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I'm looking for a little advice on a striped sapele back set that I inadvertently thinned a little more than I would have liked (doing multiple sets, and just got confused / distracted). Anyway, some of you may know this wood - it's from Bob C's last batch of striped sapele. It's relatively heavy, stiff wood... not as stiff as rosewood, but pretty heavy and stiff. Anyway, I was planning on stopping around .100, but one set is down to .090 now. This set is for a 000/OM sized guitar, very stiff sitka top... that's about all of the related info I can think to pass along.

I know that best way to tell is to take it in your hands and flex it yourself in person, and that otherwise, it's just a guestimation, but... is there any criteria that I can use to judge if .090 is too thin, in this case? Can I compensate by leaving the braces a bit higher that I normally would?

TIA,

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Ken Mitchell
Durham, NC

It's not too thin, structurally. Other things equal (are they ever?) the gtr will speak a bit more quickly
and have a little less sustain, imo. -CW

One thing you could do is to make the bracing on the back a lattice.
Check out the links below. They show tops with lattice bracing, but you could do that to a back pretty easily and it would look way cool and add plenty of strength.


http://www.schrammguitars.com/lattice.html

http://www.danielbrauchli.com/Acoustic_Concepts.htm

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"An adventure is only an inconvenience rightly considered. An inconvenience is an adventure wrongly considered." G. K. Chesterton.

I think you are fine. I have seen Martins with backs as low as .090 and sides at .065. No need to overbrace, Once you have it braced you should get a feel for it. Sapele is pretty stiff once braced . I build at .090 for the backs.
john hall

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Thanks, guys. I really appreciate the input.

Of course, now I'm starting to rethink the other two that I'm preparing... I left those at around .100. (???)

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Ken Mitchell
Durham, NC

.090" is fine, (It'll go a bit thinner with final sanding, but that's OK). Consider using and X braced back. Something like this and it'll stiffen it up a bit. Also consider a slightly wider centre reinforcement.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

I built an SJ with Ribbon Sapele that started at .090 at the back and .080 at the sides. I reduced another .005 from final sanding. It worked out fine.

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JJ
Napa, CA
http://www.DonohueGuitars.com

JJ - that sounds like what I'll be doing as well. Thanks for the feedback.

Colin - I like the X-braced back. Do you just cut the other diagonal brace(s) and butt the ends up to the X-brace?

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Ken Mitchell
Durham, NC

Sure .090 is great and what I would do as well. The OM I am currently setting up has a .090ish Cuban Mahogany back.

Ken thanks for your post and others for your reply's. I am in the process of thicknessing some Queensland Maple (not a true Maple) and got a little carried away with with my no 4 smoothing plane. Thought I could save myself some hand sanding time and took one too
many swipes and tore out a few chunks of grain. I wanted to go thinner with this one but wasn't thinking .090 . I am building another Dread hopefully a lot more symetric than my last one. In any case you have dispelled a lot of my anxiety with regards to this dilema and am once again very grateful for the forum and it's members.
A drum sander has moved to the top of my acquisition list.

Regards
Craig.

Another vote for go with it. I go a sapele set at Martin's Guitar Maker Connection store last weekend, that the girl said was thicknessed to factory spec, and the back is .090" and the sides ate .070". Boy they bent really nice!

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Rob

.090" is fine. Don't worry about it. No need to change bracing.

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.