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Stabilizers on planing yachts?

Discussion in 'Stabs, Tabs & Gyros' started by Jage, Apr 28, 2007.

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  1. Jage

    Jage New Member

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    I have been perplexed that I rarely see stabilizers on planing hulls, most notably the italian/eurostyled yachts. I have cruised in the med on a 53 hatteras which had stabilizers and certainly needed them. I would love to hear the opinions of yacht owners, captains and crew that have had experience with the italian/eurostyled yachts in the 65-80ft range in snotty conditions..Do these planing hulls really not need stabilizers? Thanks for any comments.

    Jage
  2. AMG

    AMG YF Moderator

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    Are you thinking of trimtabs? This is anyway what some planing yachts have, especially if they have a deep V hull. Traditional stabilizers are more effective on certain semi planing hulls in speeds below 20 knots.
  3. Jage

    Jage New Member

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    Thanks, I was indeed referring to active fin stabilizers and not trim tabs. I have been researching used yachts in the 65-80ft range from the mid 1980's -mid 1990's. (mostly 25 knot Itallian/eurostyled vessels) Maybe 1 out of 100 of these type yachts in that vintage utilize active fin stabilization. I was wondering why that was? From your answer it would seem that if a planing yacht traveled above 20 knots the utility and value does not present itself for active fin stabilization? How do these planing yachts act in rough conditions? Can they maintain 20+ knots or would they be forced to slow down and as a result be even more unstable.?

    It also could be assumed that perhaps some loss of speed on these type yachts from active stabilization may affect owners reluctance to stabilize the yachts because afterall "speed" is one of the major advantages of a planing hull to begin with.

    Thanks for your thoughts

    Jage
  4. ESYD

    ESYD Member Removed

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    The most obvious reason that you don't see stabilizers on planing yachts is that the loads on the blades and their stocks would be way too high at higher speeds. You would not be able to build the stabilizers strong enough to handle the loads. Also, the blades would cause a lot of drag at higher speeds and therefore they would reduce speed considerably. I am talking probably a few knots here, which is a lot.

    Control is another matter. Stabilizers get their power from the speed of the water going over them (actually, the load is a function of speed squared) and the angle of attack of the blades to the flow. The faster the boat goes, the less angle of attack is required to obtain any given amount of lift. So as the boat goes faster and faster, the angle of attack gets tiny, and very small shifts of angle of attack can cause enormous amounts of heeling force. You don't want that at high speed. It would be too difficult to contol the proper angle of attack at high speeds, I believe. The alternative to this is to design very small stabilizers (small planform area) to do the job, but then they would be worthless at lower speeds. And you still have a control and drag problem.

    A planing boat achieves a lot of dynamic stability from the hydrodynamics of a well designed bottom. You should not need stabilizers to adjust the roll or trim of such a vessel. That is usually handled sufficiently well by the trim tabs. Stabilizers are intended primarily for displacement and semi-displacement vessels where the speeds and loads are relatively low and easy to design and build to.
  5. nilo

    nilo Senior Member

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    dear jade,

    although eric has replied to your enquiry quite extensively, there is still a point which i feel needs clarification. that is, what happens when planning boats are not able to go up the plane due high seas.

    there is a simple answer, it is a very uncomfortable passage, if not dangerous. the boat becomes very unstable, it is like a a bath tub on the water. however, when you can go up to planning speed she is much more stable than displacement boats without stabilizers. so, you watch out the weather and if it gets bad you use your speed to run away to a secluded place. in fact a boat with planning hull is a coastal boat, in line with the italian way of using them.

  6. Jage

    Jage New Member

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    Thanks! That explains a lot. Would active/dynamic trim-tab stabilization system be the best way(effective) to stabilize these type of yachts? Suggesting that when conditions present themselves for high speed cruising the active trim tab system would not need to be activated, there by eliminating the drag issues. And of course during rougher conditions , the activation and increase in drag that may be caused by the active trim tab system would be perfectly acceptable if you can actually stabilize the roll in those rougher conditions?

    Well I really like that style of yacht and certainly the speed aspects of those yachts but I remember the type of rolling we experienced in the Hatt 53 (realzing it is a different style hull and yacht) when the stabilizers were inoperable due to a stolen part. Generally speaking what is the roll like at anchorage in an "itallian/eurostyled yacht?" They tend to have a lower-profile (in regards to wind), usually a tad beamier(but maybe because of the protruding exhaust ducts), and deeper drafts than the old hatteras I have had experience in . Just trying to guage the differences.

    Thanks again! This discussion is much appreciated.

    Jage
  7. Jage

    Jage New Member

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    Thank you for your reply Nilo. The areas I am most interested cruising in are the greek isles. Is that consistant with the "itallian" style of cruising? That is actually why I have been focused more on the Itallian/eurostyled yachts( fast, low profile, flybridge, walkaround deck, and aft deck). Could they be considered Island hoppers in the aegean and that part of the med? I think you would probaly know being in Turkey. Any thoughts are welcomed. Thanks

    So in short that style of yacht is stabile at speed(goodweather), scary when conditions require slow traveling? If that is a fair assesment...that is helpful to me in realizing the limitations of that style of yacht for where I would want to cruise.
  8. ESYD

    ESYD Member Removed

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    Active trim tab: You don't need one, generally. The helmsman sets the trim tab angle for the conditions at hand. For any given sea state and speed, you use the trim tab setting that will give you the best average speed and motions. They are NOT to be used actively because of the possibility of sending the boat out of control. Trim tabs are operated by joy stick or hand lever, and adjustments take mere seconds. If the motions or trim and roll of the vessel are too great and uncomfortable, then you have to slow down. It is the helmsman's and Captain's responsibility to operate the boat in a prudent manner for the conditions at hand. You cannot take the human out of the equation and expect all boat motions to be all automatic.

