"Words Mean What I Want Them to Mean"

[LouieAtienza]

Originally Posted by Cambrian Guitars

Suffice to say I don't do my bracing like that any more!
I should take that old video down....it's embarrassing!
As the discussion in the video's comment section says, I agree that there's nothing parabolic about any of the curves....perhaps they should be called parabollocks curves? I got "caught up" in the marketing hyperbole, sorry.

My "internal heel" idea is still alive (just) and I may revisit the idea later this year. I have continued to do experiments of all kinds with new materials and building techniques. Looking for my niche in the market I guess....

E.g. my all-spruce triple-top with strat-like arm relief curve experiments seems to be working out - I have a couple more experimental guitars in the pipeline with improvements (thanks to some useful suggestions from other builders and players) - stay tuned.

Cheers,
Dave Fifield

Dave, I also experimented with a heel-less design, and have built one guitar in that fashion. I'm still trying to recover files from my older computer so I hope to post a pic sometime. It does look cool...

[gpj1136]

I have seen an acoustic with a neck that bolted on like a fender electric. It looked strange, but might have looked better if it had a cutaway, which would seem to give it purpose.
I'm not against stirring things up in design that guitar looked funny to me though.
Howard has incredibly beautiful nontraditional builds for example. I guess you just need to be careful how you name your mods to avoid criticism.

[LouieAtienza]

Originally Posted by gpj1136

I have seen an acoustic with a neck that bolted on like a fender electric. It looked strange, but might have looked better if it had a cutaway, which would seem to give it purpose.
I'm not against stirring things up in design that guitar looked funny to me though.
Howard has incredibly beautiful nontraditional builds for example. I guess you just need to be careful how you name your mods to avoid criticism.

As Dave mentioned, I placed the "heel" within the body outline, which has a cutaway, and gives a "seamless" look. I worried about the length of the playing area possibly making the neck unstable, though it seemed fine. The guitar was a "mule" of sorts and I built it just for proof-of-concept (so I didn't make the heel the whole depth of the body) but it was still contoured to blen iinto the upper bout.

[redir]

Whats wrong with shaping braces like that? Semantics set aside. Seems to me that having strength in the middle of the span where it is weakest tapering out to the rim where it is strongest makes sense to me. I don't do my back bracing like that but I don't see anything wrong with it either.

I don't see how anyone could knock time tested and proven scalloped bracing. I've done all kinds of bracing but I prefer tapering the top braces now due to the above mentioned. If some one wants 'that' sound then I will scallop.

[arie]

regarding solely the video that charles originally posted, i don't see anything really groundbreaking or controversial going on here unfortunately, it's been done before. in fact all of my braces except for the utg, have a parabolic cross section to them at their highest point that tapers down to a flat as they near the kerfing. it just intuitively seems to make sense to me and it's very easy to do. the braces retain their needed height, (which needs to be a bit taller then the norm) and the reduction in cross section trims down the weight -simple. nothing i've actually calculated out though, it's just organic more or less.

can't comment on the other back stories involved in this thread other then to applaud Mr. Fifield for actually going out there, posting videos, working out ideas, and doing something. you certainly won't find my mugg on the internet anytime soon...


this might help:

[Howard Klepper]

Originally Posted by arie

this might help:

That does not show a hyperbola. A hyperbola has two asymptotes, and is taken from the intersection of a plane with a circular conic surface that has two nappes, i.e., a double cone. This drawing only shows half of that.

[charles Tauber]

Originally Posted by redir

Whats wrong with shaping braces like that?

Nothing. If it works for a maker, go for it.

[arie]

Originally Posted by Howard Klepper

That does not show a hyperbola. A hyperbola has two asymptotes, and is taken from the intersection of a plane with a circular conic surface that has two nappes, i.e., a double cone. This drawing only shows half of that.

correct. is this better?

[arie]

Originally Posted by charles Tauber

Nothing. If it works for a maker, go for it.

Quote:
Originally Posted by redir
Whats wrong with shaping braces like that?

Nothing. If it works for a maker, go for it.

Quote:
Semantics set aside.

That was part of my objection. In discussing technical details, the terminology matters.

