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first back done - critique?
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10101&t=16683		 Page 1 of 1
Author:  Heath Blair [ Tue Apr 01, 2008 12:37 pm ]
Post subject:  first back done - critique?
well, im more or less done voicing the back to my first guitar and while i realize that its both subjective and difficult to do over the internet, i thought i would ask for a critique before i went ahead and glued it to the rims. so some specs... peruvian walnut, which to my untrained hand felt pretty floppy, especially towards the edges in the lower bout where the grain goes more flat sawn. current thickness is .090". all brace stock is .250" adirondack spruce. the two lower braces are approximately .700" high and taper to about .500". the two upper braces are approximately .500" high and taper to about .400" high. all braces are scooped 1.750" from the edge down to about .050" and will all be tucked into the linings. i hope all of that makes sense.

to me the sound is a deeper sustaining rumble. not really much of a ping. while i would like a semi active back, what i was hoping for is a guitar with decent projection. not sure if i accomplished that or not. i dont really know what im listening for yet and thats ok because this is my first and im well aware that there is a learning curve. all part of the fun. any advice, tips, criticism, encouragement accepted. bring it on.

also, sorry for the poor picture quality.
Author:  Bruce Dickey [ Tue Apr 01, 2008 12:57 pm ]
Post subject:  Re: first back done - critique?
Hey that looks great. Pics are fine.

You are your own worst critic.

Glue it before it gets away..........................

[:Y:] [clap] [:Y:]

If I were going to change anything, it would be to widen the lower bout braces more to the tune of a Martin Dred plan. But I'm betting your setup with the thin lower bout braces will work just great. So there..........

Nice work.
Author:  Hesh [ Tue Apr 01, 2008 1:07 pm ]
Post subject:  Re: first back done - critique?
Heath buddy it looks great to me too! [:Y:] [clap] [clap] [clap] [clap] Nice job!
Author:  Michael Dale Payne [ Tue Apr 01, 2008 1:09 pm ]
Post subject:  Re: first back done - critique?
It looks very good.
I do have a couple questions.

First is; are you planning to chisel out the back graft to accommodate the neck and tail block? Assume so. You may want in the future to pre plan the start and end of the back graft to fit from tail block to neck block rather than coming back and chiseling it off to fit.

Second is; the waist brace seems to have a bit of a bow shape in it. This may be an optical elusion in the photo. But if not I would hope the bow was not caused by clamping it into a bowed shape during glue up because it would then have induced stress that adds a possible path of failure.

Also your taper offs seem a bit sever. You might want to allow a bit more length in the transition such a sharp fall off adds a bit of a stress riser in the high corner
Author:  Heath Blair [ Tue Apr 01, 2008 1:45 pm ]
Post subject:  Re: first back done - critique?
thanks for the qucik replies and encouragement!

michael, thanks for those observations. pre-planning the start and end of the back graft would have been the smart thing to do and i just wasnt thinking about it. no big deal to chisel it off though. next time ill definitely save myself some work by doing right.

i took a second look at the waist brace and placed a straight edge against it and all is well. i think what you are seeing is that the triangular profile didnt follow the centerline of the brace perfectly even though i drew a line right down the middle of it. sloppiness on my part. and thats like the one brace that everyone is going to see :oops: !

