Builders: Can you tell if a top will be mismatched right away?

[ChalkLitIScream]

I understand that runout is caused when the top is cut off quarter. Will a top cut 88 degrees instead of 90 be enough to cause runout?
And can you tell just by handling and examining the 2 pieces of wood?

Thanks all

[LouieAtienza]

Having a board that's rift sawn has absolutely nothing to do with grain run-off. You can have an apparently perfectly quartersawn board that has run-off. The only way to really know is learn how to read the grain at the edge of the boards. Or split the billet yourself - that would guarantee you the least run-off possible.

One reason you'd get run-off with "perfectly" quartered wood is that many trees actually grow on a spiral of varying degree. Usually, however, the tree is sawn relative to its axis, since the yield is higher than splitting.

I probably would rather use a set that was a bit rift sawn but zero run-off than a perfectly quartered board with significant run-off. You could use boards with slight run-off, though you'd probably work them slightly thicker.

[Carl1Mayer]

I don't know about everyone else but I usually can't tell if theres runout by eye before the finish is on. The biggest give away to me in the build process is how it cuts. I typically don't worry too much about runout but I know from carving arch tops that cutting the surface with the grain going downhill leaves a rougher surface and typically requires a little more force. From personal experience this effect also seems more pronounced with duller chisels and planes and sharper cabinet scrapers. So in theory if theres runout you could scrape or gouge a little chip off both sides (pushing the scraper/gouge in the same direction) on some corner thats going to get cut off and see if theres a difference but I have no idea if that would give you under 2deg precision.

The other option is to sand and finish a small corner on each half and see if you get that shifting contrast effect but I don't think you can easily quantify the degrees from runout from that either.

[redir]

It''s not easy to tell in many cases unless like you said you are planning it. In severe cases you can sometimes see the fibers.

[Ned Milburn]

Originally Posted by ChalkLitIScream

I understand that runout is caused when the top is cut off quarter. Will a top cut 88 degrees instead of 90 be enough to cause runout?
And can you tell just by handling and examining the 2 pieces of wood?

Thanks all

No... A top will not exhibit run-out if cut off-quarter. It will exhibit run-out if it is not cut parallel to the grain of the wood.

The best way to ensure least possible run-out is to split the wood first, then re-saw along the split face, since trees sometimes twist their grain as they grow upwards.

So, if you have a twisted grain piece of wood cut perfectly quarter sawn, it WILL exhibit run-out to the degree of its grain twist.

There are ways to check for run-out. If the wood is wider than necessary, splitting a small cut off strip is an excellent way to tell, but the grain can sometimes be straight on one edge with run-out on the other edge.

[Truckjohn]

As several here have posted - generally runout is caused by trees with twist.

You don't really appreciate just how good our guitar wood really is until you try to cut a top out of decent looking lumber.

The thing is - for the way the guitars sound - a top with a bunch of runout will make a pretty darned good sounding strummer or vocal accompaniment. They don't do as well for pure fingerstyle. To my (carefully calibrated and inerrant ) ears - all else being equal - they are more likely to produce a sound with a faster decay and less sustain than a top with almost no runout.

But... It's not always "equal"... And there have been many many fine guitars made with tops that have a lot of runout. Including classical guitars... Why? Nothing is ever perfect... A maker may well choose a very low density, creamy white, uniform top with more runout vs a more dense, uneven grain top with no runout...

I mean seriously.. Look at the million dollar Martin that went out with a top with huge runout... It took a lot of flack on the forums - but somebody still bought it..

[arie]

Originally Posted by ChalkLitIScream

I understand that runout is caused when the top is cut off quarter. Will a top cut 88 degrees instead of 90 be enough to cause runout?
And can you tell just by handling and examining the 2 pieces of wood?

Thanks all

runout is not caused by an off-quarter cut. it's caused by an off-parallel cut or wood that has grain aligned in such a fashion that poses difficulty in obtaining a parallel cut.

2 degs off quarter is ok. the usual rule of thumb is 5 deg btw.

[ChalkLitIScream]

Thanks for all of the responses folks. Glad to know I was misinformed about runout and off quarter cutting.

Potentially not knowing the presence of runout until AFTER the top is finished kind of scares me. I just cannot live with the mismatch. Sometimes being a perfectionist is quite a burden.

[arie]

Originally Posted by ChalkLitIScream

Thanks for all of the responses folks. Glad to know I was misinformed about runout and off quarter cutting.

