Carbon / Kevlar Hulls - Experience?

[Curmudgeon]

When I was looking for a boat I wanted an exotic material that is more resistant to repetitive stress than fiberglass or aluminum, has better thermal and acoustic characteristics, resists galvanic corrosion and is stronger, pound for pound, than anything except possibly steel.

So I chose wood.

[Weyalan]

Originally Posted by Curmudgeon

is stronger, pound for pound, than anything except possibly steel.

So I chose wood.

Nothing wrong with choosing wood. Great material for building boats. Lots of great wooden boats.

Stronger, pound for pound than epoxy / carbon fibre, epoxy / kevlar etc. I doubt it.

[Curmudgeon]

Well, the wood on my boat is coated with epoxy (stich and glue construction).

It's probably not stronger than carbon fiber or kevlar pound for pound, but it's alot cheaper pound for pound, and probably easier to repair.

[Weyalan]

Originally Posted by Curmudgeon

It's probably not stronger than carbon fiber or kevlar pound for pound, but it's alot cheaper pound for pound, and probably easier to repair.

No argument with that!

[MarkJ]

Originally Posted by Weyalan

There are risks with buying old racing boats, but you do get a lot of boat for very little money.

The ad says it had new racing sails a few years ago.
So its had 20 years bashing into the Freemantle Doctor? Lucky its not putty by now.
I think your Huon Pine would be matchwood too. I haven't sailed over there but there must be some West Aussies here?

[thinwater]

Originally Posted by RigelKent

I'm looking for a first purchase and many people have recommended GRP hulls for ease of maintenance.

I've seen a few listings of Carbon/Kevlar and other synthetic materials. Does anyone have an idea of the pros/cons of this material for hulls? There is a 1989 Farr 40 made of this material and I'm wondering if it is worth an inspection.

As for the "life" of the material, there is no real known limit at this time. The notion that it can "rot" is provably untrue as long as properly protected. In this case, that means keeping it painted for UV protection. Clear finishes are a problem.

As for blisters and such, they are generally unheard of. Kevlar boats are generally epoxy constructed, and at least amoung the Stilettos, there has never been a blister.

Toughness is exceptional. However, repairs are more difficult; a matter of knowing what you are doing, mostly. Kevlar is more inclined to "fuzz" than sand well, but it technique more than anything. The correct epoxies must be used to get good secondary bonding. That said, I seen boat cut in half, stretched, and serve for many more years.

The Stiletto owners site (stiletto.wildjibe.com) is a good sorce of information. They are out of production.

Ofcourse, everything that was said about racing boats for cruising is true. Hourses for courses.

I have no experience with carbon.

[Wotname]

Originally Posted by MarkJ

<snip>
I think your Huon Pine would be matchwood too. <snip>

I don't think so - sorry but I couldn't resist that attack on one of the finest boat building timbers of the world

[bene343]

Here's a pic of what happens when a power boat hits a Santa Cruz 70 with a Carbon?Kevlar Hull. She is all fixed now

[RigelKent]

Ouch!

While were on the subject (loosely) would anyone care to explain the difference between a solid fibreglass hull and a fibreglass hull with foam core? "Solid" sounds better - is it?

Update: I'm stymied. No boat pens available in Perth. Even the waiting lines have waiting lines.

[roverhi]

A cored hull relies on the bond between the core and the skin material for strength. It works like an I Beam. Should the core/skin bond breakdown, the overall strength of the hull is compromised. There is also the problem of water intrusion which increases weight, at a minimum, and can destroy the core in balsa cored boats.

Cored hulls can be built lighter for the same strength as uncored boats. They also tend to be quieter and more comfortable in weather extremes because of insulation factor. Personally, I'll stick with uncored hulls. I'm not a lightweight aficianado so the weight considerations aren't important though the insulating factor has piqued my interest.

Aloha
Peter O.

[Dockhead]

Originally Posted by Solosailor

All I can say is Kevlar is organic. I can rot. I have the inside of my little cedar strip racing skiff laminated with Carbon/Kevlar. I made sure it was well encapsulated with epoxy. I didn't want any end fibres exposed to moisture. It will wick up water.

