Official Luthiers Forum!

Solely owned and operated by Lance Kragenbrink
It is currently Sun Jun 25, 2017 10:34 am


All times are UTC - 5 hours


Forum rules


Be nice, no cussin and enjoy!




Post new topic Reply to topic  [ 20 posts ] 
Author Message
PostPosted: Wed Feb 15, 2017 10:10 pm 
Offline
Brazilian Rosewood
Brazilian Rosewood

Joined: Wed Feb 20, 2008 7:15 pm
Posts: 4555
First name: Ed
Last Name: Bond
City: Vancouver
Country: Canada
Focus: Build
Status: Professional
Has anyone experienced problems from cracks from the tremendous stress riser between the sides and solid linings?



These users thanked the author meddlingfool for the post: Joe Beaver (Thu Feb 16, 2017 10:20 pm)
Top
 Profile  
 
PostPosted: Wed Feb 15, 2017 10:28 pm 
Offline
Brazilian Rosewood
Brazilian Rosewood
User avatar

Joined: Thu Feb 12, 2009 12:12 pm
Posts: 2252
First name: Bryan
Last Name: Bear
City: St. Louis
State: Mo
Country: USA
Focus: Build
Status: Amateur
That's interesting. I never really thought about the stress riser there. My solid looks in are pretty square so there indeed is one at the top and side. I suppose the most significant one would be where the lining meets the side since it would be along the grain. On a closed box, there doesn't seem to be too much stress in that direction though. I suppose the danger would be from impact.

I'mno engeneer so I'm probably wrong, but it feels to me like impact would cause a crack most often at the spot where f the impact. With the mostly curved sides, it would be difficult to flex the side enough for the stress to build at the riser, rather just cracking along the grain where the force tried to bend the side. Again, this is all gut feeling on my part.

_________________
Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.


Top
 Profile  
 
PostPosted: Wed Feb 15, 2017 11:02 pm 
Offline
Contributing Member
Contributing Member
User avatar

Joined: Mon Aug 23, 2010 11:42 pm
Posts: 1126
First name: John
Last Name: Parchem
City: Seattle
State: Wa
Zip/Postal Code: 98177
Country: USA
Focus: Build
Status: Amateur
I have not and have not thought about stress riser, but I do taper the lining going into the sides. My linings are made with three laminates I stagger them a bit when I glue them up and sand in the taper.

_________________
http://www.Harvestmoonguitars.com


Top
 Profile  
 
PostPosted: Thu Feb 16, 2017 1:13 am 
Online
Contributing Member
Contributing Member
User avatar

Joined: Thu Feb 09, 2006 2:35 pm
Posts: 2382
Location: United States
First name: Joe
Last Name: Beaver
City: Lake Forest
State: California
Focus: Build
Status: Amateur
No cracks but I have been concerned about the potential. That's why I put in full length side braces that go from plate to plate.
Like this:


You do not have the required permissions to view the files attached to this post.

_________________
Joe Beaver
Maker of Sawdust


Top
 Profile  
 
PostPosted: Thu Feb 16, 2017 4:19 am 
Offline
Brazilian Rosewood
Brazilian Rosewood

Joined: Wed Feb 20, 2008 7:15 pm
Posts: 4555
First name: Ed
Last Name: Bond
City: Vancouver
Country: Canada
Focus: Build
Status: Professional
Nice looking work there!


Top
 Profile  
 
PostPosted: Thu Feb 16, 2017 10:24 am 
Offline
Koa
Koa

Joined: Thu Feb 12, 2009 10:27 pm
Posts: 1792
Location: South Carolina
First name: John
Last Name: Cox
Focus: Build
Status: Amateur
I suppose theoretically it may be an issue..

The thing is - I really don't see cracks around the edges of the linings... Often as not - cracks are in the middle of the sides rather than at the edges.

Stress wise - normal kerfed and reverse kerfed linings would cause a stress riser just like laminated ones... So we would expect to see a problem... But we don't.


Top
 Profile  
 
PostPosted: Thu Feb 16, 2017 10:29 am 
Offline
Brazilian Rosewood
Brazilian Rosewood

Joined: Wed Apr 08, 2009 9:34 am
Posts: 2393
Like those laminated back braces!

_________________
J. Brentrup Guitars & Mandolins
http://www.brentrup.com


Top
 Profile  
 
PostPosted: Thu Feb 16, 2017 2:57 pm 
Offline
Brazilian Rosewood
Brazilian Rosewood

Joined: Sat Jan 15, 2005 12:50 pm
Posts: 2981
Location: United States
Side braces can cause cracks along the edge of the liners, if the braces are not inlet.



These users thanked the author Alan Carruth for the post: Joe Beaver (Thu Feb 16, 2017 10:22 pm)
Top
 Profile  
 
PostPosted: Thu Feb 16, 2017 4:50 pm 
Offline
Koa
Koa
User avatar

Joined: Tue Oct 30, 2007 9:13 am
Posts: 1084
Location: United States
State: Texas
Focus: Build
Status: Professional
I have made solid 1, 2 & 3 part laminated linings since the first guitar 40 years ago. I am not aware of a single instance of side cracking at the lining, or anywhere else on the sides (I make wood strip reinforcements).
Why does a solid lining make a "tremendous" stress riser compared to any other type of lining?

