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Cafe wall guitar

PostPosted: Mon Jul 10, 2017 4:06 pm
by Peter Wilcox
A friend of mine made a cutting board using the cafe wall illusion http://www.michaelbach.de/ot/ang-cafewall/ so I thought I'd try a guitar. Note that though all the lines are parallel or perpendicular, they appear to be wedge shaped. The illusion works best on the back, where there are no interruptions of the pattern.

Woods are alder, walnut and myrtle for the body, alder and walnut neck, and maple fret board. I have a bunch of leftover Fenderish parts, so I used a strat body and headstock shape, tele bridge, control plate, and pickup configuration, tele type rail split coil bridge pu, strat type rail split coil neck pu, 5 way switch giving bridge humbucker, bridge single coil, one coil each from neck and bridge, neck single coil, and neck humbucker.

Finish is sprayed gloss Zar water based polyurethane.


finished-1a.jpg


finished-2a.jpg


finished-3a.jpg


finished-4a.jpg

Re: Cafe wall guitar

PostPosted: Tue Jul 11, 2017 10:46 am
by Gordon Bellerose
I like the strips of wood in between the rows. I think it helps with the optical illusion.
The fingerboard is interesting also.
Nice.

Re: Cafe wall guitar

PostPosted: Tue Jul 11, 2017 12:24 pm
by Peter Wilcox
Thanks Gordon. Actually, the strips are absolutely necessary for the illusion.

Re: Cafe wall guitar

PostPosted: Tue Jul 11, 2017 1:37 pm
by Jim McConkey
Cool illusion! I assume you glued the light and dark layers in stripes, then sliced and offset? Any construction pics?

Re: Cafe wall guitar

PostPosted: Tue Jul 11, 2017 7:08 pm
by Peter Wilcox
Jim McConkey wrote:Cool illusion! I assume you glued the light and dark layers in stripes, then sliced and offset? Any construction pics?


Correct. When I did the offset, I inserted the myrtle strips between them.

Alder and walnut cut to 2x2. The 2nd one is for a matching bass.
rough-cut-2x2s.jpg


Glued and sanded.
glued-sanded.jpg


Sliced and offset, with myrtle strips inserted, then glued and sanded to 1.75" thickness.
cafetile2sm.jpg


glue-up.jpg


Body roughed out with bandsaw.
body-rough-cut.jpg

Re: Cafe wall guitar

PostPosted: Wed Jul 12, 2017 10:25 am
by Barry Daniels
The optical illusion of converging lines is really cool. Well done.

Re: Cafe wall guitar

PostPosted: Thu Sep 21, 2017 6:25 pm
by Peter Wilcox
I got the matching bass done. The illusion is not so prominent on this one - same pattern, same wood, same finish - I don't know why. I'm pretty much satisfied nonetheless. It was interesting.

Re: Cafe wall guitar

PostPosted: Fri Sep 22, 2017 3:28 am
by Robert Smallwood
..ohhh...nice job...but if it moves I think it'll make me seasick.. :o)

Re: Cafe wall guitar

PostPosted: Tue Sep 26, 2017 2:52 pm
by Karl Wicklund
My list of Things To Build is already longer than I could accomplish in two more lifetimes, but this gives me the itch. Thanks for sharing!

Re: Cafe wall guitar

PostPosted: Tue Sep 26, 2017 2:56 pm
by Bryan Bear
Very Cool!

I wonder if the effect on the bass is less because it is longer compared to the width? Is the effect more or less pronounced with smaller sections (relative to the total surface area)?

Re: Cafe wall guitar

PostPosted: Tue Sep 26, 2017 3:13 pm
by Bob Francis
Bryan Bear wrote:Very Cool!

I wonder if the effect on the bass is less because it is longer compared to the width? Is the effect more or less pronounced with smaller sections (relative to the total surface area)?

Wondering the same thing.

Re: Cafe wall guitar

PostPosted: Tue Sep 26, 2017 9:10 pm
by Dan Smith
Those are great Peter!
Really cool!

Re: Cafe wall guitar

PostPosted: Wed Sep 27, 2017 1:05 pm
by Peter Wilcox
Well, I've figured out why the bass doesn't show much of the illusion, but not how it happened. It's not the length of the checkerboard or the shape/squareness of them. Here's a stretched pic of the guitar, still showing the illusion:

stretched-guitar.jpg


The effect is dependent on the relative brightness of the intervening strips as compared to the light and dark squares, needing to be intermediate between the two. Somehow the brightness of some of the myrtlewood strips on the bass finished very close to that of the alder, especially on the left side in the pic below. The illusion is absent on the left, and somewhat blunted on the right. I don't know why this happened - maybe grain orientation or variation in the figure of the wood I cut them from. Anyway, I should have used a darker wood like mahogany.

illusory-effect3.jpg

Re: Cafe wall guitar

PostPosted: Wed Sep 27, 2017 1:37 pm
by Bryan Bear
Interesting. To my eye, the effect is definitely present in the stretched out pic. I wouldn't have thought about the color differential. I suppose one would need to choose wood for color and keep future color changes in mind. Perhaps the myrtle will darken in time.

Re: Cafe wall guitar

PostPosted: Wed Sep 27, 2017 6:47 pm
by Peter Wilcox
Bryan, it's not the color but the relative luminance (brightness or darkness) between the "tiles" and the "mortar lines" that determines the degree of the illusion. Here's the interactive site I referenced at the beginning of this thread where you can change different parameters to see how they affect the illusion.

http://www.michaelbach.de/ot/ang-cafewall/