Potentially not knowing the presence of runout until AFTER the top is finished kind of scares me. I just cannot live with the mismatch. Sometimes being a perfectionist is quite a burden.

I hear you about perfectionism. I have a crippling case of it myself which makes my guitars take a long time to build.

SOP is to "wet" the wood at a point where it's near net thickness with alcohol or naptha to observe how the bookmatch will finalize. Helps with that effect that looks like two different pieces of wood were used on the top when they really weren't. I don't know the technical term for this effect though. Works particularly well with top woods (spruce, etc..) and mahoganies and maples.

[Ned Milburn]

Originally Posted by ChalkLitIScream

Thanks for all of the responses folks. Glad to know I was misinformed about runout and off quarter cutting.

Potentially not knowing the presence of runout until AFTER the top is finished kind of scares me. I just cannot live with the mismatch. Sometimes being a perfectionist is quite a burden.

As I mentioned above, you can cut off a few mm of each side edge and split them to see how it is.

Or just buy cedar, which is said to be less prone to run-out, and this matches my own experience.

[printer2]

I do a lot of work with a razor blade for a knife/box cutter. I could not find my scraper and used the blade. I could get a finish quality surface on a corner of a board in no time, to the point where it shines. I just checked the board I was working on, the two bookmatched corner looked fine.

You look at the boards at a off angle (45 degrees) and move over the piece untill you are looking at it off angle from the other board side. I then flipped over the board, shined it up with the razor blade and did the same check. One was shiny and the other one looked dull until I got over 90 degrees on top of them.

Now how fine tuned this method is I don't know. Will I have runout appear when finish is applied where with no finish it looked fine? Give it a try and see if it can help you out.

[Carey]

If you take a flash photo of the topwood, making sure to keep the two halves
in the same plane, there will be a flash image on the top. The more diagonally
skewed this flash image is, the more runout the top has. This works pretty
well for me.

[nacluth]

Run out is something that people have different sensitivities too. Yes, to answer the OP, you can always tell runout when working with the wood. There is some perceivable runout in every piece of Spruce I have ever seen. However, I’m very sensitive to seeing it (though it typically doesn’t bother me). Many other species (especially back and sides) get built all the time with clear runout. The key is what level of runout can you stand. Splitting the wood helps, but gluing the right edge together is key to minimize the visual effect.

[Shuksan]

In line with what Carey said above about using a flash photo to see runout, here's something I posted about a year ago in a thread on the same subject. It was a repost of a post by John Arnold on the Mandolincafe forum a couple years ago.

"It is possible to visually detect runout on unfinished wood, but it helps to use a long, thin light source (like a fluorescent bulb). The light is oriented straight across the grain, and the two bookmatched halves are placed in the same plane.
Under these conditions, the light reflected appears as a bar across the grain. If this bar is straight across the grain (perpendicular), that means that the tree had little spiral. If this reflected bar runs at an angle, that means that the tree had some spiral. In the latter case, the point where the two bars are on the same level is where the wood has no runout. With spiral growth, there is only one place on the width of the board that has no runout. If this point is on the joining edge of the top, then the two halves will reflect the same, and the runout won't be visible at the seam.
Here is an illustration. On the left, the tree has excessive spiral. The white lines are the reflected bands. The pink line is where these bands are on the same level. Where the white and pink lines intersect is where the top has no runout....indicated with the blue lines.

[IMG][/IMG]

The top on the left would show less runout if the outer edges were joined."


There is one seller of wood for guitar builders on ebay who photographs his top sets this way.

[LouieAtienza]

In the brief time I've built acoustics, I've personally resawn all but three sets of top wood till about last year, when I started sending my woods out for resawing (by guitar-builder extraordinaire Chris Ensor, nonetheless, who provides this as a service and does an exemplary job.) I got good at reading the wood, since I used to thickness all my tops with my surface planer (!) even up to .090" thickness. If I put it in the wrong way, unless it was zero-run-off, it would tear, or even shred, the top. Disheartening watching chunks of top wood spit out by the planer, but hey, they were probably no good anyway.

I've taken my side woods with the planer up to .085" as well. Again, learning to read the edge of the board helps greatly. Not possible with figured hardwoods; even perfectly quartered hardwoods can have interlocking grain and can tear, and sometimes feeding at a bias can help. I don't own a thickness sander, nor have a segmented nor helical blade in my thickness planer.