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Old 27-08-2006, 20:42   #1
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Kevlar in the hull?

When I purchased my boat last year, I thought it a little bit strange that a mid 80's racing boat was built with a solid glass hull. I mean, it was my understanding that, at that time, most fibreglass boats were being built with a balsa or foam (divinycell?) core.

My boat was listed as solid glass. However, having removed some thru hulls recently, and cleaned off whatever the gunk was that was used to seal those through hulls, it looks to me as though the hull may have some kevlar in it. There are a couple of layers that are quite distictly tellow in color and they look (to my relatively inexperienced eye), rather like kevlar. If correct, this is, with my limited understanding, rather a bonus to me. It will mean that the hull should, theoretically, be stronger than solid glass. Also, it should mean that polyester resin was probably not used, which means there is less likelihood of osmosis (hence the surprising lack of evidence of osmosis in a boat that age).

Anyway, the question is: Do any of you have any experience with GRP/Kevlar composide hulls? If so, are there any pitfalls or disadvantages that I need to keep in mind?
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Old 27-08-2006, 22:53   #2
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Solid Glass was still extensively used through the 80's. It always has and probably always will be used. Foam, Balsa, honeycomb and some others were also used to build boats. But the materials were new and very very expensive, I mean really expensive. It was mostly found in the real top shelf big budget one off racing hulls where budget was not so much the issue. Very rare to find production boats or lower budget Racing hulls built of it. Same goes for kevlar. Back then, the stuff was very expensive and as Carbon fibre was still Rocket science stuff, Kevlar was the new kid material on the block. It was usaully used as Kevlar and Resin only. I have not heard of one layer of Kevlar being used in a layup of Glass. It is possible that this is in a high load area and the Kevlar is giving added strength in that area. Kevlar is very strong in tension. It wasn't till late 80's early 90's that the composite materials started making their mark on the more everyday racing sailor as the composites came down in price. And once Carbon fibre came in to the game, Kevlar tended to take a back seat in composite technology.

As for what the Resin is, does it smell when you cut into it? The esters always have that characteristic smell. It never goes away. Epoxy resins are often orderless, or close to.
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Old 28-08-2006, 07:35   #3
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I owned a 1985 Laser 28 that reportedly was kevlar/vinylester (Kevlar definite, vinylester less certain), but most of the Laser 28's aparently were Kevlar with polyester. By the mid 1980's Kevlar was in pretty widespread use in high tension areas of race boats. The Laser was actually a cored hull.

Kevlar became a lot more affordable during the mid to late 1980's as the U.S millitary began using it in vast quantities for helmets and armor, bringing mass production costs down. Kevlar takes more skill to work with as it wants to float out of the laminate. As vacuum bagging and infusion molding became more of the norm than the exception, mostly for EPA reasons, kevlar became easier to use. Kevlar is a great material that is finding its way into more mundane production boats (Hunter and Beneteau use it extensively). Kevlar works best when used with vinylester resin, with epoxy a more expensive, but technically a close second.

Uncored hulls were still pretty extensively used in the race boats of the 1980's but more so outside of the U.S. (For example, my 1983, South African built Farr 38 was designed and built as a solid hull with close frame spacing). During that era, the better built, uncored race boats often had very closely spaced framing in the form of tranverse frames and bulkheads and longitudinal frames, flats and stringers. One last point, even cored hulled race boats of that era typically had solid glass in the areas around through hull fittings.

Carbon fiber has some advantages but its is less resilient, lacks Kevlar's toughness, and harder still to work with, so I don't expect to see as wide spread use of carbon as Kevlar in production boats but I could be wrong.

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Old 28-08-2006, 08:11   #4
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My understanding about Kevlar (from the local builders) is that you have to be careful in that, over time, Kevlar will wick moisture more readily than glass or CF. For a small racing boat application that will spend most of its time out of the water, this is probably fine. But for a cruising boat that will sit in the water most of it's life, you have to be SURE you will keep moisture out of the laminate.
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Old 28-08-2006, 12:30   #5
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That is not true at all. This bit of missinformation refers to the days before vacuum bagging was popular. Properly wet out kevlar is less likely to wick water than fiberglass. They also may be mistaking carbon which has a sizing that if improperly wet out or exposed to electrical current will provide a path for moisture.

