To stabilize or not to stabilize?

kraftee said:

Sorry Larry. Thought that would be pretty obvious with my built-in bias! Great Harbour.

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Sorry, but you lost me. I see you have a Californian 45.

"...like the FD purists demand?" Not sure what that statement means as most modern full displacement tugs, workboats and fishing boats have hard-chine hulls.


And yes, all Great Harbours have hard chines - but make no mistake, they are DEFINTELY true FD hulls!


ERIC

Yeah, my liveaboard is an old Californian - but as I have posted in many other threads, I was Sales Director for Mirage Manufacturing/Great Harbour Trawlers for 9 years. Thought you had participated in some of those threads. My mistake.


ERIC

kraftee said:

Yeah, my liveaboard is an old Californian - but as I have posted in many other threads, I was Sales Director for Mirage Manufacturing/Great Harbour Trawlers for 9 years. Thought you had participated in some of those threads. My mistake. ERIC

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Well heck, that explains it.

I've heard lots of boat salesmen say that this boat or that boat is so stable that it doesn't need stabilizers. It's a great sales line, but dodges the fact that ANY boat gets more stable with stabilizers.

...ANY boat gets more stable with stabilizers

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Actually, that is a pretty broad statement. And like many broad statements, it is true in some cases, but not in ALL cases - and not in the case of a Great Harbour hull. But then, like you said, I'm just a "salesman". Maybe Lou Codega will weigh in here with a much more educated discussion on the topic.

Our Grand Banks 46 has Naiad active stabilizers. For us they make a huge difference in comfort underway. We use them all the time and have found them to be reasonable from a maintenance perspective. Ours were fit to Avalon in 2000 and I believe the systems have improved significantly since then.

However, the installation is critical and if you purchase a vessel with active stabilizers installed after manufacture I'd recommend having the fin actuator installation to the hull surveyed very thoroughly. A practice of many installers in the late 90s and early 2000s was the install the actuator blocks to the hull using 3M 5200. Such installations may eventually fail, ask me how I know, and the current practice is to fully glass the blocks to the hull making them one integrated piece. Even though the blocks and actuators are through bolted, sandwiching the hull, the block must be glassed in making it one piece with the hull. The pressures underway from the fins and actuators are significant and require an extremely strong mounting platform.

I don’t believe we would ever go back to a boat without active stabilizers. For us they really make cruising much more enjoyable in all conditions, particularly in poorer conditions and in areas with significant boat wake traffic.

Tim

Insequent said:

Probably around $60k, yard installed. If retrofitting, it depends on access. Ideally they will be midships, but anywhere in the middle third will likely be ok.

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Set on Bay Pelican cost $40,000 US in 2012.

Even if a vessel has a lot of initial stability, like the Great Harbor boats, the idea that they would not be improved with stabilization can't be correct. They may be just fine most of the time, but when the seas are moving under you at 30 degrees, you will heel 30 degrees without stabilization. That may not be a frequent occurrence and so perhaps the cost isn't worth it to some, but ALL vessels will benefit from some form of stabilization in some conditions.

Modern, properly sized, active fins are said to eliminate as much as 90% of roll. Although I can't quantify the benefit on my boat, I can tell you that my kids immediately know from the ride whether the stabilizers are on or not (and insist that I keep them on, which I am happy to do; I only have them off when docking and leaving the dock since having them on makes it real tough to control them boat with either engine in reverse).

For my Naiad's, the install is such that at under 4 knots or if either engine is in reverse then the stabilizers are centred (off). It is possible to bypass these features if for some reason you wanted to. And yes, it is very rare for me to not have them on, even in the river where ferry wakes would otherwise be annoying.

Even if a vessel has a lot of initial stability, like the Great Harbor boats, the idea that they would not be improved with stabilization can't be correct.

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Delfin, I'm just not sure just where these stabilizers would be mounted on a GH hull. Sticking straight down from the bottom and doubling the draft? Or sticking straight out on the hull sides like curb feelers - adding 6 or 8 feet to the overall width of the boat? Tell you what: Eventually Lou will stumble across this thread. As a Webb Institute trained Naval Architect and an MIT grad - and the designer of the GH hull - his opinion should carry some weight.

kraftee said:

Delfin, I'm just not sure just where these stabilizers would be mounted on a GH hull. Sticking straight down from the bottom and doubling the draft? Or sticking straight out on the hull sides like curb feelers - adding 6 or 8 feet to the overall width of the boat? Tell you what: Eventually Lou will stumble across this thread. As a Webb Institute trained Naval Architect and an MIT grad - and the designer of the GH hull - his opinion should carry some weight.

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I'm basing my observation on the simple fact that the ocean is not flat, at least not all the time. An unstabilized vessel, even if it never varies except in inclination to the seas, will nevertheless incline along with those seas. That is not the case if the vessel is stabilized. If it is, the gyro senses the inclination and largely corrects it. This doesn't require a degree in naval architecture to understand - just a passing understanding of sea states in the ocean.

The GH may not be able to use stablizers if it has a flat bottom without some significant modifications. The slower the vessel, the more the fins have to be as horizontal as possible to be effective. That doesn't suggest that the boat wouldn't be more stable if they were installed, but it does suggest the cost would be prohibitive and if you want the kind of lack of roll you get with a stabilized vessel then perhaps a GH isn't your first choice.

