one piece top

[phynie]

I was just taking peek at the site and noticed that Mr Brentrup was building a 3 pointer with a one piece top. What would be the advantage(if any) to having a mandolin with a one piece top?

[arbarnhart]

I have really limited experience, but will throw out the obvious answer anyway. A glue line interrupts the natural vibration. Done well, there is almost no impact, but there is impact. The flip side is that two parts are often bookmarked so the vibration characteristics should be symmetric.

BTW, I am building a 3 part mando top mixing woods. I may soon discover why no one seems to do that...

http://home.nc.rr.com/abhobby/images/sound%20boards.JPG

Below it is a top with even more pieces (will be put together and sanded smooth) for a bari uke that is largely decorative but will be playable.

[Spruce]

One could make the argument that if a one-piece top had wide grain on the bass side and tight grain on the treble, it might be advantageous.....

Hard to prove in any event...

It sure is a cool look, whatever the tonal outcome....

[PaulD]

I always used to like the symmetry of a nice bookmatch, but the more one-piece instruments I see here and on MIMF the more I like that look. I don't know tonally how much difference it makes... I don't have a sophisticated enough ear to tell. Since there are excellent and violins built both ways (and, conversely, mediocre mandos built both ways), I figure it's really a matter of aesthetics and, as Chris Baird (IIRC) said in another thread, "If it looks good and sounds good, it is good!"

Paul Doubek

[Dave Cohen]

There is absolutely no physical evidence that a glue line "interrupts the natural vibrations", unless either (a) the glue line is very poorly done, or (b) one uses something extremely inelastic for glue, like, say, silicone bathtub sealant, or some such.

[arbarnhart]

Most of the articles I read (you can easily find them googling for sound board glue vibration) were what you might consider "poorly done" I guess, as creep over time and use of adhesives with a lot of solids were mentioned as primary factors in problems. So I believe that you are correct that if it is done perfectly it poses no problem.

[Michael Lewis]

The main benefit to a one piece top is that there is no glue joint to make.

Gluing dissimilar woods into one top may well introduce stress from different expansion rates of the woods as the humidity changes.

[Dave Cohen]

So many assumptions.

Michael, what do you think the consequences of "stress" are? I ask because I don't think that anyone has made an objective attempt to answer that. Young, in his guitar making book, held tenaciously to his hypothesis that any "stress" in the building process should be avoided. As he presented it, it was really nothing more than a hypothesis.

Otoh, numerous mandolin and archtop guitar builders have deliberately "sprung" their braces or tone bars when gluing them into their top plates, insisting that they got a noticeable increase in acoustic volume from the springing. Benedetto, in his archtop book, argued against the springing of braces, giving the reason that over time, the "stress" or "tension" in the sprung braces would go away as the bracewood relaxed into its configuration, and the acoustic volume would then decrease as the instrument aged. My point here is that ALL of this (i.e., both viewpoints) is conjecture. I don't think that there has been a measurement offered in support of either position. Oh, sure, lots of anecdotes in the form of audition, but nothing that is either verifiable or falsifiable.

Here is something to think about. Harry Fleischman has been building guitars with half spruce/ half cedar or redwood top plates for some time now. I think that his guitars hold up over time. You could always ask him about it.

[Spruce]

"Harry Fleischman has been building guitars with half spruce/ half cedar or redwood top plates for some time now."

Then there's the infamous half-and-half A-model built by Will Kimble...
Engelmann on the bass side and Red Spruce on the treble...

[arbarnhart]

Well it looks like I am in good company! My top is cedar and mahogany. It will be a few days (at the very least) before it gets played. This being my third instrument, built from only general instructions, it is likely to be far from perfect in other areas anyway.

[Michael Lewis]

My main concern with different varieties of wood glued into one piece is that you may well get different expansion/contraction rates from the different woods. This is where I surmise the stress would manifest. You are probably right Dave, it could work just fine with no detrimental consequences. The structure of an instrument is already 3 or more varieties of wood, I wouldn't add more to my instruments. That's my gut feeling. http://www.mandolincafe.net/iB_html/non-cgi/emoticons/wink.gif

[GBG]

Engelmann/red spruce tops sounds like an interesting concept. I wonder how they work, or is there any way to really tell?

[Will Kimble]

Just saw my "half & half" mandolin at Merlefest this weekend, and it sounds great. #No signs of stress from the different top woods, and the arching looks beautiful. #

I haven't built any others this way, but can't think of any reason not to...

Will Kimble

[John Bertotti]

Will Kimble, thanks for the update I have been vary curious of that instrument since you first posted it. Thanks John http://www.mandolincafe.net/iB_html/non-cgi/emoticons/smile.gif