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CFM upgrades
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10101&t=56948		 Page 1 of 1
Author:  phavriluk [ Fri Jan 10, 2025 11:53 pm ]
Post subject:  CFM upgrades
I just read in Another Forum a wannabe Martin Custom Shop customer's musings about optioning a baked Adirondack spruce soundboard for only a $1084.00 upcharge. HUH? I'm dumbstruck that Martin would have such nerve and a customer was tapping that much of Martin's Kool-Aid. And the amen chorus puffed on about the advantages and high merits of such an option. DOUBLE HUH.

People tolerate this?

Even in the gouge-anybody-dumb-enough retail market, wouldn't such a soundboard cost way less than that?

I thought I was a wasteful hedonist when I spent fifty bucks on an Alaska Specialty Woods bear claw soundboard.

What am I missing?

Thanks!
Author:  doncaparker [ Sat Jan 11, 2025 9:20 am ]
Post subject:  Re: CFM upgrades
Last weekend, Brad Combs and I visited a friend of ours who is a builder, but who also has access to huge amounts of torrified red spruce tops, tops that have not been overcooked (some can be way overcooked). So, these are good quality tops, as far as torrified tops go. This builder said he won’t build with torrified tops any more, now that he has experimented with them. They are hard to work with, according to this builder. They don’t take glue well, and they are easier to break at a grain line if you flex them too much.

I don’t know if the Martin up charge is an example of price gouging, or just recognizing the extra effort and cost involved in using torrified material, or both. But I trust this builder’s assessment of the difficulties involved, so I figure at least some of the up charge is justified.
Author:  SteveSmith [ Sat Jan 11, 2025 11:11 am ]
Post subject:  Re: CFM upgrades
I've built with at least four torrefied Red Spruce tops. I've had zero issues with glue, I use Titebond Original and brace with non-torrified Red Spruce. I make sure I wet both sides of the joint. The torrified wood is more brittle and, yes, they will break along the grain if you wiggle too much; I broke the first one I joined checking for the 'sheet metal' sound. You can still check for the 'sheet metal' sound you just have to be aware of the material properties and wiggle a bit more gently. The best sounding guitars I've built have torrified tops( not my assessment but I agree) but maybe they just sound better because I'm a better builder now idunno

FWIW torrified maple is sure pretty but don't waste your time trying to bend it for mandolin sides gaah laughing6-hehe
Author:  meddlingfool [ Sat Jan 11, 2025 12:07 pm ]
Post subject:  Re: CFM upgrades
No need to be afraid of torrefied tops. I’ve built 40+ guitars with it and it’s fine. As mentioned, it can be overcooked, but if not overcooked it’s perfectly fine. I use TB OG as well, I just use more glue than I use on non torrefied tops. I also ditched torrefied bracing for standard wood.

My experiments with before/after torrefaction was a consistent 15% drop in density, permanently. It is also much more dimensionally stable.

Tonally, you can expect it to have less complexity than standard wood, but it works as advertised giving an immediate smooth, worn in type of response. I consider it something of a niche wood, in the same way an all mahogany guitar is a niche sound. I quite like it.

As to whether or not it’s worth a thousand dollar upcharge, well, that’s for the buyers to decide I guess.
Author:  bcombs510 [ Sat Jan 11, 2025 4:11 pm ]
Post subject:  Re: CFM upgrades
Ed, I was hoping you would chime in here. A question - how do you handle material properties analysis with torrefied wood?

When I try to run freq response from a torrefied plate through the spreadsheet it says I should thin the top to .060” (or something similarly crazy). What are you doing with your tops?


Sent from my iPhone using Tapatalk Pro
Author:  meddlingfool [ Sat Jan 11, 2025 6:29 pm ]
Post subject:  Re: CFM upgrades
There has to be something wrong with your data there. I don’t use the G/G method, I use deflection testing and just do the usual…
Author:  bcombs510 [ Sat Jan 11, 2025 6:58 pm ]
Post subject:  Re: CFM upgrades
Hmm… I don’t know if it’s a data problem. I went to Greg Maxwell’s shop before covid and we tested some tops. He uses the Gallup method and it also was saying take the top super thin.

Both G&G and Galloup testing methods say to take the tops really thin. I wonder if there is some type of adjustment needed because the formulas weren’t designed with baked tops in mind?

I will try some more plates and see what I get. I have a whole stack of roasted Sitka from StewMac. It’s the early tops they offered.


Sent from my iPhone using Tapatalk Pro
Author:  bobgramann [ Sat Jan 11, 2025 7:55 pm ]
Post subject:  Re: CFM upgrades
I made an OM-sized one with a StewMac torrified top in 2016. I thicknessed by deflection. It came out at .104”. The guitar sounded wonderful. Its sound when first strung up matched one of the best I’ve ever made (the one I made for myself) that was 10 years old.

Figuring that it took a normal top only ten years to get there, and that you’d miss the thrill of hearing the improvement over that period, I wasn’t sure that it was worth the extra effort. (That 10 year old guitar did give me a lot of pleasure as I heard it develop—not that there was anything wrong with its sound on day 1). I did feel that the torrified spruce was a bit more delicate to work with than unbaked spruce and required a bit more care in handling. I decided that I would build again with it on request but not on spec. So far, no one has asked for it.

For a long time (since way back before that torrified top), I have been making my tops slightly thicker than they could be and making the bracing a bit lighter. On some of the thinner tops, I would notice bellying below the bridge between the braces. A little extra thickness seems to keep that from happening. I don’t know how that lesson would apply to the torrified top, but I still went to the same deflection that I would have had with any other top.
Author:  SteveSmith [ Sat Jan 11, 2025 8:37 pm ]
Post subject:  Re: CFM upgrades
My torrefied Red Spruce tops for dred and 000 size are all right around 0.100" to 0.110". I thickness and voice my tops the way I learned from Carlos Everett many years ago. Sorry, no measurements, just feel and sound. I'm with Bob, I try to keep them a bit thicker and lighten up on the bracing.
Author:  meddlingfool [ Sat Jan 11, 2025 9:21 pm ]
Post subject:  Re: CFM upgrades
Brad,

Not sure what to say, a .060 top is off the charts for me. The torrefaction process reduces density, and therefore also stiffness. So my torrefied tops usually end up thicker than standard wood, but with less mass.
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