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First build - bracing philosophy advice
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Author:  Jeremy Douglas [ Sat Apr 05, 2008 8:49 pm ]
Post subject:  First build - bracing philosophy advice
Ok I'm about to start building my kit from LMI (as soon as I build a mold) and I'm still thinking about how I'm going to do the bracing. The guitar will be a dreadnaught for flatpicking mostly and to be blunt, I'm going after a pre-war D-18 sorta thing. I'm thinking about leaving the kerfling flat, rather than radiused, both front and back. For the bracing I'm thinking about making a couple radius bars and and radiusing the top X brace to 28 feet and gluing it flat to the soundboard then radiusing 3 back braces to 18' and the upper bout back brace to 28' and gluing those flat also. This way I won't have to buy radius dishes and the method is similar to Martin's from that era. Does this sound ok :?:

Also, how should I go about taking care of the fretboard hump past the 14th fret? Should I radius the TB brace the same as the X and sand my neckblock at an angle to match? Obviously I'd have to figure out how to match the neck angle and top of the neckblock to these radiuses... my brain hurts [xx(]

Thanks for any help, Jeremy
Author:  Dave Livermore [ Sat Apr 05, 2008 10:05 pm ]
Post subject:  Re: First build - bracing philosophy advice
Jeremy,

Welcome to the forum.

Which of the standard texts are you using to guide you through the first build?

Each of them has a little different approach to the build and with a little clarification, most can be amazing instruction manuals, even with kits. Generally on a first build there will be a number of instructions that the users of this forum can lend great help in clearing up the ambiguities.

Good luck.

Dave
Author:  Jeremy Douglas [ Sat Apr 05, 2008 10:14 pm ]
Post subject:  Re: First build - bracing philosophy advice
Well I've got the DVD that came with the kit and I'm about to order Cumpiano's book right now. Maybe it's just me but I don't see why O brian's DVD isn't just a book; it's just dialouge and pictures. Of course, doing it like I said would be different than the DVD.

The reason I'm gluing flat to the linings is because that's how Martin did it. H&D also makes a traditional series dread with a radiused top but glued flat to the sides. I really liked the way it(TD-M) sounded compared to their regular dreads. I've also read Martin put a radius to their braces and then glued them flat and then once unclamped they would spring back to their radius and then they would be shaped. I also plan on using 'forward shifted' bracing. I'm doing that for the sound but also to save money on radius dishes.

Really what I'm concerned about is the neck setting and keeping the fretboard on a straight plane.
Author:  grumpy [ Sat Apr 05, 2008 10:55 pm ]
Post subject:  Re: First build - bracing philosophy advice
Leave the top flat if you wish, and from the tone you're after, please do.

But the back.... Martin had a radius to the back, even in the 19th century. Not the perfect sphere we think about today, but a serious radius nonetheless. The sphere(dishes) makes perfect joinery possible, and in my opinion, this makes it very valuable. The difference in tone will be very subtle, given a perfect join of either one, so my recommendation for the first 20 or so guitars, is always to use the dish. Once your joinery "chops" are up to snuff, then, go ahead and try to old style. Don't fool yourself into thinking you can nail it on the first try! Even God had to come back and patch things up [:Y:]

Go study...
Author:  Jeremy Douglas [ Sun Apr 06, 2008 11:31 am ]
Post subject:  Re: First build - bracing philosophy advice
Thanks, I'll follow the plans for the back and probably go flat for the front. Yeh, I got a lot of studying t odo.
Author:  Dave Livermore [ Sun Apr 06, 2008 12:56 pm ]
Post subject:  Re: First build - bracing philosophy advice
Jeremy,
Good call on the Cumpiano book. It is a GREAT reference.

If you are planning to forgo the radius because you don't want to drop the $80 for a dish, that there are other ways to radius a brace and the rim.

Check out this radius jig
http://liutaiomottola.com/Tools/BraceArchJig.htm

If you have a band saw, it is a cinch to make. I just did one yesterday. (if you don't have a bandsaw, it is still possible to do, (I've used one for a couple years) you just have to sand more to get a consistent surface.

Then make a matching radius sanding stick (which is the radiused part of the jig, twice as thick, with sand paper stuck to it.

Its like having an inch and a half wide section of a dish to work with. But YOU made it, and it didn't cost you $80.

Good luck with your build.

