Building your own resonator guitars and resonator mandolins
Anyone care to swap stories on building resonator-type instruments?

Jon Whitney - 05:53pm Apr 29, 1999

This discussion is an outgrowth of a discussion on metal plating which is found in the "tools, glues, and finishes" section of the forum.

I mentioned that I had built a metal bodied resonator mandolin, and Mike Dotson wanted to know more about it. I thought the discussion would be more appropriate here.

Several years ago I got a hankering for a metal bodied resonator guitar, and not being so irresponsible with my money so as to go buy one, I began to think of building one myself. As I had no experience up to then in building instruments, but being cocksure and bullheaded, I decided to first see if I was capable of such an undertaking by building a smaller instrument - a mandolin.

After a little advice from a local luthier and reading a few books - the most influential of which was "Building Musical Instruments" by Irving Sloane - I started in.

My first step was to go into a music store with a tape measure and write down some of the critical measurements - neck length and width, body dimensions, etc. Next, I needed to get a few critical parts in order to get precise measurements. I bought a cheap set of mandolin tuners from a music store. I went to a thrift store and spent 25 cents on a 9-inch pie tin - the kind they give you when you buy a pie at Marie Callendar's but without her name embossed on the bottom. This was to become my resonator. With these in hand, I proceeded to draw a full scale plan.

The next thing was to procure the rest of the materials. I was able to get some used sheet steel at a local supplier, in two gauges - heavy and heavier. I bought a hard maple board (slab cut) and a few of what they called maple flitches from a hardwood lumberyard. The maple flitches were about 1/20" by 5" by 36", fairly rough and soft. Also cheap. I bought a leftover piece of teak veneer from them also.

I got a rosewood preslotted fretboard, a truss rod, and a few other small parts, plus fretwire, from Stewart-MacDonald.

With the maple flitches I laminated a banjo pot type of hoop, following the method outlined in Sloane's book. It wasn't perfectly round but it was strong. I built a neck by laminating four pieces of the hard maple side to side, with a center strip of the teak veneer. After many long hours of manually sanding it flat on top (this was before I had a jointer) I judged it ready to bandsaw a profile. I dreaded the prospect of trying to carve the neck but actually found it to be the easiest part of the whole instrument.

Meanwhile I built the body from the sheet steel. I used one strip for the sides (the mandolin is pear shaped or "A" style), one for the top, one for the bottom, and some notched strips bent into brackets to fasten the top and bottom to the sides. I soldered the brackets to the top and sides, but soldered some nuts to the brackets and fastened on the bottom with flat-head machine screws after plating. I built a heel block out of maple and a brace between it and the laminated hoop. There was about a half inch gap between the hoop and the tail end of the body, which was filled by a maple tail block. The wood pieces were fastened into the body after it was plated, with screws.

I made molds out of the heavier gauge steel to emboss an egg-shaped area on the mandolin back, and to pound out a cover plate. The cover plate was also made of the heavier gauge steel. I cut an oval hole in it where the bridge sticks up through and drilled a nice pattern of holes for grill work. I also cut some F-holes in the top using a drill, coping saw with hacksaw blade, and files.

I attempted to build a tailpiece from the steel which looked nice but failed when I eventually strung the instrument. So I bought a commercial tailpiece and screwed it on.

After getting the metal parts plated at an automotive plating shop, I assembled the instrument. I let the pie tin into a rabbet in the top of the hoop. The bridge was sawn and carved from a piece of maple - it is about 1 1/2" tall and rests directly on the pie tin, sticking up through the cover plate. It has a Corian saddle. It could probably use a lot more refinement.

I strung the instrument up and (after replacing the tailpiece) was pleasantly surprised to hear that, considering the pie tin resonator, it didn't sound half bad, was fairly loud, and was playable. It could use some slight adjustments to the action and intonation. And if I had to do it over, I would do it in a way to be able to solder on the back rather than screw it on, while still allowing access and disassembly. But all in all I consider it a successful experiment.

I never built the guitar yet - I've been busy remodeling, building cabinets etc, and meanwhile I've become interested in building banjos more than guitars anyway. But someday I might do it still. And when that day comes, I'll know that I will be able to do it successfully.

P.S. I'll try to get a picture or two of this beast scanned in and submitted.

