Luc,
Interestingly, a new Aeroyacht 42 (
http://www.aeroyacht.com/sailing-catamarans/aeroyacht-alpha-42-catamaran/
) recently had to be abandoned due to damage to rudders sustained in
a storm:
http://www.sailfeed.com/2014/01/helicopter-evacuation-abandoning-be-good-too/
QUICK SUMMARY
Jib sheet tore, making it tough to use the headsail, and batten
pockets/cars were damaged, making it questionable to hoist the
main. The genset and motors stopped charging the batteries, and
eventually all three stopped working.
The biggest problem, though, was that both rudders became useless
after the boat was thrown back by a rogue wave.
Both rudders broke their set screws, allowing them to turn
independent of the steering system, and one rudder's stock bent,
freezing it in place. They tried to sail and steer the boat after
the weather calmed down, but no combination of sails and motors
allowed them to go in a straight line, even after they semi-fixed
the steering.
While the boat itself was floating fine, it was too far from land
to request a tow in such conditions, and being unable to make any
progress, the skipper and crew abandoned her.
Some questioned the design of the boat, but other than being a
normal catamaran with spade rudders, I can't find fault with much.
One person commented that the rudder stocks should have been
linked with something beefier than the set screws that were used,
but that's a tough call. Another mentioned that one actually
/wants/ the set screws to break. Perhaps there should have been
spares fastened to the steering arm, along with instructions, but
how many boats are that well prepared?
DESIGNING SAFETY
The problem is that the boat had standard features that most
sailors have come to accept as normal, and perhaps even desirable.
The problem has nothing to do with the Alpha 42, and everything to
do with failures that would have plagued most 42-foot catamarans.
While the safe harryproa I mentioned the other week could
potentially have been disabled by the same storm, I'll make the
argument that it could have escaped relatively unscathed. Something
that put a half-million dollar performance cruiser out of commission
could have instead just been an annoying few days.
Here's how the proa might have made it through:
- Torn jib sheet. No jibs = no torn jib sheet. Okay,
that's an oversimplification, but it's worth noting that the sheets
on the proa would have been much more lightly loaded than the jib
sheet on the catamaran, particularly if they used a 2:1 purchase.
The mainsheets also wouldn't have to be routed across various bits
of deck hardware, having nearly a straight shot back to what might
be a single winch.
- Blown batten pockets. With a Wharram soft wing, or a
swing-wing junk rig, there are no highly-loaded battens to fail, or
have their pockets fail, or have their links to the cars fail, or
have their cars fail, or have the track fail. No battens, pockets,
links, cars, or track. Lots less to fail.
- Flexible reefing. Without blown pockets, the
mainsails could have been used, and with these two rigs, it's easy
to build in many reef options. They could have had just the right
amount of sail area up.
- Ease of reefing. Dump the sheets, mess with the
halyards while looking /downwind/, finish reefing. That's a much
less stressful process than reefing a big cat in a storm.
- Rudders 1. Kick-up rudders probably would have kicked
up. Maybe they'd break a fuse and have to be reset, but that's the
most likely outcome of something that wants to wrench the rudders
from their normal alignment.
- Rudders 2. But let's say that the rudders did somehow
fail, and the fuse couldn't be easily reset. What then? Raise the
rudders from the water, and/or remove them from their mounts. Now
the boat can be steered again by the remaining rudder. Or a long
oar. Or the sails.
- Rudders 3. Or perhaps things as things were getting
really ugly, the crew could have raised the rudders, paid out the
series drogues, and went below for some tea.
- Rudders 4. And with that schooner rig, there would
have been some nice sail-steering options, even if both of the
rudders had to be removed.
We could go on, but the basic idea remains the same: design away
the risks that can be designed away and the boat becomes a lot
safer.
Regardless of what I spend, I'd rather have a boat that can sail
its way back home, and then sail it home, than to have to call the
coasties and get a lift. I have no idea what that costs, but it
can't be cheap to get a helicopter ride that far from land, nor to
abandon such a nice boat.
- Mike
http://www.john-shuttleworth.com/Articles/NESTalk.html is about seaworthiness in different types of catamarans. Some of this is applicable to proa's. Again, the relative importance of any option is the difficult part. Luc