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Well I tuned up my new Bellucci Macassar Ebony/Redwood for the night last night. This is the loudest classical I have ever played. I also had a good friend of mine play it and I listened from 20 ft away. Amazing!!!! I put Salazar stings on it last night and there was a big loss in the clarity of the bass but better response, if believable in the treble. So I put the EADG D'Addario's back on it. Sweet!!!

Anyway my question is how thin in general do you classical makers thin the top 1-1/2"-2" behind the bridge? The reason I ask is this Redwood is thinned to near 1.20-1.15mm 1 1/2" behind the bridge. I just barely touch it and I put a small crack in it. It was easy to repair and I will fix the finish this weekend but I was really surprised to find it this thin there.

That sounds really thin for cedar/redwood to me. Most, from what I read, spruce tops are 2 - 2.5 around the bridge area, and depending on stiffness, etc, 1.8 - 2.0 at the perimeter. NO wonder it is so loud and responsive. I'm sure there are exceptions to those measurements, and I know some Torres guitars were 1.4 - 1.5 at the perimeter, but most were 2 to 2+ in the bridge area.

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Waddy

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That is what I expected. it does go to 1.6 when measured directly behind the bridge but tappers off quick. 1.2 at 1" behind the bridge and 1.2 at 1.5" behind and goes as low as 1.15 the thickens out just before the lining. Means I must be gentle when changing strings

How did you measure it? I have seen specs on some plans, it seems to me, that say for cedar/redwood, 2.5 - 3.0 in the center and 2.0 - 2.5 at the perimeter, depending on the stiffness. I could be all wet though. I only know what I read. I have an old cedar top guitar, a "Barbero"(Not really a Barbero), from Sherry Brenner, back in the 70's they had them. It is a cannon, and the top seems thin, and you can see some radiating of the fan braces through the top, but I don't think it's that thin. I don't have anything to measure it. Long scale guitar, huge bass.

Anyway, I would use a protector bib on the guitar when restringing. Heavy cardboard or thin plastic, or something. I have a big slot in mine where the high E snapped out of its tie. Didn't go all the way through, but it looks like it could have. If you use a bib stiff enough, that would protect the top from your heavy handedness too! Then can put another bib on you to keep from getting drool all over that beautiful guitar.

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Waddy

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Sounds very thin to me as well Michael, my recent La lena, before I did the final thinning of the lower bout with the guitar strung up, was 2mm behind the bridge and about 1.8mm at the edge, this probably went down about .2mm at the edges of the lower bout, but stayed around 2mm behind the bridge. This was in a very stiff piece of Caucasian Spruce, not redwood. This is close to Torres usual thickness, though some of his went thinner. I always thin my tops to their final thickness with the bridge on and strung up to gauge response.

Even my lutes, which have very thin tops, never go below about 1.5mm.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

Do you have one of them magnetic caliper? Sound awful thin to me as well. Redwood is said to split very easily.
Maybe it is a lattice braced top? That would explain the very thin top and the loudness.

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I am going to re-check the dimension to night I could have miss measured. but non the less it is very thin an inch behind the bridge.

no it is fan braced per 1946 Hausser Sr.

I assume it has a bridge patch, though, I don't think it makes much difference in the thickness there. Romanillos doesn't think they have much impact anyway, and the cross grain of the patch could even create problems.

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Waddy

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Michael,

I agree with Colin and the rest. 1.15 sounds a bit thin. I have a '76 Ramirez 1A with a redwood top and the thickness below the bridge is in excess of 2.3 mm. It's a 664 scale and therefore the string tension on the bridge is a bit more than a 650. I've had the guitar for quite a while and I'd have to look through my files to get the exact measurements if you are interested. I would re-measure and handle with care. YMMV

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Peter

Yep. The patch is about 1.5mm thick and is equal to the width of the bridge. I guessing I miss read the calipers last night. The calipers are clam shell type with zero-able veneer type scale on the back end. not sure how good they are. The only thing I could find to use on a closed box last night.

Ok The next question is If I decide to put a thin patch plate say 1mm to reinforce the where the crack happened how much affect should I expect?

Ditto on what the other guys said, I've never taken a top that thin, especially behind the bridge. I have a top that is around 1.8mm now and I am going to turn it into a double-top because it is too thin. Typically I'd be in the 2.3-2.6 range behind the bridge tapering down to 2.0 around the edges.

I think your strings are also explaining what's going on. The strings you added that killed the tone are probably higher tension (even if labled the same, they vary by brand). The higher tension strings could be pulling your top too tight restricting movement, so when the D'Addarios went back on (presumably lower tension), the guitar sounded good again. As for the volume, I think you may have gone just a bit past the envelope between balancing weight and structural integrity. For classical guitars (because of the much lower tension than ss), you want to build the guitar as light and stiff as possible. Lighter weight usually equals better volume, but you're constantly pushing the envelope trying to maintain structural integrity. I think small changes in guitar weight are much more detectable in classicals because of the low string tension.

John

I did not build it It is a Bellucci. Anyway I remeasured and it is 2mm at the bridge. 1.7mm at the crack. I cosed the crack with no issue using fish glue using teflon backers and rare earth magnets. Next question is should I add a patch graft and if so how dramatic would you expect the affect?

1.7mm is much more normal, though probably not for cedar.

If this were someone else's guitar I'd put a small cross grain patch behind it, around .5mm thick. I usually make it like a diamond so it doesn't run along any grain lines.

If it were a guitar I owned and I knew how it responded to the conditions it lives in and know I am going to take care of it I'd probably forgo the patch.

There have been a lot of heated discussions about the Bellucci guitars (I think I may run a close second as controversial subject matter at the GSI forum, though for very different reasons)... I'd put in a patch. I wouldn't expect it to effect the sound very much.

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The last cedar I did was 2.4 mm behind the bridge tapering to 2.2 mm at the perimeter.

Indeed a small patch will not affect anything significantly.......Your latter measurements sound a bit more in the ball park than the earlier ones though I'd agree that they are still on the thin side.
My newest guitar is about (old European Spruce) 2.4 mm at the bridge and
1.8 at the periphery though there is a treble bar and single long cut off bar that add a little cross grain stiffness as well as the top being quite good and firm as well.

I have to say that the workman ship of the joinery is excellent. the playability is fabulous. the tone is wonderful. Being a steel string player for most of my life my knowledge on classicals is somewhat limited but I am quite pleased. I too was glad to see that my thickness readings last night was flawed as 1.2mm is scary thin. I agree that this guitar is built fo low tension strings.

I will add a patch about .5mm thick.

As far as my early opinion of Bellucci guitars, at least this one is they are fine playing and for the most part well crafted. time will tell besides I am not about to look this gift horse in the mouth.

I have a pattern, I go from 2.6 in the center to around 2.2 at the edges. I try to always stay above 2. I would think if it is as thin as you are measuring there would be a pronounced expression of the fan brace pattern on the top of the guitar. Is there?

No there is no pronouncement of the braces visible through the top. I added a graft last night all looks good. I will string back up tonight.

That sounds a bit thin to me for a redwood top, but it's hard to say. If it's tight grained stock and somewhat dense it could well be very stiff along the grain: I've measured redwood that had a Young's modulus along the grain as high as that of Indian rosewood. If that were the case it might not be too thin in terms of resisting the static string tension, so long as the bridge saddle is not too high.

The Achille's heel of redwood is it's lack of split resistance, though. You seem to have run into that one already, and that does not bode well. As the top bellies over time behind the bridge that puts it into tension across the grain, and any little shock can start a split.

The other thing to keep a close eye on is the back edge of the bridge: if it starts to lift it could do some real damage to such a thin top.