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SeaKeeper vs Naid At Rest Stabilization

Discussion in 'Stabs, Tabs & Gyros' started by Gulfer, Feb 10, 2020.

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  1. LuvBigBoats

    LuvBigBoats Member

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    Agreed--great to see.
    Are those vector fins?
  2. olderboater

    olderboater Senior Member

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    Sidepower has similar videos on their website. Well, now they have a split boat which I don't like. Still, here's their link.

    http://slides.sleipner.no/stabilize...47.2.1609865386810&__hsfp=2324073213#research

    For those thinking of trying without stabilizers, I offer this too. Not only is there the matter of known comfort as you cruise or anchor, but the issue of seasickness. Good stabilization virtually eliminates seasickness under any type of normal conditions. Good stabilization reduces seasickness by 90% at anchor and at speeds up to 20 knots or so. Now that's based on typical roll angles. If you're rolling 40 degrees then no such promises.
  3. mapism

    mapism Senior Member

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    No, they are not. Sleipner's fins are patented, and of course they claim that they are more effective.
    But I've yet to see one single independent comparison proving that for any given installation there is a meaningful difference between straight and curved fins.

    The simple truth is that fins are the most effective way of stabilizing roll, and it doesn't really matter whether they are straight or curved - it's mostly a matter of having a sophisticated control unit capable to consider all crucial parameters, elaborate in real time the optimal fins movements, and drive some powerful and fast actuators. Btw, that's mostly relevant when operating at zero speed, because under way, the 30 years old gyroscope-based Naiads, with zero electronics and obviously straight and very basic fins, which I enjoyed for 17 years on my old timber trawler, were impressive also by modern standards.
    Besides, leaving aside what a source that I consider highly reputable confirmed me in this respect, I had a chance to try, on top of the previous CMC fins, also most others: Sleipner, ABT, Wesmar (not Humphree, though - not yet, anyway, but I can't see how they could be any better).
    And all of them, bar none, are amazingly good at their job.

    So, IMHO it's impossible to go wrong with fins, it's just a matter of having them sized and installed properly.
    Which is a given when fitted by the builder (though also among builders some are better than others), but it can be tricky when retrofitting, particularly on boat models where fins were never factory installed - as is the case of the previous Canados and also of JustAzimut's boat.

    Regardless, the key reason why imho electric fins are a no brainer when retrofitting is the MUCH easier installation, with a lot less critical components.
    Which eventually also means higher reliability and overall lower costs, though never trivial, obviously.
    Last edited: Jan 5, 2021
  4. olderboater

    olderboater Senior Member

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    You're right, Mapism, in pointing out the effectiveness of all fins. The big question on fins is whether they're also effective as "zero speed" and whether that's important to the buyer. We've used Naiad and Sleipner/Side-power extensively while only brief time with ABT and Wesmar and Humphree and none with CMC. We do have a boat being built with Humphree. We've also tested Seakeeper Gyros. I've found all deliver what they promise basically if installed correctly and sized right.

    If you want to get seasick just turn the Humphree off on this page. https://humphree.com/

    I've also seen no third party objective comparisons. All comparisons are paid for by someone seeking confirmation. However, I can tell you from experience the incredible job Side-Power does on certain boats. As they've been planing hulls and I've compared Seakeeper on those hulls, there's really no comparison at speed. Similarly another fin that wasn't zero speed would likely not match up at anchor. I believe there is merit to their design, but I also believe whoever, has the latest and greatest may have the best too for a time. I think the success of Gyro's drove all fin manufacturers to improve.

    I just don't understand using Gyro's in planing hulls unless it's in addition to Fins.
  5. mapism

    mapism Senior Member

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    Well, the video I previously linked was at zero speed, with the engines off and the boat drifting into a long and gentle swell.
    And I witnessed that same CMC installation working very well in even worse conditions, including irregular navigation wakes.
    But also ABT fins, which I tried on very different boats (S/skr 80 Yacht and Outer Reef 700, both factory installed), never failed to impress me, both under way and at anchor.

    The way I see it, I would put it this way: in a scale from 1 to 10, where 1 is a non-stabilized boat and 10 is a boat on the hard, any half decent fin stabilizers, properly sized and installed, deserves an 8, if not 9.
    So, trying do determine scientifically if one system is 8.4 and another is 8.7, aside from being almost impossible, is totally irrelevant in practice.
    Hence my suggestion, particularly for refit, to follow the easier and less expensive route.
    But only as long as the installers aren't at their first rodeo! :)
  6. Capt J

    Capt J Senior Member

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    Holy Cow does that thing rock and roll in a very very moderate sea without stabilization. What a mess.
  7. Capt J

    Capt J Senior Member

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    With a seakeeper you don't have any additional protrusions in the hull. No fins sticking down to get wacked, or fishing lines caught around or anything creating drag......so they have their place in the food chain. On fast boats with great hull designs, you don't use the seakeeper at speed. On most fast SF any stabilzation at speed is detrimental to ride as the hulls already ride so great, it makes the boats too stiff and ride worse a lot of times. It depends on the boat and situation. For slow speeds and at anchor, seakeeper does a really good job. They also do a great job with Arneson rocking when running at speed.
  8. mapism

    mapism Senior Member

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    C'mon, you know even better than myself two things:
    Firstly, sea state always appears in video smoother than it is.
    Secondly, adrift boats tend to settle against beam sea - which is precisely what we wanted, in that occasion.

