Neck reinforcement: Carbon? Graphite? Adjustable truss rod? - created 03-10-2010
Hoffer, Eric - 03/10/2010.19:52:13
Well, I'm just about done with the first one, and I ordered the stuff for my second. It came in the mail today from LMI. Its going to be a 3/4 size guitar inspired by Kathy Matsushita's...
http://home.comcast.net/~kathymatsushita/moreprojects/htmlpages/five1.html
a bit different materials but the shape and size will be similar.
engelmann spruce top
sapelle sides and back
sapelle neck
ebony FB and bridge
undecided on the binding and rosette.
Here is my question...Kathy didn't use a truss rod, instead she just used a carbon fiber strip in the neck. Well, LMI doesn't sell carbon fiber so I got a graphite reinforcement strip. I meant to get a 1/2" x 1/4" piece but I ordered 1/8" x 1/2" on accident. I'm pretty sure this will not suffice.
-What are your thoughts on small guitars and neck reinforcement?
-Is graphite alone good enough?
-Is my piece of graphite too small?
Thanks so much. This forum has been so much help to me over the process of my first build.
-Eric
Eric, what LMI calls "graphite" is actually carbon fiber composite. Graphite is what is in your pencil. For some reason they have not changes this designation on their site.
EDIT: Your 1/2 x 1/8 rod it likely enough for the short neck of a size-5. If you want more add a 1/8 x 1/8 steel rod below it. Or maybe the piece you bought is long enough to double-up.
EDIT EDIT: I've made a similar size instrument and I used 3/8 x 1/8 carbon with 1/8 x 1/8 steel below it and it worked fine. I also used Spanish cedar for neck wood which is not as tough as your sapele.
The carbon fibers in the composite are chains of graphite molecules, so it's as much graphite as it is carbon fiber, it's largely resin either way.
Fly rods, golf clubs, things like that used to be made of "graphite", but they now are "carbon fiber" even if they're still made of the same stuff. Perhaps the whole "pencil" thing made the makers change the name, but what's in a name anyway?
I think your 1/2" by 1/8" piece will suffice as long as it is properly installed, if you want more peace of mind just get another and lay them in side by side like Chuck suggested.
I once received this advice from Mike Doolin, and have been grateful ever since.
" Spare the rod and spoil the neck".
I would put the carbon fiber in and an adjustable truss rod.
Those rods, if well made have very, very little resin in them. Probably about 20% by weight - just enough to hold the fibers straight.
Generally graphite has the carbon in "diamond" sheets that slide relative to one another (makes it a decent lubricant). Carbon fiber is generally "diamond" strings or tubes.
After a bit more research, I see that my generalizations are generally true (
"Diamond" has been used to represent carbon atoms covalently bonded to each other.
Curious. On my size 5's (I've made about 15), I use an adjustable truss rod and no carbon/graphite/epoxy/whatever you want to call it. My thinking is that the added stiffness of the carbon isn't necessary on such a short neck but the ability to adjust relief and limit the wood's inherent creep is ALWAYS a good thing. I don't see any advantage whatsoever to leaving out the truss rod, with or without added stiffeners.
By the way, what is the point of adding a steel rod under the carbon? Seems like you'd be decreasing the carbon's efficiency and adding unnecessary weight. The carbon has great stiffness at lower mass than the steel, and is most effective when close to the back of the neck.
The carbon has great stiffness at lower mass than the steel
Right, and that's exactly where everyone gets into trouble. Its stiffer than steel, by weight. But not stiffer by size. So when we're limited by shape as to how large a CF member we can use, we may not be able to attain the required stiffness, so steel is still called-for.
Good quality CF has very little resin, BTW. And while technically it's okay to call it graphite, for those of us who have worked with true graphite, it's frustrating as hell to have CF called graphite, as it only lends to confusion..
Thanks everyone.
