Hey everyone,

I'm about to take on a great project for my Composite Materials class. I am a Mechanical Engineering Student at RIT and we have the opportunity to pick an object we want to make out of composites and I thought a bass would be awesome!

Of course I have to buy the materials. Any of you have any information on what would be the best materials for taking on this project?

I am planning on modeling it after say a RainSong guitar or a Modulus but with a Fender style body.

I don't think I'm in over my head as my professor even suggested this as a project. If worse comes to worse I could just make a replacement composite neck for my Fender J bass.

I am looking for any insight into this project. If I don't get enough information, I'll just end up making a composite hockey stick or something else less interesting. Thanks for any help!

I've read a couple of the patents for graphite basses and necks. One method (I think the one patented by G. Gould of Modulus) uses graphite pieces on a mold with epoxy. Other methods use graphite cloth over a core with epoxy and yet another uses graphite dust mixed with epoxy on a cast. Too bad those guys don't hang around here.

hey KF,

Excellent idea for a project! :hyper: Here's a couple of thoughts -


* For US Export Control reasons, you will not be able to discuss the engineering details of your part in this international forum. A Google search on US Export Control will keep you out of hot water

* But ... at a high level we can discuss your choice for materials (just not the engineering details of application of this choice) So will you be utilizing a hand lay-up process, or are you looking more at a chop fabric or RTM process?

* The original Steinbergers utilized a chop fabric approach from what I can see. Same thing for at least the outter ply on a Modulus neck. Most of the carbon fiber stiffening bars utilized in neck construction are of a pulltrusion origin

* If you plan to utilize hand lay-up, will you also be working the design with a CAD system? I kinda know just a little bit about this subject ;)

* There's a TON of good information available on NetComposites.com, and several other on-line resources for purchasing your materials.

* Be aware that several large commercial aerospace programs are grabbing up most of the carbon/kevlar fabric materials available today, so you may be forced to adjust your design to utilize a fiberglass material with epoxy resin ... and fiberglass designs are not Export Controlled(!)

all the best on this and do keep us posted

R

If you need help, I can definitely let you know where to get carbon composite materials- no need for the fiberglass that Rodent mentioned. I do huge amounts of carbon fabrication and can give you some pointers if you need.

I would suggest the easiest way to go about it would be using dry or pre-preg uni (non-directional) carbon over a core. The most difficult part of the entire process will be the mold and core fabrication, not the layup part itself, which is fairly simple once you get the process down, but do expect to make more than 1 before you get it correct.

A neck would be a good place to start, even if somewhat difficult. Beyond that, it would be easier to make an acoustic a la Rainsong than a full composite instrument like a Status. Either would be difficult, though.

Subscribed.

My first post was a little in haste as I was between classes and had to get goin. I'll update and edit the first post with generalized information from the other posts.

A little more organized thought process would be this:

Project: Composite Bass Fabrication

Focus Options:
-Composite Neck
-Composite Body
-Full Composite Bass

Idea Tree:
-Composite Neck
+Smaller mold
+less material (less expensive)
+Bolt on replacement for a Fender Jazz Style Bass
+Specification areas: neck radius, fretted (#) or fretless (#, lined unlined)

-Composite Body
+Hollow body or Solid Body (lost wax process, bladder inflation)
+Could be any design
+Would need space for electronics
*Active or Passive, Pickup placement, pickup type
+Complex design?
+Can be coupled with composite neck for complete composite replacement options

Full Composite
+Largest mold
+Increased chance for flaws
+Increase in materials
+Whole part possible for scrap

This is a rough outline, and as it currently stands the bolt on neck sounds really enticing as I could put it on any Fender Bass and would look really cool. I'm thinking if I use an epoxy resin with a fretless neck that would not only be easy but sound very *mwah*

I'm going to discuss this more with my professor over email.

There's way more to it than that.

I would not recommend either lost wax or bladder inflation for your part. Lost wax will melt during the curing stage (the temp of which depends on resin or prepreg curing temp, usually in the 175-300 degree F range) and will ruin your part. Bladder inflation makes very imperfect shapes when put in tight radius's or small areas- it's really only meant for large, open shapes.

A full composite body not only requires lots of material, but more specialized materials, too- you'll need much much wider rolls of weave if you do not use uni, and you'll have to make a significantly larger oven. Stick with a smaller part the first time through, it'll save you a lot of cash. Carbon is very expensive and very easy to mess up, but still less of a pain than fiberglass!

Either way, you won't be able to use carbon weave or uni for a fretboard. Epoxy or polyester resin will be part of the curing process, as it is part of what holds the carbon in shape, but it is not suitable for a fretless fretboard. You would be playing right on the resin, so when it starts to wear, you're wearing into the carbon, which is not really repairable. You'll want to adhere a fretboard of some sort (perhaps composite) onto the neck you make, especially if you want the adjustability of a truss rod.

What you should be thinking, more than anything, is "how am I going to make the mold?" because that is by FAR the most difficult and time consuming part. 95% of your time will be spent with the mold, and the other 5% with making the actual part. I'd think about that before anything else.

