William Cumpiano's
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No time to write
new stuff...too many letters to answer! © William R. Cumpiano 2000, All Rights Reserved
No, I'm afraid I don't have what you ask. But I'm even more convinced than ever
that this scheme amounts to Classic Bracing 2000. There are dozens of approaches: Alan
Chapman uses an exceedingly fine soundboard with a very fine grid of criss-crossing braces
(with thin strips of graphite glued to their tops) that travel all the way to the sides
and up to the upper transversal (he dispenses with the soundhole in the usual location,
and places two smaller "ports" above the upper transversal. Tom Bazzolo places a
three-finger tic-tac-toe just under the bridge. Both get truly outstanding results. All
thin the lattice array as they approach the sides. You'll have to go it on your own! BOOK AND WEBSITE INFO MISMATCH You're so right. The book was written in 1985, before the hardware joint was even
a gleam in my eye. Some extrapolation is necesary. I'm working on a new set of headblock
and joint three-view diagrams which I will upload to my webpage soon. But your solution
should hold. The top bolt is just for alignment, since the neck is actually pushing INTO
the headblock up there. The top bolt just has to be a little snug. The bottom bolt is
carrying the load because the tip of the heel is pulling AWAY from the body. You shouldn't
have a problem. You're all right if the neck shaft and the rim of the soundboard exist on the same level plane. The center of the soundboard in the region of the lower transversal face brace is obviously going to swell a bit because of the arch in the brace. But what the method calls for is that the neck and the rim be flat. Some provision, however, is going to have to be made on the workboard to account for the swelling of the center of the soundboard--you might break something when you squeeze everything down to the workboard, i.e. when you rope on the back or clamp the sides down. Now in practical terms you can either raise the neck and soundboard rim from the workboard with a cork/paper shim (like the book shows), allowing the center of the soundboard to clear or "float" above the workboard--or you can dispense with the shim altogether by actually hollowing out the workboard in the swelling region only, allowing the neck shaft and rim to lay flat directly against the workboard. I chose the shim method for the beginner because it's easier to use a razor and a scissor to make a cork/paper shim than to laboriously and appropriately hollow out the workboard (I use a router and a scraper blade). In the end, however, the hollowed out workboard is superior, but only if you're going to make not just one more guitar, but several. Given all of this, as much as you try to insure that the neck shaft and the rim of
the guitar end up on the same plane after the back is glued on--things happen: the
workboard flexes when you rope the back on, things shift minutely. Some builders I know
use aluminum workboards or bolt their workboards on top of a massive center beam to avoid
any sagging whatsoever. It works for them. The simplest solution for beginners, I believe
is to HOW ABOUT FOUR PIECE BACKS?
IS THE NEW NECK BOLT
SYSTEM PUT TOGETHER DRY? My new bolt system can hold the neck on entirely without glue, which I have done to string up the unfinished guitar to make tonal adjustments and final evaluation before finishing. But I glue down the fingrboard end at the very end of the process, after the finish is applied and polished, just to insure against any possibility of future rattles. DO YOU RECOMMEND USING THE NEW SYSTEM ON CLASSICAL GUITARS AS WELL? The smaller soundhole could make access to the bolts more of a problem, but there
is no good reason not to. But there is no reason to, either: the low tension and
unlikelihood of the need for a future neck reset makes it unnecessary to change the far
simpler, traditional one-piece system. Think of it: the traditional joint consists of two
slots. Period. Okay, polishing the finish in the heel-body crevices are a chore. So take
your pick. 12-STRING STRUCTURE DESIGN UPGRADE Just a bridge patch that is about 15% thicker and about a 1/4" wider below
the bridge and a top that is about 15% thicker. Everything else the same, except for the
dimensional fingerboard and bridge requirements for the additional strings. The
traditional problem with 12 strings is that people go nuts beefing up the structure all
over the guitar. Most 12 string sets are not twice the tension of 6-string sets, because
they usually consists of considerably lighter gauge components, and most people drop the
tuning by half a step. Yes, there is always a chance that someone will put on heavy
strings and play it up to pitch. They could also drop it on a concrete sidewalk. You could
respond to those fears by beefing up the entire structure for no flex whatsoever, but
there is a price to pay in the instrument's freedom of response. TIE BLOCK BRIDGES ON STEEL STRING GUITARS The rotational stresses on the bridge are actually primarily determined by the neck angle (and the consequential saddle height), and not as much on the bridge design. There are no unusual tonal or structural problems with a tieblock bridge to be expected on a steel-string guitar. For my money, the main problem with a tie-block bridge is that it makes setting up and replacing steel strings a bloody nuisance.
PROS AND CONS: HEADBLOCK VEE JOINT Due to the strength of modern glues, a well- executed scarf joint is perfectly adequate for the stresses imposed across the steel-string headstock. From a cabinetmaking point of view, a v-joint was technically superior, particularly in the olden days when the glues were less reliable. If you use a v-joint people will shower you with praises for your skill and those in the know will guess that you don't have to make a living at making guitars. I have a Delta unisaw with the Incra fence system, so I have 1/1000 inch adjustability, and joints like that are pretty routine for me. Terrific. Then the v-joint is appropriate for your situation.
