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Building Too Thin - Tops Collapse
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Author:  rich altieri [ Thu Jan 03, 2008 12:35 pm ]
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I finished up this small parlor guitar about year ago and happy with the look, feel and sound. Brazilian B/S with Englemen top.

I went pretty thin on the soundboard trying to extract as much bass and volume out of this small guitar as i could. Think I went down to around .10 and thiking small area, stiff top, should be fine. Went thin trying to improve on bass and volume. It worked, except

Noticed the other night the soundboard is collapsing a little on the bass side of the guitar just north of where the x brace ends adjacent to the sound hole. The area between the upper traverse brace and the x brace is very short which added to my surprise that it couldnt handle the stress.

Not sure what to do at this point but thinking of removing strings and reinforcing soundboard with a spruce patch that would go between the traverse brace and the x brace to add some weight and strength to this are of the sound board.

Any thoughts (besides build a new soundboard)?

Author:  Jody [ Thu Jan 03, 2008 12:46 pm ]
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  this time of year , it could be a drop in relative humidity causing your top to sink in ..  I have a martin d-28... was using the wood stove before I  was informed of the importance of humidification ... I took it out to play it and the strings were flat on the fingerboard,!  I was very very lucky the top didnt crack on me  !  after a few weeks ( or maybe a month) in the proper environment , the top returned to normal....     Jody
Author:  Lab1 [ Thu Jan 03, 2008 2:11 pm ]
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[QUOTE=rich altieri]


Any thoughts (besides build a new soundboard)?


[/QUOTE]
To me you have learned a valuable lesson.....It's a great opportunity to learn more.I would remove it and build a new soundboard...Larry
Author:  Steve Saville [ Thu Jan 03, 2008 2:32 pm ]
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Collapse is a strong word.  Do you have any pictures? I build light and expect my tops to have the braces showing after some time.  Is it collapse or just some movement? 
Author:  Mark Maquillan [ Thu Jan 03, 2008 4:37 pm ]
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I'm just starting a Parlor model roughly using an existing plan. It calls for the top to be .090. Is this too thin to start with? Since Rich is having the problem with his top I'm a little concerned.


 I have been more dilligent with using my Planet Waves humidifier with my everyday guitar since I have been running my wood stove also this winter.


Rich, what type and size bracing did you use?


Mark
Author:  Kent Chasson [ Thu Jan 03, 2008 4:58 pm ]
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Noticed the other night the soundboard is collapsing a little on the bass side of the guitar just north of where the x brace ends adjacent to the sound hole. The area between the upper traverse brace and the x brace is very short which added to my surprise that it couldnt handle the stress.


As Steve suggests, a photo would be helpful. Or at least a diagram or some clarification. The area where the X-brace ends is not typically adjacent to the soundhole and not a place you typically see caving.
Author:  TonyKarol [ Fri Jan 04, 2008 2:56 am ]
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Sounds to me like a bracing issue Rich .. 0.100 is TONS for a parlour, heck my full size (16 inch+) spruce guitars are usually between .105 and .115 once completed .. I would bet that alot of the ES schooled folks are pretty thin as well. I am thinking the upper transverse is not as stiff as it should be, and the top is diving in from the neck forces .. the bridge is likely too far back to be causing this, although it can have some affect. How thin/tall is the X brace in this area ??? What is the action and bridge/saddle height (strings above the top measurement) ????
Author:  Steve Saville [ Fri Jan 04, 2008 3:16 am ]
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[QUOTE=Max1157]

I'm just starting a Parlor model roughly using an existing plan. It calls for the top to be .090. Is this too thin to start with? Since Rich is having the problem with his top I'm a little concerned.[/QUOTE]
Mark,
It depends. If you bought the plans from a reliable source and you know that other guitars have been built successfully from the plans, then you'll be just fine. If you are nervous, add .005".
I build OMs, 000, and SJ with tops as thin or thinner than .090" without issue, but I have redesigned my bracing to accommodate that.

My 4th guitar is an OM traditional build with a .110 sitka top and it is dipping in front of the bridge. Why? Because I shaved the X braces too far and didn't make them tall enough. I say that to let you know that top thickness is only part of the equation.

Author:  Laurent Brondel [ Fri Jan 04, 2008 4:31 am ]
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[QUOTE=rich altieri] Think I went down to around .10 and thiking small area, stiff top, should be fine.[/QUOTE]

Did you measure the top at .100" before assembly? Englemann, like WRC and redwood, sands very easily. How much did you sand the top before finishing and what grits did you use? The top could easily lose .010" to .015" with machine sanding. A picture would be great though.
Author:  grumpy [ Fri Jan 04, 2008 4:43 am ]
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Measurements mean NOTHING. I have a red spruce top here that is .156" thick. It would collapse within 2 weeks if I used it as a guitar top. It is that weak...

But if I wrote here that I have a 2 week old guitar with a red spruce top that is .156" thick, ad it looks to be imploding upon itself, we'd all say that something or another went wrong, but for sure, I can't be the top because red spruce at that thickness MUST be super stiff and strong. Right? Right!

But we'd be dead wrong....

With that, let's not look a the numbers. Lets look at what else may be wrong. Perhaps it was sanded too aggressively before finishing(a coomon issue with everyone's first instruments is that we don't always know when to stop, and the one thing we do know is that any scratch or ding can only be fixed by more sanding <bg>).

Could be the brace pattern. Could also be how the braces were shaped; I see a lot of y'all's photos of your tops here and cringe at where y'all remove material!).