Alright, after a few classes and some research into the patent office I've come up with these ideas:

Modulus uses carbon fiber and epoxy for their necks. It is a unidirectional fiber running longitudinally along the axis of the fret board for increased stiffness when string tension is applied.

Also, Modulus uses a hollow core and affixes a composite fretboard.

Modulus also claims that the use of carbon fiber eliminates the need for a truss rod.

My Ideas:
Same as modulus with unidirectional fibers, however, maybe using a honeycomb foam core.

For the mold I am planning on buying a used Fender neck on Ebay (or maybe a friendly TB'er has a donation? :)) as a plug from which I will cast the mold. Tuning peg holes will be post manufacture machined via CNC.

My questions:

Should I incorporate a truss rod if I'm using carbon fiber?

If so, I was looking into using a shape memory material such as Nitinol Tubing or a traditional mechanical truss rod.

If I make a hollow core neck, I also may incorporate LED lighting for finger markers.

What are some constraints on the neck I should pay close attention to? Should I go Fretted or Fretless and what factors will affect my itonation significantly?

Thanks again for any insight guys.

Ok...somewhere along the line, the enthusiasm is there but you aren't fleshing the ideas out to their full extent.

The fibers that Modulus use are commercially available, but only ever seen them available in very, very large quantities from Aerospace supply companies. Even if that weren't a problem, the process is- part of it's strength comes from being subject to very high pressure during the curing process. You do not have technology available for this.

The better option for you, in my experience, would be to use woven carbon cloth, like Status uses. You could achieve a similiar end result with unidirectionally woven carbon cloth. It's sometimes a bit hard to find dry (you aren't ready for pre-pregnated carbon yet), so you could achieve similiar stiffness using directionally-woven (standard) dry carbon and using a few layers oriented at different angles- requires a bit of calculation if you want to be sure of stiffness, but you could also just go with standard proven angles.

The advantage here is that it doesn't require high pressure to cure to adequate stiffness. You could get away with only using a vacuum pump and a small, homebuilt oven to cure the pieces. The curing materials are much cheaper this way, too.

The other thing to think about would be the honeycomb core- do you have a CNC machine to cut it to the internal profile of the neck? Got anyone to do the CNC programming and machining? It's very expensive. This is NOT a material you can cut or carve by hand, and a changing-radius/thickness/width shape is extremely difficult. You might want to look at something more like a hard foam (not at all similiar to sytrofoam) or something similiar. It'll be much easier for your first few attempts.

Also, for what it's worth, both Modulus and Status use truss rods. Even carbon fiber will move in changing temperatures. Nitinol is not what you want.

Avoid things like LEDs and stuff- it will overcomplicate your build to a huge extent. You'll have enough on your plate learning everything else anyway. These will only get in the way and increase costs.

Do you have a budget in mind?

I have experience in programming CNC and am ASTM certified in running a Computer Numerical Controlled mill, lathes and the like. So that resource is readily available in the machine shop. Also I do have access to an autoclave and heat treatment oven.

Thanks for the idea about status, so far I've only looked at Modulus. Fortunately, commercial vendors for pre-preg Carbon Fiber is available.

I have the next 8 weeks for this project and am estimating a budget from as close to $300 as possible.

My ideas as the moment are still strictly brainstorming so the hatchet isn't ready to fall yet so to speak and I really appreciate the almost devil's advocate approach to get me thinking about alternatives.

Edit: Also I have a rough sketch drawn up in AutoCAD and Mastercam, just the specifics such as fret placement are yet to be added. I saw in the Luthier's FAQ a calculator to find that.

Pre-preg woven, though, right? Pre-preg doesn't specify how it's arranged.

The modulus-style carbon shards still require high pressure during curing, which is unlikely to be available.

If you are going to be using pre-preg, you'll need a very large freezer to keep it very cold (otherwise it'll be ruined), and it'll be quite expensive. It's also easier to screw up the lay-up, even if ideally it's lighter per stiffness.

$300, though?! Not with pre-preg, and unlikely with dry. You might want to want to have a little more handy than that. And that's assuming it goes smoothly the first/second time! You could easily spend that much just on one lay-up.

Sorry, I wasn't too well educated when I started naming materials. I talked to my professor today and like you suggested he said I should go with unidirectional Carbon Fiber, oriented at 0* and 90* and aligned at a 45* angle on the neck to account for the tension of the strings on the neck. He said that the problem with a person trying to make a guitar before is that the tension bent his neck like a bow.

So for materials I will use unidirectional carbon fiber layers with an Epoxy resin.

I want to make the neck hollow, so I'm think I will use blue-foam for the core, then when the part is cured I will wash away the blue foam with acetone.

I can use CAD and CNC to machine the blue foam and other methods to get the shape, radius I want.

I am also thinking the neck should be 2 parts, 1 part being the bottom U shaped neck, and then affixing the 2nd part fretboard that will also be a composite.

Now what did you say about needing a truss rod? or not needing one? I'll look into other posts about incoporating that into the design. I have to give a presentation thursday about my project.

Thanks again!

Leave the foam....

Cheers ROdy

Leave the foam....

Cheers ROdy

So go foam core over hollow?

