Official Luthiers Forum!

Owned and operated by Lance Kragenbrink
It is currently Thu Mar 28, 2024 9:06 am


All times are UTC - 5 hours


Forum rules


Be nice, no cussin and enjoy!




Post new topic Reply to topic  [ 9 posts ] 
Author Message
PostPosted: Sat Apr 07, 2018 9:10 pm 
Offline
Walnut
Walnut

Joined: Thu Jun 12, 2014 3:04 pm
Posts: 5
First name: Wade
Last Name: Bick
City: Jenks
State: OK
Zip/Postal Code: 74037
Country: USA
Focus: Build
Status: Amateur
Hi- Over the past year I've been collecting wood for my first acoustic build (000 size) and building some jigs that I figure I'll need once I start construction. Looking at the back plates recently, I noticed one of them is warped (maybe cupped is technically the correct term). It's cupped about 1/8" in the center of it's 8 1/2" span. The other plate might be about 1/32", so not too concerned about that one. They're Honduran mahogany and about .200" thick right now.

So, I'm wondering, once I thickness the plates down to .100-.125" or so, will they limber up and the cupping won't be much of an issue? Or is this a big problem? The humidity here in OK is a little low right now (~40%), maybe it will flatten out once we get into spring/summer?

Comments? Suggestions?

Thanks!


Top
 Profile  
 
PostPosted: Sat Apr 07, 2018 9:11 pm 
Offline
Brazilian Rosewood
Brazilian Rosewood

Joined: Wed Feb 20, 2008 7:15 pm
Posts: 7219
First name: Ed
Last Name: Bond
City: Vancouver
Country: Canada
Focus: Build
Status: Professional
Not a problem.



These users thanked the author meddlingfool for the post: CheapSquier (Sun Apr 08, 2018 10:40 am)
Top
 Profile  
 
PostPosted: Sun Apr 08, 2018 12:11 am 
Offline
Koa
Koa

Joined: Sun Apr 25, 2010 4:46 pm
Posts: 501
First name: Mark
Last Name: McLean
City: Sydney
State: New South Wales
Zip/Postal Code: 2145
Country: Australia
Focus: Build
Status: Amateur
It should be fine. When you get it to building thickness and then brace it you shouldn’t find it fighting against you. But pay careful attention to humidity control at that stage if the build. Bad things happen if the wood is too humid (or dry) when you glue up the bracing, or close the box.



These users thanked the author Mark Mc for the post: CheapSquier (Sun Apr 08, 2018 10:39 am)
Top
 Profile  
 
PostPosted: Sun Apr 08, 2018 11:04 am 
Offline
Contributing Member
Contributing Member
User avatar

Joined: Thu Feb 09, 2006 2:35 pm
Posts: 2951
Location: United States
First name: Joe
Last Name: Beaver
City: Lake Forest
State: California
Focus: Build
I'm 100% with what Mark and Ed said. Especially the part about taking care not to brace or close when humidity is out of whack (technical term), although you can usually get away with being on the dry side, but not the wet.

_________________
Joe Beaver
Maker of Sawdust


Top
 Profile  
 
PostPosted: Mon Apr 09, 2018 11:06 pm 
Offline
Brazilian Rosewood
Brazilian Rosewood

Joined: Thu Feb 12, 2009 10:27 pm
Posts: 2082
Location: South Carolina
First name: John
Last Name: Cox
Focus: Build
Status: Amateur
For me - the "worst" place for warp is on the glue line - because it makes aligning the glue line more difficult. But a little warp that flattens quickly under light pressure is no problem.

If you are concerned - iron the offending piece flat with a hot clothes iron and a little water. Once it "flattens" (you will feel it relax) - pile some heavy junk on top of it to keep it flat for a while. Works like a charm.


Top
 Profile  
 
PostPosted: Tue Apr 10, 2018 1:07 am 
Offline
Contributing Member
Contributing Member
User avatar

Joined: Thu Feb 09, 2006 2:35 pm
Posts: 2951
Location: United States
First name: Joe
Last Name: Beaver
City: Lake Forest
State: California
Focus: Build
If there is a mistake to be made, I've probably made it.

Somewhere along the way I discovered the true test wasn't how well you built a guitar, but how well you were able to recover from the many follies.

_________________
Joe Beaver
Maker of Sawdust


Top
 Profile  
 
PostPosted: Tue Apr 10, 2018 4:36 am 
Offline
Contributing Member
Contributing Member

Joined: Tue Dec 17, 2013 10:52 pm
Posts: 2953
First name: Don
Last Name: Parker
City: Charleston
State: West Virginia
Zip/Postal Code: 25314
Country: USA
Focus: Build
Status: Amateur
Piling on here:

1. That type of warping can be managed. Not a huge problem.

2. The higher humidity that you are hoping for is actually something to worry about. The worst of all worlds is when you brace the plates and close up the box in high humidity. When the winter comes, that moisture leaves the wood and the chances of cracks in the plates go way up. WAY up. I was not smart enough about relative humidity for my first several builds, and I have the top cracks to remind me of that folly. Before you move forward with any bracing, get on top of accurately measuring (harder than you think) and controlling relative humidity.


Top
 Profile  
 
PostPosted: Tue Apr 10, 2018 8:19 am 
Offline
Brazilian Rosewood
Brazilian Rosewood

Joined: Tue May 13, 2008 10:44 am
Posts: 6232
Location: Virginia
You may find too that when thinning the plates the side that you plane or sand on will cup. Flipping it over will reverse that cupping direction and even it out. In the end though you are just going to arch the plates anyway so you may as well brace the side that is 'pre-cupped' so to speak. 40%RH imho is perfect conditions for bracing.


Top
 Profile  
 
PostPosted: Wed Apr 11, 2018 8:07 pm 
Offline
Contributing Member
Contributing Member
User avatar

Joined: Wed Sep 08, 2010 12:17 am
Posts: 1263
First name: John
Last Name: Arnold
City: Newport
State: TN
Zip/Postal Code: 37821
Country: USA
Focus: Repair
Status: Professional
Let me guess....the concave side was exposed more than the other side. With low humidity, the exposed side shrinks more, causing the cupping. If that is the case, all you have to do is turn it over.

_________________
John


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 9 posts ] 

All times are UTC - 5 hours


Who is online

Users browsing this forum: No registered users and 59 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
Powered by phpBB® Forum Software © phpBB Group
phpBB customization services by 2by2host.com