Rob, I think there are a couple of math hiccups in your response - bear with me here...
50K carbon tow is spec'ed as 410 ft (125 m)/lb at the CST website, which works out to
around 275m/kg - that's good. That means you'd get 46.8m in 6 oz. That's 51.1 yards of
50K fiber in a square yard of 6 oz. cloth - call it 50 yards.
BTW, does impregnated perpendicularly laid tow of similar weight have the same
mechanical characteristics as an impregnated woven fabric in terms of shear strength? I
suspect it's better in tension, as there's no crimp.
Mike
--- In harryproa@yahoogrou
>
> Rob,
> This is a great post.. I have learned a lot with the pictures and
> specifically the captions on them. You are a great resource for those of
> us that do not have your extensive professional background.
> john in bastrop
>
> On Wed, 21 May 2008 22:06:25 +0800 "Rob Denney" <harryproa@.
> writes:
> G'day,
>
> 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
> http://www.harrypro
> 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.
>
> Regards,
>
> Rob
>
> On Wed, May 21, 2008 at 12:09 AM, captian_rapscallion
> <captian_rapscallio
> > --- In harryproa@yahoogrou
> 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
> >>
> >> >
> >> >
> >> > Rob,
> >> >
> >> > I was hoping to get more info on your low cost carbon fiber.
> >> >
> >> >
> >> >
> >>
> >
> >
>
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