I was thinking hollow would be more "sound resonant" as Modulus claims anway. But I think with a foam core it would be more structurally sound and would probably make adding a fingerboard and truss rod easier.

But I think with a foam core it would be more structurally sound Only to the extent that the foam has some actual structural strength, and MOE. These are likely very low with respect to the other materials (as in one or two orders of magnintude); plus, the foam is at the core, which is surrounding the neutral axis/plane for any conventional bending analysis, therefor further minimizing its contribution.

Only to the extent that the foam has some actual structural strength, and MOE. These are likely very low with respect to the other materials (as in one or two orders of magnintude); plus, the foam is at the core, which is surrounding the neutral axis/plane for any conventional bending analysis, therefor further minimizing its contribution.


Good point. I guess I was going on the idea that the foam would improve impact strength, but I don't think my fingers are going to be punching through carbon fiber/epoxy PMC. Thus I would remove the foam only for the purpose of improving sound resonance.

The foam initially is necessary though because it will provide the plug and basis which I will wrap and hand lay up the expoxy carbon fiber. I am unsure whether I will make a separate fingerboard to place on top of the board or just make the fingerboard part of the mold.

My professor suggested that I make the neck U shaped so that the strings are laying on an open surface to allow for slide gui**ring. I don't think I will go with that considering who would want a bass exclusive to sliding.

I believe making a fretless will be easier than trying to add frets to the composite fingerboard. I could always buy a soft wood material fretboard and lay it on.

Now my question is how am I going to attach the neck to the body of my bass? heh.

KF, sweet project! I'm an RIT ME too. I graduated back in '02.

Like Angus has been saying, I would recommend keeping your project as simple as you can. I'm assuming that you'll only have 7 weeks left after break and you've got other class work as well. Time flies when you're working hard, and projects you are passionate about always seem easier at the beginning.

If you need a cheap neck for your mold you might want to get a used one off the bay, or get a cheap one from rondomusic.net. They sell a $40 bass neck.

I think that a truss rod is a good idea for your neck. That way you'll have some adjustability. Until you've tested your design it will be thought to know just how much the neck will flex when it is strung. If you go without one and it flexes too much there isn't much you can do. Unfortunately, fixing the truss rod into the hallow carbon neck sounds like a lot of work too. It's not like wood where you can just take a router/mill and create a slot for the truss rod. I imagine you'll have to mold that in.

This sounds to me like a really challenging and fun project. Let me know if you have any machining or mold building questions. (Unless you're on the F1 team, because then you'll already know everything ;) ) I worked in Rochester for a while (with Rob Kraynik's brother) in that industry and still have many good contacts. Please keep us posted.

Aww man, you're lucky KF, I'm doing MET up here in Ontario and we didnt get any project like that for our materials class. But good luck to you and hope it turns out awesome!:hyper:

OK, I am ready to buy one!!! :)

You could also go with a solid one-piece, graphite composite moulding concept like the AWESOME design that is featured on my Status Stealth bass.

I would perhaps go fretless on your first test build, just to keep your costs down. The last thing you want is a great "shell", potentially ruined by a tricky fret installation. But, kudos to you if you come up with a way to put in STAINLESS STEEL frets!! :)

Good luck and keep up the hard work!

Cheers,

Jay

Good point. I guess I was going on the idea that the foam would improve impact strength, but I don't think my fingers are going to be punching through carbon fiber/epoxy PMC. Thus I would remove the foam only for the purpose of improving sound resonance.

The foam initially is necessary though because it will provide the plug and basis which I will wrap and hand lay up the expoxy carbon fiber. I am unsure whether I will make a separate fingerboard to place on top of the board or just make the fingerboard part of the mold.

My professor suggested that I make the neck U shaped so that the strings are laying on an open surface to allow for slide gui**ring. I don't think I will go with that considering who would want a bass exclusive to sliding.

I believe making a fretless will be easier than trying to add frets to the composite fingerboard. I could always buy a soft wood material fretboard and lay it on.

Now my question is how am I going to attach the neck to the body of my bass? heh.

Only to the extent that the foam has some actual structural strength, and MOE. These are likely very low with respect to the other materials (as in one or two orders of magnintude); plus, the foam is at the core, which is surrounding the neutral axis/plane for any conventional bending analysis, therefor further minimizing its contribution.

I agree.....and I disagree. You are correct in saying that the foam has no bending stiffness to speak of. But that does not mean that it has no significant contribution. Sandwich contructions, especiall using fiber composites as a skin, work mainly on the principle that the load-bearing members are placed at a distance from the neutral plane where they are used in tensile mode which is the mode in which they are most effective, and where, due to Steiner's parallel axis theorem, they produce a moment of inertia proportional to the square of the distance to the neutral line (assuming this coinsides with the center of rotation). In order to maintain both these conditions, this distance must be maintained and no buckling must take place. The way to do this is to place the skins on top of a highly incompressible core. This is the reason why balsa wood is not to be scoffed at. Balsa wood, especially used with its fibers perpendicular to the neutral plane (iow, the compression forces act along the fibers, not across it) can make a very effective core material for sandwich constructions as it is very incompressible and lightweight.

