carbon or carbon/kevlar?

[vvviivvv]

pros and cons of each please.

[Jeff]

The kevlar with the carbon leaves a fuzzy edge from the kevlar, hard to sand a nice edge.

[vvviivvv]

i mean strength wise, whats gonna stand up against a 100mph impact better? hulls come ready built just need to install water pick ups

thanks.

[DISAR]

I tried both, the carbon is more flexible the carbon-kevlar is stiffer and I think stronger

[Ub Hauled]

I thought that Carbon is the stiffest, followed by Carbon/kevlar and the "softest" being Kevlar... hmm.

[vvviivvv]

So carbon only makes for a better hull?

[Simon.O.]

I have been out of composite engineering for a while so some of this may be rusty.
Carbon is generally the most rigid
Glass is next
Kevlar is the least rigid.

Now all of this comes down to the weave of the cloth, the weight of the cloth, the resin type and the actual layup.

To say that one material is stronger than another is apples and oranges.
You must compare cloths in a given application.

Kevlar (Aramid Fibre) woven with carbon gives the yellow/black look and to me is great matrix.
If I were to build a hull from composite I would make it so that the hull shell is glass and all of the rigidity and frames are from carbon.
I would skip kevlar altogether as it is not friends with water.

Like I said, I have been out of the industry now for 10 years but some stuff sticks.

[DISAR]

Simon is right, it also depends on the weave, weight, epoxy. When I used them they were different. I was wrong, carbon is stronger and stiffer than kevlar. For the same weave and weight, kevlar will elongate more before breaking.

[Fluid]

I've seen two carbon/kevlar boats after high speed crashes, and they resembled bags of broken parts. The Kevlar kept the hull in 'one peice' but the carbon was completely shattered so the shape was only a ghost of the original. I know nothing about the construction of either hull, they may have been assembled with the wrong epoxy, wrong bagging technique, etc.


.

[Gerwin Brommer]

Carbonfibre is ONLY strong in the lenght of the fibres !!!!!!!!!!!!!!!!!
But it's stronger than glasscloth.
Kevlar has NO strenght in the lenght of the fibres, but can resist a HUGE side-impact.
A woven cloth is NOT the strongest, wile the fibres are crossing others so they ain't straight.
If your boat is big enough and a few ounces extra don't care : unidirectional, 45 degree
(multiple layers overlapping in an angle) is by far the strongest type of " cloth "

Why do many manufacterors of CF/kevlar hulls make beautiful upper- and lower parts of a hull and connect them with 1 layer
of glasscloth ??? I even saw "peelply" used to connect the bottom and top of a boat !!!!!!!!!!!!!!!!!
That stuff is so not good to use for that purpose !!!

[sailr]

what is peelply?

[Gerwin Brommer]

Sailr ;

When you're laying up the laminate for a hull but can't complete it in 1 day, the last layer
of the laminate should be "peelply".
The next time you work on the hull/laminate, the peelply can be peeled off, leaving a nice
rough texture, very suited to continue your work, the following layer of resin will stick to the surface without the need to sand it first.
( as you know, cured epoxy has a "waxy kind of skin" (parrafine, if i'm not wrong) that has to be removed before adding the next layer on top )

http://www.ttel.co.uk/1peelply.htm

[vvviivvv]

gonna go with carbon kevlar...

[Chris Harris]

Something else no one mentioned is that Kevlar is a real pain to work with.
It will eat up a pair of scissors in a hurry, even the really expensive so called "special scissors" that are supposed to be for cutting Aramids dull quickly.
It is really, really, really hard to make a straight cut even with carbon/kevlar hybrid fabric.

For my carbon hulls I use Kevlar tapes on seams because of it's tear strength and they are only an inch or two wide so it's much easier to deal with.
The tub on my P SAW rigger has survived crashes at 110mph with virtualy no damage. That's with using a quality epoxy resin. Polyester or Vinylester resins are not quite as strong IME.

Chris

[sailr]

Good info Chris. Your little riggers are a work of art and a testament to your construction methods. Absolutely agree about the epoxy over polyester or vinylester! They are brittle and will break easily.