Carbon fibre neck reinforcement question

[michaeljking]

Hello,
I am preparing to make my first mandolin for myself to play(I am a luthier but make mostly medieval instruments), Its a celtic style model,. My question was one of neck reinforcement, looking at using two rods of carbon fibre over an adjustable truss rod?

Seems I can only get the solid carbon fibre rods from the USA ( I am in England)

It may well be a bad idea but does anyone have any thought over using the hollow section carbon fibre rods for reinforcement?
http://www.tjdmodels.com/cfibre-rect...mt-p-2869.html

Any thoughts about this would be welcome,

Michael J King

www.michaeljking.com

[Tavy]

Michael, I'm also in the UK and I use the carbon fibre batons from these guys. I don't add a truss rod as well, frankly on a short mandolin neck you probably wouldn't be able to move it if there's CF in there as well: though others around here I know have other ideas.

[michaeljking]

Michael, I'm also in the UK and I use the carbon fibre batons from these guys. I don't add a truss rod as well, frankly on a short mandolin neck you probably wouldn't be able to move it if there's CF in there as well: though others around here I know have other ideas.

Do you use the 2mm thick section as it is in pairs or do you laminate it?

[Tavy]

I use a single 2x12mm baton sandwiched between the two halves of the mahogany neck. No issues so far strung up with FW74's, but my oldest is just coming up to it's second birthday, so you know, take with the usual pinch of salt

As I understand it, it's the 12mm depth that matters, the thickness is not so important, as long as there are no torsional stresses on the neck.

[michaeljking]

I use a single 2x12mm baton sandwiched between the two halves of the mahogany neck. No issues so far strung up with FW74's, but my oldest is just coming up to it's second birthday, so you know, take with the usual pinch of salt

As I understand it, it's the 12mm depth that matters, the thickness is not so important, as long as there are no torsional stresses on the neck.

Thanks, That gives me some ideas to play with!

[GarY Nava]

Interesting thread guys! I’ve been using the StewMac carbon-fibre (0.200" x 1/4") and have really struggled to find a UK supplier of a similar section. I contacted Dragon plate in the US and they wanted $200 to ship 20 pieces, which seemed a tad expensive to me. So I’m still looking- I like the looks of the tube Michael. I think a few calculations are needed!
Cheers Gary

[Graham McDonald]

Las Alamos Composites will sell you a 1/4" x 3/8" x 18" (6mm x 10mm) CF bar which will do you for two mandolin necks. I rout a 12mm deep slot and epoxy the bar in the a wooden spline on top. That sets the bar a little lower in the neck, which makes it more efficient and an oversized spline can then be planed/sanded down flush to the top surface of the neck. Alternatively you might try a couple of lengths of 5-6mm diameter CF arrow shafts, stacked on top of one another and epoxied in place in the same way. Never tried it, but I can see why it wouldn't work. Any Archery supplier will have a range of different sized arrow shafts.

cheers

graham

[bmac]

As s luthier makin medieval instruments, why do you assume you will need a truss rod at all??? The short neck of a mandolin reduce the necessity of a truss rod to almost zero... Unless you are using unsuitable wood for the neck, or trying to make the neck too thin there should be no need for a truss rod... I speak not as an expert but an amateur repair and rebuilder of old mandolins and banjos. Unless the instrument was junk to begin with the truss rod is overkill in my opinion. In my small collection early to mid 20th C. mandolins none suffer from a bent neck. Lots of other problems but not bent necks.

[Jim Baker]

For my current build I'm using 2 carbon fiber bars 1/8" x 3/8" together on edge. No truss rod. If I could find bars 1/4" x 1/2" I would prefer that.

[ardbeg]

Tonetech in Stockport supply carbon fibre truss rods.

http://www.tonetechluthiersupplies.co.uk/

[Tavy]

As s luthier makin medieval instruments, why do you assume you will need a truss rod at all??? The short neck of a mandolin reduce the necessity of a truss rod to almost zero... Unless you are using unsuitable wood for the neck, or trying to make the neck too thin there should be no need for a truss rod... I speak not as an expert but an amateur repair and rebuilder of old mandolins and banjos. Unless the instrument was junk to begin with the truss rod is overkill in my opinion. In my small collection early to mid 20th C. mandolins none suffer from a bent neck. Lots of other problems but not bent necks.

Several reasons - while it's true that no historical instruments had truss rods, they usually had short necks (10th fret body join on bowlbacks, often 7th fret join on older historical instruments), while modern instruments often have 15th fret neck joins, slimmer necks, and higher tension strings - try putting J75's on a historical instrument and very rapidly you will see a neck problem!