Thanks for the info Jon. I built my National knock-off using a blueprint from Resophonic Outfitters. I used .32 galvanized sheet steel. a national cone and a reproduction tailpiece and coverplate from stew-mac. I also got a pre-slotted 25' ebony board and other assorteds from s/m. The neck is one piece flamed maple that is way too pretty for this guit. Since plating is so expensive and this was also my first time beating out a metal guitar I painted it in the style of a 1930 walnut sunburst Triolian. It turned out great, plays like a dream and the volume and tone is unreal. The type of cone you use is vitally important as I've found from playing with Dobro's over the years. In a biscuit cone type like this or Jon's mandolin use either a quarterman or the one's from National Resophonic. National will sell you cones but tend to be hesitant with tricone parts and coverplates. They stated to me that they inadvertantly created competition for themselves over the years and only want to sell for replacement and not to builders.

I've also done a solid body resonator similar to the Resolectric.

If anyone else has some experience with these types of guitars or knows of any basket case Nationals please let me know.

P.S. been at the forum for 2 days and I'm lovin' it!

I'd very much like to see photos of your metal bodied resophonic instruments! I enjoyed the mention of the 25 cent pie pan for a cone, as I've done the same myself. I've used the burner pan from electric stoves for the cone...the biscuit style bridge sits nicely in the hole, and a really good rummage sale will provide you with heavy gauge steel pan covers to fashion into resonator covers. I just picked up a serving plate with a very fancy pierced design that will make a great cover. The most unusual thing I've made has been a resophonic lap steel guitar. The cone was made from a spun aluminum popcorn bowl cut down to size. I've also made a solid bodied "resolectric" style guitar...I tried the corian saddle too, but replaced it with a piece of fret wire notched to recieve the strings. The tone is a little "twangier" that way, but still not what I'd like.

Here are Jon's pictures of his resonator mandolin:

  

Jon, what a fantastic looking instrument! Is there any special reason for the tear shaped raised area on the back?

I added the tear-dropped area for two reasons - looks and also to give the back a little more rigidity - I wanted the cone to resonate, not the body.

Hey all, I've created a couple of rezophonic Frankenstinian guitars meself and have had surprising results. I began looking for one of those National or Dobro guitars about thirty years ago. After twenty years of looking I came close many times but never did get one. So frustration drove me to make my own. My first attempt, now ten years ago, was primitive. An aluminum top and back, brass side, bolted together with 52 erector set brackets. My sound well was an old banjo body, the neck from an old guitar, the bridge was a piece of a vegetable steamer, (Dobro type cone), the vegetable steamer had a big hole in the middle of it so I filled it with a circular slice of wood, (not unlike the biscuit used by National) and viola (that's a French word which means you have a rezophonic guitar). This is the first time, that I'm aware of, that the two forms Dobro and National have ever been sucessfully combined to create a new form. I call my hybridization the Nobro. It seemed only right to include a bit from each of it's parents in the name. That was my first attempt and five years after that creation I decided it was time to try another. My second, now five years old, is a testimony to lessons learned. It looks much nicer, works better, sounds better and plays easier. I made the back and sides out of brass and the top out of spruce from the sound board of a one hundred year old German piano. The idea for this was not my own. I saw an old National in a music store near my home in WA, it had a steel back and sides and a wood top. They sold it for five thousand dollars! There was no way I could afford that kind of $$$, which is partly the reason why I made my own. The idea of combining wood and metal bodies was a sound one and I intend to create a few more. I've also got a hankerin' to toy with that tricone idea a bit and maybe reinvent a few ideas there. I'll let y'all know how they turn out. Reggie

One other note, a friend, after hearing about my exploration into the Rezo Zone decided he would create his own resonator out of a speaker, that's right a speaker he had. When I saw his results I couldn't help but be amazed. It worked and was good sounding too. There doesn't seem to be much that one can't accomplish if properly inspired. Reggie

Hi Reggie, welcome to the rez. I've sent a photo of my steelbody resonator as it was just before the finish was put on and final assembly. It's kind of neat to see all the parts that make up one of these guitars. You're instruments sound great! Very inventive. By the way, didn't that piano sound awful after you took a chunk out it's soundboard? Ha-Ha.

Here's Mike's picture:

Thanks for the shot Mike and Deb. Another quick note, I have a similiar experience to share where someone, after hearing me tell how I made my guitar, was inspired to build two resonator guitars one for a friend and one for himself. They had all Brass bodies, f-holes, electric guitar necks and were set up with National style cones. We all got together one day and compared sounds. All of them sounded great. Their electric necks made the action on their guitars easily adjustable. Here's one more for good measure. A friend of mine plans to create an acoustic rezophonic twelve string foot piano bass soon. I can hardly wait to see that one.

