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Hot Box for Soundboard Before Gluing Braces
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10101&t=54960
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Author:  davidson [ Thu May 05, 2022 6:03 am ]
Post subject:  Hot Box for Soundboard Before Gluing Braces

I see in piano and harp building it is common to dry the soundboard in a hot box before attaching the braces. You can also see Jonny Kinkead possibly doing something similar in the build series linked below:

https://www.youtube.com/watch?v=aAV9U3WzzP8
Dan's Acoustic Guitar Build Part 1/5 With Master Luthier Jonny Kinkead

Does anyone building here have an intentional heated drying session before gluing the braces?

Thanks,

Chuck

Author:  Colin North [ Thu May 05, 2022 6:22 am ]
Post subject:  Re: Hot Box for Soundboard Before Gluing Braces

Hard to find with no reference in your post to specific time /part - ?/5 no.
I bake my tops (and bracing) in a hot box (95-100 deg C 1.5 hrs) and leave them to re-acclimatize them before jointing the top and bracing it to pre-shrink and condition them (quite a common practice - taylor etc.), but would hesitate to heat the soundboard in a hot box before bracing because of the glue joint.
I've heard Martin used to keep their tops in a warm area (attic?) before bracing if that helps.

Author:  davidson [ Thu May 05, 2022 6:54 am ]
Post subject:  Re: Hot Box for Soundboard Before Gluing Braces

Thanks.

Kinkead video part 1 of 5 around 12:02.

Author:  Colin North [ Thu May 05, 2022 8:09 am ]
Post subject:  Re: Hot Box for Soundboard Before Gluing Braces

In a drying cabinet he says, looks like he's using a domestic a domestic air conditioner, maybe to feed dry air (which will be warm) into the drying cabinet.

Author:  jfmckenna [ Thu May 05, 2022 9:10 am ]
Post subject:  Re: Hot Box for Soundboard Before Gluing Braces

I have used an oven before but if you keep your wood in your controlled shop you should not have an issue with it imho.

Author:  Pat Foster [ Thu May 05, 2022 9:37 am ]
Post subject:  Re: Hot Box for Soundboard Before Gluing Braces

I bake all my tops just to get put them through the first cycle of shrinkage and let them acclimate before gluing on the braces. A world-class classical builder I know dries his tops to 3% and glues his braces with the tops still at 3%. When they acclimate to his shop humidity, they expand, forcing a dome.

Author:  Jim Watts [ Thu May 05, 2022 10:17 am ]
Post subject:  Re: Hot Box for Soundboard Before Gluing Braces

Pat Foster wrote:
I bake all my tops just to get put them through the first cycle of shrinkage and let them acclimate before gluing on the braces. A world-class classical builder I know dries his tops to 3% and glues his braces with the tops still at 3%. When they acclimate to his shop humidity, they expand, forcing a dome.


Pat, does he brace the top in a flat condition? Interesting.

Author:  Pat Foster [ Thu May 05, 2022 1:18 pm ]
Post subject:  Re: Hot Box for Soundboard Before Gluing Braces

Jim Watts wrote:
Pat Foster wrote:
I bake all my tops just to get put them through the first cycle of shrinkage and let them acclimate before gluing on the braces. A world-class classical builder I know dries his tops to 3% and glues his braces with the tops still at 3%. When they acclimate to his shop humidity, they expand, forcing a dome.


Pat, does he brace the top in a flat condition? Interesting.


Jim,

Couldn't tell you. If I get a chance, I'll ask him next time I see him.

Author:  Jim Watts [ Thu May 05, 2022 2:13 pm ]
Post subject:  Re: Hot Box for Soundboard Before Gluing Braces

Thanks!

Author:  davidson [ Thu May 05, 2022 6:46 pm ]
Post subject:  Re: Hot Box for Soundboard Before Gluing Braces

Thanks all.

Author:  Hesh [ Fri May 06, 2022 5:24 am ]
Post subject:  Re: Hot Box for Soundboard Before Gluing Braces

Bracing in extremely low RH has been done by piano manufacturers, violin makers, mando makers and guitar makers. It's another approach to producing instruments that can withstand RH swings to a greater degree, hopefully. We think it's helpful but it's not anything new it's been done for a very long time and likely was done before we had machines to manipulate our environments by batching work and jobs for seasonal opportunities when the RH is right.

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