Spruce and maple avg. weights

[A.Taylor]

Been lurking on the forum for a long time. I built my first mandolin some months ago and it turned out good. I was well pleased with the look of the mandolin but the sound was not what I was looking for. I'm starting the second mandolin now and I will change the arch height to 14 mm from 16 on the old one. Now for a questions? Is there a weight or S.G. Of the wood ,that you start to change your arch or graduation mapping? High weight/ft3 equals lower arch and/or grad. Map? What is a avg. weight/S.G. of red spruce and maple?----thanks allot A.Taylor

[CarlM]

What is a avg. weight/S.G. of red spruce and maple?

Here is a link to the woods database page on hard maple. They have density, stiffness and other property data on other species of maple, spruce and a host of other woods as well.

https://www.wood-database.com/hard-maple/

[sounds_good]

There is a table. --> Density of various wood species

Maple is listed at 0.62 to 0.75

I notice though that after listing spruce at 0.48 to 0.78
the table then lists 4 kinds of spruce at 0.45

For those not familiar the units are relative to water = 1

Sorry, I don't know about carving the wood. I guess
for a sound board you might care about the stiffness.

When I visited luthier Andy Bennett, who makes very
good guitars, he showed me how top blanks ring when
he held them by the corner and tapped them.


Thanks,
sounds_good

[sunburst]

...Is there a weight or S.G. Of the wood ,that you start to change your arch or graduation mapping? High weight/ft3 equals lower arch and/or grad. Map? What is a avg. weight/S.G. of red spruce and maple?

If I had measured all of that and kept good records for the last 30+ years of making mandolins there very well might be a formula. As it is, I just go by feel and experience. Not only overall experience, but results that I have gotten from various wood sources. In other words, I have spruce and maple from different sources and my experience with using those woods, and with using various wood combinations, informs my arch heights, arch shapes and grads. As an example, I currently have an A5-style mandolin that I particularly like the sound of. I have more (quite a bit more) of the top and back wood, so if I want to make a similar sounding mandolin I can use wood from the same sources and refer to my notes for arching and graduating. I will expect very similar results if I do that.

Oh, and by the way; I vary top arch height from around 14mm to 16mm. In other words, 14mm is one extreme and 16mm is the other for me, so in my "system" going from from 16mm to 14mm would be going from one extreme to the other. I don't know how that will relate to you and your building, but unless I wanted a pronounced difference in sound I would probably make a more subtle adjustment in arch height.

[A.Taylor]

Thanks for the help .just looking for a better way to set the arch on this project. Reading through the forum is great help and I could have never built the first mandolin without it.---thanks again

[j. condino]

Weight (SG), stiffness, arch height, plate thickness, bracing, aperture size & placement. Those are the primary independent variables for just the top. Asking about only two of them leaves out a lot of information. Once you get a plan for the top, then there is the other 80% of the mandolin to think about.

Having access to a Lucci meter and calculating the radiation ratio may be of more help in your analytical search for the truth. Even so, I find when using that approach I will keep similar outside arch modeling and vary the inside plate dimensions.

Vary the arching and you'll have to vary all the body & neck geometry every time you get a new spec piece of timbers. Vary the other parameters and you can still standardize much of your build geometry.