Organic? What are you smoking? (I want some). Kevlar, like its kissing cousin Twaron, is an entirely synthetic aramid fiber. See: Kevlar - Wikipedia, the free encyclopedia

[Maren]

Originally Posted by roverhi

A cored hull relies on the bond between the core and the skin material for strength. It works like an I Beam. Should the core/skin bond breakdown, the overall strength of the hull is compromised. There is also the problem of water intrusion which increases weight, at a minimum, and can destroy the core in balsa cored boats.

Cored hulls can be built lighter for the same strength as uncored boats. They also tend to be quieter and more comfortable in weather extremes because of insulation factor. Personally, I'll stick with uncored hulls. I'm not a lightweight aficianado so the weight considerations aren't important though the insulating factor has piqued my interest.

Peter nailed the I-Beam/weight issue but the big advantage isn't weight, insullation or sound damping (but they're all damn nice), it is stiffness per unit of unit of weight.

To go back to your original question, I disagree that there is little to no use for carbon or Kevlar in cruising boats. Both are good in spots but you quickly reach a point of diminishing or negative return. A good designer will engineer the loads and match them with the materials needed. That may or may not include the use of carbon.

Below is an example: This is part of the Finite Element Analysis racer/cruiser by John Shuttleworth, a very well respected multihull designer. He needs the cabin top and supporting lateral structure to be stiff enough to support the compressive loads but also needs to keep the size down. Otherwise you end up with a 3 foot this cabin top and 5" of clearance above the waves (ok, I admit that's extreme, but you get the point). Even if that was fine, he would still have a problem in that not all the loads are up and down, some are side to side or twisting. In a really thick piece of composite foam construction, the foam itself would fail -- it would sheer. This kind of load is aptly called the Sheer Load. So using carbon judiciously gives him the strength needed and helps prevent another problem.

Oh, and wood? Love it. Miracle fiber 'W' as Chris White calls it. That is, as long as it's encapsulated in epoxy.


Well, that was a little long but at least it rambled.

[Maren]

Originally Posted by Dockhead

Organic? What are you smoking? (I want some). Kevlar, like its kissing cousin Twaron, is an entirely synthetic aramid fiber. See: Kevlar - Wikipedia, the free encyclopedia

Ummm, yeah. I think that depends on how you are using the words.

From entry you cite (all the way down at the bottom):

Categories: Organic polymers | Personal armour | DuPont | Synthetic fibers | Brand name materials | 1965 introductions | DuPont products

But I know what you mean. It isn't organic in the "my sandals are made from organic industial hemp", or even the "you can find this on Earth naturally occuring". But it does meet the minimal standard of a chemical compound containing carbon.

But, Solosailor, I really don't think you have it right either. Think I'll just leave it at that.

[RigelKent]

Lovely FEM. There's more similarity between boats and guitars than I thought, stiffness being a key aspect to the construction of both!

[thinwater]

Originally Posted by Weyalan

Nothing wrong with kevlar and / or carbon per se. Plenty of decent kevlar or carbon racing boat -> crusing boat conversions out there. An old IOR 50' flush deck racer has been very nicely converted just along the marina from me.

My IOR 40' ex racing boat is slowly becoming a comfortable cruiser. It has a fair amount of kevlar in the build and is still stiff and strong.

There are risks with buying old racing boats, but you do get a lot of boat for very little money.

Epoxy construction (used with kevlar/carbon) means no blisters, ever.

Rot? Only in the lightest applications, and it is far more likely sun damage. I don't thing biological rot is possible. Carbon can't rot. Nonsense. You have to keep kevlar painted. Easy.

High performance vs racer? Yes, understand the compromise. You might like it, or not. You will be adding some weight.

Damage from hard use? If it isn't cracked now, it won't be. Carbon and kevlar do not fatuige easily.

Too high tech? Silly. We use GPS, fiberglass, nylon, denmena... we don't use hemp or wood (OK, a few ). High tech materials are only a problem when they are engineered too close to the edge. A careful inspection will tell.

I doubt you would want to make a blue water boat from it. Too many compromises. But it might make a very fun coastal cruiser. Keep the weight down.