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Jointing a 4 piece back, sequence?
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Author:  Colin North [ Wed Aug 09, 2023 1:02 pm ]
Post subject:  Jointing a 4 piece back, sequence?
Got some 2 piece Pernambuco & flame maple sets coming, what's the best way to joint them?
Both woods have distinct flame in them.

I'm thinking joint the left 2 and the right 2, then joint the center seam to try to keep the widths even, but what do you guys think/suggest?

Also thinking to use backstrips or purflings to "define" the joints, which may give some adjustment if things are slightly off - comments?
Author:  banjopicks [ Wed Aug 09, 2023 1:16 pm ]
Post subject:  Re: Jointing a 4 piece back, sequence?
This is the first time I've seen this done and can't wait to see what you do with it. I have no advice to give. This is definitely deserving of Eat Drink
Author:  Ken Nagy [ Wed Aug 09, 2023 1:19 pm ]
Post subject:  Re: Jointing a 4 piece back, sequence?
Colin
I think you have the right idea, join the lefts and the rights.Then join the center. The joints will have to be even, no matter where you put backstraps or purfling in; if you do. They won't cover anything. The way it is now is perfect. Skim and glue. Now if the joining goes horribly wrong, backstraps could be your friend.

It will look very cool.
Author:  Pat Foster [ Wed Aug 09, 2023 1:52 pm ]
Post subject:  Re: Jointing a 4 piece back, sequence?
I think a thin .5mm black strip between the pernambuco and maple would give a nice finished look without drawing too much attention.
Author:  Skarsaune [ Wed Aug 09, 2023 2:03 pm ]
Post subject:  Re: Jointing a 4 piece back, sequence?
I'm looking at a 3 piece back, walnut & maple, and considering some of the same issues.

For yours, I would do lefts, then rights, then join the center.

Mine being all odd angles is going to be a little different, but I'm still thinking one joint at a time.

I do like the idea of a "defining line" between the woods.

Interested to follow your progress.
Author:  DennisK [ Wed Aug 09, 2023 3:45 pm ]
Post subject:  Re: Jointing a 4 piece back, sequence?
The center wedge looks too wide to my eye... How about just using one of those maple pieces and make a smaller guitar? Or one of them plus two 1/2"+ ebony or African blackwood strips to widen it out and provide contrast. Perhaps with some white MOP inlays in the middle of the strips.
Author:  James Orr [ Wed Aug 09, 2023 4:17 pm ]
Post subject:  Re: Jointing a 4 piece back, sequence?
This is a four-piece back. I did it just like you described. Joined the left two and the right two, then glued it up like a normal two-piece book-matched set. With yours, just really focus on symmetry. I’d make myself a few sets of witness lines just to make extra sure.

I also agree that adding some black purfling lines between them would help visually.

Image


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Author:  Colin North [ Wed Aug 09, 2023 4:58 pm ]
Post subject:  Re: Jointing a 4 piece back, sequence?
DennisK wrote:
The center wedge looks too wide to my eye... How about just using one of those maple pieces and make a smaller guitar? Or one of them plus two 1/2"+ ebony or African blackwood strips to widen it out and provide contrast. Perhaps with some white MOP inlays in the middle of the strips.
I agree about the width of the centre, but I would like the figure to be at right angles to the center line. I'm also considering using a different wood for the centre strip, one piece instead of the two.

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Author:  oval soundhole [ Wed Aug 09, 2023 9:12 pm ]
Post subject:  Re: Jointing a 4 piece back, sequence?
How big is the guitar you plan to make? If it isn't a dreadnought I'd personally reduce the taper a bit, wide tapers for multi piece back like the Martin D-35 never quite look right while Spanish guitars, especially guitars by Torres are a masterclass on the subject.

I'd probably use .5mm black lines to separate the maple and pernambuco with a 1mm black central inlay between the two maple pieces. If you can find a wood that compliments the color and pore structure of the pernambuco, Cuban mahogany for example, I think that would be a bit more aesthetically pleasing than plain maple too. Most of my output has 3 or 4 piece backs, done right they're not only more economical but can also be visually stunning while allowing one to use spectacular timbers that otherwise would be tossed aside.
Author:  Clay S. [ Wed Aug 09, 2023 11:06 pm ]
Post subject:  Re: Jointing a 4 piece back, sequence?
I would be inclined to increase the angle of the taper of the maple center pieces and use more of the Pernambuco in the upper bout (adjust the outline so the upper bout outline is at the outside edge of the Pernambuco, which will reduce the width of the maple in the upper bout. I might do a simple black purfle between the Pernambuco and the maple, but nothing between the maple pieces. I would prefer the "look" of a 3 piece back even if using 4 pieces.
Author:  TRein [ Thu Aug 10, 2023 1:53 pm ]
Post subject:  Re: Jointing a 4 piece back, sequence?
You asked a specific question about joining the woods in the pic so my comment is a bit off base. If I were building with these woods I'd get in touch with the person who supplied the pernambuco in the first place to see if more pernambuco pieces like the ones in the pic were available.
Author:  rlrhett [ Fri Aug 11, 2023 3:56 pm ]
Post subject:  Re: Jointing a 4 piece back, sequence?
I think contrasting woods AND a back strap (AND purfling?) would be a bit too Rococo for my tastes, but maybe that’s what you’re looking for.

I’ve done a few four piece backs. Perfect when you have a pretty board thick enough to get sides AND back out of, but not wide enough for backs. Left and right first, then two halves. Why? No idea. Just seemed right.


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Author:  RNRoberts [ Sat Aug 12, 2023 10:42 am ]
Post subject:  Re: Jointing a 4 piece back, sequence?
You might want to hit the boards with a quick wash of shellac before glue up as well to see if you are happy with the effect of the figure as well as any "two tone Tommy" effect that the runout in your wood might create.
This is a 4 piece on an 1840 Martin reproduction prototype. For some reason the 2 tone effect of the honduran mahogany's runout has bothered me for a decade and a half, and was not noticeable until finish was applied.

Sorry can't seem to get the jpeg to attach...
Author:  Clay S. [ Sat Aug 12, 2023 8:54 pm ]
Post subject:  Re: Jointing a 4 piece back, sequence?
I made a quick sketch of the idea I was trying to convey above. It would allow you to use more of the Pernambuco. I would probably use a dark piece of straight grained EIR for the center section, but that is a personal choice.
Author:  Colin North [ Sun Aug 13, 2023 1:05 am ]
Post subject:  Re: Jointing a 4 piece back, sequence?
Clay S. wrote:
I made a quick sketch of the idea I was trying to convey above. It would allow you to use more of the Pernambuco. I would probably use a dark piece of straight grained EIR for the center section, but that is a personal choice.

Pretty much what I was thinking for the central wedge.
I did consider EIR, but now I am thinking Wenge which seems to have shrinkage figures closer to the Pernambuco, less potential stress on the joints.
I am also considering using the Pernambuco ribs for the outer back wings (same width) and Wenge ribs which would give me 4 complete sets + lots of rosettes and headplates.
I do already have 3 Wenge sets.
Author:  Clay S. [ Sun Aug 13, 2023 7:48 am ]
Post subject:  Re: Jointing a 4 piece back, sequence?
For the D-35 guitars I believe Martin was using up sets originally cut for the smaller guitars when Dreadnoughts were all the rage. For the center piece I think they would cut a back half at an angle to get two "wedges" and not waste any material - they were a pretty frugal bunch, IIRC.
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