Official Luthiers Forum!

I realise I am probably being a bit simple minded, but those of you who laminate your linings, how do you deal with the radius of the back? I mean, if you just bend the linings to the contour of the sides wont it run out when it gets to the change in height of the sides created by radiusing?

Sorry if I haven't worded that clearly but hopefully you understand what I am asking!

I bend my laminates in the side bender then glue then up in the rim so when dry they match the contour exactly...the first and second laminate are trimmed then put in the rim with the second glued to the first...the first laminate is not glued to the rim at this point , both clamped tightly, then the 3rd laminate is glued to the other two making the final lining assembly , then the lining assembly is clamped tightly to the rim positioning the lining just proud of the top, final sanding is in the radius dish to shape...

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MK5acoustics.com

I've never had a problem bringing them in flush with the back. Now cutting a consistent rabbet with the dips and turns of the back is more of a concern to me.

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Joe Beaver
Maker of Sawdust

Flounder, I kept encountering the same problem.

I use a bunch of small G clamps with cork glued to both faces of the clamp. On average about one clamp ever inch. However there is nomally a little more depth (of the linnig) at the waist.

Like Jeff, I kinda bend them in and don't expect them to be the same height around the rim either. I do a rough shaping of the back radius before I install the linings and start clamping at the waist. My lamination are thing and are able to conform to the curve well enough. There may be small sections where the surfaces between laminates are not totally mated because of a tiny (for lack of a better word) kink. It really doesn't matter once it is all glued up. A small void in the middle of the linings does not compromise its strength; Think of reverse kerfed linings, they are riddled with voids.

I used to glue the laminates in and level the top leaving the inside surface of the laminates unkempt. On my current project (an uke), I put tape inside the rim, glued the laminates together clamped in the rim then removed them. I cleaned up both faces, removed the tape and glued them in. An extra step, but a little cleaner looking. I was thinking about doing the same thing with wider laminates and scribing the back radius and cleaning them up to keep a constant height. Honestly, I'm not sure it is worth the effort as no one would ever look in the soundhole and notice the differing height unless they were tipped off to it.

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

Thanks for the feedback chaps. It seems I am over thinking things and should just get stuck in and have a go, and as Bryan says, if it ends up with varying heights then no-one will actually know!

I laminate two .095" layers. First I profile the sides. Next I glue in side supports that are the same thickness as one of my layers. Then I glue in the first layer between the side supports. After that the second layer is glued over the first layer and the ends of the side supports. Then I carve the linings in place and sand them smooth. I've made some little clamps to apply more pressure and eliminate the voids. First I use hot-rodded clothespins to hold the layer in place then I use the clamps to replace some of the clothespins where I need more pressure. The wing nuts can be tightened with a 3/4" socket.

Another way that Burton LeGeyt uses is to laminate some wide boards and then cut out strips that follow his side profile. Then he can shape them before he installs them. Maybe he'll chime in.

Here are some pics of what I do.

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Ken Franklin
clumsy yet persistent
https://www.kenfranklinukulele.com

Doesn't have to be laminated linings to encounter this problem. The worst model I've come across for this is the Stauffer. It's obviously not built with a radius dish and the dip up to the heel (from the waist) is severe. You end up with virtually no lining.
The method that I use is to cut a kerf at or near to the waist area. The lining is cut top to bottom (not in it's depth like a normal kerf) but not quite all the way through. I leave 4 or 5 mm's. It's enough to be able to physically bend and point the lining in the right direction. If you cut all the way through you end up with two pieces and an ugly looking joint. This way I end up with a kerf which is wedge shaped after the lining is glued. I cut a suitable wedge shaped piece from the same lining material to fill it. It looks fine and more importantly, intentional. I refer to it as a lining dart.

Thanks Ken and Michael for your input too! Michael, do you have a photo of your dart?

This should give you the idea. It's very delicate after cutting the slot, easy to break it. Normally I would just use a wedge of the same material. In fact it's pretty difficult to see it once the box is closed.

I use a method similar to Burton's. I laminate mine from material that is about the same width as my sides then trace the radius and cut the individual linings to that radius.

I just let it be a little shallower near the heel and butt; as long as it's > 1/4" tall or so I don't sweat it. I like the idea of a little kerf at the waist though... I might have to do that from now on.

I've used oak linings about 0.06" thick, and they were flexible enough to conform to the back radius. The downside is it takes between 4 and 6 lining strips, depending on the purfling.
I glue them in one at a time, each just a bit proud of the previous one. I use a radius sanding stick ala Cumpiano to sand the back radius into the sides & linings.

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A man hears what he wants to hear, and disreguards the rest. Paul Simon

I love this place! That Kerf and dart at the waist is a great idea. I don't really need a huge amount of adjustment at the waist, I'm sure I could just saw a kerf and let it close up as I clam them in. It won't look quite as fancy but I'm okay with that.

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

Laminate up your thin pieces a bit taller than you want finished. Clamp them into the sides, mark them along the back edge
and plane off the height on the opposing, unplaned areas of the linings so they finish at a consistent height.

Lots of good options! I made a photo group of how I do mine which is archived here:

viewtopic.php?f=10117&t=21455

I still do it the same way, it has gotten very quick for me. Lately I have been using Paulownia wood instead of mahogany, mostly for the light weight.

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