Quote:
Seems to me that having strength in the middle of the span where it is weakest tapering out to the rim where it is strongest makes sense to me.
Of course. So the question is how should the "tapering" occur?

Quote:
Originally Posted by arie
i don't see anything really groundbreaking or controversial going on here unfortunately, it's been done before.

Agreed, but for calling it "parabolic", which it is not.

Quote:
in fact all of my braces... have a parabolic cross section to them at their highest point that tapers down to a flat as they near the kerfing.

While I haven't seen how you shape your braces, I suspect they are not parabolic in cross section. Sure, they have some curvature to their cross section, but it is unlikely a parabola. If it isn't, why call it that?

Quote:
it just intuitively seems to make sense to me and it's very easy to do. the braces retain their needed height, (which needs to be a bit taller then the norm) and the reduction in cross section trims down the weight -simple. nothing i've actually calculated out though, it's just organic more or less.

Hmmm.

Here's the deal. To a first order of magnitude, the top (or back) is rigid at its glued connection to the sides: it is very, very stiff, allowing no motion of the top or back at the glued connection. The further one moves away from the constrained edges, the greater the flexibility. So, for a first order approximation, assuming a simple drum-head like behaviour, we have two known points. The first is zero amplitude, very high stiffness. The other is mid-span, maximum deflection. So, how do we connect the dots?

For a rectangular cross section - for our first-order approximation we'll assume that braces are rectangular in cross section - the stiffness of the brace is proportional to the cube of its height. Thus, the shaping/contouring of the height of the brace (i.e. longitudinal shaping) will in large measure determine the stiffness distribution (due to change in second moment of area, I) along the brace. How do we want that stiffness to vary? A convex shaping maintains the stiffness for a greater distance from the center than a "scalloped" concave shaping.

Obviously, people have been successful in producing what they want with both approaches, concave and convex.

Quote:
this might help:

The picture hides the fact that each of those conics is defined by a very specific relationship: they are not arbitrary shapes.


so what would satisfy you here charles?

[charles Tauber]

Originally Posted by arie

so what would satisfy you here charles?

Simple: accuracy and honesty.

Call something what it is, not what it is not. Yes, I'm aware that I'm paddling upstream.

[LouieAtienza]

Originally Posted by charles Tauber

Simple: accuracy and honesty.

Call something what it is, not what it is not. Yes, I'm aware that I'm paddling upstream.

The person in question had recanted here, in public. Are we going to stone him to death, too?

[charles Tauber]

Originally Posted by LouieAtienza

The person in question had recanted here, in public. Are we going to stone him to death, too?

Originally Posted by arie

in fact all of my braces except for the utg, have a parabolic cross section to them at their highest point that tapers down to a flat as they near the kerfing.

.................

[arie]

Originally Posted by charles Tauber

Simple: accuracy and honesty.

Call something what it is, not what it is not. Yes, I'm aware that I'm paddling upstream.

of course. no worries.

so if i shape the cross section of my braces with a plane and sandpaper and the final result looks like a parabola, or a hyperbola, or an involute profile, or a nurbs curve, but apparently technically speaking, really isn"t, then what then should one call it?.

if we examined it on a cmm we would certainly see a curvature of some type but depending upon the resolution of our data points, which one might it be? and as inaccurate as the hands are with sandpaper and hand tools, this contour will certainly change along the length of the brace morphing from parabola to hyperbola to whatever.

getting duller as i age, did i miss somewhere in this thread on what this amorphous shape should be called?

[LouieAtienza]

Originally Posted by charles Tauber

.................

OK maybe "parabolic-like" or just "parabolic" in quotes would be better. I might call the cross-sectional shape of my braces "gothic arch-like" though it may not conform to a true gothic arch shape.

Next thing we'll be prosecuting Mickey D's because their hamburgers don't have real Ham....

[arie]

so after speaking with several of the particle physicists at the day job, the general consensus is that there is no real name for this geometry. one in specific called it "book keeping". because of the constantly changing cross section throughout the length, it's a tough one to really define. perhaps a "tapered arch" is ok? i was advised to research cantilever arms and diving board design. it's an interesting question.