following sea

Discussion in 'Stability' started by 7228sedan, Jun 11, 2010.

  1. 7228sedan
    Joined: Nov 2009
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    Location: New Jersey USA

    7228sedan Senior Member

    I finally got around to take my single screw 28 foot sedan brige out to a few wrecks & reefs off of the jersey shore. On our way back in, the seas picked up to 3-5 ft with an occasional 6 footer mixed in there. Overall I was very pleased with how the boat performed. However, running with the following seas was a bit of a challenge. The boat is a single so you're very busy at the helm in calmer seas. Running with the wind & seas at my stern seemed to be a struggle. The bow would bite in coming down off the face of the swell & the boat would start to turn to port pretty hard. At one point, I had the wheel at full starboard to maintain a constant straight heading. Has anyone had any experience with this?
     
  2. Stumble
    Joined: Oct 2008
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    Location: New Orleans

    Stumble Senior Member

    A following sea of this magnitude shouldn't cause this much problems, but when it gets that bad take a suggestion from sailboats, and tack downwind. Head off at a 30 degree angle or so from directly down-wave and see if that helps.
     
  3. 7228sedan
    Joined: Nov 2009
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    7228sedan Senior Member

    I didn't think that 3-5's would have that much effect on her. My thought was perhapse the rudder is too small?
     
  4. Fanie
    Joined: Oct 2007
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    Location: Colonial "Sick Africa"

    Fanie Fanie

    I almost doubt it, a bigger rudder isn't going to make that big a difference, what happens is the bow starts to act like a front rudder and it wants to turn like a forklift with the front wheels steering and you attempt to correct with the rear wheels.

    I've experienced the same but on a smaller boat, easiest way to capsize. For the life of me cannot think of the 'right thing to do' I just know when I'm there :eek: Speed for one is important. If I think it through I'll comment on it.
     
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  5. jehardiman
    Joined: Aug 2004
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    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

    Actually, this is very common even with larger vessels. When running with the waves, the wave orbital at the crest is moving in the same direction as the vessel. This reduces the flow over the rudder and therefore generates less control force.

    It is really bad is the vessel's length is close to 1/2 the distance between crests. In that case the bow is in the trough where the orbital velocity is against the vessel and pushes the bow aft, while the rudder is on the crest where the orbital velocity is with the vessel and it pushes the stern forward while the rudder has no bite. If the vessel is going just the wrong speed, you can lose rudder control totally and broach beam to, often capsizing the vessel as Fanie alluded to. This is why it is recommended, like Stumble said, to turn to take the waves on the quarter rather than dead astern. It is not too much of a problem is the vessel is travleing much faster than the orbital speed, or much slower.
     
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  6. mark775

    mark775 Guest

    I can't put it into words as well as the above responders but I have been there and I agree. A bigger rudder does nothing here unless you are applying power, which is a scary proposition when your boat wants to swap ends. For easier running without picking up the seaward quarter and tipping over the not-so-buoyant downhill bow, move some weight aft and to the uphill side. I know the above reasoning but I prefer to steer directly down sea and punch it or back off as needed if I'm about to get pooped or feel like I'm about to start surfing. Look over your shoulder with your periferal vision and anticipate the ones that will land on your deck or cause you to surf (surfing is fun and fast but know your limitations - In short, you shouldn't do it in mean stuff). Of course, running an inlet on ebb, or such, can be harrowing and shud be planned against if sea is running or going to run. Have the wherewithal (fuel) to stay at sea, if need be, be prepared to jog into a sea as you will have more control, have the power to get out of there or run ahead of the wave(or out from a tight spot), and practice with an inflatable skiff in surf with a Mustang suit (I know an outboard has vectored thrust and doesn't relate well to an inboard but it really helps to feel what a boat will do to actually capsize, flip, pitchpole, and ground in a controlled circumstance - work into this slowly! Is there a class in this anymore? - I don't know.) It can really help to practice running before a sea and steering directly downsea has the advantage of allowing you to fine-tune your steering and anticipate which way the sea will kick you. Do it as safely as you can without innocent loved-ones aboard - that is why I recommend a lot of skiff time (smaller skiff matches well with smaller breakers and shallower water). For your boat, right now, try moving a little weight aft.
    One thing has me thinking... "The boat is a single so you're very busy at the helm in calmer seas" - what do you mean? It wanders? There might be an issue to be addresssed. What boat is it, what are the proportions, including balance, of your rudder and what does it look like underwater? My boat is a single and I sometimes don't touch the wheel for several minutes...
     