And, here's the biggie, could be nothing wrong, and simply a nicely built, yet lightly built, guitar beginning to show some age. Have you studied some vintage Martins and Gibsons? I mean, 1939 or older? They ain't flat tops no more...

So, put down the tools, take a good photo to sow us how much sinking you have. Do NOT rush-in to fix something that most likely isn't broken.
Author:  JJ Donohue [ Fri Jan 04, 2008 5:53 am ]
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[QUOTE=grumpy]...Could also be how the braces were shaped; I see a lot of y'all's photos of your tops here and cringe at where y'all remove material!)...[/QUOTE]

I'd be real interested in knowing more about those observations. I don't care to know whose bracing you observed (unless it's mine!)but it would be educational to hear what you have seen and where we can improve.
Author:  grumpy [ Fri Jan 04, 2008 6:49 am ]
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My New Year's resolution was to not argue or hurt feelings here <g>

Y'all are doing great! Lovely work...



I'll make it a point to say so next time I see something goofy. But I'll say it, and likely not go back for the follow up arguments.

This forum's become much more fun, and simple, since I figured out who's posts and threads to read and who's not to.
Author:  grumpy [ Fri Jan 04, 2008 6:51 am ]
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Hey! Crap!

When did I go from cocobolo to koa? That's a backward move....
Author:  Don Williams [ Fri Jan 04, 2008 8:01 am ]
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[QUOTE=grumpy] Hey! Crap! When did I go from cocobolo to koa? That's a backward move....
[/QUOTE]



Not if you're building Ukes...   

Hey, don't feel too bad, according to mine, I'm still a sponsor! What's wit dat?
Author:  grumpy [ Fri Jan 04, 2008 9:14 am ]
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Not if you're building Ukes...

And that would be yet another backward move.



<running>

<ducking>
Author:  Heath Blair [ Fri Jan 04, 2008 11:05 am ]
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not that i didnt like the old grumpy, because i really did, but i also like the new year's resolution  grumpy. youre cracking me up man. Big smile
Author:  rich altieri [ Fri Jan 04, 2008 9:25 pm ]
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Thanks for all the posts. I was away for a couple days but will take some pics, take some measurements and do some posting. Maybe a good learning opportunity for all - for sure a good one for me.

Hey Grumpy - I love your responses. Don't ever worry about offending me - that goes for the rest of ya as well.

Look for some pics over the weekend and thanks again
Author:  rich altieri [ Sun Jan 06, 2008 10:50 am ]
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As promised, here are some pictures to show the problem. Pretty difficult to capture and hope this helps.


Drew in a couple lines that show approx location of x brace and sound hold brace. What is caving in slightly is the are in the middle.

The above shot shows a straight edge sitting on top of the x brace and going to the fret boad area of the soundboard just north of the soundhole.

Also, the xbrace is showing the outline on the soundboard just where the problem starts (not the entire length of the brace)

FOllowing are some pictures of the guitar which is Brazilian back and sides with I think an adi top but cant remember. It's in the middle of some repairs to some binding that came loose and applying some additional french polish were it got scuffed up from bring on the road with me.






Author:  Alexandru Marian [ Sun Jan 06, 2008 11:04 am ]
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Not the first place a top would cave in, isn't it?  Odd.

How is the connection because upper transverse and sides. Was the bar of good spruce?  Is there any distorsion on the side or on the back.  Wondering if the neck might be creeping up.

With a steel string guitar, the neck first wants to creep out of it's joint. If it can't move from there, then it pulls on the box...primitive thinking but it seems that is what happens. (my impression from the dovetail neck classicals fitted with steel strings we use around here as campfire beaters)



Author:  rich altieri [ Sun Jan 06, 2008 12:17 pm ]
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Alex, I suspect you are right. There is no movemen of the sides or back and it looks to me like the fretboard pressure is more than the soundboard can handle. The soundboard in the area most effected seems very thin. Perhaps I thineed it too much when finish sanding. I dont think the braces are failing from what I can see.

Also, just a correction, I said this was Englemen in the early posts and then in error said it was Adi. It is definately Englewood so it might be too thin for Englewood.

I might try putting a Spruce path in the area, kind of double the soundboard just between the traverse brace and x brace. Dont think it will impact the sound all that much and if that fails I will make a new top.

Author:  Alexandru Marian [ Sun Jan 06, 2008 12:41 pm ]
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I hope it turns out alright.... its a pretty little guitar!
Author:  Alexandru Marian [ Sun Jan 06, 2008 12:50 pm ]
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Ironically, a couple days ago a friend brought in his cheapo steel parlor with a serious neck disjoint, theres already more than 1mm of gap and the action rocketed. 

I just put a straight on it and the cave-in is huge. Ladder braced. The lower bout looks just fine though. Insanely overbraced as well.
Author:  Alain Lambert [ Sun Jan 06, 2008 12:54 pm ]
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Very nice little guitar.

This is a 13 fret to the body. Was that the original plan or did you adjust the bracing accordingly?
Author:  rich altieri [ Sun Jan 06, 2008 10:10 pm ]
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The 13 frets to body was part of the original plans.
Author:  grumpy [ Mon Jan 07, 2008 4:44 am ]
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That doesn't look bad enough to warrant replacement, for sure. Just keep a eye on it, ad it it continues further, come back ad ask again. For now, get the feeler gauges out, and measure the dip(straight edge, feeler gauge), ad record it. Check again in 6 months, then a year, etc... It should stop at some point(wood can only move so much before it takes its set). Only if it doesn't ever stop moving should yo interfere.
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