advice on building oval hole mandolins

[WoodyMcKenzie]

My summer project will be an oval hole mandolin built from some beautiful koa that I have acquired and I am looking for some advice.

I bought an A2 mold from a fellow off ebay. I am wondering if all the Gibson oval holed mandolins have the same body shape-- does anyone know?

I spent the last few days at the Mt. Airy, NC fiddle festival and was lucky enough to get to see and hear several old Gibsons. Some of the A models seem to be quiet and unbalanced, with more bass and weak treble, though sweet. I brought a borrowed Hacklinger gauge along with me and took some measurements on two outstanding sounding F4s, a 1916 and a 1921 with a truss rod. Very rich tone and plenty of volume even on the treble side, these two instruments were quite consistent in the thicknesses of their back and top plates. They were also essentially twins in tone and indistinguishable to my ear.

During my limited experience building, I have gotten good results with X bracing and think that it is a structurally sound approach, but after hearing these F4s, I wonder if the conventional bracing scheme is worth trying. Is there a preference for bracing these? What do most builders do nowadays? Some of the old oval hole Gibsons I have seen appear to have sunken tops and I wonder if it is best to go with an X brace. Advice?

Also, were all those instruments arched similarly? How #high to make the arching? I have been told that the treble might be helped if the arching is brought up a bit. Do you believe that?

When you build an oval hole instrument, do you keep the body depth the same as an F holed instrument or should it be deeper?

What effect does it have to join the neck past the 12th fret on this style of mandolin? This would move the bridge closer to the sound hole. Is this ill-advised?

Should I elevate the fingerboard? That is what I am used to doing anyway. On these mandolins, does it matter, since the sound board is "broken" there by the sound hole anyway.

Finally, if you were using koa for back/sides/neck, what would be your choice for a top wood? (I have nice Englemann spruce and redwood which I bought from Spruce already on hand.)

Thanks for any advice you can offer. And I like to get opinions as well!

Woody

[BruceD]

I own several plans for oval hole mandos and have studied them quite a bit. They all seem a bit different, but also have some common features:

The plans I've studied:

F-4 set from Roger Siminoff
Loar A-5, A shape with F-hole, raised fingerboard from Roger Siminoff from the one-of-a-kind A model Loyd Loar Gibson (on the first or second Grisman Tone Poems CDs)
A model from Stew-Mac (matches their kit)
A model form Elderly (early teens a model Gibson)

Plus, I have traced some A models and owned a few.
Traced & owned a 1997 (or so) Gibson A-5L (different shape than the above Loar A-5)
I own a one-of-a-kind Weber A model with oval hole (hole was traced from a f-2, different than their stock oval hole)

I have owned several teens A-models, and an F-4 (should have NEVER sold that one!).

Differences/simialarites:

The old Gibson A model body is 13.5" inches long. They had a traverse brace (running parallel to the bridge) between the hole and bridge. Some tops have some cave-in, especially mandolas and mandocellos.

The stew-mac body is a shape under 13", like 12 7/8, pretty much like the length of an F-5 w/o the scroll and points. They recommend an X-brace, with the legs lined up with the posts on the bridge (X joint ahead of bridge). This puts the oval hole up higher than the gibson's.

My Weber is X-braced, with the X joint under or slightly ahead of the bridge.This puts the hole lower than the Stew-Mac - haven't measured to compare it and a teen's Gibson.

The Simnoff Loar A-5 plan is a teen era Gibson A model body with raised fingerboard, extended neck (joined at the 15th fret), and tone bars like an F-5. This puts the bridge up higher on the body than the old Gibson's that were joined at the 12th fret, (plus they were 13.75 scale length) instead of the F-5 13 7/8. Looks a little weird to my eye. Just imagine a teen Gibson with the bridge up about 1 1/2 inches.

My 1997 A-5L had an shorter body, F-hole, tone bar braced, joined at 15th fret. Pretty much an F-5 without the points and scroll.

Sound: I think the old f-4's and Gibson A's have a very distintive (and different) sound. The As being more bassy and woody, but lacking in high end like you noticed.