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  7. tom28571
    Joined: Dec 2001
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    tom28571 Senior Member

    In conditions that are becoming serious, I try to run directly with the waves downwind and a bit slower than the wave train. This avoids surfing into the wave ahead and having the stern slew around into a broach. Having an outboard of adequate power is the best situation to control the boat in downwind waves. I don't have experience in steering an inboard with a small rudder in these conditions. I would probably elect to avoid getting in the downwind steering problems mentioned. Without the steering moment provided by an outboard, such situations can be dangerous.

    The idea of running with the waves on the aft quarter doesn't sound good to me. An overtaking wave finds the boat already starting to broach and can easily finish the job. In any case, the boat wants to roll back and forth and the steering does the same when taking waves off center. Even on a sailboat, this course makes the helmsman's job very difficult and tiring but much less dangerous than a powerboat.
     
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  8. Fanie
    Joined: Oct 2007
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    Location: Colonial "Sick Africa"

    Fanie Fanie

    If the waves overtake you then your steering direction should change.
    Instead of having the rudder full to one side the rudder should be in the other direction to have an effect. It helps to look backwards when you steer like this :D No really. I did it on the small sailboat.

    I usually go faster down the wave and slower up and over it. Of course it depends on the wave length if this will work. Worst weather is short choppy boat length waves.
     
  9. Zappi
    Joined: Oct 2008
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    Location: Puget Sound

    Zappi Senior Member

    I have had the same following sea issue with rudder being hard over to compensate. I see moving weight aft to be a potential help. Would it be wise if I find myself in these conditions to drain the 75 gallon fresh water tank placed in the bow???
     
  10. Fanie
    Joined: Oct 2007
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    Location: Colonial "Sick Africa"

    Fanie Fanie

    What boat have you got ? Lifting the bow would lessen the possibility of a broach, but reverse steering could be applied, you have to go slower wrt the water to do so, or go faster than the water and do normal steering.

    No use losing the fresh water and die a day later of thirst.
     
  11. Zappi
    Joined: Oct 2008
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    Location: Puget Sound

    Zappi Senior Member

    Boat is a twin diesel Pacemaker 35'. Reverse steering or more throttle sounds like possible solutions. I tend to cruise about 7 knots but can comfortably cruise at 10-12 if necessary. Would semidisplacement mode help this?
     
  12. mydauphin
    Joined: Apr 2007
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    Location: Florida

    mydauphin Senior Member

    It is all about playing with the throttles ...Unless it is grossly under powered, or under prop. Try to stay on same spot on wave, let wave push but not grab you.
     
  13. fg1inc

    fg1inc Guest

    Fascinating sequence of photos on The Hull Truth.net(search Water Dog) of a sport fish entering our local inlet last week. The boat apparently carried too much speed and went "over the falls" throwing the skipper right out of the boat. He was an experienced captain with many decades of running that inlet in all weather conditions. It can happen to anybody.
     
  14. srimes
    Joined: Sep 2008
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    srimes Senior Member

    link?
     

  15. Easy Rider
    Joined: Oct 2009
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    Location: NW Washington State USA

    Easy Rider Senior Member

    Yea...I'd like the link too.
    Someone said rudder size was not important. I profoundly disagree. Most fast power boats have very small rudders and handle badly in following seas. My 30' Willard has a large rudder and I don't think I've ever gone over 1/2 deflection ever to maintain a heading in following seas. Perhaps the depth of the rudder is more important than it's area. My rudder is over 3' down. No boat is perfect as I often change course to avoid rolling in beam seas.

    Easy Rider
     

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