Less expensive carbon fiber reinforcement

[Bruce Johnson]

You give me all kinds of ideas for ways to make sawdust and firewood from bass necks!

And with enough epoxy and a spool of carbon fiber, you can put them back together, stronger than they were! I also use this general technique for nasty repair jobs, like broken off headstocks and split necks. Drill little holes and stitch it back together with carbon fiber thread and epoxy.

 

[Roxbororob]

And with enough epoxy and a spool of carbon fiber, you can put them back together, stronger than they were! I also use this general technique for nasty repair jobs, like broken off headstocks and split necks. Drill little holes and stitch it back together with carbon fiber thread and epoxy.

This crazy talk is confidence inspiring!

 

[Engle]

This crazy talk is confidence inspiring!

I know. Makes me want to get this stuff!

 

[BunchyMutt]

The other alternative is to buy carbon fiber TOW (that's what it's called) instead. That's the bare carbon fiber stranding, which comes in a roll. I bought a roll of 6K TOW, about 5000', for $30 on ebay. That roll lasted me close to 20 years. I just recently opened a new roll.

You can use the TOW for all kinds of reinforcements in musical instruments. Basically, you set the raw stranding into a bed of hard epoxy. I use West Systems. You rout a slot in the wood, to any dimensions or configuration that you want. It can taper or even go around corners. Lay in the strands, as many as you want, and pour in the epoxy. You are effectively casting the "carbon fiber bar" in place.

The carbon fiber bars that you buy aren't solid carbon fiber. They are bundles of the TOW, which have been molded into rectangular bars with polyester resin, in a process called pultrusion. The result is similar to what I'm doing with the epoxy.

The TOW is available in different sizes; the common ones are called 4K, 6K and 12K. That refers to the number of individual strands of carbon fiber in the bundle. 6K TOW is 6,000 teensy little strands. If you twist it and pull it taught, 6K TOW is about 1/16" diameter. 12K TOW rolled up, is about 3/32" diameter.

In terms of strength, a single 6K bundle has a tensile strength roughly three times the same diameter steel piano wire. Reinforcing a bass neck, you really don't need very much. That's why I don't use the commercial bars. It's just putting big blocks of plastic in the neck. I can get all the necessary reinforcement from my own small cast-in-place bundle.

Anyway, that's an alternative to the bars. And it's much cheaper per neck. I typically put in 2-10 strands of 6K TOW; 4 to 20 feet from the roll.

Older post but I've been thinking more on this recently. How do you keep the TOW taught after laying it in the channel?

 

[Bruce Johnson]

Older post but I've been thinking more on this recently. How do you keep the TOW taught after laying it in the channel?

The TOW doesn't need to be held taut when laying it in the bed of epoxy.

 

[BunchyMutt]

The TOW doesn't need to be held taut when laying it in the bed of epoxy.

well alrighty then

 

[Rob Page]

The other alternative is to buy carbon fiber TOW (that's what it's called) instead. That's the bare carbon fiber stranding, which comes in a roll. I bought a roll of 6K TOW, about 5000', for $30 on ebay. That roll lasted me close to 20 years. I just recently opened a new roll.

You can use the TOW for all kinds of reinforcements in musical instruments. Basically, you set the raw stranding into a bed of hard epoxy. I use West Systems. You rout a slot in the wood, to any dimensions or configuration that you want. It can taper or even go around corners. Lay in the strands, as many as you want, and pour in the epoxy. You are effectively casting the "carbon fiber bar" in place.

The carbon fiber bars that you buy aren't solid carbon fiber. They are bundles of the TOW, which have been molded into rectangular bars with polyester resin, in a process called pultrusion. The result is similar to what I'm doing with the epoxy.

The TOW is available in different sizes; the common ones are called 4K, 6K and 12K. That refers to the number of individual strands of carbon fiber in the bundle. 6K TOW is 6,000 teensy little strands. If you twist it and pull it taught, 6K TOW is about 1/16" diameter. 12K TOW rolled up, is about 3/32" diameter.

In terms of strength, a single 6K bundle has a tensile strength roughly three times the same diameter steel piano wire. Reinforcing a bass neck, you really don't need very much. That's why I don't use the commercial bars. It's just putting big blocks of plastic in the neck. I can get all the necessary reinforcement from my own small cast-in-place bundle.

Anyway, that's an alternative to the bars. And it's much cheaper per neck. I typically put in 2-10 strands of 6K TOW; 4 to 20 feet from the roll.

Bruce, wow. Thank you. On ebay right now.

 

[Rob Page]

Bruce, is this the stuff you're talking about? 10 Meter TORAY T1100GC 12K Carbon Fiber tow continuous filament Yarn thread | eBay

 

[dwizum]

That's the right stuff. That item is 12k which is a good size but probably about the biggest you'd want for this (24k tow is sometimes sold too, I would not use it, it gets a little bulky and harder to control). That's a recognizable brand, not a bad deal for $1 a meter and probably a better product than the unbranded stuff that's usually on ebay.

 

[Bruce Johnson]

Bruce, is this the stuff you're talking about? 10 Meter TORAY T1100GC 12K Carbon Fiber tow continuous filament Yarn thread | eBay

Yes, that's the stuff. But that's pretty expensive. 30 feet of it for $10? That guy's making some money. A few years back, I bought a whole roll (about 5000 ft) for $35.

