Wave-piercers - marketing myth or design ingenuity?

A few more nice wavepiercers

 

I've been away from the forum for a while and so I missed this entertaining thread.

I know the background behind the 'invention' of the WPC rather intimately, but will avoid the whole 'do waver piercers actually pierce waves, and how?' discussion yet again.

I will say this..I will always be gratefull for the appearance of the WPC. The invention of the WPC led very soon therafter to the critical need for, and invention of, fairly elaborate and expensive active catamaran stablization systems.

 

One must go to the invention of wave piercing hulls to understand them. They were first applied to sailing hulls with fixed maximum length: a class with a maximum hull length of 20 feet, used in the Worrell 1000 races in the mid 1980's. They have continued to be proven effective in A class catamarans, where there is a maximum length of 17 feet. So its not an "extension" as AH suggests, its an elimination of reserve bouyancy.

If you were watching the America's Cup racing, it was very clear that the wave piercing bows of USA resulted in substantially less pitching motion than the much more buoyant bows on Alinghi.

So we can argue, or we can simply do experiments and observe. The experiments and observations clearly show wave piercing bows are faster because pitching is less.

 

OK..I've collected/recorded (or those working for me have) the real-time motions data from nearly all the passenger WPC's ever built. Said data collection an output of the active motion control system that they (WPCs) all require to tame the otherwise very passenger unfriendly pitch motions in seas above SS2 or 3. (i.e...conditions in whihc they have to operate quite often).

So whoever the 'we' is that might be arguing the merits and actual performance of large WPCs..I'm not one of those 'we's.

 

Quote is from the second link:

This is not a waver piercer with a flat deck, but the concept of stepping expands the topic a bit.

 

I am on fullly your side. But, I cant imagine the point of bothering to 'measure' the unfriendliness of the motion - just go for a ride on the things.

I actually got paid $50 to go to a 'research' meeeting (along with a couple of hundred other passengers) about the trials of the fast ferries across Bass Strait here in Australia. Some confused person paid thousands of dollars (as in your case) to prove the F%&*@!ING obvious, that every passenger could tell you half an hour into the voyage, its a shocking ride!!!. They took the boats of the run!

At the risk of repeating my story, there is another 'feature' of catamaran travel that gets little attention. Rather than use rudders, the autopilot on the big Cats would steer using the throttle, on the port and starboard hull engines. So, every four minutes, when the compass had accumulated enough 'badness', the revs on one side would be increased for a minute (say, the port side). This would point the boat slightly off course (say, to starboard) in the other direction. When the starboard error got too bad, the starboard engine would be throttled up briefly to push the boat to port.

This results in a regular 5-10 minute 'yaw' that was very sick making.

While I am still on my soap box, a word to all the 'interior designers ' of all commercial boats. Why the heck do you insist on cramming boat seats together as if they were an plane ???????

We have the ridiculous situation in the Tasmanian Ferries where the two huge ferries take dozens of empty cabins on every trip, empty because they are quite expensive.

Meanwhile, the smallish 'sitting up only' space at the front of the ship is booked out months ahead, because they are cheap.

I was watching a desparate plea in a TV ad last night for these ferries, for more passengers - (thousands of dollars a second in TV ad time) when all they have to do is provide some realistic leg room in the sitting only areas, with seats that actually fully recline. They could use the redundant cabin space for this. hell, you could put four recliners in a cabin with a Tv for every seat, and their own bathroom, and fill them every trip.

Thanks - I feel soooo much better now

 

'twas not bother or unusual expense..that data collection part. It's a normal part of every new vessel commissioning (or, later, after-service trials) and that includes, of course, the active stablization system.

Oh..and that rather nasty yaw instablity you so vividly described? That rude behavior resulted in yet another invention of of ours - the actively controlled flapped yaw stability skeg, operated by the same gyro and controls package that manages the foils and stern tabs for pitch and roll damping. More wiggly bits to get motions under better control..we like that, of course. The yaw damping part of the system has, alas, been fitted to only a few cats thus far.

 

Bravo ! Of course the accountants will always say "Thats more off the bottom line".

