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How important is centerseam ?
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=20029		 Page 1 of 1
Author:  Lars Stahl [ Sun Dec 14, 2008 11:58 am ]
Post subject:  How important is centerseam ?
the question might be stupid, but still ! :D . Can I, as an example, put wooden "diamonds" between the braces of the back instead of the centerceam ? just as on a top. ?



Lars.
Author:  jack [ Sun Dec 14, 2008 12:21 pm ]
Post subject:  Re: How important is centerseam ?
Good question;
Even if it were to be structurally sound ,to use diamonds instead of a continuous center seam, I'm not sure it would be as pleasing to my eye. If it turned out to be structurally suitable, and you think you'd like the look, I'd say try it.
Just my thoughts,
jack
Author:  J Jones [ Sun Dec 14, 2008 12:43 pm ]
Post subject:  Re: How important is centerseam ?
Andy Manson uses something similar

http://www.andymanson.co.uk/photos-group-90.html

look at the photo of the back about 1/2 way down
Author:  Lars Stahl [ Sun Dec 14, 2008 12:44 pm ]
Post subject:  Re: How important is centerseam ?
Quote:
I'm not sure it would be as pleasing to my eye.
AND
Quote:
I think diamonds or back grafts are overkill on a properly joined plate


Are we talking about the same thing ? the only time you SEE it is when you look into the soundhole !! and then with a nicely jointed back you will mostly see the paper logo ! I am talking about the centerseam that goes lengthwise between the braces on the back.
Are you saying its there "mosly" for looks ? not as much as structural purposes. ?

Lars.
Author:  Howard Klepper [ Sun Dec 14, 2008 12:47 pm ]
Post subject:  Re: How important is centerseam ?
What are you calling a "centerseam"?
Author:  Lars Stahl [ Sun Dec 14, 2008 12:54 pm ]
Post subject:  Re: How important is centerseam ?
OK sorry, way lost in a cloud of dust :D I was talking about the BACK GRAFT !!!!! But the question stands ! . - Can I, as an example, put wooden "diamonds" between the braces of the back instead of the BACK GRAFT ? just as on a top. ?
I´ll blame my mistake on that I am from Sweden and got blond hair. guess it goes for men to huh, hahahaha.

Todd. About the unnessesarity of the backgraft,! but then why are almost everyone using it ???

Forgot to mention a thanks to Jones that was exactly what I was thinking. thanks.
Author:  ChuckH [ Sun Dec 14, 2008 1:21 pm ]
Post subject:  Re: How important is centerseam ?
Howdy Lars,
Great question. I can tell you're thinking alot about why and how guitars are made the way they are. You're starting to think outside the box. Or inside the box......lol

Anyway, I think Todd Stock said it best. If you are just gluing the two halves of the back together without a decorative inlay strip then a properly glued joint does not need the Back Joint Reinforcement strip. It would be just like joining the top, there is not a strip used . Although, some builders do glue in a cleat over the glue seam near the bottom. Otherwise, if you do glue in a pretty backstrip it would be wise to go on ahead and use the Back Joint Reinforcement strip. As the name for it implies, it reinforces the back joint. Having no experience in using diamond shaped cleats other than for repairing cracks in violin tops, I see no reason why you could not use them instead of the BJR strip. It would be interesting to find out how far apart you would need to put the diamond cleats. Maybe just two between each brace would be sufficient.
Author:  Alain Moisan [ Sun Dec 14, 2008 1:37 pm ]
Post subject:  Re: How important is centerseam ?
Well, I think 'overkill' is a bit of a strong word. I'd prefer to call it 'pretty darn good insurance against backseam ungluing'. You really know if you didn't do a good job at joining the halfs together when they split a few years down the road. Why risk it? To loose some weight? the 5 or 6 grams that a spruce backgraft weight is insignificant, I think.

Also, the analogy with the top not having a 'topgraft' is not a good one IMHO. A significant amount of the top seem is either not present (the sound hole) or is already reinforced by the fretboard extension, the bridge, the bridge plate and a bunch of cross grain braces. There is only a few 1.5" to 2" sections of the seam that are not reinforced. And as it is already mentioned, some builders (me included) do reinforced those sections of the seem with small diamonds.
Author:  Lars Rasmussen [ Sun Dec 14, 2008 2:12 pm ]
Post subject:  Re: How important is centerseam ?
On some recent guitars ive had the back sink pretty badly round the centerseam between the braces, where its been reinforced. With a .70 back I wont have room to sand them away. Now Ive had to fill with epoxy, which looks pretty bad... Anybody else experienced this?
Author:  Lars Stahl [ Sun Dec 14, 2008 5:14 pm ]
Post subject:  Re: How important is centerseam ?
All good points ! I will dig deeper into this :ugeek: ! The 2 guitars I am making, both or atleast one of them will have X-braced back "Michaels back bracing" ! this is mainly why I askt, I felt its already well braced and that the Back Joint Reinforcement strip was perhaps something I could take out of the equation.

Lars R, Beautiful guitar on the other post !! I misst the show though, "will watch the clip you attached" [:Y:] also give ya a call someday soon so we can have that cup of coffee.

Lars
Author:  Clay S. [ Sun Dec 14, 2008 5:32 pm ]
Post subject:  Re: How important is centerseam ?
I've had that happen on a couple of guitars. Now I let the back seam dry for a week before adding the back graft, and I glue the graft with a non- water base glue. I use epoxy.
Author:  Lars Rasmussen [ Sun Dec 14, 2008 6:42 pm ]
Post subject:  Re: How important is centerseam ?
Thanks Clay. Did that get rid of the problem? I saw a pic of a traugott somehere where he used a brace on top of the reinforcement. Its something Ive been thinking of, to help the curve of the back. Alse it just striked me that this has been a more common problem since I started making the reinforcement strip really thin...
Author:  LuthierSupplier [ Sun Dec 14, 2008 6:43 pm ]
Post subject:  Re: How important is centerseam ?
I own a custom EVD guitar that is joined with no decorative inlaid strip, and it has not centerseam graft installed. The guitar was built in 2001 and it has had no problems in very dry weather. I'd say if you are using a decorative strip in your back, then use a center seam graft, otherwise, do what you feel comfortable. I was thinking of inlaying little keys down the back using a contrasting wood, but have never experimented with them. But I think they would look cool. This is what I'm talking about http://www.rockler.com/product.cfm?page=21284&filter=keys
Good luck!
Author:  Lars Stahl [ Sun Dec 14, 2008 8:03 pm ]
Post subject:  Re: How important is centerseam ?
That might look pretty cool Tracy ! [:Y:]

Lars.
Author:  Lars Stahl [ Sun Dec 14, 2008 10:55 pm ]
Post subject:  Re: How important is centerseam ?
Thanks Todd, Why then are there so few without it ?? is it just tradition thing ? or like "better be safe then sorry" :D

Lars
Author:  Frei [ Mon Dec 15, 2008 1:24 am ]
Post subject:  Re: How important is centerseam ?
Lars, no cutting corners!! [:Y:]
Author:  Fleck [ Mon Dec 15, 2008 1:30 am ]
Post subject:  Re: How important is centerseam ?
It is very dry in Alaska during the winter, we do lots of humidity related crack repairs. I have had moments where a repair would have been easier without the back graft (larrivee), because of uneven back plates at crack above graft and the graft making it difficult to work glue into and level crack.
Mike Fleck
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