 

[dwizum]

Yes, that's the stuff. But that's pretty expensive. 30 feet of it for $10? That guy's making some money. A few years back, I bought a whole roll (about 5000 ft) for $35.

Yours was a bargain! I worked briefly at a composites lab, 20ish years ago, and we were buying 10 pound rolls - probably what yours was - for like $250 each.

 

[Bruce Johnson]

Yours was a bargain! I worked briefly at a composites lab, 20ish years ago, and we were buying 10 pound rolls - probably what yours was - for like $250 each.

I think I bought my current roll around 2012? The price and availability of surplus rolls of TOW have gone up and down over the years. I remember that there were a few years when TOW was almost unavailable. That was when Boeing was starting up production of the 787, and they had bought up all the TOW production capacity. Then, a few years later, it became available again. Now, with widespread internet entrepreneurs are buying up any available surplus rolls and selling it off in small quantities, at a big markup.

 

[Rob Page]

Thanks guys. I'll order some and give this a try!

 

[T_Bone_TL]

Yes, that's the stuff. But that's pretty expensive. 30 feet of it for $10? That guy's making some money. A few years back, I bought a whole roll (about 5000 ft) for $35.

Speaking from unpaid experience adding them to the winter-build-off prize pool from my mile-and-a-half-or-so roll, when you buy short lengths, you're paying for labor getting those short lengths dispensed and packaged and mailed by human labor, since essentially nobody is doing so by automated machinery.

For typical bass-sized lengths (pretty short), you can easily "split" 24K (which is often more easily found) to "approximately" 12K or 6K, enduring a little loss.

 

[Rob Page]

Well here's my first swack at this. Not sure if I'm doing it right but there's three strands of 12K TOW in each channel and a ton of epoxy. Once it's dry and sanded I'm moving on to fretboards and just assuming this is going to be equivalent to putting in Dragon Plate carbon fiber bars. Fingers crossed!

 

[MPU]

Ideally cf is placed as close to the back of the neck as possible. I use cf tow under truss rod.

 

[Rôckhewer]

Very cool that this thread came around again...now.
I was just going to buy some pre-made cf rods for the monster 7 string I'm doing.
Instead, I ordered a small roll of 6K TOW... to sorta dip my.. toe... ...into the CF fabrication thing.

Question for Mr. @Bruce Johnson :
You mentioned you cram up to 10 strands into a slot... then.. flood with West Systems Epoxy?
...and it saturates through all strands... to the bottom of the slot?
Or do you cram a few strands...add some epoxy... few more strands....more epoxy... etc ... ??

Thanks.

 

[Bruce Johnson]

Very cool that this thread came around again...now.
I was just going to buy some pre-made cf rods for the monster 7 string I'm doing.
Instead, I ordered a small roll of 6K TOW... to sorta dip my.. toe... ...into the CF fabrication thing.

Question for Mr. @Bruce Johnson :
You mentioned you cram up to 10 strands into a slot... then.. flood with West Systems Epoxy?
...and it saturates through all strands... to the bottom of the slot?
Or do you cram a few strands...add some epoxy... few more strands....more epoxy... etc ... ??

Thanks.

Hey Kevin;

Yes, West Systems epoxy is thin enough (low viscosity) that it will flow all around a bundle of CF TOW, completely saturating it and grabbing every strand. No need to worry about that.

If you've got 6K TOW, you really don't need more than 4 strands per slot. Beyond that is just a waste of carbon fiber.

To use CF TOW to stiffen a neck, the point is to place a bundle of CF down as deep as you dare. The bundle should end up within 1/8" of the final back surface of the neck. You are embedding a small super stiff cable in there, that will go in tension when the strings start trying to bend the neck forward. These cables are acting like guy wires holding up a pole.

So, stacking up more CF and epoxy above those bottom 4 strands really isn't adding much...except cost and weight. I recommend filling the rest of the slot, above the 4 strands, with a strip of wood.

Pour a layer of epoxy along the bottom of the slot, maybe 1/8" thick. Then lay in the 4 strands of CF TOW on top of it. Pour in another 1/8" thick layer of epoxy on top of the CF. Then set in your wood strip, which is slightly narrower than the slot and a bit taller. Lightly clamp it down, and epoxy should squeeze up the gaps at the sides. Let it cure like that, then trim off the excess height of the wood strip.

Now your embedded CF reinforcement is about 1/4" wide x maybe 1/8" tall, buried down deep in the neck. All 24K teensy strands of CF are bonded solidly to the wood around it. That back section of the neck is Not going to stretch when the strings start pulling. That's how you stiffen the neck with minimal added weight and cost.

 

[Bruce Johnson]

Well here's my first swack at this. Not sure if I'm doing it right but there's three strands of 12K TOW in each channel and a ton of epoxy. Once it's dry and sanded I'm moving on to fretboards and just assuming this is going to be equivalent to putting in Dragon Plate carbon fiber bars. Fingers crossed!

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Yes, like MPU said, you want the CF strands to end up deep down in the neck, close to the final back surface. How deep were those slots? And the upper part of the slot is better filled with a wood strip. There's nothing really wrong with pouring the slot full of epoxy...except it's a waste of epoxy. Two or three strands of 12K TOW per slot is plenty, all down in the bottom of the slot. No need to pile more strands up on top of them.

 

[RichterScale]

@Bruce Johnson
Would something like this work? epoxying the TOW between neck lams during construction and then epoxying the whole structure at once?