I am thinking about the string angle on the top of the box on my latest build.
My thinking is that the steeper the angle behind the bridge the harder the bridge presses onto the top of the box. The bridge must push down hard enough to get the most sound out of the top but not so hard that is starts to suppress the sound, this is also dependent on the thickness of the top and such.
Anybody got any thoughts on this, I know the Banjo crowd consider this a deal breaker, but I do not know how it translates to acoustic CBG's. Must be the same with resos to "drive" the cone just right without squishing it to much so it only squeaks.
Cheers Ron.
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Most instruments i've seen with a high bridge often routinely either add a reinforcing wood plate under the bridge (guitar class) or a base bar/melody bar combo (violin class). Haven't gotten to examine a banjo yet-perhaps the skin used is tough and elastic enough, or maybe there's something under that hide...no idea.
My first successful build (very recent too) was a two-box Cello with a decently high bridge-rather than angling the neck, I used a variation of the Uncle Crow guitar build. I placed a full reinforcing bar under the lid top to bottom, added the neck straight across, bolting through the lid, then a tailpiece bolted through and the bridge inserted directly into the tail. Inside where the boxes join I placed a vertical bar from the reinforcing bar to the lid as a built in Melody post. Action is almost straight across as a dulcimer would be. I'm not happy with my other design choices (I made the neck long and the post on the base too short leaving me either hunched over like Quasimodo or bracing in a chair) but i'm happy with the sound and there's no hint of give on the soundboard so far at full tension...
I'll probably play with an angled neck when I actually know what i'm doing...but when I do i'm having some kind of reinforcement under the bridge.
I just finished my first CBG slider. No angle on the headstock, because i don't have a table saw. It has a thru neck with a couple of inches of neck protruding out the tail. I drilled the thru holes for the string-anchors there, in a place that just "looked about right", but it sets the strings at a particular angle which puts front-to-back pressure on the eye-bolt I'm using as a bridge. This prevents me from locating the bridge exactly where I want it.. My intention was to set the bridge so that the 12th fret exactly is between the bridge and nut, but the pressure angle of the strings keeps pushing the bridge back toward the soundhole. Since it's a fretless guitar, I can kind of compensate for any slight intonation issues, but I'd like to figure this out for my next project.
Any help or comments greatly appreciated.
With the present build I have a box with a thin lid, about the thinnest I could find. I don't think I will produce a angle that will crush/damage the lid. I think their is some merit in trying some testing. I will measure the lid thickness and try out a few bridge hights. It will be hard to translate this to diferent lid thicknesses but could be a start. This sort of thing seems to have been worked out with other instruments, maybe some sort of ratio could be found such as for every mm of lid thickness the bridge is best at X mm high. Thanks all for your thoughts.
Cheers Ron.
mark this is true and a good point
Josh, yes but do you not agree that just because we are jammin a stick into something that was originally packaging for something else does not mean we ought just ignore the science and engineering learned from the last couple centuries of luthiery? I have conducted exactly the experiments you're talking about, but on cookie tins, and I'm quite convinced of what I'm saying. ( I did not keep any readings or data cos I wasn't out to prove anything for anybody else) fella called Sanddraggin made an extreme neck angled CBG following discussions about exactly this over at the other forum, and he was in complete agreement with me too.
this is Sanddraggins experimental build, he claims to be very familiar with this exact type of box, and so he felt the experiment was quite successful.
I will be very interested in anybody else's findings in this matter, as far as I know Sand and I are the only people who have actually conducted experiments into it
Ive been a big proponent for neck angles and tall bridges anytime anyone asks about em, I honestly feel that angling my necks and tapering em was when I really started to be happy about my own builds. There have been one or two where Ive overdone it on the angle a little, particularly a neck thru solid body Im doing right now, the bridge is gonna be quite tall, but overall I'd much rather have too much angle than too little, and the action on my necks is much much nicer and more consistent across the whole length than i think could be possible on a zero degree plane..
Remember, more pressure from that taller bridge means you may have to add bracing as well. I found this out with one of my builds; the 1/8" ply top started to collapse.
On the mandola I use as my sig, I used a 5 degree neck angle which is pretty much standard for this type of instrument. The bridge ended up being about what you'd expect, and the near 1/4" solid-cedar top seems to be holding up just fine, though I did add an "X" brace.
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