Square neck spider resonator

[Peter Wilcox]

I'm building a square neck Dobro type instrument, but it's going ever so slow - not much physical or mental energy these days. Maybe by starting this thread it'll get me off my butt. Any suggestions or constructive criticism appreciated. I started this thread http://www.mimf.com/phpbb/viewtopic.php?f=3&t=4593 when I was thinking of doing this so already have some good feedback.

25" scale, solid maple, no plywood (may be a mistake.) The top and back are resawn from the same billet. For some reason I thought I'd joint the edges of the back and made it too narrow, so added some darker maple and walnut in the center to widen. The top is 7/16" thick, and the back about 1/8".

[Peter Wilcox]

The reason I made the top so thick was so I could cut the cone ledge into it without having to make a separate ring or sound well, and possibly get away with minimal bracing if the top can hold it all together.

[Peter Wilcox]

The sides are about 0.1".

More later.

[Brian Evans]

You could probably laminate a ring of plywood under the cone ledge, to have a plate to locate the sound posts if you go that route. If you go with a baffle ring, it can land right under the ledge, and reinforce it that way. With a top that thick, you could go with no baffling at all inside (my 1935 Model 25 has an open sound box, no baffles). Ultimately the relative height of the edge of the ledge sets all of the geometry of the string path and the neck, so it's quite important. That's a lot of solid maple, if nothing else it's going to be a substantial little puppy! How are you going to bind the edge of the top, with a top that's almost a half inch thick?

From memory, my Model 25 has a 1/4" top, a plain hole with a 1/2" thick ring glued to the top that forms the ledge, and that's it. No other bracing. I don't know how thick the back is, but it's birch plywood.

[Peter Wilcox]

Brian, I'm hoping that with the top that thick it won't need any bracing under the cone. I'm going to brace the back so that if I end up having to use sound posts they will have a resting place on the back. I think with the top that thick the posts can just butt underneath the cone ledge. Although I could be wrong, I don't see any significant downward force on the top, as the break angle is so shallow, and the downward string force will be spread out over the periphery of the cone. The longitudinal force from the string tension may be another story, but I'm hoping the thick top attached to the sides will be enough to counteract that. I am planning on a top brace just above the cone hole to make sure the solid maple stays flat - plywood would not need that.

[Peter Wilcox]

I decided to split up the sound holes. I wanted to make one semilunar hole on each side, like f-holes, but I would have felt obligated to bind them. So being lazy, I calculated the area of the 2 round screened holes on my Chinese instrument, plus the 3 small central holes (5.1 square inches total), and made some Ovation type holes of the same area. They will probably port the box volume differently, and I'm making the volume greater anyway, so I guess I won't see how it affects the sound until it's done.

[Peter Wilcox]

I'm planning on beveling the top like this, and binding with walnut, though a narrower strip. I'll have to figure out how to transition at the tailpiece and heel, where I'll want a 90 degree angle with no bevel.

[Bob Francis]

Thanks guys this is a very interesting build.

[Peter Wilcox]

Some progress.

Gluing the sides to the top.

Gluing some lining.

[Peter Wilcox]

The back, probably over-braced, especially if I decide not to use sound posts, but the braces are there if I need them.

[Brian Evans]

You might like this, if you haven't already seen it; http://www.hangoutstorage.com/resohango ... 252011.pdf

Basically, compared to his guitar, yours is about 400% tougher.

Brian

[Peter Wilcox]

Thanks Brian, but I've been using that as a major resource for building mine. He doesn't give many measurements, but I've been using my Chinese reso to get most of the major ones. The Chinese one has a scale length of 24.5", and I wanted 25", so I made the neck 1/4" longer and moved the center of the cone 1/4" toward the tail. I've also increased the interior body depth from 3.5" to 3.75", in the hopes of eking out a little more bass response.

[Peter Wilcox]

The rough construction of the body is now done (I think) except for gluing on the back. I put in some side stiffeners and blocks to attach a baffle if I use one. I'll need some time to think about any unintended consequences of gluing the back at this point, like not being able to access or change something because it's closed. I've got the neck and fingerboard almost done - it's bolt on, and I think I 'll be able to get it on and off ok through that big hole.

[Peter Wilcox]

The neck. I made a rough paper template from the Chinese instrument and cut out 3 pieces from a maple board.

Jointed the pieces, interspersed walnut slats

and glued it up.

Rough shaping. The middle piece is tapered toward the heel to match the back, and left wide at the headstock for the necessary width.

[Peter Wilcox]

More shaping, and making a slotted headstock. I'm lazy, and it's easier to tune the instrument in playing position.
The farrier's rasp is my friend.

Put in the insert nuts.

[Peter Wilcox]

Made a finger board (doesn't have to be a very hard wood) of Peruvian walnut and maple. No frets needed -just position markers - so made maple "frets".

I bound it with more maple, and added a walnut headstock veneer as I didn't like the naked look.

[Peter Wilcox]

Starting to take shape. The back's still not glued on.

[Dan Smith]

Looking great Peter!

[Peter Wilcox]

Gluing on the back.

Screwed some clamps to the bench to hold the guitar vertically.

Cut the end graft channel with #10 blade and chisel.

Glued in the end graft.

[Peter Wilcox]

Routed binding channels.

Top

Back

Cut some walnut strips and bent the bindings.

Glued 'em in.