Fin stabilisers

Discussion in 'Stability' started by dick, Jun 15, 2014.

  1. dick
    Joined: Aug 2008
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    dick Junior Member

    I am thinking of fitting fin stabilisers to my Offshore 52 we do long distance cruising at 8-10 KNOTS all the manufacturers i have looked at Niaid,wesmar,AB track say theirs are the best and claim to remove 90% of the roll has anybody had good or bad experiences with brands or performance related issues i would love to hear from you.
    Regards Dick
     
  2. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Hi Dick,

    I don't know much about the Offshore 52, other than what is available on various websites. But if you're cruising at 8-10knots the Niaid wont help that much in reality. Since they need fwd speed to provide the lift and 8knots is not much!

    Firstly why are you thinking of fitting for stabilisers? If it if for roll damping, there are other measures you can employ. Simple ones such as bilge keels, or even Quantum Maglift all have aparsitic drag in shape or form, so your top end speed will be compromsied.

    Thus, what aspects of the performance of your boat are you willing to compromise to achieve better roll characteristics?

    There is not much one can do with a small boat...changing the VCG may help, but that too comes with pro's and con's.
     
  3. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    The active stabilizers are very good even with the boat stopped. But I guess this is too expensive for such a small boat and equipment also requires major changes in the structure of the bottom/side.
     
  4. rustybarge
    Joined: Oct 2013
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    rustybarge Cheetah 25' Powercat.

    The smallest boat that I know of with stabilisers is the Aquastar 43' manufactured in the UK....

    http://www.aquastar.gg/Aquastar430

    So it seems to work on the smaller hulls.
     
  5. keysdisease
    Joined: Mar 2006
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    keysdisease Senior Member

    Maybe take a look at

    http://www.seakeeper.com/

    Not cheap, much easier to install and pretty self contained in the one unit.

    :cool:
     
  6. Eric Sponberg
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    Eric Sponberg Senior Member

    In my experience from the design side, all three manufacturers are high quality. We put them (Naiad and Wesmar) on my Moloka'i Strait motoryachts--round bottom displacement cruisers up to 10 knots, and they worked fine. One of the builders like ABT--American Bow Thruster, which is what I guess you are referring to by "AB". I am not sure what your Offshore 52 looks like--the ones marketed in the US, built in Taiwan, appear to be planing cruisers--is this the same boat? If so, I don't know that I would put them on a planing boat because the stabilizers would cause a lot of drag and poor control issues at high speed. They are meant for slow speed boats. You say you cruise at 8-10 knots, but if the engines have power for high speed running, I wonder about running them at slow speeds--not best for the engines. But I digress.

    Since, in my opinion, the quality of the three brands is about the same, then I would shop on price and serivicability--who is going to install them (someone close by?) and are they authorized installers and service people? Get the best price, installation, and service package to where you are.

    Eric
     
  7. rustybarge
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    rustybarge Cheetah 25' Powercat.

    What would be a 'ball park figure' for the average installation?
     
  8. Eric Sponberg
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    Eric Sponberg Senior Member

    I have no idea. I am not up to speed on prices. You would have to ask the suppliers for a quote.

    Eric
     
  9. Tad
    Joined: Mar 2002
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    Tad Boat Designer

    I believe hydraulic stabilizers are second only to watermakers in their service requirements. Thus as Eric says, the dealer and his willingness to show up and fix the thing are really important.

    Offshorehull.JPG

    These are beamy, flat-bottomed(relatively) hulls intended to cruise at 14 knots and top out at 17-20. At intended cruising speed dynamic stability is quite good, at 8-10 knots there is little dynamic stability. The problem is that the hull is too stable, motion is very quick and unless your stabilizers are really smart and start to anticipate, they will do nothing. The other problem is that because the hull is so stable, the fins must be large to work at all (to overcome the snap roll stability built into the hull).

    You have to drag those big stabilizers through the water wherever you go, no matter if the boat is rolling or not.

    I would be inclined to
    A) spend the $50k that stabilizers cost(plus anticipated service costs and added fuel cost for the life of the ship) on fuel and run the boat faster in rolling conditions.
    B) spend some effort on slowing the rolling by raising the CG (lead on the flying bridge), or perhaps a flume tank on the roof.
     
