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2001 Horizon 76 - Sea Trial

Discussion in 'Horizon Yacht' started by TahoeJohn, Oct 8, 2020.

  1. TahoeJohn

    TahoeJohn Member

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    Thank you, great information. At this point, I'm looking for recommendations on a technician who knows these 20 year-old Naiad stabilizer systems inside and out. The seller's agent did admit that the Naiad guys sent out seemed to spend more time on the phone with the home office, looking for answers, than they did actually fixing anything. I think the key will be to get someone on the boat who can tell me exactly what is working and what isn't. Suggestions as to whom to call are welcome.
  2. Capt Ralph

    Capt Ralph Senior Member

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    While there are many shops that say they work on Naiad equipment, The Naiad factory shop was just to the west of you.
    Sadly, getting them out to your boat takes a while.
  3. Capt J

    Capt J Senior Member

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    I don’t think that it’s abnormal to need to use a lot of trim tab on one side on a sky lounge motoryacht that size, if you have sea or wind off of the beam. That yacht has a lot of wind age. What did it do going in the opposite direction?
  4. TahoeJohn

    TahoeJohn Member

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    Not really sure what the right answer here is... We made an offer on the boat because it fits our needs / wants better than the other ~two dozen boats we've been aboard. It has a lot going for it for a 19 year old vessel.

    And I don't know how to answer your 2nd question. I'm not going to disclose where we are with the price, but it's off significantly from asking and I believe very fair for this size boat. That being said, the owner is working with us on this heeling issue and I think we're all motivated to getting it fixed. If we can do that, then this is for sure the boat for us.
  5. TahoeJohn

    TahoeJohn Member

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    I believe that it was actually Naiad who has been doing all this work. The problem (prior to us making an offer) is that the techs out at the boat only appeared to be trained on the new stuff, with the assumption that they primarily are working with customer issues on new yacht builds and deliveries. As I mentioned, I think that we need to find the right person, whether he/she works for Naiad or something independent, who really understands these older analog systems.
  6. Pascal

    Pascal Senior Member

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    trim tabs at hull speed pretty much don’t do anything.
  7. Oscarvan

    Oscarvan Senior Member

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    Trust your instincts and step back. Make sure you know the "walk away" dates in your contract.
  8. Capt Ralph

    Capt Ralph Senior Member

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    Then what are the stabs doing then? They keep the boat vertical. Both need water flowing.
    On a stabilized boat, the only reason I see tabs are for bow trim (up/down - not P&S) and maybe to help the stabs with a constant beam wind.
  9. Capt Ralph

    Capt Ralph Senior Member

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    The older systems (IMO) were the best.
    No computer or logarithmic functions programing (operator tuning). Just a trusted hydraulic gyro and some electricity to turn it on (two solenoids on the top).
    Performance mostly depended on boat use / fin size selection, once set, never have to touch it again.
    Only a few things to go wrong, most diagnosed with a pressure gauge.
    Sometimes the hardest part of fixing something; Understanding what the failure is. It may not be all the tech's issues.
    Heck, You may already have a loose fin.

    That later super Naiad model (Multi-Sea System II) Burned my temper on performance and repair cost.
  10. mapism

    mapism Senior Member

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    Not even that, actually, 'cause that old "Center-Off-On" stuff had no interfaces at all.
    The system is totally unaware of the boat speed, gear position, rudders angle (if any).
    So, fins only depend on the embedded gyro inputs, and it's irrelevant whether the boat is rolling or constantly leaning.
    If necessary to keep the boat horizontal, fins can stay slightly rotated forever.
    In other words, yep, tabs should strictly be used for trimming, in any boat with those stabs.
  11. TahoeJohn

    TahoeJohn Member

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    This is interesting, thank you. My takeaway from this is that the controls are based on differential / change of angle of the boat, for which the fins will compensate. They do not try to "right" a boat that's heeling. Good to know and makes sense in this case.

    The seller is taking the boat out again tomorrow with more personnel on board. Hopefully they figure out what's going on.
  12. mapism

    mapism Senior Member

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    Nope, actually that system should indeed straighten not only a rolling, but also a heeling boat, regardless of the reason - be it beam wind, steering, weight distribution, whatever.

    The system is not driven by acceleration sensors and several other inputs, as modern stabilization systems are.
    There is "only" a very accurate gyroscope, which senses in real time even the slightest deviation from the horizontal position of the vessel.
    I mean, transversally horizontal, of course.
    The system doesn't care about longitudinal deviations, i.e. pitching, because fins can't contrast that.

