Thanks Arnold, I was hoping to get some feed back BEFORE I start carving, possibly saving me from foolish errors.

My back plate has the oval type of graduation, so I am familiar the pattern. Also, the oval pattern seems to be common in the other string instrument family instruments.

As far as the f-holes go, should they be cut with the little knives, or are the knives for paring to the line? I was thinking of using a small coping saw and possibly drill bits for the circles.

Again, Thanks for the info.

Cut into the wood on the outside with a knife and scribe the line so you don't get tear-outs past the edge. (I pare twice so I actually have a little channel.) Then use whatever tools you want to chop out the bulk; pare to the line; clean it all up.

1/08/08
 

Thats the author of this thread drilling holes on the underside of the top. Its cold, so I am wearing a coat, hat, and scarf.

Chopping it out by hand.
At the moment, there is little, in the way of extra funding available for a power carving machine, (we are saving every penny for the fingerboard).

I got rid of the bulk of material so the top would be easier to work with.
The thickness is about 15 mm overall, or a heavy 1/2".

Now is the time to retrieve my luthiers notebook and figure out my graduation patterns.

Thoughts on Graduating the top
 

I am building from a Peter Chandler plan. His graduation pattern for the top plate has a thick 8 mm center "spine" running top to bottom. Here are some ideas for different patterns, for thinning the top.

The first is a simple peanut type shape. Starts off thick in the middle and gradually thins at the edges. Seems simple and straight forward.

The second is based on a cello pattern. Ovals in the center, thinned out in the upper and lower bouts or "lungs" as they are sometimes referred to in this sort of pattern. Good pattern for cellos and violins but unsure with double basses.

What is the accepted "normal" patterns used by manufacturers past and present?

Would the tea leaf and audio oscillator set up help out in this situation?

The further I go on this project - the less I know.
If anyone wants to chime in on graduating top plates, the forum is open.

well..
 

Not having ever made a Bass I have been inside quite a few of them and outside as well. My worry on the second pattern for Cello on the right is Bass bar sinkage. I think the one on the left (Peanut?) is the more common and trusted way to go.

The 6mm all across the bottom might be ok but why take the chance. Also, I have heard that Panormo made some Bass at 6mm all over without any graduations. Each piece of wood is different and has different strengths and weaknesses even within the same piece of wood end to end. What you can do is try something more on the heavier side like circles in the center 8-10mm and gradually thinning and turning to oval graduations as you move outwards. After the Bass is done you can always go back and re-graduate if you like. I have seen some Basses with a slight built up platform under the Bass Bar, the entire length (and soundpost area too). This is done to add strength to that area. If re-graduated with the 'Bar in place, it would be ok to work around it leaving the platform. My Gilkes as made that way and I know of an old attributed Maggini that was as well. Someone re-graduated that Maggini thinking it was wrongly made and guess what? The Top sunk under the Bar afterwards, so the former owner told me some 3 1/2 decades ago. Things like that you don't forget!

Thanks Ken, The extra material under the sound post and bass bar is a good idea.

It would be interesting to take a hacklinger gauge and measure the tops on various basses. Might be the best way to get answers to some of my questions.

But..
 

Unless the wood you are using as well as the models between Basses are exact, copying measurements might not produce the exact same results.

I'm not qualified to add anything here, but I spoke with Bill Merchant not too long ago about this and he said that he has seen quite a few modern basses with 6mm or 7mm tops coming back in for repairs. He said that they sound good initially but sink over time. Then again perhaps it works with certain woods, designs etc...

craig you can get fine-tooth blades for coping saw that work really well for carving out the ffs. Until I found these, coping saw was hopeless, and fretsaw was just too fine.

Right now I'm glueing back the top of Sirente after regraduation. I'll soon tell you if the chandler "spine" is a good idea tonally or not, since I removed it ...

1/16/09.... f~holes... Thinning top plate.
 

Thanks for the tip Matthew, we are looking forward to the regrad results...

Photo #1
The f~holes are cut.

Photo #2
Removing excess wood, to achieve the optimum tone and response from the top plate.

Craig you may have to wait a good 24 hours for any result from me. The top is on but I need to cut a new soundpost and get it all singing again.

Another weekend 1/24/09
 

The top now graduates from 10 mm in the center to 5 mm at the edges. It is very flexible in some areas and yet, extremely ridged in other areas. Bass bar is next.

100% hand carved plates, blisters and splinters as testimonial.

Impending disaster?
 

The top is spruce (white wood) while the ribs are cherry (reddish brown color). This could be a problem down the road. I would like to keep the cherry natural (center photo) and match the spruce to the reddish brown of the ribs. I have been doing samples with the cut offs from the top.

I have a fear the finishing will come out looking like a 7th grade shop project. More experiments to come.

I advise you resist the urge to color the raw Spruce. You would be better off sealing it and then adding color coats to match it to the Cherry. You can put a very light water stain on the spruce first if you like, but any concentrated stain will have a tendency to get extremely blotchy, because of the mixture of face and end grain in the carved table. Are you planning to use oil or spirit varnish?

did you weigh it?

The cherry looks great with nothing on it, wile the spruce needs some toning, to help it blend with the rest of the instrument. I am definitely leaving the cherry natural, so its only the spruce that will need "doctoring up".

Spruce is a softwood, cherry is a hardwood. They take a finnish completely differently. Some lighter maple dyes work well with the spruce; gives a good base to build up upon; sealing is a good idea. Most of these samples were "just playing around" wile I carved the top. When things get closer, I'll start some more serious samples.

Leaning towards an oil finnish, but still experimenting.

Do you mean an oil finish as in Watco or Linseed? Or do you mean an oil-based varnish?

Originally, I was looking at the Hammerl oil varnish, with the idea of mixing various colors to come close to the cherry. The only problem is, buying 3-4 little cans of oil varnish imported from Germany could be expensive.

I may use a product called Bush Oil (sounds political) for the top coats ; It works like a Watco type oil but only much better. Linseed is defiantly out because it dries too slow.

An oil finish is a bad idea on a spruce top. You can get a litre of Hammerl varnish from International Violin for about $30. It's good stuff.