I have recently returned from doing sea trials on the new 95' INACE EXPLORER. One of the major point of these trials was to test the new Quantum Marine ZeroSpeed rotary stabilizers. This is the first application of the rotary for zero speed uses and the whole Quantum Marine brain trust came in. First I have to say it was a pleasure to have them aboard and see how they work. Not only was this the first rotary stabilizer system for zero speed but it was the first time the rollers have been fitted on a LARGE HARD CHIME DISPLACEMENT VESSEL. The team encountered a number of technical problems and other issues. They were able not only to work through them but to fine tune the system at the same time.
ZeroSpeed Rotary Stabilizer Deployed
Let me give you a little background on how and why we ended up with this new system on the vessel. Hard chime displacement hull vessels have a high degree of natural stability making them very hard to stabilize with an active system. This may seem counter intuitive at first but when you consider the active dynamics it makes complete sense. A vessel that takes very little wave action (force) to roll, takes very little fin action and size to counter that roll. If it takes a great deal of force (a stiff boat) to make it roll it takes a great amount of energy, big fins and a lot of lift to correct the roll. The INACE 95 has a 6.5 second roll period; the normal spread is from 5 to 9 seconds. The first reaction from most people would be "I want a VERY STABLE BOAT" (STIFF) so I do not need to worry about stabilizers" The problem here is two fold, no matter how stable a boat is IT WILL ROLL depending on conditions and if a boat is very stiff having a 3.5 to 4 second roll period it will display a condition called "snap rolling".
Snap rolling is a very quick roll with high degrees of acceleration, picture getting jerked side to side on a bad roller coaster. The different world navies have done a number of studies on sea sickness and snap rolling was found to be a major contributor to sea sickness. (Go to www.quantumhydraulic.com and John Allen can give you all of the data). So if to fast is bad then it make sense that slow is better and from a sea sickness point of view i.e. low acceleration, 9 second roll period this is general true. It can be a bit disturbing when a boat rolls over 20 degrees and hangs there for what feels like a verrrry long time (really not more then 1 or 2 seconds we hope) then starts back the other way, comfortable but disturbing as the bigger the seas the greater the heal and this can lead to something very bad. So what we are looking for goes back to the story of the Three Bears "the Goldilocks principal, not to hot and not to cold". From my discussions with designers, John Allen and others it sounds like 7 to 7.5 for a normal yacht is "just right". Of course an EXPLORER YACHT is not a normal yacht so we want it to be a bit on the more stable side, if the stabilizer fail, safety is first comfort is second. There is also another variable involved, the INACE EXPLORERS are designed to meet the new MCA stability requirements for all ocean service, in practice the collision stability requirements of these rules end up causing the boat to be a bit more on the stiff side. It is an interesting and difficult needle that the design team must thread.
New Quantum Marine ZeroSpeed
Rotary Stabilizer Being Fitted
If the boat is stiffer she needs more force, i.e. bigger fins. On any boat but especially a explorer yacht you do not want the fins to be out side the envelope of the hull, stinking down below the keel so they are the first thing that touches when you are gunk holing in some remote anchorage or out the side so your rub them off on a piling. Not to mention the larger fins cause more drag. So one option is to increase the keel so the fins are above it, that is ok to a certain extent but when the draft becomes excessive just to protect the fins and this limits where the boat and you can go it is counter productive. The other factor is as you add more keel and draft you make the boat stiffer bringing her closer to the "snap roll" condition. Then you add the requirement for ZERO SPEED and you have a real problem with the size of the fins, draft and the systems that drive it. It is a downward spiral.
This was exactly the dilemma I was facing when I met with Mike Perkins the salesman for Quantum hydraulics at the 2002 Monaco boat show. The owner of the 95' wanted zero speed if it was practical, but after speaking to all of the manufactures including Quantum it just did not seem possible to make the fins fit in the envelope. The owner was committed to going with Quantum’s complete integrated package and Mike and I were discussing some details when he mentioned that John Allen the head of the company had been playing with the idea of bringing the roller system back into production because of the huge size of fins that were need on some of the mega yachts AND that he felt is was possible that they could be use in a zero speed application. I have known Mike for over 20 years but had never met John, Mike said he was at the show so I decided to try and speak to him about the system. The Monaco show being what it is I was never able to get to the Quantum booth while John was there, I thought I would just have to try and reach him when I got back to Florida, my and his schedules being what they are, easier said then done, so I just put it to the back of my mind and headed for the airport.
At the airport a complete miracle occurred, my Delta Airlines sky miles upgrade to business class was approved! After settling into my seat and getting a glass of champagne, it was a long show and a long week, I looked over at the passenger seated next to me and noticed he was wearing a Quantum shirt. As you might guess it was John Allen, over peanuts, steak dinner and wine (we were both on Atkins, cheating a bit) we discussed all of the aspects of stabilization and the up and down side to the roller system. John took the time to explain all of the theory behind the system and why he felt it was ideal for a trawler for normal stabilization and zero speed. The system is extremely efficient from between 3 knots and 13 knots, fins really start working well at 10. They fold out from the side of the hull so there is no problem with draft, fold flush to the hull when not in use, they cause very little drag and because they generate much more lift then a normal fin, in theory they can create sufficient force to work at zero speed on a hard chime 6 second hull form. I reported all of my discussions to the owner of the 95 and we agreed to meet with John at the Quantum offices. We inspected all of their manufacturing facilities and John and the owner spoke about the system it was then decided to go ahead. I must say that John Allen was emphatic about the fact that he could not guarantee that the system would work at Zero Speed. He was completely confident with its operation under way but wanted us all to know that theory and practical application can often be quite different. John assured the owner that he and his team would do everything possible to make the system work with Zero speed. They designed the system and software and built it, then tank tested the system in Holland, it worked to the specifications. David the head of production flew to Holland for the tests, checked and disassembled the system himself, he then few in to INACE to pre-check the system and do the final installs. Ten days latter he few back in with John Allen and John and Hans for the sea trial. I cannot give you a complete description of all that was done during there 4 days (several of them 16 hours long) at the yard but I can say it was highly educational and entertaining for me.
So in conclusion if you are presented with a situation were standard fins create a design or operational issue, I would suggest that you go to www.quantumhydraulic.com and investigate the roller systems as an alternative.
Quantum Marine ZeroSpeed
End Cap Being Fitted
The system is still new and I will give you periodic updates as to how it is working and any issues that develop.
As always if any one out there can give a better explanation or if they feel I have made a mistake in the above information please contact me, I will be happy to post
or correct anything need.
Again on behalf of myself and my client, thank you to the all of Quantum and the brain trust that I had the pleasure to work with.
For more on this article:
95 Inace Extended Deck Explorer Yacht
Quantum Marine Engineering