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That is too cool

Looks like downtown on that CF reinforcement, Burton. Very nice. Looks like a weave so the stability of that u-shape should be remarkable.

I noticed the release agent is a hi-temp wax. If you haven't heard of it...there's a myriad of polymer bases releases that won't transfer to the part like waxes can...and are considerably easier to apply than wax. Chemlease is a typical brand name. http://www.freemansupply.com/Chemlease4190EZSem.htm

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

Burton - that is nice! I had thought about doing something similar by laminating the CF cloth and the semi-circular insert into the neck during a single operation. I like your solution. Do you have a photo of the headstock end?

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Steve Smith
"Music is what feelings sound like"

Thanks for that Stuart- I will look into it. I used a layer of peel ply as the base to isolate and sanded before I installed in the neck but I reckon you can't be too careful-

The fibers are stitched unidirectional (2" wide), so all the fiber strength is along the length. The epoxy was recommended to me by a few manufacturers as being particularly hard and the finished bar has that intense crystal sound when you drop it. If anyone is interested it is AVT's 862 resin with the TETA hardener.

I'm very new (and green) to the composites world and have a lot to learn, I appreciate any and all advice!

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Burton
http://www.legeytinstruments.com
Brookline, MA.

Steve,

Unfortunately, no I don't right now. This one shows before installing though:
I am just (carefully) sanding the angle in to the whole thing at the headstock end. It provides some great reinforcement there too but tricky with a slothead to not show the CF in the string slots.




I would be nervous doing it all in one go just because of the clean up. I figured it would be much easier to clean it up first and then carefully install it right where I wanted it then to clean up around the carefully dimensioned neck. The idea being to maximize how low it can go in the neck without coming too close to popping out the back. Right now it is 1/2" deep and the CF is 1/16 thick around the whole thing.

I also figured I would make a bunch at once and keep them ready to go rather than do it each time.

I'm very curious to measure the initial relief with this in the neck.

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Burton
http://www.legeytinstruments.com
Brookline, MA.

Burton, thank you - that answered my questions perfectly. Please let us know the results when you get the guitar strung up, I am very interested in this method of reinforcement.

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Steve Smith
"Music is what feelings sound like"

I'll just join in the chorus of appreciation for Burton's neck reinforcement It's like those hollow D tubes, but adjustable! Although personally I'd prefer the hollow version for minimal weight, but still very cool, and probably fair bit cheaper.


Is there any particular reason you don't have any bracing between the headblock and upper transverse brace? I know it's a bolt on and thus not too much trouble to reset the neck, but it pains me to see the thin woods of the body left to fend for themselves against the neck torque, with only the fingerboard extension as a puny assisting brace...
Otherwise, the bracing looks good. Lower bout fan braces seem to be becoming popular And I like when the upper transverse brace ends are kept tall like that. Nice low-profile tail block as well.

Ah....well then the U-shape isn't going to provide the torsional stiffness I originally thought. You might also look into braided carbon fiber sleeve for this. In fact...it would be ideal in this application. It comes in many different formats. It's handily flexible, allowing you to pull it tight to align the fiber length-wise or scrunch it up to align the fibers span-wise....like a chinese finger torture. You'll just use it as a lay-flat material...forgetting about the tubular nature of it. It lays flat on a roll...so...finding the right width and thickness will allow you to arrange it precisely in your mold with the fibers pulled to orient more along the length. This will maintain the bending strength of your uni-directional fiber but VASTLY increase the torsional stiffness of the overall neck. That u-shaped geometry can be a major factor that adds to the overall torsional stability but using uni-directional only works to bending strength and is quite useless against twisting loads.

You might be inclined to think that having all the fiber oriented at a +30 degree -30 angle (0 degrees oriented down the neck) would reduce the bending stiffness by too much but you'd find only a slight decrease along that axis with a large multiple increase torsionally.

http://www.braider.com/Products/Braided ... vings.aspx

I didn't look but this old supplier of mine (this is the best company supplying this stuff) used to have a flatlay calculator on their website. If you try to figure the ideal size to get to occupy the space in your mold...I bet you anything they'll sample several yards of numerous sizes for you to experiment with.

If you like....tell me the thickness of the finished carbon layer (as it is when glued into the neck) and then the width of the uni-directional material as it lays flat on the table prior to molding. I could tell you the model# that would be a good substitute and then A&P would probably sample that and the next two sizes bigger and smaller to make sure you had the perfect size.

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

Stuart, this is great, thank you! I'll look into this for sure. The ability to really dial in the exact strength you want with the material and layup is pretty fascinating.......

