Thoughts on a 4pc back

[CavalierKingCharles]

I'm working on the back for my next build. Because of the location of the two seams (see pic) I was going to use a back strip.
I don't mind the 4 pc if the "ears" fall out past the waist but as you can see I would need the back strip to make that happen.
Without the strip the seams are just inside the waist. Honestly, I would rather not use the back strip. If I do I'm toying idea below.

I would appreciate any and all thoughts, comments etc.

Scott

[tippie53]

My father was a big influence on my wood working. he always told me that if you can't hide a joint , show it off. I have seen many multi joined backs. It is a design feature you can exploit

[CavalierKingCharles]

Thanks John,

I think the joint blends together well. I'm worried about the integrity because it's so close to the waist

Scott

[tippie53]

you should be fine you have the braces that will also work . I have seen many multi joint backs. The glue joint should be stronger than the wood.

[CavalierKingCharles]

Thanks John, I'm going forward with it

[Poor Man's Guitars]

you should be fine you have the braces that will also work . I have seen many multi joint backs. The glue joint should be stronger than the wood.

Hi John, I'm kind of new at this. How do you make a glue joint stronger than the wood, and how do you know if you've successfully accomplished that? Dan.

[tippie53]

It is the glue, which in most cases, is stronger than the wood. On a clean joint where the faces mate well the glue will hold the wood better than the wood cells themselves. If you glue up a test joint, allow the glue to cure for 24 to 48 hrs then attempt to break the joint. You should see that wood fibers are still affixed to the glue but the wood has failed.

[cooltouch]

My experiences match John's comments. All I might add is that some woods can be a bit oily and with these woods, sometimes it is a good idea to remove as much of the oiliness as possible from the joint area. You don't mention the type of wood that this 4-piece back is made from, so it may not be a problem for you.

And just to add to this: a few years ago, Luthiers Mercantile International had a small quantity of Madagascar rosewood back and sides sets available. I bought three and have added them to my stash, awaiting a few special occasion builds. They look a lot like Brazilian rosewood but the trees don't get very big, so the back sets are four-piece. LMI did a very good job of matching the two pieces for each back piece such that it is very difficult to even see the glue line. I have every confidence in the integrity of their glue job and plan to use these back sets as if they were regular two-piece backs.