How do they bookmatch tops?

[blaren]

Most of the time when I see a highly figured flame, the "stripes" don't line-up along the center seam. A while back when "inspecting" my flames and other guitars it seemed like maybe they matched the sides around the center of the body...around where a middle pup would be. It appeared that the sides would run-out from each other away from the middle.

That seemed kind of odd cause the part that's most visible is usually aft of the bridge.

On many it seemed like they weren't even matched at all...anywhere..and it often looks as if...if they just moved one side up or down by a quarter inch everything would line-up.

Now I understand that when you open up the bookmatch cut you are looking at kind of the negative or mirror image of the other side so it might look...kind of "opposite"?...but it seems like most tops could be matched more closely...almost all the time.

I just looked at that EV Siggy Ltd and it looked like it was maybe matched behind the bridge but other than that, it looked like 2 halves of completely different tops almost.

I've wondered about this for a long time and just now am asking. I've seen people ask before and the reply I think, was always something like...well they're matched in one place..or...when you open up the bookmatch, you are never 100% sure what's in there...etc etc but...
Still seems like MOST of the time if they just moved one side a little, the figuring would match up a LOT better.

I'm no woodworker so I'm sure there's a good reason but to my uneducated eye...the eye that just wants to see nicely matched sides...well it seems like most tops could be matched a little better?? Maybe not.

 

[John Beef]

A couple years ago PRS did a factory tour video set, probably a full hour's worth of videos describing the process. I can't seem to find them now, anyone?

 

[]-[@n$0Ma☩!©]

This is a difficult one to explain. When a billet is cut in half, the surface of the two sides (that were once touching each other) are nearly identical. The thinner the blade used to seperate them, the more they will match.

As the two sides are carved into the violin shape, they take independent paths. the figure changes as you carve into the wood. That's why bookmatch is usually much closer between the pups than it is from the bridge to the butt. There is always a gamble because a perfect bookmatch AFTER the carve requires the figure to remain perfectly vertical through the body (if laying flat in a table). That is a very rare thing. So when you see a top where the grain matches perfectly between the bridge and the butt after it was carved, that's a little like winning the lottery.

If you search around, there are threads on TGP that illustrate the point with graphics.

 

[Sage]

A couple years ago PRS did a factory tour video set, probably a full hour's worth of videos describing the process. I can't seem to find them now, anyone?

It's called "The Shop In Detail" and the specific video that shows the process of gluing up the body is here, under "Wood Drying & Body Construction."

Great videos, one of the best pieces of marketing I think PRS has ever done because it really shows you the amount of care that goes into their work. Seeing how precise and intense the wood drying process alone can be is what made me realize I'll probably never go back to playing any other electric guitars. My dad's a woodcarver and I sent him the links to these a couple years back because they really are eye-opening.

As for the bookmatching, I think Hans has it. As you can see in the video, the bookmatching is done before the body is carved. Once you shave half an inch off the top, things may not line up as well.

 

[rugerpc]

There is even more to it.

The kerf of the saw that splits the wood into two parts is a factor as Hans said. He is also correct about the carving and the grain - it is very, very rarely dead vertical to the surface of the top. Carve into it a little and you will reveal that the grain angles away from the vertical in one or even multiple directions.

And that brings up another consideration. You will hear people talk about tops that 'move' or are '3-D'. That is a function of looking at the grain from one angle, then moving your head or the guitar and seeing it from a different angle. Different angles reflect and refract the light differently. That is how the grain in a top can seem to move when they are of course quite stationary.

Think about how the wood started before it was cut into two pieces to make a bookmatch. The slab has two large faces destined to become the back of the top - that is the exposed surfaces before cutting will become the undersides of the top - the part that is glued to the body. So one face is the left glue side and one is the right glue side.

It is the split cut that reveals the part of the top we will see and the part which needs to be bookmatched.

Now, for example, say the grain is running through the block at 30° from the vertical slanted through the blank like the cross slash of a not equal sign ≠.

Slice the blank through the parallel lines of the ≠ and open like a book. The grain on one at any one point will be slanting towards you and on the other will be slanting away from you. Even if the saw kerf was exceedingly small, you still have some grains where you are looking more down the end of the grain and on the other piece grains where you are looking at the ends more perpendicular to the grain.