My 1997 A5-L sounded very much like an F-5. I had a Flatiron F-5 I played side-by-side and could hardly notice any difference.

My Weber sounds like an F-4 with more projection and volume, but not as much as an F-5.Still mellow, but some power. Like an F-4 with balls (couldn't think of a PC discription)

My conculsions are that the teens Gibson A models have more low end and lack in high-end is because the larger cavity volume, due to the longer/larger body.

Several sources recommended an X-braced pattern to provide the oval hole the support needed (big hole in the middle of the soundboard = weakness). The traverse brace probably does not give enough support from the bridge force, but does the give the oval hole the support it needs, which is why you noticed sunken tops.

What I am going to build is a a combination of all the features of the instruments. Basically the SStew-Mac Oval-hole and X-braces, but the joint closer to the bridge like my Weber, and the more vertical shoulder/sharper bend (by the 15th fret shoulders) like the teens A models (you'll notice a difference in the shoulders between say Webers/StewMac/Flatirons and orginal teen A models. Gibson changed their shape on A-5Ls somewhere around 1998 or so. Check out the different models of A-5Ls on elderly's site, the 1998 and earlier are different from the 2001 model)

I might try the Siminoff plan, just 'cause I'm wondering what it would sound like.

Anyway, that's what I found, I could be all wet. Hope this helps - let us know what you build and how it sounds! I'll do the same...

Bruce

[peter.coombe]

My opinion, for what it is worth (around 65 oval hole mandolins and mandolas built to date) -
(1) X bracing rules
(2) Engelmann and Koa should make a fine sounding mandolin. Redwood should also work well with Koa
(3) Higher arch will improve the treble and give you better clarity, but you may loose some warmth
(4) Make the body depth the same as the old Gibson A's
(5) Stuffing around with elevated fingerboards, body depth, soundhole positioning or long necks will change the tone. If that is what you want, fine, otherwise don't do it.
(6) Strong bass and weak treble usually means the soundbox is tuned too low. If the G string booms, it definately is tuned too low. It is possible to make well balanced oval hole mandolins (I do my best to do this every time), but in my experience of playing various oval hole mandolins, Gibson and others, success is rare.

Peter

[K_D]

This is a timely post for me. Excellent information so far! I've got a stewmac A kit that I have been waffling on whether to try their oval hole plan or to use it for f-hole tone bar practice. At this point I think the oval hole is where I'll go this time but I do have a question or two for those who have built these:
1. Should I leave the top a little thicker (or consistent thickness) around the sound-hole area or are the standard graduations ok?
2. Are there any issues with using purfling (1/8" wide herringbone) around the sound-hole as a very simple rosette?

Answers to these or any other comments would be be greatly appreciated.
Keith

[WoodyMcKenzie]

My first mandolin was a Stew Mac A kit which I made into an oval hole. I did get a decent sounding mandolin from it, but don't think you will get that oval hole sound that most people identify with. Some other mandolin players told me that they liked the tone of my mandolin, but it sounded more guitar-like than mandolin-like, if that makes any sense to you. I think joining the neck at the 15th fret (which is what you would have to do with the Stew mac kit) causes the bridge to be farther forward than on an instrument with a 12 fret neck. Maybe this is what changes the tone.

Woody

[Ed Ashley]

Bill Bussman is well known for his oval hole tone, and he uses X bracing. I would go with the englemann top, but I am partial to englemann, so....ymmv. Pay no attention to the StewMac A kit, it's a watered down F5, not intended for oval hole,IMHO. I would stick with original Gibson body depth, and if Peter says don't mess around with fingerboard extensions, etc, that's good enuf for me.
I also recently acquired an A mold off Ebay,so I am going to be following in your footsteps, as soon as I finish the two in -progress <g>, which will probly require some bad weather.
ED

[WoodyMcKenzie]

Ed--

Bussman posted #a #photo on his photo album website a while back that shows his X bracing for oval holes. They gracefully and quickly curve down and appear to not extend out quite as far as I have seen braces for F holed mandolins. I have had other folk tell me to extend the baces almost to the very edge of the plate. I wonder what other folks do (PBC?) as far as X bracing. If I understand correctly, then it isn't really bracing, but rather "plate stiffening". Seems like this could be achieved more efficiently by having very thin members that are tall in cross section. Maybe this kind of scheme would improve treble...