Think of an I-beam, but taking out the | part...

In other words, leave the foam.

Cheers Rody

Rody

The theory is correct, and it does apply to the laminate sheet situation you describe. (They are fantastic materials to use!) But I don't think it is as appropriate to this application as straightforwardly (word?) as you suggest.

Specifically, this application does not so much resemble the laminate sheet construction as it does a tube, specifically in the neck. The side walls would take virtually all the compression and neutral axis shear stress resulting from beam loading, and the core would not enter into it -- just like a square or rectangular structural steel application.

The body may possibly present as situation where, due to the wide face size moving the walls significantly outward in comparison to the thickness, the core could be of some use.


Empirically, BassLab instruments have always been noted to be extremely stiff all over, despite being hollow. Curved body faces do help in this respect.

Think of when the strings are on the neck. The top (fretboard) will be in compression while the bottom side of the neck will be in tension.

From Failure Mechanics it is known that the outermost fiber is the fiber that experiences the load, not the inside. Thus, a hollow body supporting compressive loads on the fretboard and tension loads on the bottom would be the same regardless of the core.

The reason for using the foam core permenantly would be for the placement of the truss rod. The truss rod can't be suspended in space underneathe the fretboard because it would have nothing to push on.


To maintain a hollow shape, I am proposing a 2 part neck. The first part would be the bottom of the neck and have a channel running the length of the neck on top to place the truss rod in. Carbon Fiber/Epoxy will wrap blue foam core and then sit inside a mold that is a negative of a Fender style bass neck. The blue-foam can be dissolved using Acetone.

I would then affix a fretboard over this channel and seal it in. I haven't read yet how to attach a truss rod so I could be very very wrong. I will put cad pictures up as soon as I can or at least scan my preliminary drawings :)

There are way to many things to comment on here, so I will say more when I have more time.

FWIW, I'm with pilotjones on the usage of blue foam core. Pointless.

In the case of the lay-up, what is the foam core doing? Nothing. If it's already in a machined mold of the Fender neck, then what is the point of the foam core? The CF will be held against the mold under vacuum pressure (it NEEDS to be if you want it to be playable, correct shape, and light, as the excess epoxy will cure hard if not sucked away).

I'm still getting the feeling you're diving head first into this without reading up on the manufacturing process in great detail, which is the first thing you should do. How can you design something without knowing how it's made? Goes for both CF layups and instrument neck construction.

Post up some drawings or model files, in .jpg if possible. It's more easily viewable than .dxf. That will be a big help to see what you are thinking, what you aren't clear on, etc, as it doesn't sound like you've got a clear idea on what the neck will actually look like internally, or how you could/can attach fretboard, truss rod, etc.

From Failure Mechanics it is known that the outermost fiber is the fiber that experiences the load, not the inside. Thus, a hollow body supporting compressive loads on the fretboard and tension loads on the bottom would be the same regardless of the core.You're right, but for the wrong reasons. The tensile and compressive stresses are indeed on the outer fibers; but, there must be a mediating material between. In a tube, or a bass neck, it is the side walls; in an I-beam, it is the web of the beam; in the laminate panel, lacking side walls, it is the foam or balsa core. Just ask Prof. Budynas.

You're right, but for the wrong reasons. The tensile and compressive stresses are indeed on the outer fibers; but, there must be a mediating material between. In a tube, or a bass neck, it is the side walls; in an I-beam, it is the web of the beam; in the laminate panel, lacking side walls, it is the foam or balsa core. Just ask Prof. Budynas.

I'm looking at the almost semi-circular tube neck as a whole but I see what you mean with nothing in between to transfer the load then it is going to fail.

Angus, I know I must still seem diving head first but really I haven't even ordered the material yet. This is all preliminary brainstorming before I get my hands dirty (or sticky) I'm learing a lot already just from this discussion and looking up resources. We have made 2 parts in the class so far. A hillside washer from fiberglass and a library ladder hanger from CF-epoxy.

You're giving me good feeback on the foam core. The way I see it, it will give the neck a smooth finish on the inside and stabilize the structure while it hardens. I will have vaccuum from the ouside of the mold and as I vaccuum the air the foam will expand pushing the CF to the walls of the mold.

After curing I will wash away the foam core and have a smooth finish on the inside as to reduce flaws and stress points within the neck structure.

Lastly, I will of course post in .jpg form. I hate cad file extensions just as the much as the next guy :)

No, in that case especially the foam core does absolutely nothing. It will actually give the neck a TERRIBLE finish- foam is too porous, and the neck will come out feeling very rough and looking dull (like frosted glass). A machined aluminum female mold will give a proper finish- smooth and shiny. Foam will only lead to very bad finishes.

You need to make a female mold of the neck and layup into that. The vacuum bagging process will hold the CF against the Al mold far more accurately than any foam piece will, and the foam will inhibit removal of excess epoxy during the curing process. Lose the foam.

Calling it CF rather than CF-epoxy is fine, as epoxy is just one of the chemicals in the curing process. No different than saying your bass is made of alder, rather than "alder-tung oil".

