This comes at a hefty price, but seems impressive.....

Discussion in 'Stability' started by Mr Efficiency, Sep 11, 2020.

  1. brendan gardam
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    brendan gardam Senior Member

    so if i had one of these gyros so guests don't have to experience a boats natural movement do i have to keep a generator running to power it even when i am drift fishing, because that would get quite annoying.
     
  2. BMcF
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    BMcF Senior Member

    It only imparts a moment opposing roll motion (i.e in opposition to roll angular rate). There is no "static" restoring force like you'd be able to obtain from a fin while underway.
     
  3. Mr Efficiency
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    Mr Efficiency Senior Member

    OK, so in the case of a deep-vee powerboat, if a weight shift within the boat causes heeling, it will only act to keep that angle of heel, in a beam sea ?
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    Huge potential in these things, I think, I recall seeing one demonstrated on a TV inventions show a very long time ago, it was the brainchild of a retired engineer, but it must have been a busy retirement to get it to that stage. That might have been 30 years ago, which makes me wonder why they have been so slow to get to the recreational market, is there an electronics module in them that would have been beyond the capabilities of such things at the time ?
     
  5. brendan gardam
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    brendan gardam Senior Member

    You see great potential in gyros running a generator but can't see any merit in flooding keels.
     
  6. brendan gardam
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    brendan gardam Senior Member

  7. BMcF
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    BMcF Senior Member

    They are apples and oranges..part of a whole fruitbasket full of vessel stabilization solutions that includes active interceptors, paravanes, stabilizer fins, active trim tabs, anti-rolling flume tanks (both passive and active), flapped foils, pendulums, and so on. What works on one vessel won't work well on another. There is also the degree of effectiveness to consider; some active systems can nearly eliminate roll and/or pitch motions entirely...while others claim a 20% improvement as victory enough.
    '
     
  8. philSweet
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    philSweet Senior Member

    Brendan,

    Passive flooded keels have a very limited capabilities and a lot of undesirable side effects; and frankly, it's rarely worth the bother of fitting the feature to the vessel. The only thing you can really accomplish directly with them is to change vessel's trim at rest. Fitting the flooded tank and fairing it in results in more deadrise, which shifts the center of pressure forward at speed; so the cg gets shifted forward, meaning the boat sits flatter at rest. If sitting flatter gets more hard chine in the water, that can help the boat feel less skatey at anchor.

    Honestly, if you are going to go to the trouble to flood part of the hull, you should use pumps and valves to get the most out of it.

    There are a whole bunch of undesirable side effects to passive tanks. Nosing one up on a beach or a bar creates an interesting predicament. The boat requires more depth to launch and recover. Moray eels are fond of the holes. Motor fitting, especially big four-stroke singles, is problematic—will the leg clear the water when tilted? Is a jack plate required?

    The typical application is for boats that aren't too worried about these things; namely, offshore trailer boats such as the Bar Crusher. That's a pretty small market segment. Avon RIBs also have this feature, and the designer was an acquaintance of mine when he retired and we both lived in Key Largo. In the case of the Avon, stability was a major issue, but not many boats have the cross section of a RIB. In the case of the Avon, you were paying a premium for static stability in a compact footprint.

    What free-flooding tanks generally do—

    1. They permit a deeper vee at the same trailer weight. The deeper vee can improve ride comfort, and may also facilitate a more practical cg location on high-powered outboards.

    2. If beam limits are an issue, and they normally are on trailer boats, you can slightly improve the stability of the vessel by ballasting down. But the main play is to adjust the trim of the vessel at rest. The cg is already further forward because of the deeper vee, and to this, you can flood more volume forward, although this is not as easy as it sounds. But getting more chine in the water forward has a noticeable effect on the boat's feel. And having the resting trim and the running trim similar has important engine-fitting implications. Drowned engines offshore are no fun.

    So, while the marketing department may go to great efforts to tout the stability benefits of a flooded keel, that's not why it's there. But since it is there, sure, take advantage of it in any way you can. Particularly in ways that will cover the costs of the thing.
     
    Last edited: Oct 11, 2020
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  9. brendan gardam
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    brendan gardam Senior Member

    there are several glass boats here that use this system. The whole idea is to permit a super deep v in a narrow beam for better rough water capabilities. Look up seadevil boats among others. I can see gyros being fine in a larger boat that runs a genset all the time but useless on anything under 30ft because of the power draw.
     
  10. brendan gardam
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    brendan gardam Senior Member

    You say flooded keels are only beneficial for a small segment of the market,where I live offshore fishing is a large market for Australia anyway. We have some of the world's worst bar crossings and bass straight throws up some pretty wild conditions. That's why these type of boats are popular. They started with abalone divers and spread to the amateur fisherman.
     
  11. brendan gardam
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    brendan gardam Senior Member



    These are built near me and very popular in the pleasure boat version and have flooding keels. Seem to handle twin 300s ok at rest and no problems at the launch ramp that I have seen.
     
  12. brendan gardam
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    brendan gardam Senior Member

    I am posting real examples Phil.
    Do you have anything to prove what you have been saying is correct.
    i am not trying to be rude , i just want to post facts not conjecture.
     
    Last edited: Oct 11, 2020
  13. Mr Efficiency
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    Mr Efficiency Senior Member

    That Whitepointer has the ballast tank, Brendan ? Not sure that would be needed, on that boat. I don't say they are not potentially useful, but not really comparable with the gyro stabilizer, but also far cheaper.
     
  14. brendan gardam
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    brendan gardam Senior Member

    that one has, they offer their boats with or without. they are very deep v and narrow.
    the 1 thing i would still like to know is what powers the gyro in a small boat. as i posted earlier i can see the merit when you are running a genset all the time anyway but surely you would not put up with it in a trailer craft.
     

  15. Mr Efficiency
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    Mr Efficiency Senior Member

    The power draw equation certainly has to be reckoned with, a generator is not an option most would consider. Batteries I don't know, but it would all be calculable. The Whitepointer is a boat taken from the Haines 243 hull, not an extra deep vee, and I'd have thought stable enough without ballast.
     
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