Bert Eendebak CG design

Construction and repair of Classical Guitar and related instruments
ernandez R
Posts: 269
Joined: Wed Dec 26, 2018 6:06 pm

Bert Eendebak CG design

Post by ernandez R » Thu Jan 10, 2019 7:33 pm

I used a lot of the information from Bert's website for my guitar builds. I used his main dimensions and most of his sound bar ideas.

Sent a couple emails his way but received no reply so I wanted to thank him publicly for providing so much usefull and concise information. Thanx!

Wondering what other builder here think of his ideas and has anyone played or heard his guitars for Comparison.

His website
https://www.designofaclassicalguitar.com/home

HR
I hate sanding wood or anything else for that matter I just happen to be good at it...

Stephen Faulk
Posts: 1161
Joined: Tue Jul 03, 2012 3:27 am

Re: Bert Eendebak CG design

Post by Stephen Faulk » Sat Jan 12, 2019 12:51 am

Building a plan that many other people have made gives you more people who can talk about what's going on. The stuff he does is fine, but getting regular feedback might be easier with a more accepted plan and lots of people willing to share information.
Patience at the bending iron pays in rounded dividends!

ernandez R
Posts: 269
Joined: Wed Dec 26, 2018 6:06 pm

Re: Bert Eendebak CG design

Post by ernandez R » Sun Jan 13, 2019 2:46 am

Stephen Faulk wrote:
Sat Jan 12, 2019 12:51 am
Building a plan that many other people have made gives you more people who can talk about what's going on. The stuff he does is fine, but getting regular feedback might be easier with a more accepted plan and lots of people willing to share information.
No doubt you are correct. I was just hoping someone on this forum was familure with his work.

Couldn't tell you exactly why I was drawn to his construction or why I thought i should adapt his ideas into something that I had zero experience with. Let's just say it rang true. I have many years building and repairing composite aircraft so I have a good grasp of structures and material limatations and I love the idea that I can take ideas from here and there and incorporate them into a new whole. Way easier on a guitar then an aircraft.

That being said I will be grinding off the bridge on my Mk-II this evining because I made it too thin and from a piece of wood not suitable. I knew it was softer yet I glued it on anyway... I didn't use Bert's bridge design and was proud I had a super light one at 10g-ish. Silly me. I keep thinking of a carbon fiber bridge... but that is not the way I want to roll. I just unstrung her and I'm feeling less then pleased with myself that's for sure...

HR
I hate sanding wood or anything else for that matter I just happen to be good at it...

Stephen Faulk
Posts: 1161
Joined: Tue Jul 03, 2012 3:27 am

Re: Bert Eendebak CG design

Post by Stephen Faulk » Sun Jan 13, 2019 3:45 am

I can't tell whether you're trolling us or you are actually trying to get information.
Patience at the bending iron pays in rounded dividends!

ernandez R
Posts: 269
Joined: Wed Dec 26, 2018 6:06 pm

Re: Bert Eendebak CG design

Post by ernandez R » Sun Jan 13, 2019 8:44 am

image.jpeg
Trolling? I am sorry Stephen, I'm not that safestacated. The thread on my build should make it obvious I am a rank begainer.

I am really securing to learn from others only I have a good two thirds of a life as a craftman/Renaissance kind of man with a diveres background. Only thing I couldn't fix was my timex watch some years ago, and my poor spelling. I've done advanced composite repair on the triple seven and sewen a baseball stitch on the belly belly of a super cub.

Two be honest I have this feeling that most luthiers are of a like mind.

Back to Bert's CG design. What to you make of the direction he has taken. Most is straightforward. Hard to move away from so many years, centuries, of evolution. Have to admit I am intrigued by multi course instruments but have enough sense to that to,others more talented then I.

I really did grind the bridge off my second build this evening, made a new one more stout, and glued it on. Not my finest moment but I knew these first guitars would be a learning process. Wrote up a new thread about my next builds and it went away before I could hit send :/

HR
You do not have the required permissions to view the files attached to this post.
I hate sanding wood or anything else for that matter I just happen to be good at it...

Alan Carruth
Luthier
Posts: 3180
Joined: Mon Dec 24, 2007 6:56 pm

Re: Bert Eendebak CG design

Post by Alan Carruth » 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.

ernandez R
Posts: 269
Joined: Wed Dec 26, 2018 6:06 pm

Re: Bert Eendebak CG design

Post by ernandez R » Mon Jan 14, 2019 7:32 am

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.
Alin,
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...