3-part lining for a guitar with wide purfling/binding

Image

_________________
http://davidnewtonguitars.squarespace.com/



These users thanked the author David Newton for the post (total 2): Joe Beaver (Thu Feb 16, 2017 10:22 pm) • pat macaluso (Thu Feb 16, 2017 7:08 pm)
Top
 Profile  
 
PostPosted: Thu Feb 16, 2017 6:12 pm 
Offline
Brazilian Rosewood
Brazilian Rosewood

Joined: Wed Feb 20, 2008 7:15 pm
Posts: 4555
First name: Ed
Last Name: Bond
City: Vancouver
Country: Canada
Focus: Build
Status: Professional
Image
Solid lining, much stiffer than the sides, very specific strength difference point between side and lining...

Image
Normal lining, where the tip is less than the thickness of the side, spreading the point out a bit...



These users thanked the author meddlingfool for the post: Joe Beaver (Thu Feb 16, 2017 11:22 pm)
Top
 Profile  
 
PostPosted: Thu Feb 16, 2017 6:58 pm 
Online
Contributing Member
Contributing Member
User avatar

Joined: Thu Feb 09, 2006 2:35 pm
Posts: 2382
Location: United States
First name: Joe
Last Name: Beaver
City: Lake Forest
State: California
Focus: Build
Status: Amateur
[quote="David Newton"]I have made solid 1, 2 & 3 part laminated linings since the first guitar 40 years ago. I am not aware of a single instance of side cracking at the lining, or anywhere else on the sides (I make wood strip reinforcements).
Why does a solid lining make a "tremendous" stress riser compared to any other type of lining?

I sure like the look of your 'variable thickness' solid liners. What wood do you use? Bass wood?

_________________
Joe Beaver
Maker of Sawdust


Top
 Profile  
 
PostPosted: Fri Feb 17, 2017 10:13 am 
Offline
Koa
Koa
User avatar

Joined: Tue Oct 30, 2007 9:13 am
Posts: 1084
Location: United States
State: Texas
Focus: Build
Status: Professional
Yes, Basswood, I bought several boards of it and stripped it all out for liners, though I have used Mahogany, Walnut, and many other woods that accumulate in my shop.

I don't do the thick, one-part liners that you see on some Spanish guitars, but always laminate 1, 2, or 3 thin strips, gluing them a strip at a time on the sides. It certainly takes longer than any other type of lining, but I feel the result is worth it and is a distinctive part of my construction method. The sides assembly is very stiff on its own, and the overall effect is to make my guitars lighter and yet stronger for its weight.

_________________
http://davidnewtonguitars.squarespace.com/


Top
 Profile  
 
PostPosted: Fri Feb 17, 2017 12:10 pm 
Offline
Contributing Member
Contributing Member

Joined: Wed Nov 14, 2012 6:47 pm
Posts: 139
First name: john
Last Name: smith
City: hemet
State: ca
Zip/Postal Code: 92543
Country: usa
Focus: Build
Status: Amateur
I understand Ed's question, with kerfing the wood is separated between and angled very thin. Solid linings have a very sudden ending so one might surmise stress at that point. I am surprised that no one seems to have thought of it. If a side support creates a riser as was mentioned a solid lining would as well. The fact that no one on this thread has reported any such event is interesting to me.


Top
 Profile  
 
PostPosted: Fri Feb 17, 2017 12:59 pm 
Offline
Cocobolo
Cocobolo

Joined: Sat Jan 19, 2013 7:33 am
Posts: 461
First name: Willard
Last Name: Guthrie
City: Cumberland
State: Maryland 21502
Zip/Postal Code: 21502
Country: United State
Focus: Repair
Status: Semi-pro
We see side cracks that are on or very close to linings once or twice a month, and just had a Martin 000-16GT in that had a pretty ugly repaired crack just this past Wed. Cross-grain reinforcements help in keeping the crack from propagating once the impact occurs, but if the guitar takes a hit on or close to the linings, even kerfed, triangular linings, which should result in a less adverse rise in stress, will focus the crack energy on the edge of the lining. From my point of view, side crack repairs that sit directly over a lining are not my favorite thing to do.

_________________
Consensus is the business of politics.
― Michael Crichton


Top
 Profile  
 
PostPosted: Fri Feb 17, 2017 1:17 pm 
Offline
Brazilian Rosewood
Brazilian Rosewood
User avatar

Joined: Thu Feb 12, 2009 12:12 pm
Posts: 2252
First name: Bryan
Last Name: Bear
City: St. Louis
State: Mo
Country: USA
Focus: Build
Status: Amateur
Woodie G wrote:
We see side cracks that are on or very close to linings once or twice a month, and just had a Martin 000-16GT in that had a pretty ugly repaired crack just this past Wed. Cross-grain reinforcements help in keeping the crack from propagating once the impact occurs, but if the guitar takes a hit on or close to the linings, even kerfed, triangular linings, which should result in a less adverse rise in stress, will focus the crack energy on the edge of the lining. From my point of view, side crack repairs that sit directly over a lining are not my favorite thing to do.


