Kevlar reinforced GRP?

[boatpoker]

Thought you guys might find this interesting.... I did some work with my friend Derek Hatfield on Spirit of Canada (an Open 60) when he built it. Carbon fibre / Nomex (basically paper honeycomb), the stuff is astoundingly light and amazingly strong. I was playing with thermal imagery at the time and wanted to capture a thermal image of a fracture in this composite laminate. It took me 20 swings with a 7lb. sledge hammer to put a crack in it. I kept a few pieces for the dog'n'pony shows I do a couple of times a year. Photos are an off-cut from the transom.

[boatpoker]

Originally Posted by boatpoker

Thought you guys might find this interesting.... I did some work with my friend Derek Hatfield on Spirit of Canada (an Open 60) when he built it. Carbon fibre / Nomex (basically paper honeycomb), the stuff is astoundingly light and amazingly strong. I was playing with thermal imagery at the time and wanted to capture a thermal image of a fracture in this composite laminate. It took me 20 swings with a 7lb. sledge hammer to put a crack in it. I kept a few pieces for the dog'n'pony shows I do a couple of times a year. Photos are an off-cut from the transom.

Sorry .... wrong photos. These are the 18" X 3" tomahawk steaks for the bbq tomorrow . Here are the carbon/nomex photos

[thinwater]

In the 70s and 80s the Stiletto 23, 27, and 30 were made of Kevlar prepreg, and I think the great majority of them are still floating. They are rather tough, in their own way. They are light and simple to recondition, making them a favorite with hot rodders.

Pregpreg solved most of the wetting problems. However, the tabbing and bulkheads use glass for this reason. Repairs require attention to detail--as others have mentioned, sanding is different. And of course, only epoxy.

Tough? Yeah. I once dropped a hammer 40 feet onto a deck that has less than 1/16" skin over honeycomb. It bounced. Stiff? Not really, but OK with enough core. For impact resistance on a larger yacht? I'd go with a few extra layers of glass for reasons others have given.

I liked my Stiletto, but I'm not sure I'm sold on Kevlar as a building material for boats. I've used carbon in combination with glass. Unless engineered carefully, the huge difference in stiffness an cause stress risers.

[merlyn]

Greetings, I'm interested in buying an 89 jeanneau sunkiss 47. I read that not all were built with kevlar. How can I know that this one has kevlar ? And how and where it was used ? Much appreciated.

[Group9]

Originally Posted by neilpride

Kevlar its mostly abrasión resistance , then a boat made of kevlar sándwich composite is dificult or imposible to repair if is seriously damaged , simple as if you try to grind kevlar the result is a smooth Surface,, i see a kevlar race boat totaled when holed in a local regatta .. for local áreas of the hull could be ok like the bow section in front of the FWD trailing edge of the keel , or in rudders, and also Carbon its best suited for boat construction , i cant see any reason for use Kevlar this days... Cheers.

All you have to do is cut a piece of fiberglass woven mat with scissors, and then try and the same thing with Kevlar woven mat (like from a bullet proof vest) to see the difference in working with the two different materials.

I always thought the whole Kevlar boat building thing was just a marketing ploy, because Kevlar is such a well known product. Because, there are a lot of newer, but not as well known, synthetic fibers used in body armor these days that I never hear of being used in boats.

[FPNC]

Having built many vessels out of Kevlar both solid laminate and cored laminate, I can state that it is not the wonder material it is made out to be. If a manufacturer wanted to build a superior laminate for an average vessel he would use vinylester resin and 'S' glass in the laminate. Even vinylester and 'E' glass would be my preference to having Kevlar used in the construction. If a manufacturer slips a single layer of Kevlar in a laminate it is purely a marketing scheme than actually beneficial to the product. Particularly if they are using polyester resins.

[Group9]

Originally Posted by FPNC

Having built many vessels out of Kevlar both solid laminate and cored laminate, I can state that it is not the wonder material it is made out to be. If a manufacturer wanted to build a superior laminate for an average vessel he would use vinylester resin and 'S' glass in the laminate. Even vinylester and 'E' glass would be my preference to having Kevlar used in the construction. If a manufacturer slips a single layer of Kevlar in a laminate it is purely a marketing scheme than actually beneficial to the product. Particularly if they are using polyester resins.

And, Kevlar has such a narrow envelope of performance. You can take a level IIA Kevlar ballistic vest (a very common model back in the day) and shoot it with a 9mm bullet and it will stop it without a problem. You then take a compound bow, and put an arrow right through it, or take an ice pick, and run it right through it.

[ihe2]

Here are some pics I took in Italy 2013 from a Kevlar reinforced hull taht was being being repaired. There was something really wrong with the laminate.

[double u]

bad osmosis, resin in the outer mat-layer hydrolised completely. Nothing to do with the Kevlar. These boats were built to a price point, there will be a limited amount of Kevlar in the hull, no fear.
In the 80s there were Crowther cats built in a suburb of Brisbane (Hemmant, Geoff Cruse?), which looked extremely nice to me.foam , Kevlar & Epoxi over male molds, Windspeed they were called, at least this one was still around a few years ago:
https://www.multihullsolutions.com.a...d-Rush-Web.pdf
another one:
https://www.inautia.com/used-boat-41...91019945.htmlI have never worked with Kevlar but had always thought, that it would be an absolutelytop-class material for a hull, so I am surprised by the negative side of it.
Re Jeanneau: I am prety sure it was more of a marketing gag. I worked on a Voyage 1250 in the 90ies, & it didn't look like the boat where the builder would splurge on in unseen places...