Cutting kevlar:carbon hybrid cloth

[HydroNick]

I also posted two versions of this post at Multihullforum. Apologies to those that I'm boring to death:

This relates to 8m Arrow plans that I purchased from John Shuttleworth: As I left it with John, the hull skin (inside and out) was going to be glass and I was going to use carbon:kevlar hybrid cloth for the bulkheads, main beam, and various internal lockers. Further weight saving was to be realized by replacing any specified aluminum beams or stainless steel bits with carbon (where practical), and using synthetic rigging. The mixed glass/ hybrid cloth decision was based on the high cost of the hybrid cloth. Recently I've seen less expensive hybrid cloth; so, I am considering building entirely in the hybrid cloth; but, I am trying to find out whether the cheaper cloth meets John's spec as it does not have all the "things" he lists (though nor did the more expensive cloth!).

So, here are some questions, which don’t exactly follow the preamble, related to the cloth spec. and also working with it:

1. The specified hybrid material originally, from SP Systems (now Gurit) was:
Kevlar Carbon 50:50 Unidirectional 150 g/m2 (4.4 oz/yd2) (SP Systems ACA 150)
Kevlar Carbon 240 g/m2 (7.1 oz/yd2) (SP Systems RAC241)
But, this cloth no longer seems to be available from Gurit (I have sent an email to them and am awaiting a response) or anybody else for that matter. I have found cloth described as: 4.8 oz/yd2 “Unique fabric combining 3K-Carbon(Warp Direction) and Kevlar(Fill Direction) yarns into a plain weave fabric” at http://uscomposites.com/hybrids.html does anyone know whether this is a satisfactory replacement for the ACA 150?
2. Also, multi-coloured carbon Kevlar fabrics seem to be all the rage with petrolheads and can be found on ebay and at various suppliers. Is it any good? Are there reputable manufacturers? (and vice versa)
3. Any comments on the RAC241?
4. I understand that you can buy shears to cut kevlar cloth; however, when you want to make a cut-out in the hull, how do you do it? Are there hole saws that will cut kevlar without making a mess and similarly, are there jigsaw blades/ bits available.
5. The alternative to using the hybrid cloth (other than reverting to the glass lay-up) is to get John to provide a carbon lay-up. Does anyone have scantlings for carbon over 12mm Corecell with which I could make a preliminary cost estimate?
Thanks,
Nick

[Herman]

Mixing carbon and aramide is a waste of time and material, unless you want high stiffness, and some damage resistance (as in: when damage occurs, at least you have all the parts left).

So you want bomb proof bulkheads and drawers...

If you want to save weight, make most of your interior out of lightweight materials, as in 60 and 40 kg/m3 foams, lightweight glass (80 grams) or carbon if you need some structure (100 grams biax, 200 grams biax)

For the hull you definately do not want aramide close to the surface. Once you hit it when sanding, you are up ... (never mind, you get the picture)

Also think of it this way:

carbon is like steel, glass (or aramide) like elastic. Imagine a steel cable which has a breaking load of 1000 kgs (or lbs, what the heck). Same with a rubber band (bungee jump cord) which can also lift 1000 kgs.

Now, with these 2 materials tied side by side, can you lift 2000 kgs? No, the steel cable will break, then the cord will break.

---

I would either go for carbon, or for glass, perhaps some aramide for crashpurposes, but nothing more.

[War Whoop]

Go for "S" Glass.

[GG]

Originally Posted by War Whoop

Go for "S" Glass.

I agree 100 % S- Glass - all the way.

[Herman]

Try to obtain S glass multiaxials in small quantities (boat quantities) can prove to be a difficult task. At least in Europe.

[War Whoop]

It can be found here without much of a problem Sweet Composites for one.

[Coen]

In my opinion, I would recommend glass as well. Whether this is E-glass or S-glass, it wouldn't matter to much I assume. The material properties aren't that much of a difference (in a sandwich-laminate that is).

Aramid is a pain in the ... to work with. It's difficult to repair, laminates pretty bad and as far as I know, can't with stand water too good.

If you want a top of the class racing boat, I would go for carbon, but if cost might be an issue, you could opt for a slightly thicker core. This will result in a significant stiffer panel at slightly higher costs.

Cheers

[War Whoop]

What gay boy wrote this in my rep : "h glass you meant...." Hey Sign the next time Punk! "H" Glass What the HELL is that??????

[War Whoop]

Originally Posted by Coen

In my opinion, I would recommend glass as well. Whether this is E-glass or S-glass, it wouldn't matter to much I assume. The material properties aren't that much of a difference (in a sandwich-laminate that is).

Aramid is a pain in the ... to work with. It's difficult to repair, laminates pretty bad and as far as I know, can't with stand water too good.

If you want a top of the class racing boat, I would go for carbon, but if cost might be an issue, you could opt for a slightly thicker core. This will result in a significant stiffer panel at slightly higher costs.

Cheers

Here:

[HydroNick]

Thanks for the various responses, they provide a good basis for a decision.

Nick