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Old 01-23-2013, 07:11 AM
paganskins paganskins is offline
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Question Solid topped archtop - How much tension can they take?

I'm under the (possibly misinformed) impression that archtop guitars can take greater tension than flattops, is that correct?

I ask as I'm thinking about a conversion project to a mandocello/bouzouki/octave mandolin type of thing, the donor I was considering was the loar lh-300.

Using the mcdonald string calculator, and the LH-300's scale of 24.75 inches I get 165.97 pounds for a normal medium 6 string set and 189.12 pounds for a long scale cittern set (5 doubled courses), would the extra 25 pounds collapse the top?

Mandocello conversions are fairly common and a mandocello string set seems to be 288.4 pounds.
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Old 01-23-2013, 07:19 AM
HHP HHP is offline
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Can't say for sure but the expression 'like a cheap suit' comes to mind. Take into account the fact that a lot of double course mandolin family instruments over the years developed a sunken or collapsed top. Its one of the first things you check on used mandolins.

Contact builders of mandocellos and ask them how much additional structural support they have to build in.
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Old 01-23-2013, 08:16 AM
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devellis devellis is offline
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On one hand, arched top instruments can take a lot of down force. On the other, the instrument is designed for a certain amount of pressure and going too far beyond that may either jeopardize its integrity or, short of that, just not sound that great. The idea that instruments will just get louder and louder the more you load the top hasn't been my experience at all with arched top instruments (mostly mandolins). There's a range of optimal down force and going outside it in either direction compromises tone and volume.

You might begin by stringing the instrument (I guess you'll be modifying the headstock and nut for additional strings at a minimum) with gauges that have a lower total. Start as close to the "stock" guitar total force as you can and then maybe creep up from there.

But really, maybe you should just get your hands on a Trinity College octave mandolin. They were reasonably priced last time I had occasion to check (which, admittedly, was a while ago) and I bet you could find one in the Mandolin Cafe' classifieds. They play and sound quite good fro the price and they're designed to do what you want them to. You might even find someone who'll do a trade with you, taking the Loar and giving you the Trinity College. Guitar scale lengths don't work well for tuning in fifths. The stretches are just too long, at least for me. Bouzouki tunings (usually a modification of tuning in fifths) can work for accompaniment but playing melodies will involve a lot of jumping around the neck.
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