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Okay, I admit that I'm asking because carving this dang back is taking forever. But it's my first so I'm being cautious.

My curly maple back for a Benedetto pattern is down to around 1.6 pounds (from nearly 10 to start). I still have a little ways to go in a few areas to hit the measurement targets. But I wonder what a typical carved weight is for a curly maple back plate? Do you have weight goals for your archtop parts, or do you just aim for measurements?

Thanks!
Andy

Measurements are much more meaningful.

FWIW, Current maple archtop back on my bench comes in at 1lb, 1 oz. Still needs final sanding and recurve scraped in. I never worry about weight.

Thanks. I'm sure that the measurements are more useful but I was curious.

You got me curious, so I dug out the info I have on a few. On some of them I didn't record the weights, but here's what I have.

17" ones tend to run around a pound. 16" are closer to 13 ounces, while 15" are a bit less, say 12 oz. Lower density woods yield a lighter back (or top!) all else equal, so on a 16" box the mahogany back came in at 10 ounces.

I may make mine a bit lighter than the usual. Also, I 'tune' backs and tops using the Chladni method. You can vary things over quite a range by how you make them. A higher arch will give a stiffer plate at a given thickness, or lower weight at a given stiffness. Good results probably require finding the best balance between thickness, arch shape, and arch height for the given set of wood, keeping in mind that you're trying to get the whole thing to work together, so what the back does ha to be related to how the top works.

Maple does vary according to species. My average weight for a 17" back plate is 540 grams or about 19 ounces. The most important measurement may be the plates flexibility. I like to measure deflection by applying downforce to the plates. I use a device like the one Don MacRostie shows in the GAL, number 76. These "flexing machines" work great and can give you one more way to measure your plates.

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Same range ... mine were about 14oz for a 16" and about 19oz for a 17" (but I agree flex is more the issue).

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Dave
Milton, ON

Thank you all. I'm sorry I missed the rest of the responses for a few days. What got me thinking about this was an article I had read a while ago on the blue guitars and the author said that the lightest (by far) of the archtops also had the best sound. That popped into my head as I was weighing this plate and made me wonder what "normal" was. I honestly think I have GAL 76 in the mail right now, so I'll give that a peek as soon as it comes in.

I should have mentioned that Don MacRostie is flexing a mandolin with his flex machine shown in the GAL. The same thing can be built for a guitar. The mandolin has more string tension and a steeper breakover angle at the bridge than a guitar, giving an average downforce at the bridge of around 45 pounds compared to about 30 pounds on a guitar.

_________________
http://www.cushmanguitars.com/.

A man who carries a cat by the tail learns something he can learn in no other way.
Mark Twain