    Anyway, based on these gyro inputs, fins constantly try to straighten the boat, regardless of whether she's rolling or heeling.
    That's the reason why, if fins are working as they should, there's no need to use tabs to correct heeling.
    Tabs should only be used for (minimal) adjustments to the longitudinal angle of attack, depending on speed and sea conditions.
  13. Capt J

    Capt J Senior Member

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    The old stabilizers just keep the boat stable, they don't correct an inherent list, they just keep the boat from rolling at whatever beam trim it's at. You need the trim tab to do that. The problem with almost all of these Taiwan boats is that the fuel tanks on both sides are generally connected VIA a crossover hose that everyone loves to leave open. So start out with a little list and more fuel runs to the lower side creating more of a list, boat lists a little more and more fuel runs to the lower side, creating more of a list.......combine that with the windage and additional high weight of the skylounge on a 76' MY and it's going to need the trim tabs to run level. I think it's very normal and I've experienced it many times. I've never seen old school stabilizers fix a list when running 20 knots.
  14. Capt Ralph

    Capt Ralph Senior Member

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    Righting the boat is the overall rough goal of operation. The servo valve on the fin unit itself changes the rate, the gyro sense the error.
    The bass ackwards result, the boat stays vertical but some side motion may be detected by some sensitive people as the hull is pushed back under (sideways) the roll. That is why I call BS on the trim tab story.
    BTW; I usually ensure these sensitive people are not on board again.

    The later models try to predict the next wave action and either over compensate in adjustment or don't swing that far expecting the next roll on the other beam.
    logarithmic programing, self learning and manual input may help these systems. Rate of roll (periods) is the larger calculation with the fancier systems.
    The old Servo throttle did this pretty well pending fin selection.

    The bottom line, the ship stays vertical (or very close).
  15. Capt Ralph

    Capt Ralph Senior Member

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    It's a fluid gyro. Ideal; it will keep level where it was when engaged. Constant running under a forced angle may cause some loss of level after a while (hours).
    Back to the OP issue, the boat should have never rolled on throttle up. Tabs or not.
  16. mapism

    mapism Senior Member

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    Then you've obviously never seen a boat with Naiad fins driven by their so-called Hydro-Mechanical Gyroscope (aka HMG) controller.
    As I said, that bit of kit doesn't even know if the boat is rolling or listing.
    It just rotates the fins as much and for as long as required to straighten the boat.
    Btw, at 20 kts the fins angle that it takes to correct a list is very minimal - as opposed to trim tabs, which in case of a relevant listing, on top of introducing more drag, could even be unable to fully straighten the boat.
    The righting moment that fins can transfer to the hull is huge, compared to tabs.
  17. mapism

    mapism Senior Member

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    That's pretty much theoretical, though.
    In practice, in a boat listing due to unbalanced load or strong beam wind, the fins never stay just at a constant angle for hours.
    That's what should happen if the boat would be cruising in perfectly flat conditions, but actually the fins will contrast BOTH the roll and the list.
    So, they will constantly flap in both direction - just more on one side than on the other, on average.
  18. Danvilletim

    Danvilletim Senior Member

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    For a 19 year old big boat that you are getting a fair amount off asking I seems that you will have a good handful of these size issues to deal with. Live with it or write a large check to replace it. Don’t be tempted to write an unlimited number of $3-5k attempts to make it better. I’ve made that mistake a few too many times.
  19. TahoeJohn

    TahoeJohn Member

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    Thanks for this. I think that one of the options here is to upgrade the stabilizer controls to a Naiad MultiSea II system. Perhaps this is what you're suggesting. If we end up buying this boat, that would probably make the punchlist.
  20. TahoeJohn

    TahoeJohn Member

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    We ran another sea trial yesterday. Pretty calm conditions off of Ft Lauderdale.

    Four runs:
    1) Fins locked in center, tabs up, southbound
    2) Fins locked in center, tabs up, northbound
    3) Fins operating, tabs up, southbound
    4) Fins operating, tabs up, northbound

    Each time we ran the engines up as 1000, 1500, 1800, 2000, 2100, 2200, WOT.

    The boat was dead level for runs 1-3. On run 4, it started to heel to port around 2200 RPM. Dropping it back down to 2000 it leveled out. Back up to 2200, heel to port. Trim tab down about 75% leveled it back up.

    At this point, I'm inclined to agree with Capt J in his assertion that this boat will occasionally need trim tabs to run level, depending on conditions. I don't believe that there's anything fundamentally wrong with the hull or running gear. As I mentioned in my previous post, an upgrade to the stabilizer controls to something more modern might be money well-spent.