SG .45?

[H.R.Fisher]

  I have a piece of fine grained 32 year old spruce top  with  SG of 45,  I'm soliciting your advice on the particulars of how to work with this density. Your input would be greatly appreciated. Thanks in advance.   Henry

[Davide Sora]

If you are brave enough to use it, a possible strategy would be to make an arching shape that gives a lot of stiffness by itself, so that you can thin the thicknesses as much as possible to reduce the weight as much as possible, which is the main concern when the density is high.

Probably the safest advice would be to make firewood out of it, but if the piece is very beautiful and without other defects (besides the high density) I think it's worth a try. You can always back off and replace the plate if you are not satisfied with the result, especially if you are not a professional with a client waiting for the violin...

[uncle duke]

I realize you two are the award winners around here but I must ask - how many grain lines per inch?

[Peter K-G]

SG .45 is perfect if the wood is stiff enough

[Peter K-G]

If the wood has over 6000 speed of sound and is stiff enough cross grain, with the right arching you can get a relatively thick plate under 65 g

[Don Noon]

17 hours ago, Peter K-G said:

 with the right arching you can get a relatively thick plate under 65 g

I kinda think that plate weight is very closely related to area and thickness... so I don't see how arching is going to make a thick plate lighter, as this quote seems to imply.

It's GOING to be heavier than "normal" unless you go extremely thin.  For example, if you normally deal with .37 density and 2.6mm avg. thickness, .45 density would end up 21.6% heavier unless you thinned down to 2.2mm avg. thickness.  I usually compromise... a little bit heavier, but still relatively thin, although I have never tried to use spruce that dense on a serious fiddle.  

I have used wood that dense on some experimental violins, and it wasn't as bad as I thought it would be.  I think you can still make a very nice sounding violin from .45 density (if it's otherwise good), but if you want a powerful soloist violin, that's not the right wood, IMO.

At worst, you could slice it up for nice bass bars.

[Peter K-G]

For two plates of equal density and height, one with 50 cm3 less starting volume (before hollowing out) will be approximately ~10 g lighter for equal graduation, due to straighter lines and less surface.

Old "Italian arching" have less starting volume than many modern makers do.

[chiaroscuro_violins]

/

[H.R.Fisher]

On 7/31/2021 at 12:23 PM, uncle duke said:

I realize you two are the award winners around here but I must ask - how many grain lines per inch?

The grain width of 20  to 22 gr per inch. So my question is what shape, hgt, thickness should I shoot for for best results?

                       appreciate your response,  Henry

[Don Noon]

1 hour ago, H.R.Fisher said:

So my question is what shape, hgt, thickness should I shoot for for best results?

Best according to who?  It's all personal preference, in the end.

As for thickness, I don't think there is much disagreement that high density wood should be made thinner to keep the weight reasonable.

I have heard some recommendations that arching should be higher for dense wood; also some recommend lower arching.

Assuming the wood stiffness is good, I personally would just go with normal arching 15.5 - 16 mm and thin down to 10% above normal weight or until the taptones looked like they were getting scary low, whichever came last.  But that's a guess extrapolating from regraduating cheap fiddles with bad wood, colored by my preference for fiddle sound.

[H.R.Fisher]

 Thanks Don,  I guess i'll work for my normal range of free plate At 350 M5 and 70 g weight see how that works out. 

[Christopher Jacoby]

Lower arching for higher density wood, exaggerate the cross arch through the Cs a bit— sink the effhole wings and carve a tighter radius so it will fail into something usable.

[uguntde]

Forgive my ignorance: How do you measure the specific gravity? Weigh it and determine the volume?

[MANFIO]

2 hours ago, uguntde said:

Forgive my ignorance: How do you measure the specific gravity? Weigh it and determine the volume?

http://www.fiolinmaker.no/tips-triks.php?uside=eigenvekt.en&flagg=en

 

A calculater for that.

[violins88]

I believe there is a shortcut in calculating volume. 
 

Just use the width and thickness at the middle of the billet.

sg = (mass in grams)/(volume in cubic cm)

where volume = L x W x thickness 

L = length in cm

W = width at middle in cm

thickness = thickness at center in cm

I recommend you check your answer by placing the billet in a very thin plastic bag (like from the vegetable section of the grocery). Immerse vertically in a bucket of water and mark the water level.  Invert the billet and repeat  Take the average of these two. Call this Lw. Now calculate Lw/L.

If this is incorrect, please visit me and I would be glad to discuss.

 

[Salve Håkedal]

2 hours ago, violins88 said:

I believe there is a shortcut in calculating volume. 
Just use the width and thickness at the middle of the billet.

...

Yes. That's true if all the sides of the billet are perfectly flat. My "calculator" is useful if the wood comes from i.e. Gleissner where the billets may be rough cut and irregular. Then it may be necessary to estimate the right measurements along the edges.