New commission, Coco jumbo

[Dean Kumbalek]

Good timing.

I am routing/binding the Oregon myrtle boxed material and doing the b/w/ebony bindings and your pics Grant answered my question.

Feels good to be back on this one again.

I hope Joe Sustaire gets his camera working again. I really want to see pics of him in his work space playing the boycote guitar from the back and sides I got from you.

Anyway, I am watching and learning and progressing and marking the calendar for next July.

Thanks for all you do and the inspiration.
Dean

[michael]

So your fiberglass looking covered table is actually a dish? I guess the thin braces that you use to build up are being flexed down into the dish. The new guitar looks great. Thanks for all your posts
Mike

[Joel M]

Grant that top bracing is a work of art!! Looks like a beautiful painting.

Do you have any info on how you came up with the bracing design? What is achieves over the standard X? Its very unique and Im curious how it came to be and what effects it has. Thanks for any thoughts on this.

Love the coco!!!

Joel.

[whitespruce]

Grant that top bracing is a work of art!! Looks like a beautiful painting.

Do you have any info on how you came up with the bracing design? What is achieves over the standard X? Its very unique and Im curious how it came to be and what effects it has. Thanks for any thoughts on this.

Love the coco!!!

Joel.

Thanks for the kind words,

On my back bracing:

My primary objective was to eliminate any braces glued perpendicular to the grain. Since wood shrinks and swells across the grain, braces perpendicular to the grain will tend to promote cracks in the back, whereas braces at a 45 degree angle can move slightly with the back. An X can open and close (like a scissors). However, most X bracings I have seen still have at least one straight across brace, thus defeating my objective. A single X without the cross brace, however, does not give much support to the back. So, I added another set of X braces, which actually made 4 X's.

Now, that makes for a lot of careful notching (but it could be done that way), so I chose to just laminate them up in place. This is a lot of bracing and makes a very stiff back, so I made them narrower (3/16"). The layout is simple: My pattern is a 6" square with opposite corners lined up on the centerline, the upper corner roughly centered on the soundhole. Trace around the pattern and extend the lines to the edges of the back. On large bodies (dreads, jumbos), I glue the braces outside of the lines. On smaller bodies (OM's, etc.), I glue the braces inside the lines.

This makes for a very stiff back which holds the arch better than most bracing systems I have seen.

G

[Dennis Leahy]

I think Joel was asking about the top bracing pattern, not the quadruple-X back bracing system. (I'm going to try the Goltz Quad-X on my next back - and it certainly should be a consideration for any back set that anyone has with any sort of stability issues. A tip of the hat to you, Grant. Now, you just need to grind a handful of those router bits down and sell 'em!)

Dennis

[whitespruce]

Sorry Joel, I read too fast or my head was somewhere else.

Ya, the top bracing

OK, this has sort of a long story, and I have probably told it elsewhere, but here is the gist of it.

Several years ago (like 10 or so) there was this guy named Al in, I think, new Jersey. He was buying much of his guitar wood from me at the time. He said he used to play at a ski resort now and then in New England and there was a guy who had a guitar that had an incredible sound (which he went on to describe to me). So he asked me if maybe the top bracing had anything to do with it and, if so, could I design some different kind of bracing that might give that sound Right, like I would have a clue Anyhow, I told him I would think about it and see what I might be able to come up with.

So I thought about how energy travels through solids (and liquids) partly in terms of speed and direction. In wood, energy travels much faster with the grain than across the grain. As an aside, in spruce, this difference is quite pronounced, and different in different species. For example sitka has slow crossgrain energy propagation compared to white spruce which has about twice the crossgrain energy propagation as sitka (I like to say that the white spruce parentage is what gives lutz its good sound....the only thing sitka contributes is large size to the trees )

Anyhow, another thing that I know is that energy will travel faster along ridges in a surface and can be directed by the arrangement of those ridges. This is one of the important principles in flintknapping (making of stone tools) where you can control the shape of a flake removed from a stone by establishing ridges on the surface (yes, I am an archaeologist).

So, anyhow, I started to put this and other information together and started sketching guitar tops. I eventually settled on something similar to what I am currently doing (I have tweaked it a bit since). So the next step was to build a guitar, which I did. Showed it to a few players and the concensus was that it sounded damn good. So I printed a copy of the pattern and mailed it off to Al. He built a guitar and after a few months, got back to me and said it turned out exactly how he had hoped (probably dumb luck on my part).

So that is how I arrived at what I now do. I like it also, because it allows me to march to my own drum.

As for Al? Last I heard he was going through some "life changes", and I have not heard from him for several years.

G

[whitespruce]

I glued the binding on this one today. Did not take photos because it is identical to the Beng jumbo, just different wood.

I do have one photo, though. Since my cutaway is tapered, there is a slightly different curve at the top and back. I bend my bindings in the center of my form, so they don't quite fit either. So, I use the nozzel of a heat gun as a bending iron to tweak the shape.

Only takes a few minutes. I trial fit and mark with a yellow pencil where I have to increas or decrease the bend, and I just fiddle with it until it fits well.

G

[Joel M]

Hey Grant

Thanks for the reply about your top bracing. Looks like you put alot of thought into the design, its beautiful to look and if it makes a great sounding guitar id say its the perfect marriage of form and function.

Thanks for sharing the details with us.

Joel.