HR
image.jpeg
You do not have the required permissions to view the files attached to this post.
I hate sanding wood or anything else for that matter I just happen to be good at it...

Alan Carruth
Luthier
Posts: 3180
Joined: Mon Dec 24, 2007 6:56 pm

Re: Bert Eendebak CG design

Post by Alan Carruth » Mon Jan 14, 2019 8:19 pm

As far as I can tell, from measuring the properties of a lot of tops of various sorts, spruce is spruce. About 60% of samples will fall within 10% of the long-grain Young's modulus that that you could predict on the basis of density, and all softwoods fall on the same line. The wood you show in the pics has heavy latewood lines. In softwoods this is generally a sign either of 'reaction wood', say, from the down hill side of a leaning tree, or the south/sun facing side of a tree, or its wood that came from low down in the trunk of a large tree. In either case the hard late wood grain lines are dense, and add more mass than they do stiffness, so the wood will be less stiff along the grain than the density would predict. Since light weight and high stiffness are necessary traits in a Classical guitar top, I'd avoid using wood like that if I had the choice.

I've used a half dozen or more different softwoods for tops, and none of them has been 'magical'. All of the spruces, and firs and pines I've tried for that matter, having similar damping and so on. Western Red Cedar and Redwood both tend to have much lower damping than any of the spruces. WRC also tends to have lower density on average than most spruces, but there is plenty of variation within all species, and lots of overlap between them.

The bottom line, then, is that the local spruce you can find is likely to work as well as any once you learn how to pick out the better stuff. You may have problems finding local hardwoods for the back, sides, and necks. Willow and poplar, which you might have, make good blocks and liners, and decent neck stock. Some Doug fir I've seen has been on the borderline of being 'hardwood' in terms of properties, and might make a good material for B&S.

ernandez R
Posts: 269
Joined: Wed Dec 26, 2018 6:06 pm

Re: Bert Eendebak CG design

Post by ernandez R » Wed Jan 16, 2019 5:46 pm

Alan Carruth wrote:
Mon Jan 14, 2019 8:19 pm
As far as I can tell, from measuring the properties of a lot of tops of various sorts, spruce is spruce. About 60% of samples will fall within 10% of the long-grain Young's modulus that that you could predict on the basis of density, and all softwoods fall on the same line. The wood you show in the pics has heavy latewood lines. In softwoods this is generally a sign either of 'reaction wood', say, from the down hill side of a leaning tree, or the south/sun facing side of a tree, or its wood that came from low down in the trunk of a large tree. In either case the hard late wood grain lines are dense, and add more mass than they do stiffness, so the wood will be less stiff along the grain than the density would predict. Since light weight and high stiffness are necessary traits in a Classical guitar top, I'd avoid using wood like that if I had the choice.

I've used a half dozen or more different softwoods for tops, and none of them has been 'magical'. All of the spruces, and firs and pines I've tried for that matter, having similar damping and so on. Western Red Cedar and Redwood both tend to have much lower damping than any of the spruces. WRC also tends to have lower density on average than most spruces, but there is plenty of variation within all species, and lots of overlap between them.

The bottom line, then, is that the local spruce you can find is likely to work as well as any once you learn how to pick out the better stuff. You may have problems finding local hardwoods for the back, sides, and necks. Willow and poplar, which you might have, make good blocks and liners, and decent neck stock. Some Doug fir I've seen has been on the borderline of being 'hardwood' in terms of properties, and might make a good material for B&S.
Alin,
Thanx for the info.

Find what I'm missing is the experience baseline to gage against most of what I am doing. I might purchase a nicer grade of top from the alaska tone wood dealer to play with. fortunatly I have a lot of spruce that was put up 20-40 years ago that has been in an outside covered storage. The 3/4 rough cut stock is mostly stable but I get a little cupping after resaw into 1/8. Idealy I would like to let it sit for a couple years but find I need the hands on assembly experience more then I need master grade tone wood at this stage.

I will keep a better eye on the granin structure as you have described.

There is a Lutheir who specializes in Clasical guitar building about 80 miles from where I live and just sent off an email to see if I can get some time with him.

Going to try playing with some white birch for back and sides once I get a little more handy at the assembly details. Semis all I am really lacking is a lifetime of guitar building and starting at after 50 years feel a little behind the curve.

HR
I hate sanding wood or anything else for that matter I just happen to be good at it...

Return to “Luthiers”