No, in that case especially the foam core does absolutely nothing. It will actually give the neck a TERRIBLE finish- foam is too porous, and the neck will come out feeling very rough and looking dull (like frosted glass). A machined aluminum female mold will give a proper finish- smooth and shiny. Foam will only lead to very bad finishes.

You need to make a female mold of the neck and layup into that. The vacuum bagging process will hold the CF against the Al mold far more accurately than any foam piece will, and the foam will inhibit removal of excess epoxy during the curing process. Lose the foam.

Calling it CF rather than CF-epoxy is fine, as epoxy is just one of the chemicals in the curing process. No different than saying your bass is made of alder, rather than "alder-tung oil".


Haha yeah I know that, just got a little carried away in specifying what was being used. Composites and Materials are my favorite aspect of ME.

Anyway, thanks for the tip on the female mold! and aluminum you say sounds pretty good. I had thought about the idea of a Rubber mold but it seems too flimsy. Edit: but I was just thinking instead of aluminum which I would have to machine to the specs of the neck, if I just took an existing neck and layed it up with a composite that won't adhere to my CF (I'll use PVA or other releasing agent to prevent this mostly) and then I will have an exact copy (female mold) of the neck and no machining necessary, except of course to remove flaws.

here is a picture I just drew up in MS paint of how I want the neck piece to be. Hollow with a channel on top the diameter of the truss rod so it will sit in there flush with the top of the neck. I'll then lay a fretboard over it.

[img=http://img220.imageshack.us/img220/6918/trussrodqn9.th.jpg] (http://img220.imageshack.us/my.php?image=trussrodqn9.jpg)

Except erase those lines above the channel.

Pilot,

You are correct in saying that in case of the neck the side walls have a major contribution, making the contribution of the core less significant.

Kickin, Angus,

The roughness of the foam core will not transfer to a roughness of the outside of composite, providing you use the foam directly as a base for lay-up and not to make a negative. Surface roughness on the inside is of no consequence since the roughness is in the matrix material only. This is IMHO and please feel free to disagree. If you feel worried about this you can always coat the foam with a gelcoat first and then with a release agent (in case of making a negative).

And saying that epoxy is just a curing chemical is so far off the mark you wouldn't believe it. Without a matrix material the CF is useless. It is essential in transferring shear stresses between the fibers and, well, plainly holding the stuff together.

I should add that the effects I described only hold for a very incompressible foam, which usually coinsides with a dense foam. Very open cell (springy) foam does squat.

Last point, try the matrix you plan to use (epoxy/polyesther) on the foam first to see if they do not react. Some combinations leave a puddle of molten foam....

Does anyone have any thoughts of the benefits of a core for damping of unwanted internal resonances/standing waves?

Loving this discussion!

Cheers ROdy

Pilot,
The roughness of the foam core will not transfer to a roughness of the outside of composite, providing you use the foam directly as a base for lay-up and not to make a negative. Surface roughness on the inside is of no consequence since the roughness is in the matrix material only. This is IMHO and please feel free to disagree. If you feel worried about this you can always coat the foam with a gelcoat first and then with a release agent (in case of making a negative).

I disagree highly. Using the foam in male form (such that side touching foam will make up the inside of the neck) will still result in poor finish on the inside and outside. The inside will come out with the same finish as the foam (which regardless of what kind you use, is slightly porous), and the outside will be rough due to the peel ply/breather. It will not look nice.

With gelcoat, a spray-on coating would not yield nice results unless it was sanded to a high polish. Gelcoat, by itself, yields uneven surface finishes. Better than foam alone for sure, but still not very good. When polished, though, it's much much better. Unfortunately, release agents like PVA, et al, will again dull the finish, but you can't really get away from that if you want ease of removal (without spending $$$) from gel coated parts.

The ultra glassy surface finish, imo, only comes from metal or unporous materials with a very good machined finish (which sanding will not yield). In these cases, you end up with no excess matrix because it has nowhere else to go but fill in space in the carbon and be sucked away into the breather material. This leaves the surface against the mold extremely smooth.

And saying that epoxy is just a curing chemical is so far off the mark you wouldn't believe it. Without a matrix material the CF is useless. It is essential in transferring shear stresses between the fibers and, well, plainly holding the stuff together.

Right- my point was concerning nomenclature, not structure. Reread the sentence with different inflection: "just ONE of..." not "JUST one of...". You think you missed the point.

For what it's worth, I make a good deal of my salary in CF fabrication.

Think of when the strings are on the neck. The top (fretboard) will be in compression while the bottom side of the neck will be in tension.

From Failure Mechanics it is known that the outermost fiber is the fiber that experiences the load, not the inside. Thus, a hollow body supporting compressive loads on the fretboard and tension loads on the bottom would be the same regardless of the core.

The reason for using the foam core permenantly would be for the placement of the truss rod. The truss rod can't be suspended in space underneathe the fretboard because it would have nothing to push on.


To maintain a hollow shape, I am proposing a 2 part neck. The first part would be the bottom of the neck and have a channel running the length of the neck on top to place the truss rod in. Carbon Fiber/Epoxy will wrap blue foam core and then sit inside a mold that is a negative of a Fender style bass neck. The blue-foam can be dissolved using Acetone.

