your flute. The distance of the purfling from the edge. If the inside or the outside of the purfling channel is deeper. (For example some Amati's and Andrea Guarnieri's are deeper on the inside)  And of course, how thick do you want the final edge to be. You need to experiment with a couple of gouges with different curves. You may even need different curves for the C bouts. On a new model I often make a short mock-up. 

I will do just that! Hopefully the first or second try will sort it out. Thank you.

[Roger Hargrave]

With the exception of the button and some final cleaning up, the back was more or less finished. On the belly, I have already described how the outline was rasped, (not filed) the arching roughly carved, thumb planed and finally scraped. I also pointed out that an initial channel was cut, with a tight U shaped gouge. Its purpose was to separate the two sides of the purfling fluting.  (See #87) I then cut a channel and inserted the purfling. (As described for the back). However, in contrast to the back, the belly was arched and the edge fluted. To complete the belly edge I initially cut a Cremonese style chamfer on the underside.

 

As can be seen from the picture, the finished bass belly has a rather steep sided flute with the high spot of the edge more or less half way between the purfling and the outer edge.  This is how most Amati family instruments appear to have been finished. Strad worked his flutings closer to the edge.

 

With the channel finished to the outer edge it just remained to round the edges. This was completed with a file. For once my beloved rasps were too rough.  I always leave the corners a little long. This allows me to work the outlines without the risk of them rounding at the ends. Only when everything is finished do I round off the corners and here again I beginning with a knife cut chamfer on the underside.

 

Again in this instance I have also worn the corners slightly. And as can be seen (I hope) I have drawn the soundholes on the belly and lowered the lowered wing slightly (on both sides). This was also done to give the illusion of age.  

[Roger Hargrave]

The next stage was thicknessing the belly. This was far more complicated than I had imagined. I had simply thought that the belly would be more or less of even thickness, rather like a violin belly. However, the thicknessing of bass bellies is more akin to thicknessing a violin back. Well this is what Rene told me. Of course I did not believe him. This was nothing personal, I never believe anyone. So I started asking around and everyone said much the same thing. In the end I was suspecting a conspiracy. Finally I mentioned that I had asked around and Rene asked if I did not trust him. Not quite in that way, but that is how I understood the sentiment.

 

So Rene’s system was laid out and as a punishment I was forced to do the roughing out. I was to work to within about 2mm of his system. I did this with my largest gouge. Although it was not particularly difficult nevertheless it took a lot longer than hollowing a violin belly. I was only grateful that we were not making an arched back.

 

Rene then re-marked the belly for final thicknessing, (please don’t ask).  On this site there has been some mention of a thicknessing spike that was supposedly used by Stradivari.  Stradivari graduation punch... I measured the required size and realized that such a punch would be about the size of the golden gate bridge. Rene used a drill press and a small blunted drill to mark the required thicknesses. He did not, as I had suspected he might, remove wood with a larger drill bit or a routed head. After he had done the marking it was back to the gouge, the planes and finally the scraper. Rene took charge of this operation. Maybe a further question of trust?   What I can say is that the thicknessing ranged from 9.5 mm in the center to 4.5 mm in places towards the edges. The thicknessing of this belly was entirely dependent upon the reaction of the wood which is both stiff and resonant. (Remember that at the begining I said that this was my reason for buying this wood in the first place.)  Interestingly Rene did not scoop the inside arching at the edges or at the ends. Instead the hollowing was convex as it left the sides and the thicknessing remained strong. (Mush as I would like it to be on violin backs and bellies). This idea conforms exactly to what might be expected on any Cremonese instrument of the violin family. On this bass there was also a slightly stronger band of thicknessing running along the centre of the belly, presumably to counter the crushing effect of the neck and tailpiece. Apparently this pressure is similar to that which is required to move a continent.    

 

After several adjustments had been made with thumb planes, scrapers and calipers, the belly was ready for the soundholes to be cut. However, this was not quite the end of the belly thicknessing process. Once the soundholes had been roughly cut numerous further adjustmants were made, only some of which related to the lowering of the soundhole wings. 

