Help with Installing Carbon Fiber Rods

[BassUrges]

I’m building a couple of 5ers with fairly thin necks. I thought putting some carbon fiber in the necks might be a good idea to help stiffen them up given their thinness.

I got rods that are nominally .125” x .325”, but measuring, they are actually .005” larger in both dimensions.

It’s easy to buy a 1/8” router bit, and I’m not paying for a custom .130” bit, but the resulting channels are REALLY tight. Tight enough that I worry about getting to rods all the way in before the epoxy sets.

On the other hand, a tight fit seems like a good idea to properly couple the strain. I am concerned that any effort to widen them will result in a sloppy fit and leave me dependent on glue to couple them.

How tight should the channels be?

 

[dmarino]

I use a 1/8" router bit for those, then I have had to hammer them into the grooves with some decent amount of force. They stay tight without glue and haven't caused any problems (yet?) with such a tight fit

 

[BassUrges]

A pure friction fit does have the advantage of not desperately pounding on it while on the clock. It just makes me a little nervous about shifting after the fingerboard is on and I can’t fix anything.

I wonder if some water- thin CA applied after insertion would work? An experiment for later today.

 

[David Jayne]

I'd share your concern about damage happening during or sometime after fitting them like that. .005" isn't much to sand off, which I would definitely do. This has the added benefit of providing a very good surface for gluing.

 

[BassUrges]

It’s not much to sand off, but it’s tricky to sand off evenly.

I was planning on scuffing for gluing, so maybe I’ll wind up making them fit better?

 

[David Jayne]

It’s not much to sand off, but it’s tricky to sand off evenly.

I was planning on scuffing for gluing, so maybe I’ll wind up making them fit better?

It's not important to make it perfectly even. The glue will fill the gaps.

 

[Gilmourisgod]

Sand the rods, but wear gloves and a mask, the CF rod material is NASTY, like metal splinters. I bought my rods from Best Bass Gear, fit perfectly in a 1/8” slot.

 

[BassUrges]

Sand the rods, but wear gloves and a mask, the CF rod material is NASTY, like metal splinters. I bought my rods from Best Bass Gear, fit perfectly in a 1/8” slot.

I got mine from a place that sells sailboat supplies, so, that.

 

[Huw Phillips]

The alternative is to do carbon tow and resin, then put a fillet in, this is a Bruce method that he has developed and kindly shared, I worked on two necks for me, I used the small syringes of slow Harding epoxy and it took about half a pack per carbon stiffener
Good luck

 

[BassUrges]

The alternative is to do carbon tow and resin, then put a fillet in, this is a Bruce method that he has developed and kindly shared, I worked on two necks for me, I used the small syringes of slow Harding epoxy and it took about half a pack per carbon stiffener
Good luck

Do you have a link to this method? I’m doing taxes today so no rush.

 

[Huw Phillips]

Less expensive carbon fiber reinforcement

 

[Gilmourisgod]

Carbon Fiber Rod - Best Bass Gear

 

[ArtechnikA]

3.5mm looks to be 0.137" and readily available. Donno if you'd consider 0.007" too loose.

 

[bobdabilder]

Relaxed fit. Epoxy will hold them. Use slow set epoxy. Not 5 minute.

 

[BassUrges]

The trick being to achieve a relaxed fit without messing up anything, having broken down the setup used to cut them.

 

[ArtechnikA]

The trick being to achieve a relaxed fit without messing up anything, having broken down the setup used to cut them.

Put the 1/8" bit back in the router. When you can run it through the jig with no binding, you're back on track.

 

[BassUrges]

There’s no jig. There’s a strip of 1/4” aluminum clamped to the table and then to the neck. So the setup will be a little more elaborate and will have to wait until next week.

 

[BassUrges]

Plus the truss rod channel is 1/64” too shallow. Of course!

 

[dwizum]

How thin is your thinnest (flat) file? Maybe you could run a file down the channel to give some room. Sanding or machining carbon is messy enough that I avoid it when I can. This is where an old fashioned (manual) router plane would come in handy, so you can tweak your channels for perfect fit.

Also, epoxy acts a bit like a lubricant, if the bars are fittable-but-really-tight when dry, they will slide in much easier once there's epoxy on them.

Also also, I would not scuff sand them before gluing in. Pulltruded rods have a nice gluable surface already. Scuffing will just add roughness and friction when you're trying to push them in the slot.

 

[rudy4444]

The bet time to test the bar or rod fit is when you cut the channel. If it's tight then simply add a layer of painter's masking tape to your guide and give it another pass. You can add a second layer if its still too tight.

Easy to do when you're cutting the channel the first time, but it's not all that difficult to re-create your guide setup. Chances are it won't be exactly the same and will create a wider channel when you use it.