Alan Carruth wrote: ↑
Sun Jan 13, 2019 3:55 pm
Just a couple of comments on what I saw in a quick look at Eendebak's site:
First; The brace design itself derives from Kasha's ideas, which have been the 'wave of the future' for more than forty years now, without much impact. I have seen some good instruments built from that design, but no better than what you'd get from a carefully made Torres pattern.
Eendebak's use of a modified I-beam section is also an old idea that has not caught on. You have to keep in mind that with a standard Classical guitar top most of the mass is in the top itself. All of the bracing on a Torres style top accounts for 25% or less of the total mass of the system without the bridge, and most of that is in the large transverse bars. The bridge alone can weigh nearly as much as all of he bracing. Saving, say, 10% of the bracing mass by careful shaping thus reduces the overall mass of the top by 2%-3%, you can lose that much mass by enthusiastic sanding on the top. Note, too, that it's very hard to 'fine tune' I-beam braces to refine the sound of the guitar. Given the inherent variability of wood this is a necessity.
Eendenbak's brace layout seems excessive, to put in mildly, unless he's using a top that is not much more than a membrane, say, around .5 mm to .8mm. A top that thin seems unlikely to me given the lack of longitudinal stiffness in the bridge area given by the Kasha-style 'impedance matching' braces: a thin top would allow for too much forward rotation of the bridge. Kasha got around that to some extent by using a very wide bridge footprint, especially on the bass side, as well as a reasonably thick top.
The wood you chose for the top on your guitar has a lot of heavy latewood lines. I suspect it is denser than average, and has a lower young's modulus along the grain. This is one of the few visual clues that seems to be of any use in 'reading' top wood properties. If you worked that top to a particular stiffness along the grain (rather than simply following a thickness spec) you'd find that it would be heavier than it could have been.
I don't have time at the moment to look further into his ideas. It's very difficult to make any great improvements on the 'traditional' designs, which are the outcome of generations of hard work and thought by some very smart folks. These are complicated beasts.
Thanx for taking the time to reply. I'll need to look up Kasha as I am not familure.
Thinking I have thinned my tops too much but also battling some other issues with fret board angle and too high a saddle because of it. I'm loving the challenge.
I have decided to use only locally acquired wood and we have lots of spruce around. I have one promising board, 3" X 16" X 7', in my shop but thinking I'll use the lower quality wood first. The the growth pattern indicates five to ten year stretches of different conditions... Thinking the Black spruce we have in my part of Alaska are not going to be optimum.
One idea I had was to cut strips of each grain width section say 8-10" long and do a compaireson bending test or even play each strip like a tuning fork to get an idea othe each property and then work the thickness accordingly.
To be honest none of these first two guitars are a dud but I might be biased seeing as they are my first born. I've played a lot of poor sounding CGs over the years and this was why I decided to build my own. I changed out the bridge on my second one last night and strung it back up today, played it for almost two hours, you know until my fingers hurt, then put her away. Pick it up again a couple hours later and was dancing through a D scale and my lady friend remarks how good it sounds just as I'm starting to think to my self, wait a minut, holly smoke, she is really opening up. Thinking I had been beating the strings really hard for a good 6-9'hours of combined playing time. I should keep a log of hours played after first stringing?
Interesting you mention Kasha using a wide bridge. I had to increase mine from about one inch to 1.128 wide. I added almost 2cm to the leanth and 3/32 to the thickness to keep it from distorting. I went overkill perhaps although I'm really fighting a high fretboard angle and the top of my saddle is 15mm and over torquing the top skin. I might pull the frets and plane down the angle. If she self distructs I'll hang her from the rafters and my grandkids can donate it to a musium after I havempassed and am then famous luthier...
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I hate sanding wood or anything else for that matter I just happen to be good at it...