[Roger Hargrave]

With the arching finished and the belly thicknessed it was time to cut the sound-holes. As can be seen from the photographs the sound-hole templates were recreated using rubbings and measurements taken from the original Amati bass. The first thing that became obvious was the nature of the top and bottom circles. Allowing for some distortion caused by various cracks, all of these circles were originally perfectly round and had clearly been drilled. Although both sound-holes were slightly different in shape and position, three factors were important. The corresponding bass and treble circles were exactly the same size, (upper 21.5 mm and lower 32 mm). In addition, as far as can be assessed, in spite of their different angles and overall positions on the arching, on both sound-holes the distance between the centres of the top and bottom circles was virtually identical, (approximately187.5mm). Finally the bodies of both sound-holes appear initially to have been cut at right angles to the belly arching.

 

Having drawn the sound-holes I made plastic templates. Normally I prefer to use an inside template similar to those used by Stradivari. Inside templates follow the flow of the arching better and they do not open like an outside template when it is laid on the arching. However, on this occasion we decided to employ outside templates. They are slightly easier to make and are more stable in the upper and lower curves.

 

Next I drew the holes on the arching, and drilled the top and bottom circles. In Cremona this would have been done the other way around. Rene then cut the holes out using a coping saw with a normal blade that had previously been sharpened with a triangular file. This is a trick that we learned from Wilf Saunders. (Jacobs Saunders dad) I then finished cutting the sound-holes with a knife. This job can only be described as awkward. It requires a sharp knife, a strong arm and stronger nerves.

 

From the beginning making this bass has involved considerable compromise. We quickly realized that we would need to work in the Amati family style, rather than attempt a ‘warts-and-all’ copy of this particular instrument. Perhaps it was this that made our sound-holes resemble each other far more closely than the originals do. This was not planned. In spite of my preaching I guess that I cannot shake off my modern roots either. Nevertheless Rene and I are both fairly happy with the results.

 

As I pointed out previously, in order to give this instrument some appearance of age, (we are making a worn copy), I lowered the bottom wings of both sound-holes slightly (2/3 mm). This is not an easy thing to do well; not if the wings are to blend into the arching in a natural manner. Obviously this action required some adjustment to the belly thicknessing in order to prevent the wings from becoming too thin. 

[Roger Hargrave]

With the passing of the sound-holes it was time to fit this bass’s bass-bar. The process turned out to be somewhat easier than I had imagined. Although it was fitted in the normal way, using studs and chalk, the bars 20 mm. width provided a vertical stability that violin, and even cello bars do not have. Rene had the bar fitted and glued in about the same time that I normally require for a violin. Rene then taped the area that surrounded the bar on the belly and sized both the belly and the bar. Once they were dry he re-fitted the bar and glued it in place. I secretly checked the fit while he was at the toilet. It was very good.

 

Neither Rene nor I believe in springing bars. We consider it to be pretentious nonsense, originally developed as an excuse for lazy chalk fitting. At best it does nothing and at worst it can distort a fragile belly. Arguments against this statement should be directed to Rene Zaal, somewhere in Holland.    

 

In shaping the bars profile Rene keeps the heaviest area directly under the bridge foot. The bar is then tapered and rounded on its upper edge. Here the masking tape not only keeps excess glue off the belly, it also helps protect the belly while the bar is being tapered and profiled.     

 

It was time to close the body. When I went to bed after the bar was finished, I started to remeber all the past difficulties that I have experienced fitting bellies onto back and rib structures. So the following morning I was astounded how easily it went together. Having liberally glue sized the blocks and linings and also the belly edges the previous day, we simply clamped everything together. Then removing two or three clamps at a time, we slowly worked our way around the overhang with a hot slightly wet knife. It is important to keep two or three thin pallet knives in water that is around boiling point. They cool enough in the air before reaching the belly/rib joint. These hot (not too wet) knives soften the glue just enough to reactivate it. Again this process helps prevent excess glue from spreading. In spite of this Rene again placed masking tape around the ribs to stop even the smallest drops.  

 

See neck fitting post #100.

[David Frederick]

Roger,

 

It appears in post #114 picture 6 that the purfling is closer to the edge or I should say the sting runs further to the end of the corners on the belly than on the back. Is this due to the wear done to the corner or ...? Intentional?

 

I must say, the one thing I have taken away from all this that has caused the proverbial slap to the forehead - The liberal use MASKING TAPE - why have I not thought of this!

 

Thanks again for your time and posts...

[Oded Kishony]

Jim Ham, a noted bass maker, has a novel and very efficient way of gluing a plate to the ribs. After glue sizing the rib and plate edges he clamps the plate then, using a steam generator, applies hot steam all around.

 

Oded 

[pbelin]

I must say, the one thing I have taken away from all this that has caused the proverbial slap to the forehead - The liberal use MASKING TAPE - why have I not thought of this!

