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Old 08-13-2012, 02:46 AM   #1
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which stabilizers for us?

I know this has been discussed before, but everybodies situation is different. Here's mine.

Well, the admrial does not really like the roll of our boat in the open ocean, in a beam sea.

Here's what happens.

In a moderate beam sea of around 4' (long ocean swells) which is pretty common on a nice day our 4788 gets into what I've heard describes as "parasitic rolling". This is most pronounced at rest (when we're fishing), and continues through displacement speeds. Running the boat harder, say 13-14 knots causes the stern to squat and the rolling stops.

What I've noticed is that the seas are timed just right for the natural roll period of our soft chined boat and the rolling seems to be magnified. Its amazing just how much this boat rolls in what seem to be pretty calm seas. Actually it rolls more than our old 28' cabin cruiser in these specific conditions.

Because of this I'm going to invest in some kind of stabilization.

I have a quote from the folks that make the Mitsibushi gyro type unit at $43K. Installation would be really easy. I'm skilled enough to do the job no problem. I have room for the beast in the lazarette right over a couple of stringers. This would produce significant roll reduction both at rest and under way. The most roll reduction is in the exact seas I'm describing. I have a simulation from Mitsubishi with graphs I'll try to figure out how to post.

Another option is the Naiad stabilizers. I've talked with the folks at Naiad and am having my favorite boatyard work up a estimate. I'm assuming the estimate will be in the same ballpark, possibly a tad more.

The mitsubishi seems to fill my needs better, but its a newer technology. The fins are proven technology, but won't help while fishing, or at anchor.

Which one would you go with???
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Old 08-13-2012, 02:59 AM   #2
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I went for sails since other (centrifugal or fin) were impractible spacewise in a mid-30-foot boat, and apparently for the sixth of the cost of your gyro.

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Old 08-13-2012, 03:14 AM   #3
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Fins only work while moving through the water. Gyroscopes don't need boat movement to work, but I wonder how much they can eliminate roll in significant seas. While drift fishing, perhaps a sea anchor strategically employed might help. (Strangely, I expect to be tossed about while in the open sea.)

Severely wrenched my knee on this 900-plus-foot ship with stabilizers during 50-something-foot waves.

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Old 08-13-2012, 06:06 AM   #4
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Very hard to stop roll at rest . Gyro maybe?

The flopper stopper style rigs can use special sinking platforms that seem to work.

If you are anchored , a second anchor could make it a pitching motion.

Very common in the Carib. behind a smallish island.
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Old 08-13-2012, 09:30 AM   #5
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Very hard to stop roll at rest . Gyro maybe?

The flopper stopper style rigs can use special sinking platforms that seem to work.

If you are anchored , a second anchor could make it a pitching motion.

Very common in the Carib. behind a smallish island.

Im leaning towards the gyro. That way drift fishing is doable.

Right now I have to set the anchor to fish. Then the boat weathervanes and no beam seas. If I drift then the boat naturally turns beam to the wind and waves.
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Old 08-13-2012, 12:02 PM   #6
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along these lines.....do the wing keels (small keel-like runners 8-10" tall located about 1/2 way between true keel and chine) that some sailboats have, work well at sea? Would they be a worthwhile addition to a trawler? I have seen two trawlers with them but couldn't find owners to inquire.

I'm sure that isn't the term for them, and I'm not asking about a true wing-keel i.e. the horizontal foil on the bottom of sailboat keels.

Kind of like what is seen in post 98 in the link below. Maybe not as big though, that size may be what is required to gain appreciable effects.
http://www.boatdesign.net/forums/boa...ch-5315-7.html
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Old 08-13-2012, 12:09 PM   #7
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Greetings,

Bilge keel - Wikipedia, the free encyclopedia
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Old 08-13-2012, 12:12 PM   #8
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Thanks RT exactly what I was meaning.


"A bilge keel is constructed from flat plate so as to present a sharp obstruction to roll motion. The roll damping provided by a bilge keel is more than that of a barehull ship, but falls short of other roll damping devices. Nevertheless it is considered prudent naval architecture to install a bilge keel whenever possible as it is the only device effective in the severest of seas."
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Old 08-13-2012, 01:04 PM   #9
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ksanders - have you seen this thread on the Bayliner owners forum:
soft chines, hard chines and underhulls [Archive] - BAYLINER® OWNERS' CLUB

My gut feel is that the gyro will cost you a phenomenal amount of money, and that's not including the hull bracing required. And that's even if you found a place to mount it. IMHO you might be better off buying a second boat just for fishing!

Edit: just reread your original message (I had read it on my phone) and noted the $43K cost and that you feel you have the installation figured.

I'm now hoping you do go that route and give us an update once you've had a chance to use them! <fingers crossed for you>
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Old 08-13-2012, 01:28 PM   #10
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ksanders - have you seen this thread on the Bayliner owners forum:
soft chines, hard chines and underhulls [Archive] - BAYLINER® OWNERS' CLUB

My gut feel is that the gyro will cost you a phenomenal amount of money, and that's not including the hull bracing required. And that's even if you found a place to mount it. IMHO you might be better off buying a second boat just for fishing!

Edit: just reread your original message (I had read it on my phone) and noted the $43K cost and that you feel you have the installation figured.

I'm now hoping you do go that route and give us an update once you've had a chance to use them! <fingers crossed for you>
Thanks, I did read that thread, and might have participated in it.

Underhulls might work. But they might not work that well for me either. My favorite boatyard of course wants me to install underhulls and even a hull extension. They have quoted me $30K for the complete job.

I have a little challenge in converting my boat from a soft chined hull to hard chined hull. The soft chined hull has less initial stability, but more absolute stability. I'm concerned that the conversion would in the end make for a less seaworthy boat, when the going gets really tough.

