Top flattening after braces

[ken cierp]

I communicate with John Greven occasionally -- he makes and sells some of the best reproductions being made today. I really like this essay since it comes from a very authoritative source. Note the section on bracing and deflection --- Martin was/is always working on reducing deflection/doming issues and certainly would not exasperate the problem by forcing the sound board into a more vulnerable shape. This goes back to perhaps the biggest myth of them all, Martin does not use 28' top bracing and they sand the top of the rim flat with a 1.3 degree slope -- not the popular notion that the rim is contoured with a 28' dish.

http://www.grevenguitars.com/pdfs/MartinMyths.pdf

[Dave Bagwill]

That is very interesting.

[Jim Ebert]

Thanks, Ken for the Greven article. It is very interesting and I will use it as a reference. Now that the Martin myth has been dispelled, I have a question. Everything I have read, heard or seen says that the wood should be acclimated to the shop at about 45%rh. The idea of gluing up the top on the drier side seems like it might help to protect it from exposure to drier climates. Do you think this is a good idea or will it create issues with warping and deformation? Thanks again,
Jim

[ken cierp]

The assembly rooms at most factories are set at 45% RH -- this is where the ready to use material is stored as well so that seems to be the industry standard for acclimation. You can read in the attached article where even though Taylor uses a baking process to stabilize resins they still acclimate at the magic RH number.

http://www.premierguitar.com/articles/D ... _or_Nuture

To the specific question -- assembling when the RH is lower won't hurt, might help -- but based on the article if the wood was once shrunk to its smallest dimension it may not matter.

[Jim Ebert]

Looks like I will have to wait for my wife to leave town and give it a try. I wood ask her if it was OK but I don't think she would say yes to me putting my spruce in her new Viking oven. This way if it goes wrong I could just say.... I don't know.
Jim

[ken cierp]

Be aware that baking tops in the kitchen will stink up the house. Been there done it!

[Dave Bagwill]

I will just mention that I got a sitka top 'torrefied' from Stewmac, very nice board and only a few bucks more than the untreated boards. Could save an oven!