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Well not being too bright I need your advice again. I have not been too happy with the side flex of my braced and carved top. Now I realize that the top thickness is not what I thought. Measurments were made with calipers but the ends measure .115 and .120 with the sides as much as .136. The back is similar but I'm not as worried because it would be easy to sand the back to make the best thickness. I guess I will build tool to test the thickness with my dial indicator to get a more accurate measurement. Question: Will there be a problem to thickness the top by sanding the top surface? My goal here would be to measure and sand until I get some side to side flex since it currently seems too stiff.

I really didn't know one person can make so many errors. Oh well, at least I'm learning a lot.

Thanks

Philip

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aka konacat

If you think my playing is bad you should hear me sing!
Practice breeds confidence and confidence breeds competence. Unfortunately, I'm stuck in practice.

i'm not sre what you mean by "side flex", and you didn't mention what you are building; if i recall corectly it's a uke?

making a caliper using a $7.00 dial indicator and a scrap of ply is a good investment.

i've not built one but i've read that uke tops can be quite thin, like on the order of .085 - .095" and the sides .070 or so.

it sounds like you have left too much wood around.

as for errors, don't be so down on yourself. we all make them, time after time.

Sorry, Its my first guitar and its a dreadnaught with a lutz top. If I hold the top on either side and try to flex the top it is stiff as can be. It is my understanding there should be a little flex.

_________________
aka konacat

If you think my playing is bad you should hear me sing!
Practice breeds confidence and confidence breeds competence. Unfortunately, I'm stuck in practice.

If the top is braced where abouts are you holding it when you try and flex it? If youre holding it close to brace ens then I wouldnt expect any sort of flex. If youre holding it well clear of braces then I would expect a little bit of flex depending on top thickness and brace design.

Once my tops are thicknesed I take caliper readings at close distances (every 100mm) and then mark same on the top with a pencil. I then photograph the top with markings so I have a permanent record of each tops thicknesses.

As Hesh said, the braces themselves can be adjusted at this point if you feel it is too heavily braced as well as the top being too thick. As for top thickness, I would leave it as it is until the top is glued on*. It's just easier to sand that way, with the rim (sides) supporting the top. Then you can sand, either by hand (with a sanding block) or with an ROS (before you put the bindings on, so that you can see the thickness of the top from the edge). Many people, including myself, believe that it's a good idea to thin the top more around its periphery, leaving it thicker in the middle. Your top thickness in the middle may be just fine as it is, but you could thin it down around the outer couple of inches or so, just watching the edge thickness to make sure you don't go too far - down to about .100" around the periphery (or possibly even less) should be safe, but you can decide where to stop. Another thing I would do to make sure I'm not thinning it too much anywhere is put light pencil marks ("witness lines") all over the top before starting to sand. That way you can see how much material you're removing from where. You can add more witness lines as you go, if necessary.

*If it were me, I would definitely make or buy some thickness calipers to measure the thickness of the top in several places that you can't reach with standard calipers, before gluing the top on. I'd want to know how thick it is in various places near the middle before I start thinning it further.

As for flexing, I think it's very hard to tell anything from flexing the braced top that's not glued on yet. The flexibility is so highly variable depending on where you hold it. Once it's glued on, you can gauge deflection if you want by pushing down in a certain spot (say, where the bridge will go) and get a much better idea of how much flex you have in the top as a whole.

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

Phillip, you said this is your first guitar, so my advice would be make a thickness guage, doesn't have to be fancy a cheap dial indicator in a plywood body like this takes half an hour.



Then, thickness the whole top to the 0.115" dimension and leave it alone. You can leave the bit around the rosette alone if your worried about thinning it too much. Believe me most of the large manufacturers just run their tops through the sander and leave it at that. Don't try to overthink this one, learn from it.

Don't worry, even though it's a dreadnaught it will still sound like a guitar probably better than most.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

We have a saying at my work and it is:

"If you aren't making any mistakes, then you're not working."

Everyone is human and we all make mistakes so don't sweat it. It's one of the best ways to learn.

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Thanks,
Blain

http://www.ullrichguitar.com

"89.67% of all statistics are made up on the spot."