Just ask them "Where is the equation representing loss of repeat business because the passengers had such a rubbish journey, and then told all their friends to fly rather than go by boat"

Its the same story with airlines. I could never face an international flight, and hate even domestic ones because of the really bad accomodation. And here they are wondering why they cant get passengers.

 

It's not just the accountants...the most capable of the active motion control systems seldom exceed 5% of total vessel cost. It's really more a matter of knowledge. NA's, as a group. want to believe that they can develop some hull form or other that is the killer seakeeping machine. They spend thousands or hours in a tow basin to find that 5% improvement in motions here or there and cry 'eureka' if they do. On the other hand, to include an active stabilization system in their otherwise 'unsullied design' is a badge of shame, for some reason..even though that active system can reduce the same motions by as much as 75%!!

Another factor that allows that mindset to persist is simply that there is no widely understood and applied criteria for passenger motions (there are criteria..have been for many years..but they are not understood or applied).

Thus, it is/was a real head scratcher to the NAs involved when the first large WPCs (and other cats with slender hulls and reduced forward bouyancy..to be fair) proved to be some of the most sea-sickness-inducing machines ever launched as fast ferries. Why? ..astonishingly simple really..the vertical accelerations they produce as a resuilt of their characteristic resonant pitch behavior occurs exactly at the frequency where humans are the most sensitive to those motions. ISO 2631 shows that very plainly.

 

B-Mac,

Are you suggesting, then, that NA's cease looking for ever better hull designs and completely rely on active systems for the business of designing better boats of this type?

The obvious question is... What happens to the capabilities of the boat when the active system becomes inactive?

Wouldn't it be prudent to continue to develop better hulls so that a wider latitude of customer needs can be addressed, rather than offer up a buckboard and use active systems so that it can be called a Cadillac?

Perhaps some of us have driven a power steering committed car that has the power assist unit fail in the middle of a long day running errands? I'll go way out on a limb here and suggest that it wasn't pleasant for the driver, or the passengers.

Redundant systems? Ahh, yes let's increase the cost of the boat accordingly, pass that on to the paying passengers and wonder why they find other conveyances. In all cases, if one lives by the techno wand, then one will also die by the same wand.

It's my opinion that techno stuff can be a great source of advancement of the craft, but it will never, by itself, be a substitute for good, solid design improvements in the first place.

 

It could have sounded that way..but I'm absolutely not suggesting that the unceasing quest for better hull forms is a bad thing. Quite the opposite is the case..we design hulls too.

My point was more directed toward the fact that..again using the poor WPC as an example, you can beat on that set of lines forever and not gain more than a 5-10% improvement and motions from the hull changes..but an active system can work wonders by comparison, achieving motions reduction levels that are physically impossible through hull deisgn alone.. Ironically, perhaps, the hul forms that are the best in terms of passenger comfort with active stabilization can be some of the worst if the stabilization system is down for any reason. The more lightly damped and 'SWATH-like' the hull..the easier it is to actively control. The stiffer the hull design is
stiffer in terms of the basic derivatives or the various forces with respect to immersion changes, the harder it is to control and the less effect a control system, will have on it. And generally speaking, the rougher it is on passengers. In terms of overall controllability, typical WPC designs are sort of 'in the middle', although that is in part because cats with even finer (especially forward) hull designs have come out since.

I could not count how many passenger vessels out there running now, especially catamarans, that, when faced with having the active control system down for any reason, have to cancel.

Your power steering analogy is sound. When the the active control, which is the only things standing between the sea and miserable passengers, goes down, its a bad day for everyone.

But likewise, your point regarding the used of 'techno soluitions' falls flat. If the total ship package cannot cut the mustard, the route fails regardless. I've seen plenty fail due to bad motions..and just as many fail due to chronic propulsion system failures.

 

So, that will be your opinion. Mine is quite a bit different.

 

What is it exactly you disagree about Chris ? Surely not the point about routes failing because of poor passenger experience ?

