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short back brace? to me
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Post
dcbaisden

Total Topics: 25
Total Posts: 58
should the back braces extend into the keerfing upto the sides or go all the way through the sides?
I have one brace thats pretty short \
Dave


(Photo sizes edited by Bill/Admin)

May 08, 07 | 10:24 am
davidmor

Total Topics: 34
Total Posts: 567
You can go either way. I personally like just going into the kerfing but that is just me. One thing to keep in mind if you go through the sides, make sure that the brace ends are thin enough so that the binding channel will cover it. I thin mine down to less than .1". Don't ask me how I know about brace ends being thicker than the binding channel. ;-)

My Blog

May 08, 07 | 12:05 pm
Dennis Weatherly

Total Topics: 73
Total Posts: 651
I don't have to ask you...I had the same learning on my project :-)

May 08, 07 | 12:20 pm
Ken Cierp

Total Topics: 58
Total Posts: 2262
Personally -- its a structure thing --- I would want that brace in particular to mate with the rim and kerfing as much as possible and ideally through to the outside. The advice about making sure the total height of the brace notch plus the back thickness are less than the height of the binding is very important!

Ken

www.kennethmichaelguitars.com

May 08, 07 | 1:27 pm
dcbaisden

Total Topics: 25
Total Posts: 58
I reposted this picture. I can not scroll across and read all the text. this is a smaller picture. hope you dont mind reposting your comments.

May 08, 07 | 1:57 pm
dcbaisden

Total Topics: 25
Total Posts: 58
that doent work either.
I do not have a scroll bar for some reason.

May 08, 07 | 1:58 pm
blues creek guitars Authorized Martin Repair Ctr

Total Topics: 52
Total Posts: 1011
I hate to go through the sides, this creates a weak spot and can cause some real headaches when you do binding. I like to inlet to the kerfing.
john hall

May 08, 07 | 7:59 pm
Ken Cierp

Total Topics: 58
Total Posts: 2262
John -- how does running the braces through the sides cause weak spots?? Please explain. "Taylor" (go to Factory Fridays web site to see their process) and many of the major factorys do it that way. I just seems if it were to cause structural problems they would be concerned with warranty claims. I started going all the way to the outside of the rim because it was so easy (for me anyway) to damage the kerfing when chipping out clearance for the brace ends. Another advantage that "works for me" is the fact that the braces ends and the notches create a key effect --- so when the back is glued to the rim it does not move out of place when clamps are applied. As far as the top goes I am leaning toward stopping all the braces including the X before they hit the kerfing. I don't know how well that works yet so I am not recommending it.

Ken

May 09, 07 | 3:24 am
Bill Cory

Total Topics: 158
Total Posts: 3584
Ken -- As far as cutting all braces on the top before they hit the kerfing-- I asked if this would pose any problems over on the Luthier's Corner. Al Carruth and Frank Ford both responded that it might work fine in the lower-bout end of the X, but the bracing inletting was needed in the upper bout ends of the X and the large transverse shoulder brace in order to withstand the torque of the neck and strings against the upper bout.

I am working on one with the lower-bout X stopping an inch from the kerfing --we'll see if the top is loose enough but not too loose.

Bill

May 09, 07 | 4:09 am
dcbaisden

Total Topics: 25
Total Posts: 58
thanks, the long brace is aproximately 1/2" short. It may come close to the keerfing but will not come in contact with it.
Should I replace the brace or do you think it will work.
Dave

May 09, 07 | 4:25 am
Ken Cierp

Total Topics: 58
Total Posts: 2262
Thanks Bill that makes a lot of sense - so Im guessing that the Taylor relief cut tops are similar and are only relieved from upper X notch forward, anybody know for sure? Back to the post --- Dave if it were mine I'd make sure I had a brace that went at least from inside of the rim all the way across -- think of it as a truss, its the only support across that LB area to help shape the back contour. Leaving it short MAY work just fine --- but I'd rather be safe than sorry.