Chris, If I sold them I would want to make it worth my while so it might not be the biggest value . Probably still less than those D tubes though- And, these things hollow out pretty easily. A teflon plug in the mold would probably produce a D-tube-ish insert.

It's really not all that difficult. Milling the aluminum tool would probably be the sticker for people without access to a mill but you could probably do it with a router bit if you were brave.

Dennis, I agree about the weight. I was mostly interested in pursuing this this for applications where I leave out the adjustable rod. I don't think I am that concerned about some Spanish Cedar as the middle part but who knows. I am interested to track the relief in the necks I put these in. I would love to be able to have the data to back up my ability to build without the adjustable rod rather than just my own confidence-

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Burton
http://www.legeytinstruments.com
Brookline, MA.

I actually do put ~3/4" tall support blocks on either side of the truss rod channel between the heel block and transverse brace. This pic was taken before the rims were glued to the top... after the top is attached I glue the support blocks (with grain parallel to the top's) as it's easy to get a good tight fit, then finally I glue on the back.

Edit: not sure if that made sense... a picture inside the completed body is probably better:

Stuart, the final width of the CF layer once bonded is 1/16 and I was using the 2" stitched tape which was a little wide but allowed me some room to not orient it all perfectly when clamping.

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Burton
http://www.legeytinstruments.com
Brookline, MA.

Yeah, Spanish cedar (or perhaps western redcedar) core isn't enough weight to fuss over. Just the adjustable rod that's embedded in it in the current version. But that is a good idea, prototyping with the adjustable rod first

Although now that I think about it, I wonder if the curve is really that much stiffer than just sticking two 1/2 x 1/8" bars and calling it done. Or even 3 bars, possibly putting the center one 1/16" deeper with a filler strip over it to get an effective 9/16" depth without too much danger of carve-through. A 48" CF bar (long enough for 3 lengths) is 74g, and an Allied truss rod is 120g, so you'd still be saving a fair amount of weight, while allowing the use of low density woods like Spanish cedar and butternut that might be a little too flexible if you used the adjustable rod alone. And the 48" CF bar is about the same price as an Allied truss rod, which is a whole lot less than the D tube, and I could install it with my plow plane instead of a router table as well which is a major selling point for me.

Hey Burton, it looks like the tube came out great and a big hit to boot.
Way to go!

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Jim Watts
http://jameswattsguitars.com

Burton, it looks like you're on to something with this design! Keep up the nice work!

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Brad

Why make it out of aluminium? If you're not concerned about surface finish, you can just use MDF. It wouldn't last as long, but far easier and cheaper to make. Clamp it to something flat to make sure it stays straight. Aluminium moulds are only necessary when you're cooking the part in an autoclave.

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"I am always doing that which I cannot do, in order that I may learn how to do it."
Pablo Picasso

https://www.facebook.com/FenskeGuitars

closing the boxes on 2 commission falcate guitars.......

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MK5acoustics.com

I REALLY love these threads and your posts are all so informative and interesting. Thanks so much for the effort.

I thought I'd contribute a couple pics of two guitars that I just topped. Both are my designs and test platforms for a couple new ideas.

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Thank You and Best To All

Hi Wes, looking good.
I was just wondering - it looks like you are following the design from the Gore book.
I can't see the mountings for adding side masses inside the body.
They may be there, just I can't see them from the photos.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

this is my own design , a Gore inspired guitar, I am building two of these together, one is EIR and Sitka, the other Bubinga and Euro spruce, no side mass in either.

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MK5acoustics.com

Also! Got to hang out with Bob Garrish who was in town for a competition. Had a total blast.
That was the true highlight of my weekend-

Larry,
I made one with bracing like that once. I'd be interested to hear what you thought of them when you string them up.

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Burton
http://www.legeytinstruments.com
Brookline, MA.

I've got a Port Orford Cedar and Black Walnut of the smaller design with similar bracing that sounds really nice IMO but these will be Lutz and Mahogany. What did you think of the one you built Burton?

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Thank You and Best To All

Larry,
It sounded clean, if that makes sense. I liked it, as did the guy that bought it. It was mahogany and Red spruce.

The Chladni modes were very different, I was surprised by that and don't know if it was all the long grain reinforcement in the lower bout or just the wood, I have not repeated it.
I think Michael Bashkin builds like that too.

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Burton
http://www.legeytinstruments.com
Brookline, MA.

Thanks for the input Burton - very valuable. Hard to describe the sound of the one completed git. Chimy (?) comes to mind. Similar in tone to another, older, similar braced 000 12 fretter.

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Thank You and Best To All