Sydney-Hobart 2015

The battle damage assessment is more complicated than imagined !

 

Carbon does funny things. In one of my engineering classes, we were talking about deflection of beams. We tried it with a steel ruler, and the deflection was the same that we calculated it should be. The professor does a lot of experimental research with Carbon Fiber, and he tried the same experiment in class with a piece of carbon one time.

First, he tested the brand new piece in his office, and yes, it deflected the correct amount. Then, between then and his class, he sat there bending it back and forth for fun. When he got to class, and tested it in class, it deflected nearly twice of what it should have, so the experiment was not valid, because he had been playing with it, bending it back and forth, and it was much weaker because of it. I suspect something similar happens with these boards on the maxis. I'm sure they flex quite a bit, and every time they bend some of the carbon weakens.

 

These boats remind me of fast racehorses with dicky legs, it is only a matter of time before something breaks.

 

I think you will find it is normally the resin binding the carbon that is 'weakening' as it is far less stiff than carbon whiskers. After all it is the weakest part of the system....

 

By the time four supermaxis, an 88 footer and two Volvo 70s have come by, with a total of almost 30 deep foils slicing through the water, all the local sea life has been turned into sashimi and nothing large has been left for anything else to hit. Greenpeace has been informed.

Sometimes you actually can see the sunfish that has destroyed your rudder after you have sailed the next boat in your class over the horizon a third of the way to Hobart. Trust me.....

 

Not really. Wild Oats broke their DSS foil (that is, the one that DSS collaborated on the design of) last year and replaced it with a not DSS foil (that is, one that DSS did not collaborate on the design of).

 

I can understand a horse not being able to handle a wet track, but a boat?

 

Dss

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There is no such thing as a "not DSS foil" if it looks like a DSS foil and works like a DSS foil!

 

I dunno, they just look like a horizontal daggerboard to me, nothing special.

 

But DSS foils are special ,Steve-very special......And covered by worldwide patents.

 

Not Mike but failure due to fatigue is a well known phenomenon in all sorts of materials. Some of the earlier titanium alloys became notorious for notch failure. A slight scratch or other surface imperfection caused stress concentrations which caused the crack to grow. Next thing - snap.

Materials with their yield point very close to their failure point are notorious for failing with little warning. Carbon fibre/epoxy is a classic example.

I don't care what the people on the boats said, if you look at the met data and wave height data, you can't honestly say it was a really rough race. Damn sure it felt like it to the people out there, but so what. Pushing on at 110% into foul weather might be the way to win races but it's also the way to break gear. If you design the gear for optimum conditions and it has a very small allowance for excess stress, it breaks. Where's the surprise?

Nobody got injured or killed so my care factor is zero WRT broken gear and retired boats. You want to push the structural envelope, sometimes the envelope pushes back. So sad, too bad.

PDW

 

There's a lot more than simple wave height and wind strength involved. Issues such as whether there have been fast shifts in wind direction are also involved, as is the current.

Surely in such a complex issue it is at least as reasonable to listen to those who were there and who have been there before many times, instead of someone who may never had been there at all.

 

Doug, can you please explain how it is more than just a horizontal dagger board.?

Steve.

 

Sure. A daggerboard generates lateral resistance. The DSS foil generates vertical lift that does two things:
1) the lift is displaced to the side of the boat creating a large righting moment,increasing the power to carry sail and reducing the lead and/or water ballast requirement.
2) the lift reduces the displacement of the whole boat reducing wetted surface and reducing total drag.
Side effects can include a reduction in pitching and "smoothing out" the ride.

 

So it is just a horizontal daggerboard as I suspected. Obviously it is different to a vertical dagger board, since it is horizontal. Multihulls have been using foils angled in or out for the same reasons for many decades, just not at 90 degrees. Not saying its not a good idea though.

Steve.