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Cool!  My first real guitar making question.

I was, looking at my top pieces, and while they match up nicely, I noticed that if I trimmed them to a taper, about 1 cm on one end to 0 on the other, down the center, I could probably eliminate most of the runout, or at least would have grain running more parallel to the centerline, even if there were some waves in the grain.  Would this be better, or should I join them with the bookmatch where the grain runs out along the centerline?

My goal is a classical.

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Waddy

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It's always nice to see a well joined top that looks like one solid piece.

Waddy, if you have the means, try and cut the glue edge so that it runs parallel with the grain lines like your describing so in other words, yes try and eliminate the runout as much as possible. The pieces will still be book matched.

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waddy, what you are talking about has nothing to do with runout.

runout relates to how the grain runs if you look at the side of the top pieces, if single grain lines run the entire length of the piece, no runout. if the grain lines end on the flat surface, that is run out.

have you ever noticed that if you look at some finished tops with light shining on them one side will look darket and the other lighter. that is a classic case of visible runout, the darker side has the ends of the grain lines facing you, the lighter is the ends facing the other way.

as to whether what you propose would improve the appearance of your top, without a photo i wouldn't hazard an opinion.

[QUOTE=crazymanmichael]waddy, what you are talking about has nothing to do with runout.

runout relates to how the grain runs if you look at the side of the top pieces, if single grain lines run the entire length of the piece, no runout. if the grain lines end on the flat surface, that is run out.

have you ever noticed that if you look at some finished tops with light shining on them one side will look darket and the other lighter. that is a classic case of visible runout, the darker side has the ends of the grain lines facing you, the lighter is the ends facing the other way.

as to whether what you propose would improve the appearance of your top, without a photo i wouldn't hazard an opinion.[/QUOTE]

That is exactly what I said.  The grain, even though bookmatched, runs out at the center line.  Trimming to a taper even with the grain may not take it all out, but should make the grain more parallel to the center line.

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Waddy

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UGH!  I meant to say, "That's exactly what I meant to say."  Did someone mention an EDIT button before?

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Waddy

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Hey Waddy,

Perhaps THIS will better explain for you what the term "Runout" refers to.

Cheers

Kim

And if that don't clear it up for you, then THIS most certainly will.

Midway down in that post, you will find there is a link to a visual chart showing the varying degrees of light refraction under a finish in relation to the degree of runout presented in the board, this light refraction is what Michael was referring above in his post.

Your concern as described above is a question of grain alignment rather than runout. If you can better match the alignment as you suggest, I say go for it, as any correction will certainly make the glue joint much less detectable. Just make sure you keep in pattern with the top.

Cheers

Kim

thanks kim, a picture is worth a thousand words, and both illustrate what i was trying to say.

and also the error of the idea that you can trim runout out of a piece of top wood.

Ahh!  I see the error of my thought process.  It isn't runout, but just a parallel grain situation.  Thanks for the links that explains a lot.  How important is the parallel grain thing, or is it pretty much cosmetic?

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Waddy

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cosmetic! some trees have curved grain, some straight. doing as you propose will certainly do no harm, but other than perhaps being pleasing to your eye, will accomplish naught.

Thanks guys. That's what I wanted to know.  As always, good, constructive advice.

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Waddy

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That did help. Thanks.
-j.

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Thank you Michael and Kim for the great posts on run out. I learned something I thought I already knew.

Thanks again. I love this place.

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"We have to constantly remind ourselves what we're doing....No Luthier is putting a man on the moon!" Harry Fleishman

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If your lining up you boards so the grain runs parallel and there is still grain that comes together, it is good planning if you have it happen under the fingerboard or at the sound hole so it won't be seen rather than the lower section of the guitar where it will be seen.

DavidO