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"Design Choice: Archtop, or "hybrid"
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Author:  Ken Nagy [ Sat Sep 16, 2023 12:28 pm ]
Post subject:  "Design Choice: Archtop, or "hybrid"

I got a piece of quarter sawn Wenge last year in Charlotte, MI. Went there again this year, and found another piece of the perfectly quartered Doug fir that is .56sg. Nice looking. It is 7.5+ wide, and about 84" long. 4 tops?

But maybe make the top 2 into a 1/2 thick archtop top? Really flat, so might need some extra bracing. But the wood is very stiff.

The other options are maybe spruce, A Y Cedar, or the Earthtone red cedar from ASW.

I thought that maybe the 1/2 archtop would be carved, but then set up like a regular flattop?

I'm all over the place. Opinions?

This is what I was doodling last night. 15 X 20 size dictated by the wood. The top of the Wenge can be a 5 string viola I made out of cherry. WBW purfling. That would look very cool.

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Author:  Ken Nagy [ Mon Sep 18, 2023 8:07 am ]
Post subject:  Re: "Design Choice: Archtop, or "hybrid"

First step I decided to try to rough out the 5 string back, and see how the Wenge cuts. Joining wasn't easy. It has that ribbony grain like Padauk, but a lot harder. Planing the bottom flat, I see that planing crossgrain works fast, but rips out long slivers. Careful with that.

Carving and planing the inside, cuts just as well as anything else! My plan says the long arch goes about 14mm deep in two points. It is two arches, with centers about 50mm, 2" apart. That area is somewhat shallower. I'm at 12.5mm deep now, and the arches are fairly good, a little shallow in the bouts near the blocks I think. I check them with a chain to find trouble spots. The Lie Neilson plane fits the inside of carved instruments well. A little too big for some violins. This is not too much longer, but is wider than a violin, and it seems to fit perfectly. You could just rough it all out with this, and keep moving it in different directions, and it would be done.

I add recurve in later, but apparently the Brescian makers didn't, and just left the edge flat. Maggini is a Brescian maker. This 5 string is actually a 1/2 size cello. I saw that the length from the top to the bridge on the 1/2 scale drawing I made, and changed it into a 5 string violin/viola.

A little more, and I'll flip it over. I like way it cuts.

So the back part of the archtop hybrid will work. Still thinking about the belly part. Making the long spruce board into 2 low arched arch tops would be simple, and I don't have to buy 2 wedges. Alaskan Yellow Cedar would be cool though.

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Author:  DennisK [ Mon Sep 18, 2023 9:16 am ]
Post subject:  Re: "Design Choice: Archtop, or "hybrid"

That's a nice surprise! I would have thought carving wenge would be brutal.

How about a glued bridge? So far I've never heard an archtop guitar that I liked... love the look, but they all sound choked compared to a good flat top. It would be interesting to see what happens with flat style soundhole, bridge and bracing on a carved arch.

Or you could try a zero-downforce bridge so you can forget about structure, and shape the thickness and bracing entirely for tone. Use a negative neck angle so the strings point toward the tailpiece with very little break angle over the bridge (to reduce the necessary neck angle you can use a rigid L-shaped tailpiece rather than attaching it with a flexible cord). Then file slots into the saddle to create horizontal break angles, half angled left and half right so the strings all counterbalance eachother. I heard the idea was patented 12 years ago, but never could find the number, so it may or may not still be in effect for the next 8 years. But for personal use you should be safe regardless.

Or build it more like a regular archtop because obviously many people do like how they sound :)

Author:  Ken Nagy [ Mon Sep 18, 2023 9:54 am ]
Post subject:  Re: "Design Choice: Archtop, or "hybrid"

Interesting. I don't think that my arch tops sound choked. The little 13" one vibrates like crazy when I play it, and it rings forever. The pinned bridge does seem like it would be a rock solid anchor, so maybe that would shake the walls?

The Padauk one I started will be a regular archtop, but with tone "holes" along the edges. The 13" one has the whole area below the fake humbucker open, and it vibrates a lot. Because of where it is, and the bars on either side, I don't think it matters structurally. At least it hasn't deformed yet. I'll see how that goes with the Padauk one, and maybe the Wenge on will be a hybrid, with openings around the edge instead of a sound hole. Very low carved arch, and very light bracing. The wood is very stiff. Far stiffer than the thin HD red cedar. But it is quite a bit smaller.

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