How flat the flat top?

[warren]

Im about to brace my first flat top, and was wondering if it should be flat or slightly arched. If it is arched does it only arch in the centre and flatten at the edges? if not do i just glue it on to the sides with force or do i angle the top of the sides to accomodate the arched top. Hope this makes sense. Also how thick do you like your tops?

[Paul Hostetter]

Arch it! Dead flat tops end up sagging under string tension and sound like banjos. Adding some stress by pushing it up under tension because you've glued it to curved braces will offer resistance to the string pressure and it will also have a very beneficial effect on the sound. There's one other important aspect as well: when a top dries because of atmospheric conditions and has to contract across the grain, if it's flat it'll crack because it has no choice. If it's domed (I prefer this term to arching, which implies plate carving), the dome falls a bit, but the top doesn't tend to crack.

[Dave Hanson]

Well known British builders Fylde make true flat top mandolins with no problems, both John Sheehan and Barney McKenna of The Dubliners play them.

The tops are properly braced.

Dave H

[Nihilist37]

I'm also making a flat top oval hole and had considered several different bracing patterns. I decided eventually (with the help af a luthier) on the H style bracing GMcD showed on here. I did however make a few changes. I had softer timber so I was worried a little with the idea of the top sinking. To get around this I decided to make the braces join to both the head and tail block quite firmly. There will be a slight scoop toward the ends and then goes thicker again to meet the blocks. Additional to this there will be two braces going across the body for the extra support. I did this mainly because my pattern was more guitar shaped and thus needed a more guitar like bracing system.

[labraid]

So that's how Barney gets his sound! The banjo sound is true, but only with tops thinner than 3.5mm or so, non arched. Been there! And Barney is a banjo player, so....
Man I love those guys........ The early pub days anyway!

Oh, and to add.. Many are many who will argue this, but I still stand by it. Make your tops thick if you want a sweeter sound. I'm talking 5.5mm like an archtop is at center. It will take a few months to break in, but the sound is then just edible, not peircing or tinny..... "Try it 'fore you knock it."
I use a 3mm/.125" induced arch across a 10" top.
Goodonya for paying some mind to this oft ignored mandolin.

[Jim Garber]

Well known British builders Fylde make true flat top mandolins with no problems, both John Sheehan and Barney McKenna of The Dubliners play them.
These most likely have some slight induced arch, right?

All of the vintage flattop mandolins I have seen have had some arch in it, however slight.

Jim

[whistler]

5.5mm? I wouldn't cut [/I]cheese[I] that thick! Still, anything's worth a try.... I'm gonna make me a sandwich.

[whistler]

Why don't they Italics work for me?

[Bill Snyder]

Why don't they Italics work for me?
The first i should be without the / and the last i gets the slash. just to make sure I am telling you right .

[Antlurz]

Yup. You reversed the code.

Ron

[Dave Hanson]

jgarber, no there is no arch at all, and the standard Fylde Octavious mandolin has a cedar top.

Dave H

[labraid]

We should maybe ask before wondering about bracing, etc, are they solid tops or ply?

You could always lightly bake the top before attaching it, that'd eliminate the risk of shrinkage anyway...

[Jim Garber]

jgarber, no there is no arch at all, and the standard Fylde Octavious mandolin has a cedar top.

Dave H
Sorry, Dave...

I emailed Roger Bucknall at Fylde. Here is his reply (verifying Paul H's comment above):

I dont know why your friend would say that, all our instruments have a built in arch, its an important part of their structure. Any instruments that are made without an arch are likely to suffer from climate changes and other problems.

Only on "arch top" and "carved top" instruments etc is the curve significant, and those instruments have a different tone character. So called flat top instruments generally have about 2-4mm of rise , some of which dissappears due to the downward pressure of the strings, but the built in stresses remain, to counter string tension and possible shrinkage.

Any instrument (guitar, mandolin, bouzouki etc) that is built with an actual flat top will be "hollow" or depressed once the strings are tensioned., allthough that can be a sign of other things as well.

Jim

[Dave Hanson]

You win Jim, I played a Fylde mandolin for ten years and couldn't detect an ary arching but Roger Bucknall is the man. I still have a Fylde octave mandolin, supposedly a flat top but I can definately detect a slight arch in the top.

Dave H

[Jim Garber]

We all win with an understanding of how these work. I first realzied it when I made a bridge for an old flattop and realized how high the arch actually is. Nowhere near or as obvious as the archtops, but definitely convex.

Jim

[Paul Hostetter]

And people still refer to Gibsons as "flat backed."

[MikeB]

So much of this stuff is relative, I guess. Gibsons are very flat compared to bowlbacks. http://www.mandolincafe.net/iB_html/non-cgi/emoticons/smile.gif