I believe the thinking behind the CF is that with such a small guitar, one should try to keep the weight as low as possible. (at least that is what I got from Kathy's site) After hearing all of this discussion I think i will just find a short truss rod and save my CF for another project. Lmi carries a 12" one. I haven't begun to draw this thing up but I think that should be short enough.
thanks
-Eric
I think that's a good decision. I personally can't understand why anyone would want to leave out a truss rod. I've heard all the arguments about weight and about how they affect tone but that's a very small trade off considering what the rod has to offer. Guitars invariably change. That's just a fact of life. Temp, humidity, varying climatic conditions, changes in string size or action setup, etc....all of which can have a great impact on the neck. Having that truss rod is insurance enabling you to deal with those unforeseen circumstances. In my book, building a neck without a trussrod is like plowing with a mule when you've got a brand new tractor sitting in the front yard.
Eddie, you left out the word "adjustable" three times.
I apologize. Adjustable, adjustable, adjustable. In this forum, I'd think that would be understood.
A
truss rod is still a truss rod. It plays the same role, but must be designed and installed correctly to be effective. And they CAN be effective. I've been very successful with them and so has Mario.
Just being pedantic because ... well, to make the point that there really is more than one way to skin the cat. EDIT:
"there really is more than one way to skin the cat."
I agree with you there.
So you're saying there are multiple options for removing the outer covering of a feline?
The epidermis, that is.
Eric, your 1/2" x 1/82 should be great, if you have enough, put TWO bits with a 1/4" gap in the centre of the neck. I have also used two 1/4" carbon tubes glued together like a figure 8 dropped into a 1/2" deep slot, bonded with low viscosity super glue. The deeper you can get them the better. There is also 1/2" x 1/4" hollow rectangular tube (aero modelers) which is stongest for weight. I have built 26" scale large bodied guitars, strung with 12-54s, that you can lift by the headpiece, guitar lying horizontally, and there is no noticeable change of pitch. However I make laminated necks with very carefully selected woods to guarantee stability. Your Sapele is an excellent wood. No trussrod has EVER stopped a neck from bending, it only corrects the fact that the neck bent in the first place. Last weekend I watched my kid brother gigging with an electric 12 string that I made 34 years ago. It has NO trussrod, the action is incredible, and it (in his words) has the longest sustain of ANY instrument he has player ! Look forward to seeing the finished project.
PS How many ways ARE there to skin a Pussy Cat ??
ERIC....a PS, if possible... modify the under soundboard area of the neck and fretboard so that you can run the carbon beams almost to the end of the fretboard rather than just up to the neck block. HUGE difference.
There is also 1/2" x 1/4" hollow rectangular tube (aero modelers)
Ooh ooh! Want! Want!
where do you get these? Definitely want to test 'em out.
I've got good news and bad news. Good news is I found the stuff pultruded...bad news is that the two suppliers I found it at are in the UK and the OZ. Also found some square pultruded stuff which could be laminated to height and still lighter than solid.
Rectangular:
http://www.smallparts.com.au/store/partslist/tuberectangularcarbonfibre/carbonfibrematerials/all/1/3/
http://www.elitemodelsonline.co.uk/Products/Tools-and-Materials/Building-Materials/Carbon-Fibre/Round-Tube
Square:
Hobby Lobby, Hobby King, and Dragon Plate all have pultruded square tube.
Square tube also at:
http://www.cstsales.com/carbon_square_tubes.html
A while back I bought some rolls of surplus unidirectional carbon fiber on EBay. I have been following this thread and wondering how I could use this for neck reinforcement. 1) Laying up multiple layers with epoxy in a press between sheets of wax paper and then ripping it to width? 2) Just epoxying it as is between pieces of spruce? It is not "pre-preg" - fabric just has the fibers. I think it is about 4" wide.
Stephen, I have a spool of carbon fiber tow (sounds like what you have) and I cast it into place in a groove in the neck. I take each tow bundle, cut it to length, drag it through a puddle of epoxy, run it between my fingers to squeeze excess epoxy off, and place it in place. After several bundles have been placed in the slot, I place a wood spline on top and apply spring clamps along the length of the neck. This will squeeze out even more of the epoxy. It seems to work pretty good, however, the resulting bar is not quite as stiff as a commercial epoxy graphite bar. The thing I like about this is that the wet graphite fills your slot perfectly and you get great bonding to the surrounding wood.