Dave
Author:  Parser [ Sun Apr 06, 2008 2:22 pm ]
Post subject:  Re: First build - bracing philosophy advice
Here's my understanding of the purpose of these features..hopefully this will help you decide how to build your first. I think the purpose of the radiused top is simply to "pop" the top outwards so that it will not dip in at the bridge. If you make the top flat, humidity may cause it to be popped out one day, and popped in the next. Some folks don't worry too much about this. Similarly, the purpose of adding a radius to the back is to keep it popped one way: out. It will look crappy if it is not popped out.

For building with a minimum of tools, you might be able to get away with radiusing the appropriate braces (all of the back, and some of the top) and then using Cumpiano's stick sanding method to fit the back & top to the sides. As Mario mentioned, the bowl will ensure that you get good results quickly. If you choose to do it a la Cumpiano, just be sure to take your time and get it to fit as well as you can prior to gluing up.
Author:  Jeremy Douglas [ Sun Apr 06, 2008 7:15 pm ]
Post subject:  Re: First build - bracing philosophy advice
Parser wrote:
Here's my understanding of the purpose of these features..hopefully this will help you decide how to build your first. I think the purpose of the radiused top is simply to "pop" the top outwards so that it will not dip in at the bridge. If you make the top flat, humidity may cause it to be popped out one day, and popped in the next. Some folks don't worry too much about this. Similarly, the purpose of adding a radius to the back is to keep it popped one way: out. It will look crappy if it is not popped out.

For building with a minimum of tools, you might be able to get away with radiusing the appropriate braces (all of the back, and some of the top) and then using Cumpiano's stick sanding method to fit the back & top to the sides. As Mario mentioned, the bowl will ensure that you get good results quickly. If you choose to do it a la Cumpiano, just be sure to take your time and get it to fit as well as you can prior to gluing up.


Thats what I plan on doing... making a radius jig like in the link to shape the braces and the back rim.
Thanks guys.
Author:  Dave Livermore [ Sun Apr 06, 2008 8:07 pm ]
Post subject:  Re: First build - bracing philosophy advice
One piece of advice from recent experience,

I worked for a while today on making my "new" jigs... One for putting the radius on the braces, the other for putting the SAME radius on the linings and sides.

If you do some math (or follow the recommended numbers) and use deflection to draw the line and subsequently cut along said line to make your arcs, make sure both the jig and the sanding stick match.

I've noted some less than perfect glue ups along the way due to an inconsistency in my jig. But as my system gets more and more refined so does the neatness of the rim and side joint.

It seems elementary, but even upon following the directions and doing this a few times, it never seems to come out exactly 25'. I don't really mind that. The radius doesn't necessarily need to be exactly 25' or 28' (depending on what radius you choose (or think you chose)), it DOES need to be consistent for your work.

happy building,

don't be afraid to ask questions

Dave
Author:  LiquidGabe [ Sun Apr 06, 2008 8:38 pm ]
Post subject:  Re: First build - bracing philosophy advice
There was an excellent thread last year at the MIMF on building a "long compass" for making radius dishes. Simple. It took a couple hours to put the jig together, and about that to make a dish. I'm not sure if that thread has made it to their library yet, but its worth a look.
Author:  Alan Carruth [ Sun Apr 06, 2008 9:19 pm ]
Post subject:  Re: First build - bracing philosophy advice
I keep posting the trick about using a shim on the bottom of the plane to make a radius. It's just a modern version of the old trammel that every ship builder used. Simple, quick, makes a perfect radius, doesn't cost much. You do have to have a plane that works pretty well, but you should have that anway.
Author:  Howard Klepper [ Mon Apr 07, 2008 12:10 am ]
Post subject:  Re: First build - bracing philosophy advice
What benefit there could be in building a radiused top and back and then gluing them to a flat rim eludes me, although that does seem to be what H&D describe.
Author:  Jeremy Douglas [ Mon Apr 07, 2008 7:07 am ]
Post subject:  Re: First build - bracing philosophy advice
Howard Klepper wrote:
What benefit there could be in building a radiused top and back and then gluing them to a flat rim eludes me, although that does seem to be what H&D describe.


Have you played one of those H&D's? That TD-M was one of the best dreads I've played. More importantly thats how all those pre war Martin tops were made.
Author:  Howard Klepper [ Tue Apr 08, 2008 5:04 pm ]
Post subject:  Re: First build - bracing philosophy advice
Haven't played an H&D. Thought pre-war Martins were built with flat tops.
Author:  LuthierSupplier [ Tue Apr 08, 2008 5:50 pm ]
Post subject:  Re: First build - bracing philosophy advice
livermo1 wrote:
Jeremy,
Its like having an inch and a half wide section of a dish to work with.
Dave


Dave,
I have to politely disagree with you on this point. This jig works very similar to my Brace Maker jig that cuts a 2D radius on the brace bottom. However, to get a true sphere on the bottom of the brace you would then need to sand it in a radius dish. Also, using a radius stick on a rim/sides is not the same as a dish because again it only puts a 2D radius on the rim, not a true sphere. Just my .02.
Author:  Howard Klepper [ Tue Apr 08, 2008 7:03 pm ]
Post subject:  Re: First build - bracing philosophy advice
I meant Martin tops, above. Backs were always arched. But I don't claim to be a great Martin historian.

