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Kencierp's methods do not address the problem originally posted about. The mismatch of curves exists as long as there is a taper. Even if a truly "flat as a board" back is used w/ no radius.

"its about getting the linings to follow the contour without extreme force and "clampage" while having them end up the same width all along the perimeter."
Can't argue with that part.

Since I've actually made linings as described --- I am going with it works fine.

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Ken Cierp

http://www.kennethmichaelguitars.com/

I'm not trying to offend. I think we are just talking past one another.

Re-reading the posts I think I see the confusion. Dons proposal to skew the linings in a bender will improve the fit of the bend at the waist against the side/mold. It will not improve the fit against the dished work board when sanding to receive the back.. Kencierp's will improve the fit against the dish but not improve the fit against the side/mold. I think most builders don't notice the mismatched curves between flexible linings and flexible sides on the back but it does become an issue with stiffer, and especially taller linings and a large taper.

When you are sanding the waist of a completed box, with a curved block that spans the whole side, it must be kept square w/ the top. Keeping it square to the back of a highly tapered body will sand only at the edges.

David I am sorry I can't make it clear, but I believe you may be missing something -- cutting the pattern as described eliminates the issue all together it follows the sides and glues together perfectly (off course there is the tiny radius changes at each layer). Just take a couple of bent sides (like two or three treble halves) and put them inside each other like spoons, they fit snug with a tiny excess at each end. The contour of the back edges will align perfectly and so will the top edges.

I for one have a pretty good grip on how the top and back of a the rim gets contoured


http://kennethmichaelguitars.com/contourfixt.html

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Ken Cierp

http://www.kennethmichaelguitars.com/

If you take the nested stack of sides and try and twist the top one so each end is offset 3/8" of an inch (simulating Dons 3/4" taper), the waist curves will not fit together. Unless, of course, you place your pre-contoured lining strips skewed in our bender.

It's the same reason you can't tilt a parallel sided outside mold so it's parallel with the back edge of a side on a tapered guitar box. The curves no longer match and the box and mold are too stiff to accommodate the mismatch.

The method you use obviously works because you use it. I believe, either you skew your laminations relative to the top when you bend or glue them together or flexibility in the system accommodates the miss match

Sorry I see your point now -- a good one. But yes of course you put them in the bender along the same slant as the back edge of a rim half. On the other hand some veneers may be flexible enough to be a shaped as they are glued and clamped -- never tried that approach.

I am not sure where you were going with the nested side analogy -- if you were to take and cut off segments of the rim nest at a width of 5/8" following the back contour edge they would work perfectly as a lining. As a matter of fact you could continue doing that and end up with enough layers to make a bunch of linings.

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Ken Cierp

http://www.kennethmichaelguitars.com/

Any intentional twist to the laminated linings will degrade the fit between the lining and the side that it will be ultimately glued to. Not a good thing in my book. My approach like a few others is to make a wider lamination that can be fit to fit the arch of the back on both the mating edge and the opposite edge in order to keep the strip a similar width as it circumscribes the body. I shape this edge free-hand on a belt sander before the strip is glued to the side.

Sorry for the difficulty. It reminds me how cumbersome typed words can be when talking about guitar geometry.

And just one more reminder (mostly to myself for when I try it) it will take a right and left hand version to work.

I hope you have a relaxing evening Ken.

Screw it. Going with tentallones.

Kidding. I'll report back after I have time to tinker with this in real life instead of inside my noggin.

Talk about Laughing out loud. Don I'll still be giggling tomorrow.

Glad to do it, David!

And now for something completely different:

http://youtu.be/BZwuTo7zKM8

This always cracks me up.

OK, reboot. I still have not had time to cut any stock and experiment, but I did look at something this morning, and it has sparked a different idea. Feedback is encouraged.

First, understand that I am working with radius dishes (25' for the top, 15' for the back) and outside molds. The two guitars I am in the middle of right now are basically small jumbo-ish things; dreads with a tighter waist, like an OM. Other than the tighter waist, all dimensions are what you would see in dread.

I have two sets of rims that have the blocks glued in and have been profiled with the radius dishes. As should be obvious from the context of this discussion, I have not yet glued in any linings.