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Old 28-08-2006, 13:41   #6
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Yes Carbon is a pig to work with. It takes great skill and even today, there are a few guys making a very good living out of specialising working with Carbon. A good deal of top end racing boats are built using pre-pregnated Carbon fibres. This ensures the material is properly wetted with Resin. Which is extremely hard to do as the Carbon does not easily sink into the resin if being applied seperatly and manually. The factory prepared stuff arrives on a roll and in a freezer. It is kept cold to stop the reaction. BUT! it is expensive. Even 10yrs back, you only saw very small area's using Carbon. Like Masts and Booms etc. But today, we are starting to see larger area's like high load area's of hull being made from Carbon, and the really really big budget boats like Americas Cup are making entire hulls from it.
I think it is also true to say, you can get some very enormouse strengths with Carbon, but when it fails, it fails catastrophicaly, which Kevlar and Glass does not tend to do. Would that be a fair comment Jeff????
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Old 28-08-2006, 14:34   #7
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Absolutely, carbon works until it explosively ceases to work. Kevlar and glass at least give you a chance to duck, and does not send out lethal shrapnel if they fail in compression.

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Old 28-08-2006, 21:16   #8
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IIRC, C&C used to build their prototypes (which typically became "Hull No.1") ot of solid glass, and then after the design was scheduled for production they would figure out when and where to do the coring. So solid glass wasn't unheard of.

Is your builder still in existance? Any way to contact them, or perhaps VDS in Holland to ask about what was licensed and what was intended for the construction at the time?
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Old 28-08-2006, 22:24   #9
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Thanks for the coments guys. I have sent off an e-mail to Van de Stadt Designs in Holland, on the off chance that tehy have anything on record. Incidentally, I found a link to a similar vintage Van de Stadt design 44' IOR racer that looked like a slightly bigger version of mine. In the advert, it claimed that the hull was "GRP & composite"...
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Old 30-08-2006, 02:31   #10
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I've a early 80's with kevlar in it. I think you'll find it was used quite a bit around certian areas only as extra meat and strength, back in those days. These days it's carbon carbon and a bit more carbon, just like my toilet seat Who says racing yachties don't have weight issues

Everyone here who is saying carbon does not gently give up is 100% absolutly correct. We did extensive trials and built many carbon masts in the very early 80's (18ft skiffs) and I can assure you all - 1, when it goes it really goes and with a nasty big crack noise as well, 2, millions of small incredibly sharp needle sizes bits get everywhere when it dose go, 3, wetsuits don't stop the needles 4, the carbon today is a lot better than it used to be and 5, we were not really too good at building carbon masts back then, busted 2 out of every 3 but put on a good show while doing it
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Old 30-08-2006, 02:49   #11
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Ain't ya glad the toilet seat has held up to the stresses. Ooooo Carbon failure while sitting. Not good.
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Old 30-08-2006, 10:57   #12
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Wow, a CF toilet seat?! Just the seat, or the whole bowl?<G> I think I actually saw one of those advertised from some Italian company that was honestly building them for folks who want to race, but are willing to have a head on the boat so the Mrs. will allow them to own it.

Me, I'm trying to figure out how to quietly steal the head from an Airbus. (The annoucements say I can't disassemble the smoke detector in the lavatory, they don't say anything about the head.<G>) Nice big stainless steel pot with plastic surround, looks light, strong, and big enough to fit real humans on it.

I just can't find anyone at Airbus who'll sell me the head, without the rest of the airplane attached to it. :-(
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Old 01-09-2006, 00:42   #13
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Yeah the carbon seat was a slight cause of concern in ruff weather but it was engineered to be 'butt friendly'. At this stage no carbon bowl but it has been discussed.

Carbon is surprisingly warm on the flesh by the way
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Old 01-09-2006, 06:47   #14
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When kevlar is used in composite hull construction where is it on the laminate schedule? On the outside layer where it will come in contact with the floating log or the inner layer where it's allowed to expand and maintain the hull's integrity?
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Old 01-09-2006, 13:35   #15
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Depends on what it's intended purpose is. In the case of the above boat, it was more than likely a high tension load area. Kevlar has very low stretch along with it's high strength. So this layer was most probably used for minimising movement in that area, along with spreading out a high low over a wider area of the Hull. I won't pretend to be knowledgeable in this area, so I will stop now and leave any more detail to the "jeff's" of this board.
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