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I had a customer interested in having me build a double top guitar last year, prior to that I had never even heard of it. I didn't want to do it since I never had done so before so I decided to make one for my self with some old stuff I had laying around. 15 years ago or so I dropped a classical guitar in it's mold in the shop and broke the neck into the body. I hung the ribs of that guitar in my shop as a reminder to be careful while vacuuming Anyway I got to thinking that the ribs could be used for a cut away guitar with some careful manipulation. Long story...

So I got some cheap cedar from LMI and was quite pleased at the quality actually. I routed out two D shaped cavities for the Nomex and made the sandwich. I happened to get a nice cherry back from some one right here at the forums and lots of hints for building a DT guitar. The one thing that I had trouble with is bracing. When I was finished making the top it almost felt as though it was a braced top. I was tempted to just leave it as is but then decided to do a 5 brace fan with very light cedar braces. Normal upper transverse bracing and sound hole bracing.

When I first strung up the guitar I was thinking... Ugg not so good. But you know how it is, especially with classical guitars it seems. For one thing it takes a day to get the strings stretched out. Anyway, the next day I left for Colorado for two weeks Yeehaw skiing

When I got back I started playing the guitar more and it really matured within the first month. I keep switching back and forth between one of my spruce top guitars and this double top. The differences are apparent but perhaps not as much as I expected. The way I look at the DT guitar is it's like playing an electric guitar with compression. Compression brings up the lows and squashes the highs. This guitar is loud when played lightly.

There's a bit of a thuddy dull sound to the bass though it's loud with a good presence. The highs ring very well. The sound almost breaths through the top of the guitar rather then being focused on the sound hole. I'm thinking I may have over braced it and I'd love to hear opinions on bracing a DT guitar. When I strike a note like the open low E and feel the top it doesn't vibrate as much as my solid wood guitar though it is louder. When I tune it with a tuning fork placed on the soundboard it's very quiet, isn't that odd? It's a loud little guitar but quiet when tuning like that.

Anyway I could go on for hours and if you read this far then thanks, would love to hear your experience with DT guitars.

Here are the pics...

JF, sorry to be slow in a response, I've been off the board for a bit. From your description of how it sounds a few weeks out and looking at the top bracing I'd say Yes, overbraced. It is very easy to overbrace the DTs, what thickness were the skins and Nomex? What cell spacing on the Nomex, 1/8" or 1/4"? It is easy to go in and shave the bracing down a bit, start by taking some off the lower tip ends up about half way and see if you like what it does to the bass. Then take off little bits nearer the bridge and keep checking the complexity of the tone as you go. You may be able to do this with just a scraper like a glass microscope slide working slowly. With steel string DTs I've found that often light gauge strings are in order, they are so responsive that you don't need mediums to get the sound you want.

Alan D.

Hey JF

For classical guitars, weight and thickness of the double top are the most important factors, and they do require some practice before getting them right. It is very important to control the amount of adhesive you use, and there is a fine line between too much (added weight softens the DT effect) and too little (the whole thing is not going to hold). I started getting the best results when I managed to get the amount of epoxy just right, following advice from many luthiers with experience in the matter. Plate thickness is also critical, but the best results when using nomex is around .6/.7mm for each of the wood layers. Once again, if you go thicker you will most likely lose much of the double top effect. Just to give you and idea, my unbraced top (with the rosette installed and the soundhole cut out) is only about 102 to 105g.

From the picture, I personnally don't think that it is overbraced (just my opinion...). I have examined the bracing of many fine DT classical guitars and most had more bracing than what I see on your picture. After a year and a half of experimenting with DT, I find that to go thinner with the plates and brace normally gets better results than the other way around. If you look at many pictures available on the net from well known DT classical guitarmakers (Randy Raynolds and Fritz Mueller, for exemple), you will see that their bracing for a DT is fairly similar (in rigidity at least) to what you normally see on a standard top.

I hope this helps.

Pat

Ok so far thanks so much for your replies. I'm thinking perhaps my skins are too thick then. I measure in inches (all my tools are invested in English ). What I did was aim for .04in skins with a .08 Nomex. It's the tight celled Nomex too so that's the 1/8th in stuff.

So my total top thickness was .16in.

But what I did, like I do on almost all my sound boards, was to thin the perimeter . So the center from the bridge area to the head block is full .16in but the perimeter is thinned out. I don't have measurements for that unfortunately. I did the thinning out on the top and bottom so as not to burn through the top.

As for glue, I used an epoxy called Evercoat. A friend of mine uses it to repair carbon fiber bicycle frames. I didn't weigh the amount of glue I used. But what I did was to mix up the glue and lay it out on some parchment paper on a flat board. Then I took the Nomex and layed it in, basically just touching it. I didn't lay it on thick. After it was dry the honeycomb cells were not full of glue. I could see a very very small bead of glue where the edge of Nomex touched the wood but I mean very little. The Nomex may have wicked up a bit of glue.

To glue the bottom skin on I just scrapped a thin layer of glue on the wood using a credit card. I suppose it would be interesting to see a cross section of it now.

Don't get me wrong, the guitar sounds ok I think just different. And I can't help but be biased to a 'plywood' guitar, after all that's what got me into lutherie in the first place was the solid wood constructed guitar.

Do you think a recording would help at all? I'm not much of a player but I can strum chords and pick a few classical pieces as best I can.

Thanks so much for any info, it's a new experience for me.