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[QUOTE=Hesh1956] Depending on the height of the brace some of the "lean" can be corrected by carving to get them all uniform in lean.[/QUOTE]
Ah, but then the orientation of your quartered grain won't be vertical to your brace profile. May not make any difference at all, but then again....

    The brace sanded in it's proper place in the spherical dish would of course be vertical, but also sanding outside of that position you induce parabloidal error in the shape.

   This would cause the shape to differ from what was intended. Depending on the error, which would probably not be horribly much, but I won't want to induce any errors at all.

And those are big braces in the lower bout! You could Riverdance like Micheal Flatley on the back of that git!!

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Billy Dean Thomas
Covina, CA

"Multi famam, conscientiam, pauci verentur."
(Many fear their reputation, few their conscience)

I'm having a difficult time getting why it matters where the brace is sanded...if it is truly a spherical radius it shouldn't matter.

I'm imagining myself inside of a 30' diameter (15'radius) hollow ball where the continuous spherical wall is distortion-free. Our dishes are simply a 24" diameter section of that wall. If I sand a brace anywhere on that inside wall, I get the same shape and profile. Why would it be different on a spherical dish? What am I missing?

Carlton, I'd be interested in understanding the background source for the knowledgeable advice to which you referred. If it's important and it makes a difference then I sure as heck want to know more.

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JJ
Napa, CA
http://www.DonohueGuitars.com

I'm with JJ here, i had the same thought when carving the braces for no 2, seems to me that when you sand in the radius dish, it doesn't really matter where, the braces would get the same radius anywhere? Can you please shed light for the Pear Bear?

Here's a real rough and dirty explanation.

This is an over exagerated cross section of the dome with braces in "some" location along that cross section.

Seeing as we want all the braces to be "vertical" and not perpendicular to the curve of the dome, each brace has a slight bevel on one side or the other, as none of them are truly on the center or lowest point of the dome.

Being that this is on a 15' diameter dome, I don't think it really matters all that much but this is the explanation that I've always thought was the issue with the dome versus just using arches to clamp down the braces with.

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[QUOTE=JJ Donohue] Carlton, I'd be interested in understanding the background source for the knowledgeable advice to which you referred.[/QUOTE]
Abe Wechter. Good enough for me, 'cause he understands more than I ever will. BTW, Rod's diagram nails it on the head, or the apex, if you will.

Very cool.

Makes sense, I will give it a try and do some resanding it shouldnt take much to get the positioning right. Hesh, again, everything is looking great, great tutorial as always appreciated. I had never given any thought to this brace orientation idea.

Mike

What is the advantave of having the brace vertical to the curve rather than perpendicular to the curve? I hate to keep beating on this but I just can't see an advantage. In fact, having the brace perpendicular to the curve reminds me of a spoke in a wheel...it just makes sense.

Maybe I missed something in C&N and other readings, but this is the very first time I ever heard that the braces must be vertical and not perpendicular.

Someone...Please enlighten me...otherwise I won't sleep tonight! Carlton...call Abe and please ask him to explain why

TIA

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JJ
Napa, CA
http://www.DonohueGuitars.com

if you notice, it just looks funny is all I can think of.

The dome is sooooo little that I don't really think it makes any difference JJ. I wouldn't fret over it too much.

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"There's really no wrong way, as long as the results are what's desired." Charles Fox

"We have to constantly remind ourselves what we're doing....No Luthier is putting a man on the moon!" Harry Fleishman

"Generosity is always different in the eye of the person who didn't receive anything, but who wanted some." Waddy Thomson

    Actually, one could sand in the center as long as the angle to the centerline is maintained per it's place in the radius on the back of the guitar. It's the braces angle to the centerline that's important

   To get an idea of the error possible exagerate the position even further to the side of the spherical radius. The shape would get very odd, more like a cannon balls path shot into the air than a radius.

I hope this explains it better so you can sleep!

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Billy Dean Thomas
Covina, CA

"Multi famam, conscientiam, pauci verentur."
(Many fear their reputation, few their conscience)

Thanks, guys...I'm going to have to look at this on my dishes with braces placed at various positions. One of the exercises I did early on was to gobar the X-braces dry on a top and actually go around the perimeter of the braces with a .002" feeler gauge to check for gaps. I've never found any. I need to do a similar exercise on the back braces.

But for now, at least I'll sleep tonight

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JJ
Napa, CA
http://www.DonohueGuitars.com

[QUOTE=JJ Donohue] Carlton...call Abe and please ask him to explain why [/QUOTE]
Man, I wish I could, JJ. I haven't had a chance to talk with him for more than a couple of minutes for a few years now, 'cause he's the busiest human being I've ever known.

As for why the braces should remain vertical, I just don't have a good enough grasp of the mechanics to give you an explanation. I suspect it has to do with how the braces relate to each other, and the plate to which they're attached, in transmitting vibrations. Probably adds stiffness, too, but I know that seems a bit counter-intituitive.

I usually don't like to take advice at face value without understanding the reasons behind it, but personally, I've learned over the years that Abe knows what he's talking about. He is a master craftsman, and his mentor, Richard Schneider, probably had a genius-level intellect. In this instance, I'm comfortable playing the sheep to their shepherds.

I just felt that I had a duty to pass along their wisdom, as it's one of those little details that may enhance an instrument's quality. Readers will have to decide for themselves if it should be applied to their work. I'm sorry I can't offer any more substantive evidence.

This one is STILL fun! Give Lacey an "atta girl!" for me.

Keep 'em coming! I'd suggest, though, that you start a "part deux" thread...this one is mighty long, and the dial-up guys are gonna miss the excitement!

[quote]Keep 'em coming! I'd suggest, though, that you start a "part deux" thread...this one is mighty long, and the dial-up guys are gonna miss the excitement![/quote]

Time for lunch!

_________________
Billy Dean Thomas
Covina, CA

"Multi famam, conscientiam, pauci verentur."
(Many fear their reputation, few their conscience)