BYO: The Pliage

Craig Bumgarner

BYO: (Build Your Own): Forming a pliage has had me buffaloed. I avoided it last time by doming the top with a sanding bowl, but that doesn't get the dome in the right place, under the bridge. This time, I was determined to make a true pliage. Pliage means fold and is clearly shown in the Francois Charle plans as a 6 degree bend (fold) in the top, laterally immediately below the bridge.

I knew of two methods suggested for the pliage. One is to bend it over a hot edge or pipe. The other, as shown in Collins' book, is to use a forming jig consisting of a shaped box and heat lamp. I didn't want to go to the trouble of yet another jig, so I tried the hot pipe method. Didn't have much luck. Despite preheating, good hot pipe and lots of moisture, all I really accomplished was a 3 degree bend and a fair amount of warping of the lower part. Surely this is the fault of my technique, but I'm a slow learner and I didn't want to learn at the expense of a nice top. It is amazing how resilient a 2mm piece of spruce can be.

So I changed gears. I dampened and heated the pliage area well by slapping it on the top of my wood stove (sizzle, sizzle, an electric steam iron would probably work too). Quickly transferred the top to the workbench, exterior face down and clamped a stiff piece of wood at the pliage line. Before tightening the clamps, I slipped another piece of wood under the lower portion. Tightened the clamps. I was going for a sharp pliage line, so I clamped all the way to the bench. If you want a more gradual line, round the edge of the pliage board and maybe don't clamp all the way to the bench. I ran a heat gun (hair dryer might work) over the pliage ara for about 5 minutes to cook it and let it cool to room temp. Voila

There is a fair amount of bounce back when released. I used roughly 15 degrees in the clamp up to get 6 degrees upon release. Surely this will vary with the rigidity and thickness of your particular top and the subtleties of your technique. So saying exactly what degree to set the clamp up is not possible. The good news is adjustments are easy. If you don't get enough angle, just crank the jig up and try again. I over-bent the first piece and it was fairly simple to heat it up with the heat gun and straighten it a little.

I like this system for several reasons. 1) very simple, no permanent jigs to construct or store. 2) the steady controlled pressure of tightening clamps is a lot less scary then bending a $60 top by hand over a pipe. It is probably my bad technique, but the amount of pressure I was applying was substantial and I was on the verge of having to throw my weight into it, something that I could neither control well or maintain long enough for the wood to set. 3) It worked well; really well. Here is a sketch of the clamp set up.

CB

bill raymond

Yes, that's a fine way to bend the pliage. You might want to have a look at Al Dodson's old posts on bending the pliage in the MIMF.com archives--you have to join to access the archives, but it's free--to see his method using aluminum angle and a torch. Also, there are some photos of a bend done similar to the way you did it on Benoit de Bretagne's forum (though it's all in French).

Forum member Peter Davies shared with me an email he received from Francois Charle a couple years ago, wherein Charle states that the tops were lightly scored on the underside with a cutter, then bent over a hot pipe. I've done the same successfully, scoring about 0.5mm deep, then bending over my side-bending iron, using just enough water to prevent scorching and drying out the spruce.

I've never used Michael's method, but the form he uses doesn't seem to put a historically accurate curvature to the top, in my opinion--I could be wrong, though.

frater

bill raymond wrote:

the tops were lightly scored on the underside with a cutter, then bent over a hot pipe.

I know a luthier here in Italy who does exactly the same. Guess they used commonly this technique in building "Italian" mandolins, so it would make perfectly sense Maccaferri was acquainted with it.

Craig Bumgarner

Bill & Frater,

Thanks for your input. Sounds like there is more than one way to skin a pliage (to mix metaphors). I've heard of the "scoring" method. It kind of bothers me to cut across the grain at such a critical part of the instrument, but hey, who am I to argue with success. I like the clamp on table method because it seems simple, accurate and reliable.

