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PostPosted: Thu Apr 22, 2010 8:13 pm 
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Cocobolo
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First name: Chris
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Hey all,

I'm going to start a cedar topped OM sized guitar soon. I have scalloped the braces on the spruce tops I've built, and on the one redwood guitar, I didn't scallop the braces, thinking that redwood might need some more support. Wondering what most do with cedar tops as far as bracing, bridge plate and top thickness.

TIA,

Chris.


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PostPosted: Fri Apr 23, 2010 6:57 am 
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Cocobolo
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First name: Chris
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I forgot to say last night, this is going to be a 6 string, steel guitar.

Anybody?


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PostPosted: Fri Apr 23, 2010 9:03 am 
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Walnut
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Chris: Think your question is very broad with a lot of unknowns. You may not get many answers and have to do a lot of digging for yourself in the archives.Even after looking at lots of pictures and reading lots of info on sizes etc. you will still be left with maybe not knowing the stiffness and it's requirements of your cedar in comparison to what you have found in the archives.This is one of the harder things to get a grasp on in guitar building.As a broad answer on average 10 to 15 percent heavier but from what I know it's just a WAG. Lots of reading will do you better IMO. Good luck and have fun.
Tom


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PostPosted: Fri Apr 23, 2010 9:43 am 
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Chris -

I agree with Tom's points. I think there are a couple of things you could do to be pretty precise about thickness and bracing. Regarding the thickness of the top before bracing, if you do deflection testing on your tops, over time you'll develop some goals in terms of deflection (measuring effective stiffness of the top). I know just enough to be dangerous on the topic - lots of good info and tutorials here on deflection testing. Bottom line - what you're doing is suspending the top between two points - and placing a weight on the middle to see how far it sags - measures the sag (deflection) After repeated measurements with passes on the thickness sander, it hits your target "sag" - it's the right thickness. The reason this is useful is that every piece of wood is different - maybe bigger variability between individual tops of the same species than between two "average" tops of differennt species. Some acheive this by thicknessing until the top "feels right" when flexing. I'm not quite there yet. So.....

Then, bracing.... Although I haven't done so yet, I really like the thought of doing Chladni testing - also lots of great info here on what that means, and what you're attenpting to do.

For a less "technical" approach, I'd carve them until you get a wide variety of tones when tapping from various points on the top. Tap on the part of the top supported by a brace) Dana Bourgeois has some good info on his website on his approach to carving, which I find useful. In general, I'd bet that you'll want to leave the top a bit thicker, and the braces less scalloped, to support the cedar.

Finally, make a cawl to tape the the top when your'e working with the top and soundbox and don't need direct access to the cedar top. Cedar's SOFT and you can put a ding in it extremely easily.

Might use light strings if you generally like to build them light.

Have fun - I think you'll like the cedar - almost no break in time.


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PostPosted: Fri Apr 23, 2010 10:48 am 
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Old Growth Brazilian Rosewood
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And what well known path or plan is that Filippo? I'm not aware of any plan out there that provides specifics for an OM with a WRC top.

My current guitar that I am building is an OM with a WRC top. The box is done and my top ended up being .120 and my bracing is the same as I would use on a spruce topped guitar. I don't scallop favoring tapered braces which I also used on this cedar topped OM. Not saying that scalloping sucks I am saying that I don't do it on my guitars.

Of course YMMV Chris but I think that a WRC top in the .120ish range for an OM would be a safe bet if you don't do deflection testing and have developed our own techniques and chops for voicing.


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PostPosted: Fri Apr 23, 2010 11:19 am 
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Hesh, where did you end up with cross brace height and width? What kind of brace stock?

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PostPosted: Fri Apr 23, 2010 11:42 am 
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Old Growth Brazilian Rosewood
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Steve my friend my X-intersection is 1/2" high and all of my braces are 1/4" wide and profiled into triangles.


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PostPosted: Fri Apr 23, 2010 1:10 pm 
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Cocobolo
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First name: Chris
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Guys,

Thanks so much for the replies. More digging is in store for me.

Chris.


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