Is this progress in composite construction?

[tschienque]

Originally Posted by tja

I used parabeam some ten years ago or something very simular and was not impressed. I definately wouldn't use it as a core in a boat. The other product i have never seen before........Tom

Originally Posted by Herman

I have used parabeam in boat construction, but I was not impressed also. It tends to be quite brittle, and I do not like the idea of having a hollow core.

Hi Guys,

Any details on what specifically you didn't like about Parabeam?

In both cases I detect a reluctance in attitude to the "type" of product. In Tja's case, he specifically states he prefers solid glass and Herman doesn't like "the idea of a hollow core", ruling out NIDACORE etc.

I'll be visiting the Parabeam factory in the next week or two to evaluate, so any all questions would be greatly appreciated.

Caio

[brian eiland]

One of the biggest problems in cored boat construction is bonding the dissimilar skin and core materials together, both their dissimilar properties and that property of the bonding adhesive itself. Failure occurs in shear, and then the two dissociated skins are not able to carry the load.

Witness the problems with the ORMA 60 tri's:
http://www.yachting-world.com/auto/n...431ywnews.html
Nigel Irens comments
"Last year there was a bulge in new boats being built and a wholesale move towards building in pre-preg carbon and Nomex core. Everybody had drifted towards this technology and although the stuff's been around for a long time, what went wrong was the result of that. There may be a big learning curve now underway and it may be that some people won't use these materials again. We certainly haven't used them on Ellen's boat [her new 75ft trimaran, currently building in Australia]. We've gone back to more traditional core material."

"Basically, what it's all about is the materials have very adequate static strength and there's no problem in terms of sheer pressure head. But in reality what's appears to be happening is that there is not enough capacity to absorb the loads that the skin sees. These are much, much higher than was the case with a softer, more forgiving material."


And now have a look at this latest failure....granted under extreme conditions and in a very large piece:
ANALYZING SYDNEY HOBART DAMAGE
(The designer of Konica Minolta, Brett Bakewell-White gave his view on what
happened in a story posted on The Daily Sail subscription website. Here are
a couple of excerpts.)

"The damage to the boat was relatively minor. It consisted of a core shear
failure across the cabin top from window to window - approx. 1.8m long -
the skins remained intact. The transverse crease in the cabin top was about
150mm in front of the keel tower and behind the mast. Essentially it was
caused by the keel's momentum compressing the cabin top as the boat crashed
out of the back of a very large wave. This part of the cabin top had
received a significant design effort when the boat was designed and was
capable of exceeding ABS grounding requirements, so it is rather surprising
that sailing loads have managed to exceed these quite stringent requirements.

"Whilst we tried to shore up the damage by bolting through the cabin top
with bunk tops above and below, we found that the continuous movement of
the keel began to slowly tear the carbon skins with the inevitable result
being a gaping gash across the cabin top and the possibility of water
entering the cabin. Once we turned and ran with the seas the cabin top was
fine. Over the next few days the cabin top was through bolted with plywood
either side (as we had attempted at sea) and she was motored down the coast
to Hobart. Had we had some substantial material such as plywood we could
have affected the same repair and won the race." -
The Daily Sail,
www.thedailysail.com