Craig

frater

Whatever method they used at Selmer's, it had to be a reliable one as I don't see piles of broken tops in any of the pics in R.F. Charle's book!

Craig Bumgarner

frater wrote:

Whatever method they used at Selmer's, it had to be a reliable one as I don't see piles of broken tops in any of the pics in R.F. Charle's book!

Well, you certainly have a good point there.

It occurs to me now that maybe by scoring, the inside portion of the bend compresses more compactly and the wood fibers on the outside therefore don't have to stretch as far, less chance of a failure in tension.

Craig

frater

You probably already know this link, but just in case you don't:

http://www.pluckandsqueeze.com/Mac%20pr ... roject.htm

Craig Bumgarner

Yeah, that is a very nice site, I have seen it before. Inspirational, a beautiful job. There is a page fully dedicated to the pliage which I had not seen before, thanks.

http://www.pluckandsqueeze.com/Mac%202/Pliage%201.htm

He had better luck than I with the hot pipe method. Maybe because he scored the line first. From the looks of the scorching, it looks like I might not have been getting the bend area hot enough.

Peter's site, which I gather was authored some time ago, speaks of the mysteries of the pliage, but at this point, I feel the pliage is pretty well understood. As Peter mentions lists there are a number of methods, all of which seem to work to some degree. So pick you poison and start folding.

BTW, what is Peter using on the seams in the top joining pictures. Magnets?

My recent project with pliage is strung up in the white and playing. The pliage turned out well and really puts the dome in the right place. Still getting her tuned up, but sounds pretty good. Of course all parents feel that way about their offspring . I underestimated the neck angle, so my bridge height and break angle turned out less than I wanted. Probably not taking full advantage of the pliage. Just an excuse to build another :P

Regards neck angle, I belatedly found that the Francois Charle plans show the strings with 5mm (!!) setup at the #12 fret. Wow! If you are like me and prefer 2.8mm, that requires shortening the bridge 4.4mm. Big change. I wonder if these guitars were really set up at 5mm. The plans seem otherwise very accurate, so I suppose so. I made some other miscalculations, so in the end I needed to shorten my bridge for the desired 18mm to 12mm. Sounds okay, but pretty wimpy looking. I should have thought this through more.

Craig

frater

To be frank, it has always amazed me how few hand made Selmer replicas (claiming to be the exact reproduction of an authentic Selmer...) have a real pliage. CSL and Ibanez Mac10s had huge ones and were made in an industrial environment... maybe they weren't that good but at least they knew that, according to Maccaferri, you're not doing it right without it...

Craig Bumgarner

frater wrote:

To be frank, it has always amazed me how few hand made Selmer replicas (claiming to be the exact reproduction of an authentic Selmer...) have a real pliage.

Yeah, I've wondered about that too.

I edited my previous post some after I found Peter Davies' page on pliage.

I like the way he scores and applies the bend only the width of the bridge and mustaches. This gives a more domed shape or at least a prettier shape. I notice when I glued the top to the sides, the other portion of the bend pretty much flattened out anyway. Peter's method anticipates this.

Craig

bill raymond

Pete and I had much discussion about the pliage over the years before there was much information available. Since the bend must flatten out at the very edge (being glued to sides that are straight, unlike those made by a sanding dish) it doesn't make much sense (I thought) to continue the bend all the way to the edges. However, when I visited Francois Charle's shop a couple years back, he assured me the tops were bent all the way across and even showed me an old Selmer he had in for repairs.

Nobody else who has repaired a lot of Selmers--and I've only had the occasion to examine that one in Charle's shop--mentions anything about scoring the top, but Francois did say that in his email, and confirmed it to me orally. So there you have it. I think scoring makes the bend go a bit easier, but I've never been able to independently verify that Maccaferri or the Selmer artisans ever did it, or if they did that they did it consistently and throughout the period that the guitars were made. I've suspected that possibly the early models had a scoring which was abandoned later, or that maybe Maccaferri scored his hand-built prototypes but didn't continue that technique in production??