    Rolling at anchor is a function of the swell, not the wind. The southern coast of California is particularly notorious for its uncomfortable Pacific swell. Some stabilizers have active control at anchor, but again, these are mostly for displacement and semi-displacement yachts. I believe there are also other manufacturers that make retractable stabilizers, but these are very expensive and their pockets into which they retract take up a pretty good portion of the interior. Therefore, they are best used on larger yachts. I don't know if you can get retractables with at-anchor stabilization.

    Being a matter of the swell and not the wind that affects rolling at anchor, the shape of the hull, the width of the beam, the depth of the hull, and the height of the center of gravity all come into play. The narrower and deeper the hull, the softer the rolling motions, both at speed and at anchor. Shallower and wider hulls, such as you find in the go-fast Italian style boats, all behave more poorly with regard to rolling motions. The amount of roll is not necessarily so much, but the accelerations of roll are worse. It is the acceleration of starting and stopping on each roll cycle that is uncomfortable and leads to sea sickness. Amplitude (the angle of roLL) is not important. In general, the greater the roll angle, the slower the rolling speed and acceleration and the more comfortable the motion. The lesser the roll angle, the higher the rolling speed and acceleration, and the less comfortable the motion.

    I have been in the Mediterranean but not the Adriatic. I did not think that the swell in the Med was very significant, so I don't think this should be a real major concern for that region. I defer to others who may have more experience.
  9. Jage

    Jage New Member

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    Thanks again for the color. Have you seen the arrow and archer stabilization systems by quantum hyrdaulic? They claim it works on fast yachts. I watched the demo video on their site which show the tabs operating dynamically via a control system. I don't know how effective it is but certainly it looks interesting. Have you also noticed that recently the itallian/eurostyle manufacturers are beginning to offer stabilization systems on their planing yachts? I think San lorenzo and Ferretti are among some that are offerring stabilization options on their planing hulls. I wonder if it is currently the "hot "topic or buzzword for that yacht segment..and it would be quite the turnaround from past attitudes (like in the 1980's and 90's vintage planing yachts where you seldom see the stabilization systems).

    Thanks again Eric.

    Jage
  10. AMG

    AMG YF Moderator

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    I must agree, if you think you are going to get a smooth ride in rough seas at speeds over 25 knots, you better learn how to drive a boat. I would never trust any automatic stabilizing system under such conditions.

    Zero speed stabilizers is another thing and could be nice at times.
  11. Jage

    Jage New Member

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    Hi AMG, I would agree but have never cruised on a planing yacht in rough conditions, hence the reason I was inquiring. But it would be **** sweet if ya could.

    Now in regards to the zero speed stabilizers, that too would be nice...though the only ones I have seen are the active fin style. So unless those are retractable, based on the comments here today, they would be a material form of drag and reduce control on planing hull. Are there other zero speed systems that I may not be aware of? thanks
  12. AMG

    AMG YF Moderator

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    Yes, there are some systems, like the Ferretti gyro that should prevent rolling at any speed. But I have no personal experience of it. I have of others but I am not impressed of systems that makes the boat move unnatural so you get dizzy or seasick instead. Small boats, say under 100 feet, will always move with the sea and the best is to move along for a while until you donĀ“t feel it any longer...:)
  13. Jage

    Jage New Member

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    :) thanks

    Without ever having cruised on a planing yacht I have learned quite a bit about why the 80's and 90's itallian/euro styled flybridge with aftdeck yachts are not active fin stabilized. Thanks very much for all your help and patience. It is much appreciated.

    If I may ask... How would you think a 1974 Hatteras 53 MY compares with the euro planing yachts in terms of sea-keeping and ride?
  14. AMG

    AMG YF Moderator

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    A short answer is; Different.

    The latest 53:s with more power and prop tunnels would probably compare to some of the more heavy eurostyle yachts. But the remaining are a broad variety of seakeeping and ride, from the best to the worst...
  15. Jage

    Jage New Member

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    :) Well, I know how the 53 hatteras rides with and without stabilizers and was hoping to have a benchmark for comparison's sake.

    How do you rate the eurostyle yachts? Of the older eurostyles, I have been interested in learning more about the Cantieri DiPisa, San Lorenzo, Maiora, Ferretti, Astondoa, Heesen-Versil, Falcon and Ghibli of the late 1980 and early 90's. (65-80ft) and as per the discussion today none of these yachts employ stabilizers.
  16. AMG

    AMG YF Moderator

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    At what speed were you running this Hatteras?
  17. Jage

    Jage New Member

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    We would cruise at around 15-16 knots in the Hatteras.
  18. AMG

    AMG YF Moderator

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    I am afraid that you can not compare this to the boats you are mentioning, it would rather be an older Pisa, like the Pegasus then.

    Also some older Bagliettos or Admirals. The newer models are behaving different, not always better, especially not in speeds between 15 and 20 knots where they can be pretty wet!

    But this is nothing that would change with stabilizers, it is rather the hull shape and the fact they are loaded with too much equipment...
  19. Jage

    Jage New Member

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    If I am not mistaken the yachts I have mentioned cruise at 22+knots. I realize it's difficult to compare these to a 53 hatteras based on speed, but i would think you could compare on ride quality for each type's respective ideal cruising speed. I appreciate the color on the "wetness" of the ride in those eurostyle cruisers. Is that at all speeds or just 15-20knots? Are they all "wet" rides?
  20. AMG

    AMG YF Moderator

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    If you go at their cruising speed, say 22-26 knots, they are pretty OK as long as the weather conditions allow them. I was just giving the example that going down to 15 knots as your Hatteras, will not compare right.