    If you think that the Canados 70S, back in her days, earned the status of one of the best and most iconic boats in that size bracket by being a mess, well, think again. Or maybe you're just too young... Which is good for you, of course.
  9. olderboater

    olderboater Senior Member

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    Or (C) None of the above. There were few if any in the US.
  10. Capt J

    Capt J Senior Member

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    THIS
  11. mapism

    mapism Senior Member

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    Point taken.
    Still, you've yet to read from myself a post where I label a boat I've never seen - let alone sea trialed - "a mess".
  12. Capt J

    Capt J Senior Member

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    Judging from the video, it is a VERY moderate beam sea......2' maybe.......to have a 70' MY do that, yes I would call it that. A 75' Hatteras MY wouldn't even move in that. And No, I have never, ever seen a Canados in the U.S. anywhere.
  13. mapism

    mapism Senior Member

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    Think what you like, but you are judging by the video, while I was actually onboard when I made it.
    And we were drifting in an old residual swell from previous days of bad weather, with no fresh wind.
    That's what makes the sea surface blurred and not confused/rough at all.
    But there were a few other, also larger, boats around us. And they were visibly pitching while heading offshore, with the very same swell on their nose.
    And leaving aside the fact that the motion of any boat doesn't depend just on wave height, but also on their length and period, I hope I don't need to explain you that what it takes to make a boat roll is just a fraction of the sea motion, compared to pitching.

    That said, the boats comparison is totally O/T in this thread, but hey, you got me started... :)
    Now, as it happens, while you've not even seen any Canados, I have actually been onboard a couple of Hatteras MYs, which in fact around here are more popular than their SFs.
    So, let me ask you this: can you think of any other MY where fin stabs are more popular than on Hatteras?
    It's not a rethorical question, mind. I've always been puzzled by that, because one should think that neither the builder nor most owners agree with your statement about their roll resistance.

    Me, the very little that I know for sure is that even my old round bilge full displacement 53' trawler was MUCH less prone to roll than the Hatt 53 MY of a boating mate, when we were both cruising in tandem at the same speed with centered fins.
    The other occasion when I tried a Hatt MY with fin stabs was on a 70', but when I asked the owner to center them and check out the difference, he point blank refused, arguing that he didn't want to scare anyone onboard - go figure.
    But of course, the 75' that you mentioned might be different...
    Last edited: Jan 6, 2021
  14. Capt J

    Capt J Senior Member

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    I am judging the rolling by the aft deck ceiling overhead and the horizon behind it, and it is considerable. I'm just judging what I see and trust me, I've taken LOTS of videos like that with many different yachts.

    ALL Hatteras 75' and above come standard with stabilizers. All 66' Sunseeker Manhattans and above I believe come with stabilization standard. All Lazzara's as far as I know came with stabilization....all Westports come with stabilization.......it's more of a luxury builder thing......instead of charging the buyer with every nickle and dime line item option, they are included in the build.

    Now you're talking about a Hatteras they stopped building in 1985 ish? Yes the 53' Hatteras had an air draft of 26' and only a 15'10 beam and 5' draft.....yes they rolled quite a bit......but so did most everything prior to 1985. You're also comparing a semi displacement hull that normally is running 16-20 knots at cruise speed to a displacement trawler and running displacement speeds.
  15. mapism

    mapism Senior Member

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    Fine, why don't you share them with us?
  16. Capt J

    Capt J Senior Member

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    Send me a PM with your email address and I gladly will send them to you.
  17. mapism

    mapism Senior Member

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    You can just add @yahoo.com to my username.
    But in the context of this thread, wouldn't it be more interesting to just post a link here?
    It can't be classified material, if you're willing to share it with me... :)
  18. Capt J

    Capt J Senior Member

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    I don't have a youtube account or cannot remember the password and don't know how to upload a video onto here. If you want to see around 20 amazing video's of the Abacos and Exumas, Bahamas of trips I did that the owners son took with his drone. Go to Youtube and go to "THE real bahamas" channel. Just sent you a few videos. Sorry, those are the only ones I have on my phone.
  19. mapism

    mapism Senior Member

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    I got your three clips, thanks.
    But I struggle to understand in which way they can compare with the one I previously posted.
    I can upload and link them, possibly removing the two chaps visible in IMG_1771.MOV, if you wish.
    Just because otherwise it would be impossible for anyone else to understand/contribute.
    Your call, anyway.

    PS: I also had a look at the channel you mentioned and you're right, some really nice stuff there.
    Being public domain, I assume you don't mind if I add this link for the convenience of anyone else willing to check it out.
    Not that there's anything relevant to the topic of this thread, but I'm never shy of going a bit o/t in favour of some nice clips that convey what boating is all about! :)
  20. Capt J

    Capt J Senior Member

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    You can post the movies here, just edit or blur the "2 chaps" out of them. I believe I sent 4 videos so not sure which one didn't go through.......Unfortunately I looked and I don't have any seakeeper videos for comparison.....just still photos. Posting the link is fine........