I'm also concerned that if I spend the $$ I won't get the roll reduction I'm expecting and will still be dealing with this issue.

The gyro is pretty attractive right now.
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Old 08-13-2012, 01:29 PM   #11
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I had a few spare minutes so I groveled the web looking for references to the ARG system and Seakeeper - there's a thought-provoking comparison on the Seakeeper site.

A few things to consider: the spool up time for the ARG is apparently 25 minutes, assuming you are talking about their ARG12500T you are at the uppermost end of the specified displacement, it consumes 3KW of electricity and since it's air cooled, that means you're going to have to deal with that heat in the lazarette (ok, might be easy in Alaska). 700 pounds in your lazarette might not be a problem, but if you talking about the next size up unit that's 1600 pounds.

I would also be very nervous about putting this much additional strain on the stringers without hiring some additional engineering, or seeing it proven in several other equivalent boat.

I'm still rooting for you do this so I can see what happens!
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Old 08-13-2012, 01:43 PM   #12
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Quote:
Originally Posted by ksanders View Post
My favorite boatyard of course wants me to install underhulls and even a hull extension.
I know nothing about these boats, but there are a bunch in my club and I know that the hull extension is particularly appreciated.

Quote:
Originally Posted by ksanders View Post
The soft chined hull has less initial stability, but more absolute stability. I'm concerned that the conversion would in the end make for a less seaworthy boat, when the going gets really tough.
While that may be a common yardstick when comparing hulls of different design, I'm not sure it holds true here. If you add chines to an existing hull, my gut feel is that you're not significantly changing the metacentric height, and the only point at which the hard chine would work against you is if the CG passed outboard of the chine (a truly horrifying situation!). I'm not a NA, but you might want to look into this more.

What the chines will do is change the motion of the boat since it will resist initial rolling. And the resulting roll will be sharper. But I don't think it will negatively affect ultimate stability. Just a guess.

Quote:
Originally Posted by ksanders View Post
I'm also concerned that if I spend the $$ I won't get the roll reduction I'm expecting and will still be dealing with this issue.

The gyro is pretty attractive right now.
The chine modification is common, but I'm guessing you're going to be the guinea pig on the gyro for your boat. Frankly, that would concern me more.
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Old 08-13-2012, 02:38 PM   #13
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The chine modification is common, but I'm guessing you're going to be the guinea pig on the gyro for your boat. Frankly, that would concern me more.
That is my concern as well.

I'm not going to do the chine modification.

My choice is between stabilizers and gyro.

The stabilizers are a known quantity. I have even read reports about the improvement on my exact same hull.

The gyro, while having the opportunity for at rest roll reduction does not have the history, and the testimonials that fin stabilizers have.

I enquired of the naiad rep about their at anchor system, but from his description its not viable for my boat. Just one of the issues with it is the fact that it would use 8KW steady state.
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Old 08-13-2012, 03:04 PM   #14
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Hello:

The attached photos show what a few owners of Campion 30 trawlers have done to calm down the roll a bit. The "wings" are aluminum plate I believe and owners say it does help. Never experienced myself because our Campion is wingless (and doesn't get much use since the Formosa joined the "fleet" last year).
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Old 08-13-2012, 04:05 PM   #15
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Have you considered Paravane Stabilizers?

Cheep but effective.

Low tec.

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Old 08-13-2012, 04:21 PM   #16
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Have you considered Paravane Stabilizers?

Cheep but effective.

Low tec.

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Not on my boat Dave.

If my boat were more commercial looking that would be a great solution.
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Old 08-13-2012, 04:38 PM   #17
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Im leaning towards the gyro. That way drift fishing is doable.

Right now I have to set the anchor to fish. Then the boat weathervanes and no beam seas. If I drift then the boat naturally turns beam to the wind and waves.
Given what you have laid out, I think the gyro makes sense. It's new technology for the recreational market. I can't wait to hear your report.
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Old 08-13-2012, 04:59 PM   #18
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Not on my boat Dave.

If my boat were more commercial looking that would be a great solution.
You see them on Nordhavens all the time. I wouldn't call them Commercial. What do I know.
It's only money. Spend it. Go for the Gyro see if it works.

There is the rub.
What if you don't like the way it works? Do they offer money back guarantee?

Anyone else with your kind of boat have one?

Sd
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Old 08-13-2012, 05:39 PM   #19
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As most of you know I have looked and talked about twin keels, passive, more for added assurance the Eagle does not roll over if grounded/on the hard/grid as well as reduce the roll. Twin Keels are mostly on sail boats to eliminate the long deep center keel. http://www.kastenmarine.com/roll_attenuation.htm.

I have talked to Kastern, that has twin keels on many of his trawler designs. The twin keels would have a slight negative ballast, about 6 to 10 ft long, 2 ft tall, located between the pick up points of the engine room bulk work which is 50 to 75% to the stern. I would think in Alaska and Canada twin keels would be a big advantage?



Beteeen the fins and gyro I would go with the fin stabilizers. Some boat that have fins also have kilge keels to protect the fins.
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Old 08-13-2012, 11:06 PM   #20
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The plot thickens

When I asked the mitsibushi folks if they had any test data for boats similar in size etc... to my boat I was told that they dont have any "smaller" boat installations documented. It seems that most boats are larger and use either a larger gyro unit, or use two of the smaller ones.

I have to be honest, this scares me.

What I think I'll do is either ask for a steep discount as a "test" boat, or ask for a money back refund clause as part of my purchase agreement, if I go this route. I really like the gyro concept, but I'm not interested in being installation #1 as a full price customer.

I've conveyed my concerns to the Misibushi folks and will see where this goes.

If I go with fin type stabilizers I KNOW that they will work. They just won't work while drift fishing, or at anchor.
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