It's Janko in panic mode again!

Janko

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I tried liquid courage but then I couldn't see straight and had to go to bed.
Maybe a bit of Underground encouragement can help if I may ask "again"?

I have my Ukulele top sanded down to 1/8th of an inch. My plans say .06" but good god! I pick it up and if I wasn't looking at it I would think I wasn't holding anything.
It is a Cedar top. Should I keep going? I think I can blow air through it already. I'm really worried that it will crumble or something if I keep going. It feels so fragile already. :confused:
 
What you are experiencing is normal newbie jitters. It's why most beginners tend to over build. You didn't mention what size you're building or what kind of cedar it is. I can't give you specific numbers because there's much more to it than that. But as a place to start I'd say that .060" is pretty much on the mark for a soprano, .070" to .075" for a tenor. I'm just guessing though, that's a general guide line. Someone with more experience with your particular species of cedar can put you on the right track. In any even, yes, you've got a long way to go yet. An 1/8" = .125". Waaaaaaaay thick.
 
In any even, yes, you've got a long way to go yet. An 1/8" = .125". Waaaaaaaay thick.

Waaaaaaaay More ?!
images


Ok. The top is Western Red Cedar and I'm working on a Tenor. The sides and bottom will be Walnut and the neck will be Maple.
 
A $25 orbital sander will take that cedar down to size in less than five minutes. You would need to leave some space for final finish sanding, of course, because the orbital sander will leave little spiral scratches from its rotation.
 
I haven't built a uke with a cedar top but I dunno if I'd go to 0.06 with softwood. Most plans are drawn for hardwood tops like mahogany or koa.
.125" is way too thick though.....maybe 0.09 for a softwood top??
 
I haven't built a uke with a cedar top but I dunno if I'd go to 0.06 with softwood. Most plans are drawn for hardwood tops like mahogany or koa.
.125" is way too thick though.....maybe 0.09 for a softwood top??

My plans actually say .06"+ but doesn't say what kind of wood . I used cedar. So I have to decide a thickness but I have no experience and I haven't found anything convincing on the internet yet.
.09 should be around 2 mm or about 3/32". I'll go to 3/32 if I can't find any more info about cedar tops.
 
I have made several concerts and tenors with Alaska yellow cedar. I make the tenors .075/.080 the concerts .070 I think the red cedar is a little softer than the yellow. Yellow is very springy makes great braces too.
 
My plans actually say .06"+ but doesn't say what kind of wood . I used cedar. So I have to decide a thickness but I have no experience and I haven't found anything convincing on the internet yet.
.09 should be around 2 mm or about 3/32". I'll go to 3/32 if I can't find any more info about cedar tops.

You probably won't find anything about going down to .06 on Cedar tops, but that doesn't mean you should still over build at .093 - I do my sides thinner than that. . .but not much. Then again, I wouldn't be throwing a high tension set of strings on there either, just in case.

Since you asked "again", I'll repeat what Chuck said, again, "WAAYYY too thick." I'll add, "almost 2x of where you want it to be".

Of course, if you stay at .093, and string it high G, you'll essentially have a Standard sounding Tenor. Of course, your bracing will come into play as well. If that's your goal, go for it. Personally, a softwood top tenor can bring so much more to the table than a hardwood Standard, or Concert.

But, that's just my $.02, and its coming from someone who doesn't like working with WRC. I do like the sound, but not necessarily the road traveled to get there. - Aaron
 
The mechanics of the deflection of ukulele tops is a complex subject, but we can probably make some gross simplifications for discussion purposes. The amount a material deflects under a given load is inversely proportional to its elasticity coefficient. Assuming you wanted to build a cedar ukulele whose top would deflect the same amount as the same ukulele built of mahogany, you could compare the coefficient of elasticity of one vs the other. Then, you would make the thickness proportional to that.

The properties of various woods are given here.

Cedar's modulus of elasticity seems to vary between 5,200 (Eastern white) and 8,000 (yellow). Western red cedar is about 6,500. The modulus of elasticity for mahogany varies between aproximately 8,000 and 10,000 from the tables. If we use the number for WRC and average out the mahogany, we would use 6,500 and 9,000 to get a ratio of 9/6.5 = 1.38. In other words, mahogany is about 1.38 times as stiff.

So if we wanted the top to deflect the same amount for a given string pluck, we would make the WRC about 38% thicker. For a 0.06" mahogany top, the equivalent WRC top would be 1.38x0.06 = 0.083. That would be my guess. This ignores the fact that you might want the cedar to deflect more to take advantage of a louder sound, and ignores properties such as density, which probably affect brightness etc. I might be tempted to go lower than 0.083 just to see what happens, but then I would not be too disappointed if the resulting instrument sagged after awhile.

We could refine these calculations by considering how much strain it would take to permanently set the wood, and look at elasticity in more than one direction of the wood fibers, but it starts to get complex. A copy of "Left Brain Lutherie," might come in handy for people who think such thoughts. Unfortunately, I don't own a copy.

If any of this is nonsense, blame it on the earliness of the morning (never do math early in the morning, especially on tax day).
 
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If any of this is nonsense, blame it on the earliness of the morning (never do math early in the morning, especially on tax day).

lol ...That wasn't bad for early morning. Wasn't sure what to do with the information though. Thanks everyone for your input.

Since Zog has had experience with Cedar tops I will start with about .080" on my first one just so I can get through it. and have one to play. My second build I will go thinner if the first one doesn't break in half.

I saw the pics of your 6 ukes Zog. Nice! but I noticed there wasn't a single Cedar Top Uke there? Is there something I should know about the thicknesses you mentioned? :)

If all else fails I can always resort back to Pete Howlett's method. "If it's too thick make it thinner. If it's to floppy make it thicker"

Anyway, my drill press planer finally arrived to day. I set it up like in the video I watched and it sure works nice. I tried it on Oak, Maple, MDF, Ply wood, Spruce, and Cedar. It works equally well on all the woods. Big day tomorrow. Finally!
 
I have used western red cedar on a couple of builds so far ( I build boat shaped, not the classic figure 8). Like Matt said, a hand sander will take it down to thickness in no time, just go slow and be careful. Also, wrc gets marked by anything that touches it, you have to treat it gently. I usually take my tops down to about .08" before final sanding. I'm a beginner, too, so don't put too much stock in anything I say.
 
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