Ken

May 09, 07 | 4:44 am
Bill Cory

Total Topics: 158
Total Posts: 3584
Ken -- You are right -- the Taylor relief cut around the edge of the lower bout starts just below the middle of the waist; the upper X (and transverse brace) is tied into the kerfs or side just beyond where the cut starts. (On my 2005 Taylor 510)

May 09, 07 | 5:24 am
gawlicd

Total Topics: 12
Total Posts: 44
This is why I made a suggestion for a parts dimension or spec sheet in the what's missing from kits thread. If it truly is wrongly sized or out of spec then we could get the manufacturer to replace it or possibly save a phone call and wasted time for all concerned if it isn't.
Incidently, one of my top braces with the truss rod hole in it did not meet the kerfing in my kit either, however I used it as is. I still don't know if it is a problem yet.
Dave G

May 09, 07 | 5:06 pm
gawlicd

Total Topics: 12
Total Posts: 44
I did question the use of short braces in my situation and the response was to examine what the purpose of the kerfing is for. I was told the kerfing is used as a gluing surface area for the top and back. The kerfing (at least spanish cedar has little structural strength anyway). If this is the case than having the braces go into the kerfing provides very little added strength. This made sense to me and helped me in my decision to use a brace that was in my opinion too short.
I hope some of the more experienced will comment on these thoghts.

May 09, 07 | 5:40 pm
Ken Cierp

Total Topics: 58
Total Posts: 2262
Here's my thoughts -- if it were OK and did have the possibility of causing structrual problems, all the big and small gutiar manufacturers would leave them short --That would save the labor and possibly material which converts to $$$ They have staffs of engineers to think these things out -- Since as far as I know, most if not all of them have back braces rim to rim and many through the rim --- it must be a value add item/process.
Plus -- its the combination of rim, brace, kerfing that work in unison to make a PLY structure, which lends to the strength. Two cents

Ken

May 09, 07 | 6:23 pm
gawlicd

Total Topics: 12
Total Posts: 44
Maybe they didn't attend a VAVE session. (Just kidding) Value added value engineered. Do away with processes and components that don't add value, just extra cost. I spent a week in that training exercise Ken, saves millions in the auto parts manufacturing industry.
Your leaning me towards thinking I made a mistake using that short brace on the top, but if the tolerances aren't tight enough or cant be controlled on the braces then it is conceivable to allow the protrusion thru the kerfing but I doubt as you said that is the case. I guess DCB has to call the maufacturer or supplier of his kit and perhaps post the answer.
Dave G

May 09, 07 | 6:55 pm
Bill Cory

Total Topics: 158
Total Posts: 3584
Re-examining the photo, it appears to me as if all for of those braces meet or pass the trim line for the body. The largest brace, where it is placed in the photo, might be just a tad short, but it can be moved longitudinally to where it will pass the body trim line.


May 10, 07 | 4:11 am
Ken Cierp

Total Topics: 58
Total Posts: 2262
I never really look at the picture in detail --- I think Bill is correct. It does seem that the back brace location is more or less arbitrary and a matter of esthetics. Books and prints featuring the same style guitars have them in all different configurations and locations. Moving it a bit to get to the rim would have little if any effect on the structure.

Ken

May 10, 07 | 4:34 am
blues creek guitars Authorized Martin Repair Ctr

Total Topics: 52
Total Posts: 1011
Actually from looking at the picture , the bracing layout looks fine. You cannot go by the line as you have to go by what the guitar would be in the mold.
Now as for the through notches , causing weakness the notch when it goes through the side will creat an opening. This allows a force focus point. That is what can cause the failure. you create a fault where force can exert at a given point that can cause a failur , look at a square corner , they often will show a crack that is why seldom are they sharp but usually rounded.
john hall

May 10, 07 | 8:18 pm
dcbaisden

Total Topics: 25
Total Posts: 58
Iam pretty green. i know some things will work out ok.
John is sending me another longer brace. Along with a new back strip.
the back was arched the wrong way and i tried to bend it the opposite direction and "oh darn" the strip split and i was holding two halves. It could have been worse it could have split the rosewood.
Lesson learned.....
thanks Dave

May 11, 07 | 2:09 pm



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