I would then affix a fretboard over this channel and seal it in. I haven't read yet how to attach a truss rod so I could be very very wrong. I will put cad pictures up as soon as I can or at least scan my preliminary drawings :)

Re. core, there is one thing to remember:
Regardless of how much a bass neck could resemble a tube, a modern neck does not. It is pretty flat, and thin.
BassLab necks are fairly thick (nicey!) and the material is fairly thick. Nowadays, with truss rods, they had to go down on the thickness significantly...
A core is good to keep the skin in place. With thin walls and modern, thin neck profiles, the need is imminent. The more you move towards good ol' URB style, the less you need the core.

Then truss rods. If you intend to put in a truss rod, this must be well anchored. No plastic foam I know will sustain the pressure from a truss rod, balsa might - possibly... Hence, you must anchor the ends.
This will in thurn impose a set of interesting strains on the neck shell, which will try to buckle the skin, and impose a less resistant shape to it.
Be careful, and you'll be fine.

I disagree highly. Using the foam in male form (such that side touching foam will make up the inside of the neck) will still result in poor finish on the inside and outside. The inside will come out with the same finish as the foam (which regardless of what kind you use, is slightly porous), and the outside will be rough due to the peel ply/breather. It will not look nice.

I say the finish of the inside is inconsequential in any application relying on stiffness rather than strength, as is the case here. I agree that using a positive mold of any type would leave significant finishing on the outside to be done. But for a one off in a non-industrial environment, I believe this may weigh favourably against making a smooth negative mold and doing inside lamination.

With gelcoat, a spray-on coating would not yield nice results unless it was sanded to a high polish. Gelcoat, by itself, yields uneven surface finishes. Better than foam alone for sure, but still not very good. When polished, though, it's much much better.


Finishing is implied IMO.

Unfortunately, release agents like PVA, et al, will again dull the finish, but you can't really get away from that if you want ease of removal (without spending $$$) from gel coated parts.

The ultra glassy surface finish, imo, only comes from metal or unporous materials with a very good machined finish (which sanding will not yield). In these cases, you end up with no excess matrix because it has nowhere else to go but fill in space in the carbon and be sucked away into the breather material. This leaves the surface against the mold extremely smooth.

I agree. But I do not think this is attainable for a "hobbyist". However, I yield to your experience.

Right- my point was concerning nomenclature, not structure. Reread the sentence with different inflection: "just ONE of..." not "JUST one of...". You think you missed the point.

Fair enough.

For what it's worth, I make a good deal of my salary in CF fabrication.

For what it's worth, I'm a precision engineer and have designed and built honeycomb/metal-skin structures as well as researched CF design. Let's acknowledge each other's knowledge (and resist the urge to turn it into a pissing match ;-) ) and continue this discussion.

To Suburban:

I was thinking the same thing after my previous post. New rule of thumb: Jazz neck=core, P-neck=no core ;-)

Cheers Rody

All great discussion.

As I'm sure anyone who has had experience with composites knows , the hardest part about the project is creating the mold. How am I going to get the hollow shape I want with the channel on top for the truss rod?

Female mold of say polyester/epoxy made from an existing neck will yield a female mold, but it will only produce a u shape and not closed structure. An aluminum mold sounds pricey and time consuming in manufacturing.

I figure once I get some ideas on paper and posted up here it would be easier to analyze.

I realise the finish would be less than desireable if I were to use a foam core, I forgot about the breather. The breather/peel ply should be on the inside.

This very well might end up being a 3 piece mold. Neck U shape, Truss rod channel, and fretboard.

Edit: would I be able to machine the neck post lay up? I mean if I make the top of the neck thick enough, then I can route out a channel for the truss rod.

Post up some drawings or model files, in .jpg if possible. It's more easily viewable than .dxf. That will be a big help to see what you are thinking, what you aren't clear on, etc, as it doesn't sound like you've got a clear idea on what the neck will actually look like internally, or how you could/can attach fretboard, truss rod, etc.

Just be aware that for export control reasons, these drawings should not contain your composite lay-up definition. You don't want to be wearing an orange jumpsuit needlessly

detailed composite definition data is export controlled in the US. ignorance of the law does not excuse one from the penalties incurred by failure to be compliant

all the best,

R

Female mold of say polyester/epoxy made from an existing neck will yield a female mold, but it will only produce a u shape and not closed structure. An aluminum mold sounds pricey and time consuming in manufacturing.

Have you considered electroforming a mold directly using an existing neck as your mandrel? You can create a female mold from a neck(mandrel) with the exact same dimensions and surface finish. If you don't mind destroying the neck(mandrel) in the process it wouldn't be very hard to do. There is an electroforming company in Rochester that has a few RIT grads working there. They might be able to help you out.

Have you considered electroforming a mold directly using an existing neck as your mandrel? You can create a female mold from a neck(mandrel) with the exact same dimensions and surface finish. If you don't mind destroying the neck(mandrel) in the process it wouldn't be very hard to do. There is an electroforming company in Rochester that has a few RIT grads working there. They might be able to help you out.