So, if the impact being close to the linings will focus the energy at the riser even with triangular linings (less of a stress riser), does a more squared off lining profile make any practical difference in risk? Is it a matter of having a wider impact zone that would crack at the lining? Or is it pretty close to a push; if the impact is close to the linings that is where it is going to crack no mater what, closer to the center it will crack at the weakest point near the impact? Is the hassle of tapering the ends of my linings worth the benefit?

_________________
Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.


Top
 Profile  
 
PostPosted: Fri Feb 17, 2017 1:52 pm 
Online
Contributing Member
Contributing Member
User avatar

Joined: Thu Feb 09, 2006 2:35 pm
Posts: 2382
Location: United States
First name: Joe
Last Name: Beaver
City: Lake Forest
State: California
Focus: Build
Status: Amateur
Thanks for the reply David. It sure makes a great looking 'insides'. I like to use popsicle braces. If I make them the thickness of the 1st liner and put them between pieces of liner then cover with one or two solid liners it would work well for me. Thanks for the show and tell!

_________________
Joe Beaver
Maker of Sawdust


Top
 Profile  
 
PostPosted: Fri Feb 17, 2017 2:37 pm 
Offline
Koa
Koa
User avatar

Joined: Tue Oct 30, 2007 9:13 am
Posts: 1084
Location: United States
State: Texas
Focus: Build
Status: Professional
Oh yes, I've seen plenty side cracks right at the junction of a kerfed lining thin side.
I would like to state the obvious, it is always a factory guitar, Martin, Gibson, Asian import, name your poison, where the guitar box (sides) has probably been sanded thin & flat by a machine, a vertical belt sander.
You don't sand your sides this way, do you? No, I like to control stuff in my shop.
When discussing the procedures & processes of our hand-made guitars, let's not over-compensate for the many failures of factory guitars.
Ours are made on Venus, all the factories are on Mars.

_________________
http://davidnewtonguitars.squarespace.com/



These users thanked the author David Newton for the post: Joe Beaver (Fri Feb 17, 2017 5:44 pm)
Top
 Profile  
 
PostPosted: Fri Feb 17, 2017 7:04 pm 
Offline
Cocobolo
Cocobolo

Joined: Sat Jan 19, 2013 7:33 am
Posts: 461
First name: Willard
Last Name: Guthrie
City: Cumberland
State: Maryland 21502
Zip/Postal Code: 21502
Country: United State
Focus: Repair
Status: Semi-pro
I do love the optimism, but while our guitars may be from Venus, many of them are owned by clumsy Earthlings that drop, batter, and bang our little darlings into mic stands, bass players, the ex-boyfriend's current girlfriend, and any other sharp, hard, hazardous, or just really annoyingly pretty (but so stupid) object at hand. Large cross-sectional changes will generate greater stress than more gradual changes, but we've seen very few instruments that saw cracked sides without wanton provocation.

_________________
Consensus is the business of politics.
― Michael Crichton


Top
 Profile  
 
PostPosted: Fri Feb 17, 2017 7:21 pm 
Offline
Brazilian Rosewood
Brazilian Rosewood

Joined: Fri Dec 14, 2007 3:21 pm
Posts: 2363
Location: Alexandria MN
I just had an old Gibson harp guitar that had a gaping side crack 2/3 of the length of the side and right along the edge of the lining. Gibson had used cross grain spruce reinforcement that were tapered under the kerfed lining but that didn't help in this case.

It was pretty much impossible to repair without taking the back off. No way to get an internal cleat across the crack.

How do you guys fix a long crack right along the edge of the lining without opening the box?

_________________
It's not what you don't know that hurts you, it's what you do know that's wrong.


Top
 Profile  
 
PostPosted: Fri Feb 17, 2017 10:17 pm 
Offline
Koa
Koa
User avatar

Joined: Tue Oct 30, 2007 9:13 am
Posts: 1084
Location: United States
State: Texas
Focus: Build
Status: Professional
Sure, stuff happens. I repaired a broken head-stock for a guy who set his case down behind his car and backed over it. Exactly one week later he returned after backing over it again.
I don't build guitars to withstand abnormal abuse, I let Guild do that.
All I'm saying is I don't lose sleep worrying about side stress risers, if I make the sides to an appropriate thickness.

Woodie G wrote:
I do love the optimism, but while our guitars may be from Venus, many of them are owned by clumsy Earthlings

_________________
http://davidnewtonguitars.squarespace.com/


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 20 posts ] 

All times are UTC - 5 hours


Who is online

Users browsing this forum: Bing [Bot], Joe Beaver, stumblin, WilliamS and 3 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