Thanks again for time and posts...

Same slap on my forehead;-)

Thank you very much roger, for his great thread!

Paul

[Roger Hargrave]

Roger,

 

It appears in post #114 picture 6 that the purfling is closer to the edge or I should say the sting runs further to the end of the corners on the belly than on the back. Is this due to the wear done to the corner or ...? Intentional?

 

I must say, the one thing I have taken away from all this that has caused the proverbial slap to the forehead - The liberal use MASKING TAPE - why have I not thought of this!

 

Thanks again for your time and posts...

 

Probably bad work, but then it is a copy. Glad that you caught the masking tape bug though. At least that's something from the more than nine thousand words that I have writen on this particular blog. 

[Roger Hargrave]

Jim Ham, a noted bass maker, has a novel and very efficient way of gluing a plate to the ribs. After glue sizing the rib and plate edges he clamps the plate then, using a steam generator, applies hot steam all around.

 

Oded 

 

Sounds good, but might it not soften the edges? Well perhaps not on a bass, they are quite strong, but I think I'll stick to my way for fiddles. 

[Oded Kishony]

you can see a photo of Jim using a steam generator to glue a plate here . (about 1/3 down the page) You can also see an experimental balsa wood cello that Jim developed.

 

Below is a photo showing how I set up a bass bar for fitting and gluing. This method prevents the bar from shifting or twisting when gluing. Takes a little longer to set up but saves a lot of time fitting. The entire bass bar is visible when being fitted.

 

 

 

Oded

[Christopher Jacoby]

Neat, Oded. I stopped using cleats last year, but I bet that little devil is re-usable. Clever.

[Roger Hargrave]

you can see a photo of Jim using a steam generator to glue a plate here . (about 1/3 down the page) You can also see an experimental balsa wood cello that Jim developed.

 

Below is a photo showing how I set up a bass bar for fitting and gluing. This method prevents the bar from shifting or twisting when gluing. Takes a little longer to set up but saves a lot of time fitting. The entire bass bar is visible when being fitted.

 

 

 

Oded

 

As you can see our studs were very small. In fact because the bass bass-bar is so wide and is unlikely to tip over, the studs do not need to be as large (or as high) as I make mine for violins. However although the method that you illustrate is undoubtedly good, I can see two minor drawbacks. The first is that if you wish to chalk fit the bar, it will be impossible to move the bar even very slightly back and forth to pick up the chalk. The second, is the fact that you have nothing to stop the bar from bending or sliding sidways on the arching when it is being clamped, although this is probably also more likely on cellos and violins. I don't have enough experience with basses to know what the risk of this happening might be. 

[Oded Kishony]

As you can see our studs were very small. In fact because the bass bass-bar is so wide and is unlikely to tip over, the studs do not need to be as large (or as high) as I make mine for violins. However although the method that you illustrate is undoubtedly good, I can see two minor drawbacks. The first is that if you wish to chalk fit the bar, it will be impossible to move the bar even very slightly back and forth to pick up the chalk. The second, is the fact that you have nothing to stop the bar from bending or sliding sidways on the arching when it is being clamped, although this is probably also more likely on cellos and violins. I don't have enough experience with basses to know what the risk of this happening might be.

 

The notches at the ends are first fitted with a bit of slack which allows for some small of movement to pick up the chalk. For final fitting and gluing, I slip a piece of card paper shim at the end for a snug fit.

 

But even if the bar fit tightly from the start, tapping on the top surface will pick up enough chalk.

 

As far as lateral movement at the center, if you start clamping at the ends, working towards the middle, then no lateral movement is possible.

 

What I like about this method is that I get a better, faster fit of the bar since the guides prevent any wandering while chalk fitting and glue up.

 

Oded

[Roger Hargrave]

The notches at the ends are first fitted with a bit of slack which allows for some small of movement to pick up the chalk. For final fitting and gluing, I slip a piece of card paper shim at the end for a snug fit.

 

But even if the bar fit tightly from the start, tapping on the top surface will pick up enough chalk.

 

As far as lateral movement at the center, if you start clamping at the ends, working towards the middle, then no lateral movement is possible.

 

What I like about this method is that I get a better, faster fit of the bar since the guides prevent any wandering while chalk fitting and glue up.

 

Oded

 

Yes, I like the bit about the paper shims. I will give it a try. I have never liked too much lateral movement when chalk fitting bars. I think that this is what initially led to the ridiculous idea of bass bar springing.