Electro forming, I could look into that. Yeah I don't mind destroying a neck, I can get one for probably 20-40 bucks. I'm just trying to stay true to the nature of composite building because it is a Composites class project.

Electro forming, I could look into that. Yeah I don't mind destroying a neck, I can get one for probably 20-40 bucks. I'm just trying to stay true to the nature of composite building because it is a Composites class project.

It's just another option for building your neck mold. If you think that creating your mold from cad/cam and a block of aluminum won't be an issue then I wouldn't bother.

To electroform a mold from an existing neck you'd have to paint the neck entirely with conductive pain, make it a cathode, and then drop it in a plating bath. That's it in a nut shell. Of course, you would also have to mask off the parts of the neck where you don't want plating to build up. Once enough plating has built up, you just need to seperate the plating from the neck. You'll end up with a shell of metal (Ni) to use for your mold.

This will be tought to do on your own, but if you've got the help of local experts you won't have too much trouble.

I'd consider buying a cheap neck for mold making purposes, removing the fretboard and truss rod, and using that as your mold creation form. Then you can produce your CF main neck member, install the truss rod back into it, and attach a wood or other material fretboard. This way you also can do a fretted neck w/o having to figure out how to fret CF.

I'd consider buying a cheap neck for mold making purposes, removing the fretboard and truss rod, and using that as your mold creation form. Then you can produce your CF main neck member, install the truss rod back into it, and attach a wood or other material fretboard. This way you also can do a fretted neck w/o having to figure out how to fret CF.

Haha, this has been my idea all along, but I'm not sure if I portrayed that from the beginning. My apologies. However, how am I going to remove the neck from the CF/Epoxy? The headstock would be a bit of trouble getting out. Might have to cut it off. Blue foam would solve this problem by being able to be dissolved with Acetone.

I want to do this in ADDITION to a female mold made of polyester/epoxy. This is to ensure a better finish on the bottom of the neck, while supporting the top of the neck where the TR channel will be. This is the whole purpose for either a foam core or using an old neck to be the "plug". I could very easily just do a 3 piece mold, have a U shaped female mold, but I would have 3 pieces to glue together.

Haha, this has been my idea all along, but I'm not ...
I want to do this in ADDITION to a female mold ...Actually, I meant using the de-assembled neck as a form for the female mold, not for a foam plug. Whether by electroforming, or whatever other method. So that you end up with a CF part identical in form to the wood original.

Actually, I meant using the de-assembled neck as a form for the female mold, not for a foam plug. Whether by electroforming, or whatever other method. So that you end up with a CF part identical in form to the wood original.

+1

That's what I figured you'd do too.

Check out the all composite Catalyst Tigris Bass.

http://www.catalyst.nl/products/tigris.htm

Actually, I meant using the de-assembled neck as a form for the female mold, not for a foam plug. Whether by electroforming, or whatever other method. So that you end up with a CF part identical in form to the wood original.

OHhhhhhhhhhhh. I guess all my problems stemmed from me skipping the mold step and trying to jump right into the finished part. I was working backward instead of forward. So I just use the neck for the female mold, then split er open lengthwise and viola, a 2 part female mold, complete with male top for the truss rod channel.

Thanks a lot, that will get my brainstorm brewing again.

But wait, still doesn't solve my problem of keeping the top of the hollow neck suppported while curing... or will I have to have a completely sealed mold and vaccuum it? Seems like i'd have to resort back to the U shape and truss rod channel piece. Unless of course I use blue foam to keep it stabilized.

Here is a patent I found that details a process for affixing a fingerboard to the neck.

http://www.google.com/patents?vid=USPAT4950437&id=NvElAAAAEBAJ&printsec=abstract&zoom=4#PPP3,M1

I still am plagued by the question of how do I get the plug neck out of the finished product? I don't want a wood neck stuck in there.

I will be back at school on Monday and I really haven't made much progress on this project. I am anxious to get started but I feel like there are so many factors I'm trying to rule out that will stop me dead in my tracks or make the finished product not so finished.

Re: removing the plug: I don't know--I know that Basslab has some sort of foam, surrounded by composite, and that they melt the foam out afterwards; but I don't know whether they do any molding, or it's just composite built up on a form without any cavity work.

KF. How's your carbon fiber neck coming along? How about putting up some progress pics?

The project is coming along pretty slow right now, still getting all my materials together.

I am thinking about using a wood core of a softer wood that may give optimum resonance. For instance using a softer wood core that would not be usable for a full neck because it is not strong enough to support the strings but may add different "flavors" to the sound. That is one idea I'm exploring.

I am going to try and purchase an existing fingerboard for my neck. I want to buy a premade maple fingerboard but am having trouble finding it. I have found rosewood and ebony however from Stewmac. Anyone have any other resources? Thanks, I'll update when I can.

http://www.lmii.com/CartTwo/thirdproducts.asp?CategoryName=Fingerboards&NameProdHeader=Rock+Maple+Fingerboard
You can get them there and get it slotted for nine more dollars to most common scales.