 

Opinions differ. You (and many other NAs) have built a business around yours and I've built one around mine. For over 25 years now..more than 150 actively stabilized SWATH and high-speed naval, passenger and leisure vessels are in the water operating with my junk wiggling away merrily. I always separate out SWATH because many/most SWATH are actively stabilized but are not high-speed vessels. Anyway, that would strongly suggest that neither 'opinion' is 'wrong'....just different approaches for different vessels. Wouldn't you agree?

Our current company demonstrator is a 32' aluminum Marinette sporting one of our typical pitch, roll and yaw damping systems inclusive steering and autopilot. Awesomely capable stuff..but we are certainly not proposing to ever market that system to anything remotely close to vessels only 32' in size; it is a demonstrator vessel and something to use for testing out new software, the latest servo valve, etc. so that its not our customers that are the guinea pigs.

Prior to that our company-owned demonstrator was a 43' LOA foil-assisted super-slender monohull, ama-stablized off foil. A trimaran..sorta. The cost of maintaining that thing in flight-ready condition was over the top..so its being converted in to beer cans now, after 5 years of demonstrating amazing capabilites in seas to 5' significant height. A much more impressive demonstrator when it came to showing what active stabilization could achieve...but too hard on the company pocket book at the same time.

Heck, our system on that 32' boat would equal half the boat cost otherwise. Active stabilization fits a 'niche'..only certain types of vessels in the 60'' to 250' LOA range that are required/expected, for whatever reason, to manage well in seas that are quite higher than they can ever manage in a bare hull configuration. It is indeed a niche...and as a niche is far from being a universally applied solution nor the right answer for many vessels.

Fortunately for the company bottom line..the larger WPC and other 'semi-SWATH' cats all require active stabilization unless they are operated on only the most benign routes. The smallest WPC to which active stabilization was fitted was propbably the AMD 350..or might have been the Nichols-built ex"Nantucket Spray'. Thus 35-40m LOA has historically turned out to be somehwat of a natural 'low end' cut-off point for the fitting of ride control to cat and mono hull ferries..and that cutoff is determined almost entirely by economic factors..the cost of stabilization does not decrease linearly with the size of the vessel, so when you look at your slection of vesse size v. route in that size range, its often that case that buying something 20' longer makes more sense than paying for active stablization on the smaller vessel.

 

No Wats,

There must be a thousand reasons why a particular ferry route fails, including the boat being used... but I never said anything about that part of the discussion.

My point has been clearly enunciated. We, as humans, have allowed ourselves to become much too dependent on the next techno gadget that comes down the road as our immediate salvation. As a result, we have put ourselves prostrate in the middle of the road, as it were, becoming ready victims of the eventual failure of that technology.

The gadget salvation process is a myth. We indulge our collective societal fantasy with this little voice in our heads that we'll be able to dig ourselves out of the all-consuming hole in which we currently reside. Well, that'll happen as soon as the next whiz-bang techno widget arrives to save the day.

Instead of truly smart developments in all the baseline areas of boat design, we chunk a load of expensive stuff on the boat, solve a few "in your face" problems, and then go skipping down the highway as if it's just a groovy, sunny day. Well swallowed by the masses, what we have really done is designate our activity to the whim of the electronic gods and all that they see fit to huck in the direction of system failure.

Just why do you think that there are huge masses of Indian people working in customer service centers for problems with your personal computer?

Eventually, we'll all be completely removed from our own lives and virtually totally dependent on these systems to make us all feel like we still have it together as a species.

Look around your own life and witness just how much of it you have given over to the fabulous new ideas that were ginned-up by marketing divisions in some corporate beehive. These company boys have long ago drunk the Kool-Aid and now they want you to drink it as well.

This gadget nonsense is symptomatic of a culture that is out of control and totally full of its own phony majesty. I don't know about you, but when I look around and see landfills that are brimming with cast-off electronic junk that was yesterday's fresh new techno-whiz solution for our lives, I get this eerie feeling that we've jumped the shark on our own civilization. We've even managed to teach the Chinese and the Indians all about our vapid culture and they will soon be so good at it that they will absolutely dwarf our foolishness. A thinking guy just has to shudder when that reality hits his grounded consciousness.

That's my beef.