I put one set of rims (inside its mold) on its back on my pretty flat workbench. I saw something interesting:

The highest points on the back of the rim are the waist curves. No surprise there. The interesting part is that the rims sat at rest on a tripod formed by the two waist bends and the tailblock. Between the tailblock and each side of the waist, there was a very subtle gap of air between the rims and the workbench, maybe 1/16" at the widest part of the lower bout. Then, from the waist to the headblock, there was a significantly different plane, with an air gap that gets sharply larger from the waist towards the headblock, where it is a little over 1/4" wide. When considered on its own, the area from the waist to the headblock forms its own plane that is significantly different from the plane for the area from the waist to the tailblock. But each one considered separately sure looks like the sort of plane where simple straight linings, once bent, would fit pretty well without excessive trimming or sanding.

So I said to myself: "Self, why am I so fixated on having a single piece of lining for each side edge; why not have two pieces of lining for each side edge, upper bout and lower bout, joined by a decent butt joint at the waist?"

Blew my mind. Blooosh!

I mean, I am not shy about showing glue joints on the outside of my guitars. I use a scarf joint for the headstock, and I stack my heels. Every top has a butt joint prominently displayed, and every back without a center strip shows the same thing. Why should I be uptight about having a well fitted glue joint in the freaking lining on the inside of the guitar? Plus it might not even be all that visible, after cleaning it up and sanding it. My hide glue joints disappear pretty well.

So then I started thinking about how to make such linings. Maybe I can have some of the waste at the waist, so that I can fit the butt joint really well, sort of like binding strips at the tail. I could use the same pieces on the tops as I use on the backs, fitting them the same way. The angles would be different, but the fitting procedure would be the same. I could actually just make two types of linings, upper bout and lower bout, then cut a roundover (or bevel) on whichever inside show edge I need to in order to make that piece a lefty or a righty. The laminating procedure would be way simpler than with a full side at a time. Simpler all the way around.

The worry that made me start this thread? The twist in the lining due to the taper? I think I could deal with that by simply sanding the inside edge of the linings. Apply some Stick-It to the inside of the guitar side, and slide the lining strip from top to back (not head to tail). That should wipe out any funky twists that cause a misfit.

The fact that I like working with hide glue also makes this an attractive choice. The more you try to do at once, the harder it is to get it all done before the glue gels. If I could glue the upper bout lining separate from the lower bout lining, that's way less stressful.

So, I started trying to poke holes in this idea. Does it lessen the structural benefits? I don't think so. It is a butt joint. No gap. Would it make a difference to the tone? Heck, people disagree on whether continuous linings provide better tone than kerfed linings. I don't see how a single butt joint is going to compromise the tonal benefits. Does it look bad? Well, if it is fitted properly, I don't think so. At very worst, there would be a single kerf (this is if no fitting is attempted at all). I think I can fit this butt joint to pretty well disappear, or at least look tastefully done. Plus this is the inside of the guitar. I am not one of those builders who is fixated on beauty inside the box. No offense to those who are. Just not my thing. I like it to be clean, but I have my limits.

OK, I have rambled and spouted long enough. Any feedback? Does anybody else do it this way?

As always, your comments (whatever they might be) are appreciated. These are all just ideas. Thanks.

I went over my method (a long time ago at this point!) in my tutorial on double sides and linings which is here:

viewtopic.php?f=10117&t=21455&hilit=double+sides+solid+linings

It is similar to what I have seen a few other people suggest and it works great- No distortion in the linings, no torquing to fit them etc... You do waste a little material but it isn't much. I have been using it for years and it is super quick at this point.

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Burton
http://www.legeytinstruments.com
Brookline, MA.

Your guitars are true works of art, Burton! I think I would be hesitant to go that direction, just based on your first identified "con": The investment of time. I am sure it is worth it, but boy, it sure looks like a lot of work.

Don, I can see a butt joint with a keyway cut across it, with a spline glued in. Any advise I give should be taken with the disclaimer that I'm a cabinet maker, and only a rank amateur guitar builder.

Alex

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"Indecision is the key to flexibility" .... Bumper sticker

It felt like work the first few times. not so much anymore, it goes quick now- If I could imagine a way to mate perfectly with the sides doing it in a simpler method I would do it!

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Burton
http://www.legeytinstruments.com
Brookline, MA.

Alex--

That feels like a lot of structural to-do for joining two pieces of wood that are meant to replace deeply kerfed linings, bearing 1/16" kerfs every 1/4" or so. I really don't see the need for all that. Keep in mind that both pieces of lining will be glued to the sides and either the top or the back. Nuthin's goin' anywhere! If traditional kerfed linings hold the guitar together OK (and they do), then we need not worry about joining these two pieces of wood in such a hefty manner. Same disclaimer, though: I do this for fun, not profit.