As for using a softer wood for the inside of the neck MTD made a mostly graphite neck with cedar on the outside. You could do something similar with the cedar on the inside. I know Bass Player gave it a 5 on the tone. Good luck.

I might scratch the wood fretboard and try to make my own fretboard out of Phenolics which is a thermoset polymer. The problem posed with a wood neck on the graphite neck is that wood is a "live material" that will contract and expand with humidity and temperature and would different from the graphite neck and may separate. or so I've read. :) Lots of hurdles but I'll get it eventually.

As for using a softer wood for the inside of the neck MTD made a mostly graphite neck with cedar on the outside. You could do something similar with the cedar on the inside. I know Bass Player gave it a 5 on the tone. Good luck.
MTD? Sounds like Modulus Genesis.

Luthiers:

I have some questions about incorporating a truss rod into my design. I want to use a graphite/CF truss rod for my neck. My question is, what are the restrictions to installing a truss rod? I have the idea of incorporating it in between two layers of Carbon fiber and epoxy on the top of the neck. Is there a problem with surrounding a truss rod like this? Thanks for any help or suggestions.


Also, I am ordering my Carbon Fiber from soller composites: http://www.sollercomposites.com/composites/carbon%20fiber%20fabric.html
Any suggestions on which weave may be best? If anyone has any background in this, help would be appreciated :) Or if anyone has experience in making a composite neck, that would he awesome too. Thanks again. I should begin my project next week.

What other companies order from Soller? Perhaps a product manager at those companies can give you some insight?

Again, I think that it's awesome that you are working on this project. ;)

Luthiers:

I have some questions about incorporating a truss rod into my design. I want to use a graphite/CF truss rod for my neck. My question is, what are the restrictions to installing a truss rod? I have the idea of incorporating it in between two layers of Carbon fiber and epoxy on the top of the neck. Is there a problem with surrounding a truss rod like this? Thanks for any help or suggestions.


Also, I am ordering my Carbon Fiber from soller composites: http://www.sollercomposites.com/composites/carbon%20fiber%20fabric.html
Any suggestions on which weave may be best? If anyone has any background in this, help would be appreciated :) Or if anyone has experience in making a composite neck, that would he awesome too. Thanks again. I should begin my project next week.

KF. How's your carbon fiber neck coming along? How about putting up some progress pics?

KF, Any news on your neck? How did it turn out? Any pics?

I've been procrastinating and in fact have just ordered the materials.

I am going with buying chopped strand fiberglass mat and polyester resin to lay up on the existing neck.

I will then take this mold off and lay up carbon fiber epoxy inside the open mold and apply pressure. This will create a U shape. I'll then lay up another layer of unidirectional carbon fiber inside of this shape and let it cure.

I will then flip the mold over to get a flat surface for the top of the shape. 2 layers of carbon fiber with an aluminum 1/8" tube running down the center to precreate the truss rod channel.

Then I'll lay up layers into this hollow structure for the headstock and use a piece of wood inside the structure at the base of the neck to attach to the bass. This I hope will give me a solid hollow structure. I'll document my work this week :)

good luck

I am going with buying chopped strand fiberglass mat and polyester resin to lay up on the existing neck.

What are you going to do for the prep and finish? You can't just lay the fiberglass on the neck. A) It'll stick, and b) if you just wax it, it'll still be fiberglass textured on the inside. What are your plans for the internal finish of the mold?

How are you going to make a flange on the mold?

I will then take this mold off and lay up carbon fiber epoxy inside the open mold and apply pressure. This will create a U shape. I'll then lay up another layer of unidirectional carbon fiber inside of this shape and let it cure.

Why are you doing it in two layups? It is not nearly as strong and requires a very different process. You should be doing the wet layup one time before you cure it all (under pressure and heat).

How are you planning to pressurize it?

I will then flip the mold over to get a flat surface for the top of the shape. 2 layers of carbon fiber with an aluminum 1/8" tube running down the center to precreate the truss rod channel.

This really isn't clear- how are you going to attach this to the channel, and what is the mold for it? Sorry, I didn't understand how you are planning on doing this.

Then I'll lay up layers into this hollow structure for the headstock and use a piece of wood inside the structure at the base of the neck to attach to the bass. This I hope will give me a solid hollow structure. I'll document my work this week :)

I might be misunderstanding you, but are you saying you are going to attach CF to wood to CF to make the headstock bond? You should explain this one more. Perhaps I just don't understand what you are trying to explain.

Sorry for the questions, but it seems you me you haven't really though the mold and joint work through here. Either that, or you don't understand what will/won't work yet, but so hopefully this will save you time.

When is this due again? You have a huge amount of work left to do because as it stands your first proto probably won't work.

When is this due again? You have a huge amount of work left to do because as it stands your first proto probably won't work.

Hmm. RIT just ended their Winter quarter (20062) so either it was due last week, or maybe it is a year long project and not due till May?

I keep procrastinating because I don't want to screw it up. I took an incomplete for the course so I have a few weeks to get it finished up...:hmm:

I'm a little intimidated by the cost ~$200 and I don't have that kind of cash to put into something I don't have much of a plan for. I'll post more later, right now I've got to finish up a term paper for Audio Engineering on Compressors.