CORAL NUTS AND SADDLES? Its remarkable how often I get asked to predict the tonal result of using whatever unusual nut material the questioner can come up with. Folks accord to me powers of prediction beyond that of ordinary mortals. I should be grateful for that consideration, I guess. Well, to tell you the truth, I've never held a piece of black coral in my hand (or even heard of it before) and would only comment that generally, the nut (and saddle) can act as a high-pass filter in very subtle ways, according to their density. Softer materials such as wood will attenuate some of the high frequencies, and harder materials will not, according to a range of densities. Harder materials like brass attenuate few high frequencies, giving a steel-string guitar (what to my taste is) an annoying tonal shine. Where black coral lies on the continuum has to be left for a wealthy experimenter to find out...and then tell me about it.
AVAILABILITY OF CARBON FIBER TOPS Me and my partner in that endeavor, graphite tech Rich Janes, have often talked about it, but just obtaining a sufficient number of tops for my production alone is such a chore that we've put off the plan for the time being. They have to be laid up by hand in the Orient, you know. The answer is yes, we plan to make them available, but when and for how much...you'll just have to stayed tuned. My most recent prototype yielded magnificent results: a thinline acoustic with a 1/32"-thick graphite top with NO BRACES. The top was so compliant that it yielded some very rich lows, the kind you wouldn't expect from a guitar with 1 1/2" sides. And startlingly loud and with great sustain. It's been a month and so far, the top has settled into a faint swelling behind the bridge, but nothing to worry about. Yet. I'll keep watching it and let you know.
Now in practical terms you can either raise the neck and soundboard rim from the workboard with a cork/paper shim (like the book shows), allowing the center of the soundboard to clear or "float" above the workboard--or you can dispense with the shim altogether by actually hollowing out the workboard in the swelling region only, allowing the neck shaft and rim to lay flat directly against the workboard. I chose the shim method for the beginner because it's easier to use a razor and a scissor to make a cork/paper shim than to laboriously and appropriately hollow out the workboard (I use a router and a scraper blade). In the end, however, the hollowed out workboard is superior, but only if you're going to make not just one more guitar, but several.
P.S. Glad email doesn't show tear stains . Tut, tut, tut! You failed to heed Uncle Bill's and Uncle Jon's warnings--at your peril! Did you skip TECHNICAL NOTES ON BRACING THE SOUNDBOARD on page 156 to 159? It warns of precisely what happened to you. We toooldd youu soooo!! I would have said, carve off the upper transversal and that would have freed up the cracked upper portion of the top enough to moisten the wood slightly to have the crack swell and close, so you could reglue it. But you went and gummed it up with superglue (that doesn't work on spruce anyway). So forget that idea. If the crack will eventually lie under the fingerboard (you said it was in the portion between the headblock and the soundhole), you can hide the repaired top under it. Carve off the upper transversal, scrape off the old glue, rout or saw a straight slot right into the crack, and insert a little strip of matching wood with glue. Then scrape all flush. But before proceeding to glue the rest of your guitar together, you've GOT to assemble everything in the shortest possible time. Get all the brace blanks prepared, all the blocks, the sides bent and trimmed, the kerfing, the back joined, the back braces prepared and don't do ANY glueing until you have all the parts at hand. Then reserve a long weekend and do the whole glueing/ assembly procedure without having to stop and make the parts or go out and buy stuff. Time--as you learned--is the enemy here.
GUITAR KIT BOO BOO The difference between rosewood and maple bridge patches are slight. You get a slightly glassier edge with rosewood, a little smoother sound with maple. But the effect/difference is quite marginal.
WHY TAPE UP THE DOUBLE ROD?
If you look at your hand you'll notice that the unsymmetrical pocket where you cradle your neck, between your thumb and index finger is something like the shape the neck should be. This is really only for players who cradle the neck in their palm, rather than play classical style with the thumb tip on the centerline of the shaft. In that case, a flatter shaft centerline is more comfortable. Hope that helps.
COPYING A GUITAR 1. Where I can obtain a blue-print for a 000-28S ? You got me there. I know of none. I'm thinking of preparing a series of blueprints of all those guitars (I use to be a draftsman thirty years ago), but I've got to many projects open as is. But it'll happen before long. Find one and measure it. You can get the brace pattern by "candling" the top: putting the guitar into a darkened room with a light bulb on a wire inside the soundhole. All the braces will shine through the top as if the top was transparent. 2. Will the materials provided in the D-28 be adequate (ie., large enough) and just require modification to the 000-28S ? The D28 is much larger than the 00028 so you'll have stuff to spare. 3. Do you know of any literature out there for constructing a 000-28S, or similar
size, guitar ? |