  10. rustybarge
    Joined: Oct 2013
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    rustybarge Cheetah 25' Powercat.

    Put these electric stabilisers on your list. http://www.cmcmarine.com/stabilis-electra/

    A boat owner on the MBM boat forum fitted them on a Canados 80' and is very pleased with them; they are zero speed, and work at anchor to stop rolling.
     
  11. dick
    Joined: Aug 2008
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    dick Junior Member

    Hi Eric
    My Offshore 52 is the Taiwanese build and will cruise at 8 Knots with 1450 rpm with a maximum of 16 Knots we are in remote northern Australia and we need to go long distances between fuel stops so I need to keep the fuel consumption down which probably affects the handling I have spoken to Nordhaven owners and others that swear by their stabilisers operating at low speeds, the stabiliser manufacturers claim they save fuel by keeping the boat on an even trim, the hull has already been prepared with mounting block built into the hull during manufacture the cost is around $50K US.
     
  12. Brian@BNE
    Joined: Jan 2010
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    Brian@BNE Senior Member

    I have Naiad's installed, and they are brilliant. The control box has accelerometers in it and so it picks up roll very early and starts to adjust the fins before the roll has gotten very far. Basically the boat just stays flat, in terms of roll at least. They do nothing for pitch fore and aft unless you want to spend serious money and go for a four fin option. Early models might have been troublesome, but in the 300 hr since install I have had no issues whatsoever. A good install, and adjustment of the control box by Naiad engineers during sea trial, no doubt have helped.

    My boat is an Ocean Alexander 50 Mark 1. LOA 53', Beam overall 15'6" and half load displacement around 27 tons. It is an SD hull, which did 17kn with 540 HP installed. I repowered with smaller engines as I was not interested in the fuel bills that such speeds caused.

    When planning the install we used Naiad's tech people to ensure they were sized to be effective at the lower speed levels. The rationale was that in bad conditions, where you appreciate them the most, you will have likely slowed down from normal cruise speed as well. So, with a 7.5 sq ft area for the fins I am getting good response at 6kn. They center (switch off) below 4kn and when in reverse. At faster speeds, and I generally cruise at 8 to 9 kn, the fins are getting a good bite in the water.

    I may have lost about 0.5 kn in speed in calm conditions, not really sure as I repowered so cannot do exact comparison. Bear in mind that once there is some wave and swell to contend with there might even be a speed improvement due to the boat staying a pretty constant angle (flat...).
     
  13. rustybarge
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    rustybarge Cheetah 25' Powercat.

    It wouldn't be polite to ask exactly how much they cost.:(

    More or less than US$70k....? :)
     
  14. Brian@BNE
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    Brian@BNE Senior Member

    Rusty
    They were a little over US$60k, purchased and installed in the US about 18 months ago. Labour was a bit under half the cost. There was cabinet work involved for the retrofitting of them neatly.

    Cost will depend on where you get them done. I bought them in the US and had it done at Port Townsend, WA before returning to Australia. Had I got back to Australia without them and decided they were essential it would have cost much more. eg ABT here quoted A$60k for the stabiliser components ex: factory gate in California. Then there would have been freight, import fees and 10% GST. Then installation.... But then, stuff in Australia is typically 50% to 80% higher than in the USA. Its a small market here in a global sense, but one of the issues is that although we have a strong (overvalued) currency at present, importers generally have not reduced prices. They argue that the currency will drop back from low 90's to around 80 cents and when it does they will not increase prices. Sure..... Meanwhile, they are pocketing windfall gains at present. OK, rant over....
     

  15. keysdisease
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    keysdisease Senior Member

    I'm seeing a lot of these units installed here in South Florida. No fins, no drag, small, self contained, reasonable power consumption compared to fin units, pricing looks comparable to fin units and maybe less due to ease of installation.

    I don't work for them and have no stake in their success or failure, but they due look like a very viable option and if I was looking for stabilization I would do due diligence and check them out.

    :cool:


     
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