...if you want the kind of lack of roll you get with a stabilized vessel then perhaps a GH isn't your first choice.

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Wow. What an argumentative statement. Tell me, have you ever been in a seaway aboard a NOT flat-bottomed Great Harbour? Or are you just guessing based on your "passing understanding of sea states"?

kraftee said:

Delfin, I'm just not sure just where these stabilizers would be mounted on a GH hull. Sticking straight down from the bottom and doubling the draft? Or sticking straight out on the hull sides like curb feelers - adding 6 or 8 feet to the overall width of the boat?

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The KK Manatee hull is quite similar in its acceptance of fin stabilizers. On the only application I know of, they do come out of the water. It's well known that the Manatee hull has better "initial" resistance to roll than say, a 42, but beyond a certain sea state, it is known to roll more.

There's a plethora of reasons why my first choice of boats would be a GH, but behaving like a true, stabilized vessel wouldn't be one of them. I think Codega came up with a combo that behaves like the hull it was inspired by....a design that resists roll.

healhustler said:

The KK Manatee hull is quite similar in its acceptance of fin stabilizers. On the only application I know of, they do come out of the water. It's well known that the Manatee hull has better "initial" resistance to roll than say, a 42, but beyond a certain sea state, it is known to roll more.

There's a plethora of reasons why my first choice of boats would be a GH, but behaving like a true, stabilized vessel wouldn't be one of them. I think Codega came up with a combo that behaves like the hull it was inspired by....a design that resists roll.

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There are lots of nice features of either a Manatee or a GH, but you are quite correct. Whatever those advantages are, they don't include a suspension of the laws of physics and those vessels will roll along with the seas, although certainly less than a round or fuller hull would, but also certainly more than a stabilized hull of whatever form. Having spent enough time in the open ocean on the West Coast of Vancouver Island on Delfin without having my wife's Sonicare toothbrush tip over when standing on end in the head I think I understand the function and effectiveness of active fins.

kraftee said:

Wow. What an argumentative statement. Tell me, have you ever been in a seaway aboard a NOT flat-bottomed Great Harbour? Or are you just guessing based on your "passing understanding of sea states"?

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Go pick a fight with someone who cares. That wouldn't be me, by the way.

Greetings,
Mr. MYT. "...real tough to control..." Tell me about it. I constantly forget to turn the damn things off or center them. GREATLY increases the "pucker" factor.

Not trying to pick a fight, just giving my opinion, based on about 10,000 nm aboard unstabilized GH's in all kinds of conditions.

Eric-you posed my question-Where would stabilizers be installed on the GH hull? My understanding in that they should be somewhere around 30-35 degrees below horizontal to be most effective. I see no way tht could be done on the GH hull. that makes it a moot point as to whether the boat would perform better or not.

It is hard to believe that ANY vessel at some point doesn't have an improved ride from some sort of stabilization.

Sure a hull can be designed to reduce that need...but as has been said...at some point roll is inevitable.

There are other types of stabilization that could possibly be used other than active fins...but I can't say for sure without further study.

If you are at all interested to read what Lou Codega has to say about stability...


About Great Harbor Trawlers : Design Discussions

kraftee said:

If you are at all interested to read what Lou Codega has to say about stability...


About Great Harbor Trawlers : Design Discussions

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Read it. At the risk of over simplifying, it's a barge-like hull form, so highly motivated to follow the water surface rather than oscillate. It's very much like a planing hull vs a round bottom displacement hull. The planing hull wants to snap to the water surface where the round hull will more easily roll. The GH's barge-like hull form just takes the "roll resistant" characteristics of a planing hull one step further.

Because of these differences, planing hulls require more work by the fins to stabilize them. The round hull is arguably more in need of stabilization, and is correspondingly easier to stabilize. But I can attest first hand to the huge difference fins make on a planing hull (my 47' Grand Banks). I can see how stabilizing a GH would be that much harder. Add to that a hull form which provides no suitable location for fin installation, and you arrive where we are....and if something can't be stabilized, it makes sense to declare stabilization unnecessary.

Not sure where you made the jump from the GH workboat-style hull to a "barge-type" hull - which are typically flat bottomed with a flat prow. And, wouldn't you agree that when you say that "something can't be stabilized", what you really mean is "when additional stabilization can't be added"?

Was thinking we could do a TF experiment and everyone pitch in to Have them installed on my boat and we do some before and after tests and evaluations

oh and of course everyone pitch in

Greetings,
Mr. s. I'm in but YOU buy the gas for the chainsaw.

rt firefly said:

greetings,
mr. S. I'm in but you buy the gas for the chainsaw.

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haha

kraftee said:

Not trying to pick a fight, just giving my opinion, based on about 10,000 nm aboard unstabilized GH's in all kinds of conditions.

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And in those 10,000 nm, in a beam sea with 12 foot waves, when one passed under the GH did it roll with the waves, or remain perpendicular to the horizon in defiance of the laws of gravity?

To use Lou Codega's words: It "platforms" the waves in conditions like that - in accordance with the laws of physics.

twistedtree said:

Add to that a hull form which provides no suitable location for fin installation, and you arrive where we are....and if something can't be stabilized, it makes sense to declare stabilization unnecessary.

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Seems a bit like declaring that hauling 40 tons of rocks is unnecessary because your truck will only hold 10 tons.