as for the taper offs... i dont really know what im doing and i will definitely take a look at some others work to get a better idea of what to do. it didnt seem that drastic to me, but i see where you are coming from. should it be more of a taper than a scoop? would rounding off that high point help?
Author:  Michael Dale Payne [ Tue Apr 01, 2008 1:52 pm ]
Post subject:  Re: first back done - critique?
Just take a bit more the length to fall off. The total length of the fall off is fine it is just that yours falls off very abruptly at first. Let the curve of the fall off smooth out a bit to avoid creating such a rapid fall off.
Author:  TonyKarol [ Tue Apr 01, 2008 2:02 pm ]
Post subject:  Re: first back done - critique?
I would take the two rear .700 braces down to about .590 in the middle ... IMO yours are too high/stiff. As well, like MP says, make the final scoop/taper longer .. mine start at 3 inches in from the guitar shapes edge, down to about .060
Author:  John Mayes [ Wed Apr 02, 2008 8:59 am ]
Post subject:  Re: first back done - critique?
Looks great to me. Looks almost identical to how Dana Bourgeois does on his guitars, and like what i've done on about 150 of mine :)
Author:  stan thomison [ Wed Apr 02, 2008 10:47 am ]
Post subject:  Re: first back done - critique?
What John said. John when you were at Dana's, did he (Carey anyway) taper the back center graft (is that right term only 1 cup of coffee in me so far to think) from the #4 brace to the end block to almost nothing rather than just cutting it off and butt to the block? That is how we did when I was there, and didn't know if that had been a change.

Also on the scoops, kept them a little thick at first where it tucks, then to belt sander and as took the end down to about 60 thou, would go toward the center of the brace. Also from center to toward the ends and planning them down to final heighth would put a slight curve to them and symetrical look.

Yours look fine and not at all trying to make suggestion you change them. I am just putting out there what seen and did at great shop for and general discussion. Just adds some look to them. I don't know if the taper thing makes any difference and since out of site for most part may have just made it easier and faster. John may know why Dana did that. He also has a great method of cutting the graft notches to set braces in. Always get very tight fit and makes them look really good. I would post it, but would want to check with Dana first.
Author:  Darren W [ Wed Apr 02, 2008 11:49 am ]
Post subject:  Re: first back done - critique?
Stan,
I'm only one cup in so far this morning, too, so maybe it's me, but I don't understand this:
"Also on the scoops, kept them a little thick at first where it tucks, then to belt sander and as took the end down to about 60 thou, would go toward the center of the brace. Also from center to toward the ends and planning them down to final heighth would put a slight curve to them and symetrical look."
Could you show us a picture of what you're describing? To me it sounds like you're advocating no scallop (scoop) but rather a graduating from the center down to the tuck in the lining, rounding off the bracing with a plane. Am I understanding you correctly?
Thanks in advance,
Darren
Author:  Heath Blair [ Wed Apr 02, 2008 2:41 pm ]
Post subject:  Re: first back done - critique?
hey thanks to all for the advice here. i think ill stare at it a little bit longer and then probably just end up glueing it to the rims.

thanks for your input john, since its basically your design from the videos that i used.
Author:  stan thomison [ Wed Apr 02, 2008 4:37 pm ]
Post subject:  Re: first back done - critique?
Darren

I am not really good at describing things and reason never have done tutoral.

I do make a scoop/scallop at the end of the brace and I do tuck them into the lining. I cut the braces, including the scoop by bandsaw and then pre-shape them on beltsander. I keep the leg or end of brace (whatever called) of the brace some bit thicker than the final .060 I go to for final thickness and tucking the brace.

I then glue the braces to back. I then take back to the beltsander, and use a table or jig whatever may call it to sand the brace ends. to final thickness. This is the same table use to final thickness headstock. As I am sanding the end of the brace to final thickness as noted, I push the back and brace lightly into the sander and as do so I keep checking the end thickness with piece binding until it gets me there.
This for me makes a more uniformed look of the brace end and scoop.

I don't scallop any other part of the brace and use chisel or plane and from center out of brace put a curve on them. Sort of like what some do on the front leg of X brace and described by some as parabolic. That term I am not suggesting is right or wrong because to be honest, I don't know if that is right term or not but a description of how looks, and seen here many times. Doing this is I guess "tuning" the back as I get shape, heighth and cleaning of the braces I like to see in them. I am not advocating this, but just another way I learned to them and like. Was more interested if this was what Carey and others were doing in Dana's shop when he was there. He does have top notch guys working there, and made sense to me.
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