Jon, sorry, I found your letter that answered most of my questions except about the spider or biscuit-style bridge. How is that done?

Chet

Hi Chet, Hope we hear from Jon but if not maybe I can help. Nationals mandolins used a neck stick. If you look at the picture of my guitar you can see it. It's set into a slot in the neck. This runs the length of the instrument to the end block and is also attached at the soundwell the cone sits in. Additionally there are usually screws through the fingerboard that hold it to the top. Mandolins use a biscuit style cone. I'd recommend a National or Quarterman for the best tone. but the cheaper ones will work too. As far as metal, brass will sound best for a mandolin but it is pricey. .32 sheet material works well in both brass and steel. If your ambitious like jon you can make your own coverplate, if not the 10" one made for guitars works well plus it's already chromed. Good luck.

Good to see that I'm not the only resophonic nut case out there. I recently finished a "Dobro" Made from a Weber barbeque. I hand carved a maple neck and made the sound well out of bendy board. The top is solid spruce and the hardware is all standard dobro that I ordered from Stew-Mac. It sounds great and will actually be played by a friend in concert next month.

Hi Rick, welcome to the Forum! A barbeque dobro! I think we need a picture or two to verify your claims <g>.

OK all you doubters -- here's Rick's Do-Bro-Q:

Wow, now thats a "rare" Dobro. "well done" Rick.

Help someone stop me before I pun again!

Thanks. I have had a lot of fun with it. But if you like my barbeque, you'd really get a kick out of my wheelbarrow.

Don't string us along...what's with the wheelbarrow? Tympani,steel drum,mandobass...what?

Does anyone know where you can get measured drawings (i.e., plans, blueprints) like the ones sold by the Guild of American Luthiers, but for resonator instruments, especially the metal-body ones? I'd be interested in plans for any metal reso-instrument, and I'd also love to see a plan for a biscuit type cone and bridge. Thanks. And if you want to buy these parts, where do you get them? I've seen some in the Stew-Mac catalog, but not all that I was looking for. Thanks again.

Hi Chet. Stew-mac has just about everything you need. Their blueprint for the metalbody comes from Paul beard and is what I used to make the guitar in the photo above. I'd stay away from the cheapo import cones and go with a National. Or Stew-mac sells the Quarterman, which is excellent. If anybody knows of anyplace else to get this stuff let's hear it.

Are there different cone sizes available- smaller ones for mandolins?

Hi jens. The National mandolins used the regular guitar sized biscuit bridge resonator and coverplate. Dobro made a smaller spider bridge sized one for mandolins and John Quarterman makes replacement cones. The spider is another story. I don't know if it was just a guitar spider with the legs shortened or a totally different item. I've never been inside one but I've seen a few on eBay. Hope this helps.

Mike, what are the typical cone sizes? Do you know where to get small size parts?

Jens. The standard sizes are listed in the S-M catalog. The tricones use 6" cones but are pointed on top so a biscuit can't be used. John Quarterman makes a smaller Dobro style cone that I talked about in my earlier post. S-M dosn't list it but Resophonic Outfitters does. As far as small coverplates and such you'll just have to look around. Pat Webster has used some neat cast-off items as covers. Good luck.

Chet, sorry to be so long getting back to you on this. The bridge of my mandolin is simply cut from a block of maple. It is about 2 1/2" wide at the base by 3/4" thick, tapering to 2" by 3/8" at the top. It is cut out in form so that there are two legs with feet which rest on the bottom of the pie tin. About 1/4" from the bottom there is a horizontal member between the legs, and centered on the horizontal strut is a vertical member between it and the top portion. The top part of the bridge has a slot in it lengthwise to hold the saddle, which is made of Corian. This is kind of hard to envision but if you look closely at the picture you can see most of the bridge structure through the oval hole in the cover plate. I think I stated above that the bridge could probably use a great deal of refinement, but inasmuch as I don't know how to play the mandolin anyway, I haven't been motivated to improve it very much.

As for the neck joint, I used a mortise & tenon with locking dowels which is described in Irving Sloane's book on building steel string guitars. The metal body is cut away around the mortise so that the neck can be attached into a neck block.

Rick, the Do-bro-Q looks great - I assume you play it with a slide.

Julian, you guessed it! The wheelbarrow is a mandobass. Sounds great but is somewhat difficult to play.

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