I am guessing that you also bought the A mold off ebay from the same fellow that I did-- John who runs Bluescreek Guitars. He also turned me on to quarter sawn sycamore binding which I like a lot.

Woody

[Ed Ashley]

I just remembered that Bill gave me some advice on thicknessing a while back;
"Ed- I carve the ovalhole with a 5mm area under the fretboard out to the
bridge, about 1mm thicker than the ffhole."
and
"ovalhole starting graduations-from the neck to the bridge, wide as a
tennis ball -5mm , 3/4 "wide strip on either side of that extending to the
tailblock-4mm, everything else outside the kerfing- 3mm - more for soft
engelmann, less for stiff red.
bill, sniffin the hide glue again......

I believe that Lynn D. takes his F5 tonebars all the way into the kerfing, but shaves them down so much they almost aren't there in the recurve area. Don't know how that might translate for an oval-hole.
Ed

[Bob A]

Just to confuse the issue, I notice you seemed put off by the Gibson's lack of treble. You might be well advised to at least listen to a Lyon & Healy carved-body mandolin (Style, A, B, C differ only in appointments, not in essential sound). I've found them to be wonderful mandolins, with a sweet yet balanced tone, and a strong treble presence.

[WoodyMcKenzie]

Bob--

Where can I see some photos of these Lyon & Healy's?

I have also been told that Vega cylinderbacks are loud instruments, but perhaps too difficult to build.

The sound of the best F4s I heard a few weeks ago was both rich and fairly loud. I would consider my effort a huge success if I could approach that sound.

Woody

[Ed Ashley]

Woody, check out http://www.mandolincafe.com/archives/builders/lyonhealy.html
and also
http://www.mandozine.com/index.p...._a_1925 (http://www.mandozine.com/index.php/instruments/instrumentinfo/lyon_healy_style_a_1925/)

Ed

[WoodyMcKenzie]

Ed--

Thanks!

These are beautiful instruments and remind me a bit of some of Stephen Owlsley Smith's larger mandolin family instruments. I have to wonder if they are braced similarly to Gibson oval hole mandolins. Does anyone know?

Woody

[Bob A]

Woody, if you plan to pass near Washington DC you're welcome to inspect a pair of Lyon & Healy instruments, and a cylinderback. BTW, the cyl-back is a whole different animal, much closer to a bowlback in sound, though louder, probably because of a larger top area. L&H is much closer to the Gibson concept, with arched carved top and back.

[Dave Cohen]

i did the modal analysis on a Lyon & Healy A, two F4's (including one which you heard a few weeks ago), an A3, an A4, a Vega model 205 cylinderback, and a '24 Loar F5 back in February. I had previously done modal analysis on two Neapolitans. Those results were reported in my talk at the 75th Anniversary ASA meeting in NYC on May 27th. I am now looking for a journal in which to publish those results.

The Lyon & Healy A's, B's, & C's and all of the Gibson ovals had a single transverse brace near the soundhole. Neapolitans were all ladder-braced, usually w/ three transverse braces; one near the soundhole, one near the bridge, and one further down in the lower bout. The Vega cylinderback had basically the same ladder bracing as the Neapolitans, but with some extra diagonals around the soundhole, and an extra brace above the soundhole. The back plate of the cylinderback had "cylinderback" shaped ladder braces as well. It is thus the only mandolin of the bunch with any bracing at all on the back plate.

I wrote a short article in 2002 for The Mandolin Journal in which I compared Neapolitans and archtop mandolins. TMJ is the quarterly newsletter of the Classical Mandolin Sociey of America ("CMSA"). At the moment, that is about the only place where you can find any comparison of ladder bracing to other bracing patterns. Except maybe Fletcher & Rossing's "The Physics of Musical Instruments', 2nd ed. Their chapter 9, on "Guitars & Lutes", has modal summary tables for some classical guitars, steel tring guitars, and one for a lute (ladder-braced). You may be able to get an idea of what is going on from those comparisons.