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What's your floppiest top?
http://www-.luthiersforum.com/forum/viewtopic.php?f=10101&t=44381		 Page 1 of 1
Author:  fingerstyle1978 [ Mon Oct 20, 2014 10:49 pm ]
Post subject:  What's your floppiest top?
I'm building an OM with Dalbergia Cultrata and at the moment curly redwood. It's dimensioned down to .056 and still needs to be sanded to fine grit. Across the grain it's decent stiffness. The stuff is brittle yet somehow soft and a real PITA to work. My last failed build (dropped on the floor during finishing) used a top from the same billet. I over braced it. This one though has more flex from tail to butt than I recall in the last. I'm wondering if I should laminate it to a failed lutz top that got too thin or just over brace it a bit, particularly around the bridge.

I was going to use some spruce but I am all out and I really don't feel like ordering more since I'm about to leave AK and already have this stuff on hand. I'm just wondering if it's worth the trouble. This is meant to be a relatively quick build, no cutaway, simple design, etc.
Author:  DennisK [ Tue Oct 21, 2014 12:31 am ]
Post subject:  Re: What's your floppiest top?
Really, .056", as in less than 1.5mm? You've got guts to even consider such a thing! That's about how thin I'd go with a straight grained Honduran rosewood top, which should be 2-3x as stiff (and heavy).

I'd definitely vote laminate with the spruce. Even with interconnected bracing and good support behind the bridge, that's way thinner than I'd be comfortable with, especially on a panel that largely consists of endgrain. The braces might crack right through the plate. Lattice could probably survive though, since the braces have continuous grain so there wouldn't be any potential crack points. But I kind of doubt it would sound good. You'd probably want to notch the braces into the linings at some small but non-zero height, to stiffen the perimeter. Otherwise would probably get hollow sounding trebles.
Author:  meddlingfool [ Tue Oct 21, 2014 12:57 am ]
Post subject:  Re: What's your floppiest top?
Well, that's way too thin in my books. With a capital way.

I wouldn't bother with laminating, what for? I'd switch to the lutz.
Author:  fingerstyle1978 [ Tue Oct 21, 2014 1:07 am ]
Post subject:  Re: What's your floppiest top?
DennisK wrote:
Really, .056", as in less than 1.5mm? You've got guts to even consider such a thing! That's about how thin I'd go with a straight grained Honduran rosewood top, which should be 2-3x as stiff (and heavy).

I'd definitely vote laminate with the spruce. Even with interconnected bracing and good support behind the bridge, that's way thinner than I'd be comfortable with, especially on a panel that largely consists of endgrain. The braces might crack right through the plate. Lattice could probably survive though, since the braces have continuous grain so there wouldn't be any potential crack points. But I kind of doubt it would sound good. You'd probably want to notch the braces into the linings at some small but non-zero height, to stiffen the perimeter. Otherwise would probably get hollow sounding trebles.


I'm a dummy. It's .156" not .056". And at that thickness I'm not thrilled with the long grain stiffness.
Author:  fingerstyle1978 [ Tue Oct 21, 2014 1:11 am ]
Post subject:  Re: What's your floppiest top?
This is why I don't drink beer in the shop (normally lol)
Author:  DennisK [ Tue Oct 21, 2014 2:24 am ]
Post subject:  Re: What's your floppiest top?
Ok, so about 20 times stiffer than I was trying to visualize :lol: Probably fine then. I wouldn't expect it to need any extra bracing around the bridge at that thickness, but I'm just guessing since redwood is so variable, especially when it's curly. If the last one was overbraced, then maybe floppier is a good thing.

Is the plate still rectangular? Could do some measured deflection testing.
Author:  Joe Sallis [ Tue Oct 21, 2014 3:37 am ]
Post subject:  Re: What's your floppiest top?
.156 inch is nearly 4mm. For me that seems really thick. It would take a hell of a lot of fine grit sanding to reduce that down to a dangerous level. I'm not sure that you need to worry at all.
Author:  TonyKarol [ Tue Oct 21, 2014 7:50 am ]
Post subject:  Re: What's your floppiest top?
I have a couple of curly redwood tops just like that .. you know what they are good for - not acoustics, that's what - will be used for electric caps only.
Author:  Haans [ Tue Oct 21, 2014 7:54 am ]
Post subject:  Re: What's your floppiest top?
Would make a good 12 string if it were spruce...
I just don't understand anything other than using spruce. Red spruce.
Author:  Goodin [ Tue Oct 21, 2014 8:13 am ]
Post subject:  Re: What's your floppiest top?
I'm building a 15" wide zouk with a redwood top right now. Not curly though. I took it down to .130" which seemed about right or maybe just a tad bit flimsy. .135-.140 was probably ideal for that top. On my zouks I like to build slightly heavy then string up in the white and make any adjustments to top and brace thickness before finish.

On an earlier build, I accidentally got an englemann top down to .085" and it sounded muddy, unfocused, harsh, and had very little sustain or headroom. About .125-.150" or so is about right for the softies depending on the piece. I've built with all the softies (englemann, redwood, cedar) and from now on I will stick with the hards (sitka, red, euro) unless a customer requests otherwise.
Author:  DannyV [ Tue Oct 21, 2014 8:16 am ]
Post subject:  Re: What's your floppiest top?
TonyKarol wrote:
I have a couple of curly redwood tops just like that .. you know what they are good for - not acoustics, that's what - will be used for electric caps only.

I've got a really nice one too. My plan is to laminate it for a reso with Koa back and sides............... one day. Spruce is really great for steel string guitar tops. And so is Redwood but I'm inclined to stick to the non curly variety.
Author:  jfmckenna [ Tue Oct 21, 2014 8:47 am ]
Post subject:  Re: What's your floppiest top?
That would be thick in my book but the thing that concerns me more is you describing it as brittle. I've worked successfully with curly redwood but honestly I would never do it again unless I am making a double top. It's too risky. The stuff has runout going every which way and can be very brittle and prone to cracking. So if it were me I'd make a double top using the Lutz.

But to answer your question the floppiest top I made was from an old and unknown piece of pine. It was a parlor guitar I built for one of the challenges here a couple years ago. I wanted to make this guitar entirely from wood that made up an old collapsed barn in my back yard. So I found this quarter sawn piece of pine and after resawing and finishing it I think it was something like .7in and extremely floppy like a wet noodle. I almost didn't use it because it was so thin and floppy but as it turns out the guitar sounds fantastic so anyway that' that.
Author:  TonyKarol [ Tue Oct 21, 2014 11:55 am ]
Post subject:  Re: What's your floppiest top?
Yes .. a reso would be great too, in fact I have one top that will end up on one in the new year ....
Author:  Jim Watts [ Tue Oct 21, 2014 8:51 pm ]
Post subject:  Re: What's your floppiest top?
I'm not sure I understand the redwood top thing myself.
Author:  fingerstyle1978 [ Wed Oct 22, 2014 4:44 pm ]
Post subject:  Re: What's your floppiest top?
Jim Watts wrote:
I'm not sure I understand the redwood top thing myself.


Apparently it's a good combo with Dense rosewoods. I've seen people build BRW/Redwood guitars that sounded great in which the builder was looking for warmth from the redwood. For me, this is more a matter of what I have available on hand right now without spending money on shipping etc. I'll brace it up and see how it taps and how it feels and go from there.
Author:  Joe Beaver [ Fri Oct 24, 2014 8:02 pm ]
Post subject:  Re: What's your floppiest top?
Redwood is a very good top wood in my opinion. I have used curly in two guitars and straight grained in two. So far they all perform well.
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