Top: #How Thick?

[davestem]

I've been scoping out my IV A-style kit between bouts of working on a Stewmac guitar, and also re-reading the Siminoff book. #One thing that I haven't found much about, though, is how thick (or thin, really) to carve the top and back. #I found a reference in the Siminoff book that he likes the "minimum area" (recurve, I gather) to be about .110", but other than this, I haven't found much guidance. #The drawings don't show thickness contours for the top and back.

# # I know that the experienced builders here talk about changing the graduations to suit the piece of wood, but I have no experience by which to decide how stiff my top and back are. #What are some middle-of-the-road numbers? #Or a range--the thickest and thinnest you make the tops at points in the contour?

# # I'm afraid, of course, that I'll underdo it and have a dead mando, or overdo and have the top sink. #If I can find some nominal specs, I'll just use those and hopefully get a reasonably good-sounding instrument. #Thanks very much.

[bryce]

lmi is offering the 1923 loar drawing by (I think) Ted Davis again. These drawings have a mapped out, sort of topographical section on the thickness of a particular loar. Of coarse the stiffness of the top wood on your kit may very well be different. But it would give you some idea where to head.
Bryce

[davestem]

Thanks, Bryce. I was sorta hoping for something for free, though...

(Spoiled by the wealth of information here, I guess.)

[Spruce]

Here ya go....
Courtesy of Bill Bussman....

[Spruce]

The back....

[Chris Baird]

Those are mm without the decimal. Loar spec reports vary widely and I suppose it is because Loars vary widely(?). Your arch height and shape will dictate much of your ideal thickness.

[Rob Powell]

Spruce and Bill,

Thanks muchly...love to have all the info I can get...some pretty thick spots on that one...

Davestem...the numbers are mm's not thousandths...most of 'em just don't have the decimal pernt..

[thistle3585]

I was going off Drawing 6 in Siminoff's book as a starting point. Basically, drawing lines and elevations then going back and plotting them on the body drawing(#8 I think). I compared these to Andrew Mowry's elevations posted on mimf and they came up fairly close. Thanks Spruce for the drawings above. I'm going to convert my measurements to metric and do a comparison.

[davestem]

That's wonderful. Thanks, Spruce.

[daveb]

Is anyone using these ? This converts to .157"-.165" under the bridge, and .137" in the center of the back. This is much thinner that Siminoffs plans.

Well http://www.mandolincafe.net/iB_html/non-cgi/emoticons/rock.gif I do have some good close grain red spruce.....and I haven't emploded one yet http://www.mandolincafe.net/iB_html/non-cgi/emoticons/rock.gif? May try it.

Dave

[daveb]

Anyone carving this thin ? I think the conversion is correct. (.03937 x MM = .000)

Dave

[davestem]

What do the Siminoff plans show for the thickness under the bridge? #I wonder if there are pages missing from my Siminoff book...

[daveb]

I'm pretty sure its .200"

Dave

[thistle3585]

I have three sets of plans and I have .140, .125 and .226.

[daveb]

Does anyone know the "Cave In" point with good close grain spruce ?
Is it a general belief that the best tone possible is just above the breaking point ?

Dave

[oldwave maker]

Keep in mind those loar measurements were for that piece of finegrain old growth west virginia red spruce, probably carved by someone with the sound of a mandolin orchestra in their head. One thing the hacklinger thickness gauge taught me was that there are lots of ways to skin a cat, and its hard to mess up really good tonewood.

[Spruce]

"Is it a general belief that the best tone possible is just above the breaking point ?"

It's amazing how thick (chime in here Bill) some fine-sounding mandolin tops really are...
I think that one intuitively thinks that tops should be thin, but the real cannons I've played recently are carved pretty thick...

[Hans]

My personal opinion: While a thin topped instrument may offer "instant gratification"...thin instruments sound thin. To put it another way, you will never get a fat sound out of a thin top.

[John Bertotti]

So what range are the thicker tops graduated to, round about? John

[daveb]

Thanks for all the replies, Hans that makes good sense. I just refinished my first mandolin and I thinned the top quite a bit more. I am probally around .175 in the center and .080 in the recurve. I refinished with varnish and French Polish. It is very loud now.....but as Hans stated it is pretty "thin" sounding also. It doesn't have the "Punch" I am after.

Dave

[Chris Baird]

I wouldn't go below .090" in the recurve and make sure there is a least .120" right in front of the tailpiece. That "map" doesn't show all, i.e. right under the strings.

[Hans]

As Bill said, "There's lots of ways to skin a cat". Or as they say in Minnesota, "Oooh no you don't! #http://www.mandolincafe.net/iB_html/non-cgi/emoticons/wink.gif

[Dale Ludewig]

I guess I'm going to deal with it in mm. But in essence, depending on the piece of wood, I'm in the are of 1/4" just under the bridge- now changing measurement systems, I'll go to about 2.5 on the top and maybe push it to about 2 mm on the back in the recurve area. But that's pushing it. It all depends on the piece of wood and something you have to learn. And personally, I don't think writing down all the specs of a particular instrument do any good at all. I think you have to learn to do it by intuition, within the general guidelines. And I don't think there's any shortcuts to that.

I will say this strongly- my experience leads me to believe that you leave an about 2" wide strip right down the middle that is thicker than the rest of the graduation. That is where the main stress to collapse the top, buckle the whole thing, happens. Especially between the bridge and the tailpiece. I'm not sure how much vibration in that area takes place or matters. But it has to be strong in that area, IMHO.

And Hans, in response to your quote of the meenasotans, I shall quote one of the characters from (I think it is the Vicar of Wakefield- great British comedy on Saturday nights on PBS)- "no, no ,no , no, no, YES!" Pretty funny.

Can't be serious all the time.

[oldwave maker]

So bruce hayes great 87 nugget f5 is 2.8 under the bass post of the bridge, while bruce harvies great 03 sullivan f5 is 4.5. forget the numbers, luke, use the force......

[PaulD]

Dale said:
And personally, I don't think writing down all the specs of a particular instrument do any good at all. I think you have to learn to do it by intuition, within the general guidelines.
I'm appreciative of the "general guidelines" and individual specs that are available. It gives me a range/point of reference to use when I carve my first top. Your point is well taken that "newbies" like me shouldn't look at a particular set of measurements as the Holy Grail, but I found this thread very informative and I appreciate the numbers y'all have laid down. I'm going to be carving some Englemann and Sitka; from what I know of these woods I would expect to have to leave the Englemann on the thick side moreso than the Sitka... but the only way I'll know is to dive in! http://www.mandolincafe.net/iB_html/non-cgi/emoticons/smile.gif

Paul Doubek

[daveb]

Whew !!! I'm glad we got that straight. LOL
I have just been under the impression that thick tops have more mellow tone but less volume. I, like most of us are trying to find the best of both.
My #2 mandolin is around .230 under the bridge and .100 in the recurve. Already it has good tone and woody chop. It is not as loud as one I refinished and thinned quite a bit.
But I am learning that Thin = Thin. Per Hans.

Dave

[Jim Hilburn]

Some of my early mandolins were quite thin, to the point of seeing distortions in the top. They have consistantly been the fullest, loudest, darkest ones I've made.