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I flatten by sanding. It reall is just a matter of a miniute or two to knock the hight at the center of the extension down to the height of the edges of the extension.

Those pictures, sir, are a work of genius!

Ok, so now perhaps I can explain what I originally meant...

Although in the pictures you're used a fairly austere cutaway (which, as it goes is my personal preference) it shows a cutaway of ~90 degree segment of a circle from above right?

Ok so now imagine that cutaway extended a bit to form a more pronounced 'prong'. So it becomes a ~180 degree segment of a circle removed from above. There will be a point on that cutaway where the outer edge would be taller than the inner edge...

That's what I was getting at very poorly with my ascii art.

In other words, the top, once domed, wants to have the outer edge of the inside curve of a pronounced cutaway taller than the ivver edge of the lining.

Ergo stress on glue joint, and stiffness etc which have been described as generally bad things :)

Great pictures Michael, and I am in awe of your patience with a dunderhead newbie like me :)

I gotta question...how can I get the correct radius on the heel block with a classical so the back will fit perfectly (I don't want to sand down the heel since the neck is already attached). A radius dish would get the correct arc, but would sand the heel down. Books that I have read say to estimate the arc of the back . I've always wondered about this.

First I assume we are talking spanish heel type neck joint. One way is to use a sanding dish but cut the heel a tad 1/8" or 1/4" lower than block portion first. You then build it back up with the heel cap attachment

Awesome...Yes, that's what I will do. I have always used somewhat thin heelcaps, but I can thicken them up a bit. Looking forward to a perfect fit Michael

You are going to have to sketch for me. I can't personally see at any time a point in which the outer edge of any cutaway would be closer to the center axis of the sphere. And that is the only thing that determines elevation (distance from the center axis of the sphere to the contact point on that sphere).

Give ma a sketch of what you are talking about and I be I will prove you to be over thinning the issue

oopps wrong topic

no its not

[QUOTE=Dave Bamber] Those pictures, sir, are a work of genius!

Ok, so now perhaps I can explain what I originally meant...

Although in the pictures you're used a fairly austere cutaway (which, as it goes is my personal preference) it shows a cutaway of ~90 degree segment of a circle from above right?

Ok so now imagine that cutaway extended a bit to form a more pronounced 'prong'. So it becomes a ~180 degree segment of a circle removed from above. There will be a point on that cutaway where the outer edge would be taller than the inner edge...

That's what I was getting at very poorly with my ascii art.

In other words, the top, once domed, wants to have the outer edge of the inside curve of a pronounced cutaway taller than the inner edge of the lining.

Ergo stress on glue joint, and stiffness etc which have been described as generally bad things :)

Great pictures Michael, and I am in awe of your patience with a dunderhead newbie like me :)[/QUOTE]

Give me a sketch or a phoo of the type of cutawy you refer to and I will model it for you.

I think you are thinking in only one axis. It is not nessasaraly the point closest in the "X" axis that is the closest to the center axis of the dome. it is the closest on a straight line regardles to axis.

This what I think you mean but see even though the outer or upper bout portion of the cutaway is closer to the center axis of the dome in the "X" axis it is much further away from the domes center axis in the "Y" axis therfore the inside curve of the cutaway is still closer to the center axis of the dome.

The liners and top surface of the side can slope down from the side in the cutaway, while everywhere else they slope up. Is that what you asked? The point is to put the gluing surface into the shape of the dome, not to have the gluing surface always slope up from the outside of the guitar to the inside.

_________________
Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

[QUOTE=Howard Klepper] The liners and top surface of the side can slope down from the side in the cutaway, while everywhere else they slope up. Is that what you asked? The point is to put the gluing surface into the shape of the dome, not to have the gluing surface always slope up from the outside of the guitar to the inside.[/QUOTE]

Nya ha!

Bingo! That's what I was trying to check...

That makes a lot of sense to me and I figured as I'd not seen it described like that anywhere that I'd read building tutorials it was best to check with you experts!

Many many thanks for restoring some small measure of faith in my sanity! :)

Howard,
I can not see how you can sand at any point a negative angle into the lining, no mater what. The angle of the surface sanded into the linings will always be an up angle never a down angle.

I am not trying to be a pain (pardon the obvious pun) but a downward angle is not possible. One location may be higher elevation from a given point but the angle is always up.

This is not a major deal, and maybe you thought I meant something more radical, but if the side in the cutaway runs back toward the tail of the guitar, i.e., at more than 90? to the guitar's centerline, so that the outside of the guitar at that area is facing into the centerline (picture the side in the inch or so inside the point of a Florentine cutaway with a long point), then with a domed top, the joining edge of the side and liners will slope downwards from the outside of the guitar towards the inside.

_________________
Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

OK Howard had almost convinced me that if the cutaway was past 90deg toward the center of the body that there would be a negative angle formed by the dome in the linings. But it just did not make sense to my 3d over loaded mind. So I ran another 3d model test with a cutaway that the cutaway was way more than 90 Des toward the center of the body. I want to be clear here I did not do this to prove anyone wrong. I did it to prove to my self that I was thinking correctly. I started not to post it but thought it worth while.



And just as my mind was telling me no negative or declining angles just different elevations.

Past 90? the other way. I.e., a deep scoop inside the point of the cutaway. Like a Gibson 175, for example.

_________________
Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

Cool drawings, BTW. Wish I knew how to use those programs.

_________________
Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

Like This?

_________________
Horton, MI

Still no declining angle

It ain't going to happen guys The dome shape will always form an inclining angle pointing at the center axis of the dome, unless the depth of the cutaway goes past the center axis of the dome. And we know that ain't going to happen. and even the the angle is inclining relative to the dome. Even then, it would be on other side of center axis point at the center axis so it is still inclining when view from the proper side of the center axis

I see your "point" Michael (pun intended).

Now curl that point around a couple times like a gibson "o"....

_________________
Horton, MI

You are correct no one questioned that. Some just thought that if the hook was more than 90 degrees the angle formed in the linings would decline rather than incline. The radius will always match the dome and the linings will always be higher on the inside of the rim that on the outside. The only thing that changes is the elevation relative to a given plane. That is what I have been saying all along.

it will still incline as viewed from outside the guitar or F mandeline in your point. Just at different elevations from a given horizontal plane. The inside of the lining will always be taller from a given horizontal plane than the outside of the rim.

In truth, Michael, I was picturing my own system of arching the top laterally only. But I did say doming. And you are right--a cutaway would have to hook around past 90? to a line radiating from the center of the spherical dome to get a negative slant on its top, and that would be over a tiny area.

_________________
Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

Your pictures have corrected me :)

I'm definately not as good as visualising 3D as your software :)

Ok, also just to clarify, I never saw this as a huge deal, it was never going to make the degree of difference, say, triangle vs reverse kerfed linings would, just seemed in my 3dsmax-limited brain to be a contradiction :)

At least the question's been asked and comprehensibly answered now. Many thanks for taking the trouble to do that.