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Some woods more resistant to RH swings?
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Author:  meddlingfool [ Sat Nov 09, 2013 3:09 pm ]
Post subject:  Some woods more resistant to RH swings?
I have a potential client asking me if there are certain wood combos more resistant to RH swings. It seems improbable to me, but I thought I'd ask. Are there woods more resistant to RH swings?
Author:  Pmaj7 [ Sat Nov 09, 2013 3:19 pm ]
Post subject:  Re: Some woods more resistant to RH swings?
Mahogany seams a lot more stable than the rosewoods under rh swings.
Author:  John Lewis [ Sat Nov 09, 2013 3:21 pm ]
Post subject:  Re: Some woods more resistant to RH swings?
Once dry and seasoned a bit, woods like African Blackwood and Spanish Cedar are pretty stable - most ebonies are on the opposite end of the spectrum. You should be able to find tables online that show the shrinkage rates of different woods. For topwoods, I think most spruces are fairly stable, once seasoned. Alaskan Yellow Cedar and Port Orford Cedar are very stable topwoods. Those are the woods that I can think of right off the top of my head.
Author:  Herr Dalbergia [ Sat Nov 09, 2013 4:16 pm ]
Post subject:  Re: Some woods more resistant to RH swings?
The wood being the least hygroscopic for top back, sides and fingerboard is dalbergia melanoxylon / african blackwood. This is the reason why it is the standard wood being used for high quality woodwind instruments. For the neck mahogani should be fine. For the top I would suggest Redwood or even Ancient Kauri.

Cheers, Alex
Author:  DennisK [ Sat Nov 09, 2013 5:27 pm ]
Post subject:  Re: Some woods more resistant to RH swings?
meddlingfool wrote:
I have a potential client asking me if there are certain wood combos more resistant to RH swings. It seems improbable to me, but I thought I'd ask. Are there woods more resistant to RH swings?

Yes, there are.

Western redcedar and redwood move a lot less than the spruces and Port Orford cedar. They're more brittle, but due to the smaller movement, they'll tolerate about the same percentage drop as spruce before cracking. So, if you build in extra low RH, they'll tolerate that, and due to the smaller movement, they won't poof up as much in high RH as spruce would if it was built at the same low level.

For back/sides, mesquite is the undisputed champion of low movement according to wood-database.com's numbers. Even flatsawn, it beats most other woods' quartersawn expansion. I don't have any personal experience to verify its stability, though.

Of the back/side woods I've used, Honduran mahogany seems to be the most stable. and crack resistant. My first two guitars had sitka tops and mahogany backs, built in the summer with air conditioning (probably 55% RH), and both tops cracked, and neither back. That's going down to 20% in the winter, so mahogany can take an incredible RH drop of 30+%. Spruce cracks at about 15-20% drop, I think.

The rosewoods are all pretty stable too, although Indian moves the most by the numbers. But of course, flatsawn BRW will move a lot more than quartersawn Indian.

So... my advice, use a straight grained, quartersawn redwood top, braced in 30-35%, and a Honduran mahogany back braced in 40-50%. Mahogany or Spanish cedar neck, rosewood fingerboard (African blackwood if you want the ebony look)
Author:  meddlingfool [ Sat Nov 09, 2013 5:44 pm ]
Post subject:  Re: Some woods more resistant to RH swings?
Wow, good advice, thanks!
Author:  Rod True [ Sat Nov 09, 2013 6:14 pm ]
Post subject:  Re: Some woods more resistant to RH swings?
I have a 24 year old Takamine which is Honduran mahogany/cedar. It's been to Thailand, Russia, Japan and has lived here on the West coast. It's been vary stable since I bought it new.

If I were ever asked for a guitar to be built for travelling and one that sees locations with swings in humidity this would be at the top of my list. Mind you, a good humidifier and the guitar living in the case for the most part (apart from playing of course) can be a real life saver.
Author:  meddlingfool [ Sat Nov 09, 2013 6:18 pm ]
Post subject:  Re: Some woods more resistant to RH swings?
That was the qualification. Guitar will not be kept,in the case....

Will we see you tomorrow Rod?
Author:  Rod True [ Sat Nov 09, 2013 7:41 pm ]
Post subject:  Re: Some woods more resistant to RH swings?
Not this year Ed! Got a family function.

Not kept in the case hey.......Why do people do this? Mind you, I didn't leave that Takamine in its case very often over all that time.
Author:  DannyV [ Sat Nov 09, 2013 9:32 pm ]
Post subject:  Re: Some woods more resistant to RH swings?
Plywood duh ;)
Author:  DennisK [ Sat Nov 09, 2013 9:37 pm ]
Post subject:  Re: Some woods more resistant to RH swings?
Rod True wrote:
Not this year Ed! Got a family function.

Not kept in the case hey.......Why do people do this? Mind you, I didn't leave that Takamine in its case very often over all that time.

For those of us who play frequently for short periods of time throughout the day, it's too much trouble hefting a heavy hard case around to open it, or fiddling with a zipper on a soft case. Just grab it off the wall or a stand, play for a bit, put it back. You also get to admire it a lot more often :)

And since my room has too many windows to humidify, and I like fresh air in the spring/fall, all of mine have to tolerate at least 20-70%. Building at 30-35% seems to do that. But I still need to offer one up as a sacrifice to 90+% and see if anything bad happens beehive
Author:  meddlingfool [ Sun Nov 10, 2013 2:48 am ]
Post subject:  Re: Some woods more resistant to RH swings?
Exactly. I'll only play them if they're underfoot.
Mine need to withstand being sat on, used to hold hot dinner plates, cold beer, piles of books, being stacked two to three high etc....
Author:  Colin North [ Sun Nov 10, 2013 8:22 am ]
Post subject:  Re: Some woods more resistant to RH swings?
Quote:
they won't poof up as much

Love the technical term Dennis! [:Y:]
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