Illustrate it to yourself. Hold your palms together like prayer hands, fingers flat. Put two pencils at the same angle between your middle and ring fingers where they join your hands so that if you turn your hand to the side it looks like a not equal sign ≠. Pull your hands apart without disturbing the angle of the pencils keeping one in the right hand and the other in the left hand. put your hands together palms up like you are holding something level to the ground in your hands. One pencil slants towards you, the other slants away. In this example, the backs of your hands are the outside of an uncut bland and destined to be the glue side of the top. The palms are the pare that will bee seen - the outside of the top.

 

[blaren]

Wow. Thanks for the explanations.
I forgot all about the violin carve. IDIOT.
I often explain to people how you can have a 10top with less figuring than a non-10 and vise versa. You know...cause they are graded and THEN carved etc and sometimes they expose different figuring than was on the surface.
Yeah...violin carve!! Doh!

So it's kinda like (but not exactly) run-out on not perfectly quartersawn acoustic tops. That angle thing. And then theree's silking...which is usually uniform and parallel and is just a by-product of very nicely quartered tops. The flame and quilting is not silking. Hey while I'm at it...this figuring is ...uhhh...something "wrong" with the tree/wood...correct? God I'm sounding like a newb.
I have no audio on this machine so I'll check out the vid on my tablet later on the deck. Thank you in advance for finding it.

Sawing wood.
I was a longshoreman on the West Coast in the mid '80s. When I started, we were still shipping HUGE cedar logs. Like so huge that when floating, 4 boom men could barely get one spinning. Probably 6-8' in diameter. Something happened and we stopped shipping those monsters. There were rumors of Canada not wanting to ship our jobs to Japan (kinda like India with their fretboard veneers for LMI/Gibson)..but a few months later we were shipping giant Spruce logs to Japan. Yes...Sitka Spruce. I was already a guitarist so my ears and eyes perked-up when the reply came back..."oh to Japan where they will be turned into acoustic guitars and shipped right back to us! BUT...where WE use stupid SAW blades to slice wafers from our logs, the Japanese use hydraulic and/or laser saws that create little or no waste. ....." :-O YAMAHA!!!!! grrrrrrrrrr

I said all that just so I could make a shout-out to using saw blades to split/cut wood..lol
So, just how "thick" are the PRS blades? Do they really remove enough material on the bookmatch split/cut that it exposes such different faces? And then why not use razor thin (Wilkinson?lol) blades...or lasers or waterjet tables...or even "splitting blades"...like an axe? I know I know..an ace splits along the grain but..this is the future (to an old timer like me), surely they have intelligent or cnc "axes"?
All hypothetical, speculative guessing and thinking out loud on my part.

Thank you again for the explanations. I finally KNOW!
Still though....in this age of computers, cameras, electronic eyes and sorters and classifiers and matchers etc, you'd think that they could maybe predict what the grain is gonna look like internally and then line em up with the carve in mind so that the end product would be better matched?
And PRS comes-out with SO many (often simple) awesome new innovations..one of which is/was how to really extract the most drama from figuring with stains and finishes...come on PRS, flip the bookmatching world on it's ear by making almost perfectly matched topsets. Oops...still rambling thoughts out loud. I better shut up now or I'll be here all day telling Paul how he can build his guitars better...lol

Thanks again fellas.

 

[rugerpc]

Still though....in this age of computers, cameras, electronic eyes and sorters and classifiers and matchers etc, you'd think that they could maybe predict what the grain is gonna look like internally and then line em up with the carve in mind so that the end product would be better matched?
And PRS comes-out with SO many (often simple) awesome new innovations..one of which is/was how to really extract the most drama from figuring with stains and finishes...come on PRS, flip the bookmatching world on it's ear by making almost perfectly matched topsets.

It's just my opinion, but I think PRS already does a stellar job bookmatching it's woods.

BTW, did you try the hand/pencil thing above? Look at the different grain angles on the two halves - that cannot be changed - it is the way the tree grew.

Even with a no-kerf cut, the grain on one side is angled towards you and/or to the left and the grain on the other side will be away and/or right, etc.