Do we mean the same thing by flat rim? I mean the whole edge of the rim is in one plane. Do you (and H&D) mean just that the liners are flat?
Author:  Jeremy Douglas [ Tue Apr 08, 2008 8:58 pm ]
Post subject:  Re: First build - bracing philosophy advice
Howard Klepper wrote:
I meant Martin tops, above. Backs were always arched. But I don't claim to be a great Martin historian.

Do we mean the same thing by flat rim? I mean the whole edge of the rim is in one plane. Do you (and H&D) mean just that the liners are flat?


Here's the giant '"Flat tops" vs arched bracing' thread from the Martin forum.
http://p072.ezboard.com/quotFlat-topsquot-vs-arched-bracing/ftheunofficialmartinguitarforumfrm155.showMessage?topicID=44.topic

John Arnold stated: "I believe Gibson started radiusing their top braces around 1935. I also believe that Martin has always used radiused top bracing, but is is difficult to determine exactly how much. Over the years, the combination of shrinkage and string tension tends to flatten the tops in the soundhole-bridge area.
Also, Martin has always clamped the top braces flat, relying on the resilience of the spruce to spring back into a curve once the gluing is done."

and yes, I believe H&D uses a flat plane around the entire top rim.
Author:  bluescreek [ Wed Apr 09, 2008 4:28 am ]
Post subject:  Re: First build - bracing philosophy advice
The older martins were flat but they also were at an angle to the side. The neck has an angle and so the fret board didn't rise into the strings the angle was placed on the top. The angle allowed the fret board extension to transition in a straighter line. Some tweaking was done on setting but that angle if not allowed can cause a horrible problem at setting time.
also the older martins had a different fretboard thickness than todays modern counterparts. One your first build stay withing the parameters of the kit for best results. You don't know what you don't know and with the first kit you need to get your building techniques and fit and finish down.
Mario and others of us that build can steer you but in the end you are the craftsman. Learn from others mistakes , you don't want to make them all yourself . the link below can show you how I set the body up for the back and top.
john hall
BCG
http://www.bluescreekguitars.com/blog/
Author:  Howard Klepper [ Wed Apr 09, 2008 5:30 am ]
Post subject:  Re: First build - bracing philosophy advice
Setting the neck angle or dealing with the fretboard extension is not what would concern me about a flat (single plane) rim, even if the plane is not square to the rim in back. A domed or arched (to a single curve) top or back plate that is forced down to a flat rim will dip across the waist. This is a mistake I made on my first guitar 30 years ago (on the back, which was arched--the top was not); it took me a while to figure out why. The plate is at a higher point of its arch or dome where it meets the waist, and also higher at the outside of the upper bout than at the outside of the lower bout. Gluing to a flat rim distorts the curvature of a domed plate. It also raises the pitch of the plate by forcing extra curvature. How that stress and distortion could be beneficial, or result in more bass, as claimed by H&D, eludes me.

It also doesn't look like what Martin did on pre-war guitars. I believe the tops were built flat and apparent arching is from the distortion of string pull. I've never seen or heard that they used spherical doming in that period. So I don't see how taking a spherically domed flat and forcing it to a flat rim would recreate pre-war Martin construction. If what John Arnold says on the Martin forum is right, Martin may have varied the curvature of the lateral arching of its back so that the edge of the back was a closer approximation of a planar rim. But if I understand what he is saying, the rim was not planar on the back.
Author:  Jeremy Douglas [ Wed Apr 09, 2008 6:59 pm ]
Post subject:  Re: First build - bracing philosophy advice
I can only tell you what I've read. John Arnold said that he doesn't believe that the extra stress from gluing flat to the sides last very long. He also said that the arch is stiffer and when the sides of the top are flattened more movement is allowed. There are few different ways discussed on how Martin got their top radius. One was radiusing the braces then gluing them flat and the other was to use low humidity and heat before putting the body together.
Author:  grumpy [ Thu Apr 10, 2008 9:31 am ]
Post subject:  Re: First build - bracing philosophy advice
Howard, sometimes things that don't quite make sense, actually still work quite well. This is one of those times...
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