Subject: Re: [harryproa] Re: low cost carbon fiber
From: "Rob Denney" <>
Date: 5/21/2008, 10:06 AM


The cheap way to buy carbon is as tow, which is the individual bundles
of filaments used to weave cloth or uni. I use very thick (50,000
filaments, 200 gsm/6 ounce cloth is 3,000) tow which gets a lot of
carbon down quickly.

There are 270metres of tow in a kg, so a meter weighs 3.7 grammes,
which is near enough 1.1 ounce, so you need 5 pieces a foot long to
get 5,5 ounces per sq foot. Use a wet out machine (see pictures at does not have
to be this large) and pull it through 10 or 20 pieces at a time and
lay it straight on the job. There is no lengthwise cutting required,
and no waste.

If you prefer unidirectional, it is available in 200, 300, and 900
gsm/6 ounce, 9.5 ounce and 20 ounce, any width you like. Costs twice
as much per unit weight as tow. Two layers of this at 90 degrees to
each other is about 60% cheaper than double bias or biaxial.

Carbon is essential in a reasonable size unstayed mast, makes a lot of
sense in rudder shafts, reasonable sense in beams and sense in hulls
if you want the ultimate light weight. Generally speaking, you use
about half the weight of carbon (and resin) as glass in a hull, but
there are other considerations such as impact resistance, water
proofness, etc if it gets too light. To use carbon without a vacuum
bag is pretty much a waste of money as there will be more resin (and
maybe air as well) than necessary, so the job is heavier.

Any specific questions, let me know.



On Wed, May 21, 2008 at 12:09 AM, captian_rapscallion
<> wrote:
> --- In, "Rob Denney" <harryproa@...> wrote:
> pardon my ignorance, how much does the fabric weigh per unit area? Is
> it biaxial? Unidirectional? I would use carbon if it meant a
> noticeable increase in speed. I would just be a bit concerned about
> impact strength. Perhaps a very light layer of kevlar or vectra would
> help?
>> G'day,
>> Cost varies on where you are and how much you want. Small amounts are
>> $Aus45 per kg, plus freight.
>> Regards,
>> Rob
>> On Tue, May 20, 2008 at 2:28 PM, captian_rapscallion <
>> captian_rapscallion@...> wrote:
>> >
>> >
>> > Rob,
>> >
>> > I was hoping to get more info on your low cost carbon fiber.
>> >
>> >
>> >

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