It's just the cabinet builder in me talking, Don! Once the back is glued to the lining, it should be tough enough. I would suggest not stressing the joint until the back is on, though. Even HHG is no match for an end grain butt joint, with no mechanical fastener!
I've glued up a set of linings for #2, and this topic has been really good, and given me more to think about, and some possible changes before I glue them in! Thanks!

Alex

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"Indecision is the key to flexibility" .... Bumper sticker

Don, since you want more feedback I'll try to be as constructive as I can. I think you are overthinking a fairly straight forward
procedure but that's down to different strokes for different folks. That's fine by me, I'm open to new ideas always. I've built a
few guitars by now and most of my guitar related knowledge except the Gore, Gilet books has been garnered from my reading
right here on this forum. Right now my interest lies with building a very responsive fingerstyle steel string. All construction
procedures are geared toward the sound performance of the guitar. Ok, back to your feedback! Could you do me a favor and
run a little experiment for me, since you seem already set up to do so.
Take your 15' radius dish. turn it face up on your bench. Lay the 1/2 mold on top roughly where the assembled sides will go.
Now take a single piece of lam, be it .060 or .070 inch or whatever you plan to use, the thinner the better for the sake of this
experiment as you won't need to prebend with heat, clamp it in position on the mold while pushing it down against the dish.
I think you'll find that it goes fairly easily. This is all the manipulation that's required to make them fit. Once glued up they hold
that shape perfectly. Now, if you want to consider that little twist or spring like effect as I think you put it, (I don't, my guitars are
SJ ish like yours with similar taper and it causes me no problems) draw a line on the mold on the upper side of the piece of laminate.
This will give you an indication of where the laminates will need to be coaxed up or down. Now just move the line at the head up by
the amount of taper, redraw the line and glue your linings at that that line with the twist built in. You could attach a few temporary registration blocks along the line to make glue up a snap. Hope this is helpful. For what it's worth, I don't like the butt join at the
waist idea. To me it negates the idea of using laminated linings in the first place and IMO simply isn't necessary.
Ken

Here's Colin's method of side profiling.
http://luthiersforum.com/forum/viewtopi ... e+template

It works perfectly and produced templates like this for an OM with a cutaway and a wedge body.


I used the profiles to make profiled laminated linings and glued them up 'on the skew' which also worked well, and gave me this.


Sorry about the size of the photos.

Dave, I'm curious how you, "glued them up on the skew". skewed against your bender form?, laminated in place on the sides in the mold? something else?

Ken--

I understand what you are saying about the twist not being a big deal; I really do. A few things: I will be working with thicker material (0.085"), so it is a little less forgiving than the thinner stock. Still flexible, for sure, but not without heat bending. I have tinkered a bit with the idea of using the same mold as I use for the guitar for gluing up the linings, and I had already thought about skewing the glue line, as you have suggested. So, we are mostly on the same page. I think you think we aren't, but we really are. Regarding the experiment you suggest, I have already done similar tinkering, so you don't need to worry about whether I am familiar with some of this "on the ground," so to speak. But some of that tinkering is what led me to ask the question in the first place. The twist is there. Whether it matters much is a different question, and one you have definitely answered. You find it to not matter. That's good news!

We do part ways, though, on the comment about the butt joint negating the idea of laminated linings. Negated? Really? That feels like hyperbole to me. I mean, this stuff takes the place of kerfed lining, which holds guitars together just fine. Is a single cut, that is then closed up with a butt glue joint, really going to do away with all of the benefits of laminated linings? I'm having trouble with that idea. This idea of using two pieces of lining instead of one long one is really more about making the whole job easier, but not losing anything substantial. I'm having trouble seeing the loss of effectiveness that you see.

You could think of tentallones as a bunch of really poorly fitting butt joints. Some of those old guitars seem pretty good.

" I'm having trouble seeing the loss of effectiveness that you see."

Never said anything about effectiveness. Guitar building is mostly a woodworking venture and as such I like to employ sound
woodworking techniques and KISS methods whenever possible, that's all. I guess we see things differently. I can live with
that...... And David, those tentallones, you can't get any more KISS than that!
Ken