Carbon fibre source

[blackalex1952]

I am wondering where to get some CF for brace capping in Australia. I believe the spec is 12K? Is that what people use?
-Ross

[old_picker]

I have bought bar from these blokes a couple of times - not sure what the spec is but its very tough stuff
http://www.carbonfiber.com.au/index.htm

[blackalex1952]

Easy to find the CF bar, I use it for my necks. But I am looking for thread for brace capping. I have only found ribbon, which is made from strands held together with a flexible epoxy bond. Has anyone used this? If so, how?

[jeffhigh]

Its 3k
I pull the strands from plainweave cloth 198 gram/m2

From these guys
http://www.ebay.com.au/itm/Carbon-Fibre ... SwBnVW~FLN

Also epoxy resin from them

[J.F. Custom]

G'day Ross.

I've purchased from "Carbon Fiber Australia" as well.

The "thread" you refer to is called "tow". They do sell it wrapped on a cardboard spool, but they only have 6K or 12K like that. See here -

http://www.carbonfiber.com.au/category9_1.htm

Otherwise if you want 3K tow, they sell "Plain Cloth" in varying widths, by the meter. It's woven of 3K fibre and is just looped together (no flexible epoxy bond), so you can unweave and pull out the individual strands you need for the brace capping. See here -

http://www.carbonfiber.com.au/prod15.htm or http://www.carbonfiber.com.au/category4_1.htm

Jeff's eBay reference is cheaper for the equivalent product (1m x 1.2m square sheet), but unless you need that much, buying the tow spool or cloth by meter in smaller quantity is cheap enough to get you through many guitars.

Cheers,

Jeremy.

[blackalex1952]

Thanks guys...I am wondering about this "tow" business. I came up with the 3k tow idea from one of Jeff's posts where he said he uses it. In "the book", Trevor Gore writes that they "use strands pulled from cloth woven from 198g/1000m yarn". What "tow" is this? How many strands to use top and bottom on braces, or as some makers I have heard say, only on the tension side of the brace? Also what is the increase in stiffness that one could estimate from CF, ie how to get to a target brace stiffness?
thanks in advance-Ross

[jeffhigh]

The 3K as I understand it is a fibre count, I gather Tow just refers to an unwoven or untwisted stand.You Just use one strand, I use it top and bottom as does Trevor but the local school here has simplified it to only apply to the outer face of the brace. I won't speculate as to why.

[blackalex1952]

I speculate that using CF on the tension side of a brace only might have similar properties to a T beam as compared to an I beam.
I have heard reports that there is a volume gain to be had by doing this, yet to experiment when I actually get hold of some CF. Jeff, have you used CF on a Selmeroid build? Has anyone used tension side bracing on an archtop?
Ross.

[jeffhigh]

Whilst on an archtop the outside of the brace is uniformly in tension, in a flattop with fixed bridge that side is in tension in front of the bridge and in compression behind.

Besides any increase in stiffness the big advantage of CF capping is to avoid long term creep under load (which wood is susceptible but CF is not)

My one selmeroid was stiff enough with timber bracing even at less than the Collins recommendations for brace height.

I think Rod was using it on one of his recent archtop builds.

[blackalex1952]

So between the bridge and the tail the CF would go between the soundboard and the brace, between the bridge and the neck the CF would cap the braces...a T beam. On an archtop the braces would be capped. I intend to do some testing to see then try a build.
Did you deflection test your Selmer? Did you build with the top on first so that you could deflection test then adjust the braces in the mold prior to installing the back?

[jeffhigh]

No I did not do any deflection testing prior to closing, I did think it was a bit firm so I took the braces down from 19 to 16 as I recall.
I think a lot of the strength and stiffness of the soundboard came from doing a tapered pliage (max at centre to nothing at rim) and then jointing the plates and matching the brace curvatures to the rise at the centreline.