DSK wrote:
The only way to be sure is to establish your own test lab,
buy 10 of them, test 9 to destruction and draw up a graph,
then install the 10th one with full knowledge of what it
will take.


Peter wrote:
That's what we do with mission critical stuff. In fact we built our own
test bed to test to destruction wire swages and the like.


A straight tension pull-tester isn't too difficult to
construct. Can you put on impulse loads and calibrate the
application of each successive load precisely?

Nope, don't need to for our applications.


It would be really difficult to test actuating gear the size
& strength of Skandia's keel canting mechanism. The best &
simplest way to do it would be to take the biggest tower
shaker... a gizmo cobbled up in the 1970s to test
installations at nuke power plants & simulate earthquake
conditions... pick up the boat by the keel with it, and give
it a hell of a shaking. I'm not sure that would be enough
and I'm not sure there are any around (Tadpole would likely
know).

The benefit is that that would also test the keel, the
trunnions, the hull panels.... the whole assembly.

And when you find the failure point - you build a new hull :-)

Yeah. I'd be interested in knowing just what spec the yacht designer
gave the hydraulics people so they could decide on the ram strength,
and how they knew that the load wasn't exceeded (ie, the failure was
due to inadequate spec rather than inadequate equipment). Personally I
wouldn't trust *anything* done by a racing yacht designer - look at the
failures, they obviously aren't using commercial standards for safe
working margins.

Of course not, if they were, they'd lose

OTOH contrary to popular opinion, racing yachts are built
very strongly.

Don't doubt that at all - depending on your definition of 'strongly'.
It comes back to the designer's margins for the material used. As I
said, most of what I use is designed to a load 1/4 to 1/8 of the tested
breaking load. If I planned on loading something up to 90% of its
breaking strain, and it broke, I wouldn't consider it 'strong' and I
wouldn't be blaming the materials.

One quite expensive bit of gear I use puts heave strains on a cable
that are 2/3 of its tested breaking strain. We have heave compensation,
tension controls etc to minimise the risks. Even so, we've lost 2 over
the years. Due to the depths and other operating constraints, we can't
really do anything about it. Losing gear in this case is the cost of
doing business. WRT racing boats, breaking stuff - ditto.

WRT Skandia, if a piece of supplied equipment from a 3rd party failed
at less than its specified load, it was faulty. If it was overloaded to
failure point, the design was inadequate. The article Oz quoted doesn't
have any details.

The failures tend to get a lot of publicity
and of course they always come at a bad time. It's also the
nature of the beast that very few are soft, gradual
failures. The breakage of Skandia's keel was about as benign
as could be.

Note there was no backup plan, or if there was, it hadn't been tested &
known to work.

I suspect this is a case of deep pockets.....


Has Australia learned so much from the American tort system
so fast??

Unfortunately - yes.

PDW