G'day,
Yards and feet used to be second nature, but not any more. Thanks for
the correction. Tow is what fbric is made of, so has simialr
properties. The tow does not get damaged in the weaving process so is
more likely to meet the spec. Crimp is definitely not good for
tensile stiffness, or strength, but once you are at those loads, you
probably have resin problems anyway. twill weave (over two and under
two) is a near non crimp woven fabric.
regards,
Rob
On Thu, May 22, 2008 at 6:45 AM, rattus32 <mike@vail.net> wrote:
> 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
> wrote:
>>
>> 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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