Hull extension to fill in pod

Discussion in 'Boat Design' started by Kalb0, Jan 28, 2015.

  1. Kalb0
    Joined: Jan 2015
    Posts: 2
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    Location: Brisbane, Australia

    Kalb0 New Member

    Hi everyone,
    I've got a 6m plate aluminium boat with a large pod (800mm) on the back. The pod has no buoyancy and the motor weighs just under 200kg and I'm sure this is the cause of some handling issues the boat has, especially in a following sea. Just wondering if anyone has heard of anyone getting a hull extension to fill in a pod for added buoyancy? Just wondering if firstly it's possible, if it's worth the cost and is it likely to help stop proposing and nose diving in a following sea. Also I installed some trim tabs which helped a lot and loading up as much gear as I can up at the bow also helps. Thanks in advance for any info you can provide.

    Cheers,
    Kal
     

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  2. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    Hello Kalb0, can you just clarify that the pod is effectively a continuation of the bottom of the boat ? It is a little hard to be certain from the pic. When you say it has "no bouyancy", do you mean it isn't sealed ? If it is sealed, it must be providing some buoyancy. What is the make/model boat ?
     
  3. Kalb0
    Joined: Jan 2015
    Posts: 2
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    Location: Brisbane, Australia

    Kalb0 New Member

    Hi mate,
    The boat is a custom built fisher and the pod is above the water line and only buoyant at rest. I've uploaded another photo which makes it a bit clearer.
    Thanks
     

    Attached Files:

  4. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    OK, much clearer view, that pod is a bit unusual in being dead flat underneath. Boat appears to be about 17 degree deadrise at the transom. If you 'fill it in" so as to become a continuation of the hull bottom, you certainly will notice the stern being lifted, but if there is a "problem" in following seas, it may worsen it. Is there a tendency to broach, that is, have the stern slew around, when the nose buries in the wave ahead of you ? I would expect that might worsen. There is also the possibility the boat could become a trifle more tippy at rest with a full-depth pod.
     

  5. Martin B.
    Joined: Aug 2013
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    Location: Mandurah, Western Australia

    Martin B. Junior Member

    If you "fill in" under your non-pod down to the hull bottom plating then you will get something like the standard so-called "half pod" arrangement as used to be supplied by Qld company SeaJay - I had one of their 4.6m runabout models ( also the big Q used to do a similar arrangement before the full width "pods" appeared).
    The key thing is then to have the motor height correct. The 60hp Mariner on mine, professionally fitted (?) by a Dealer was about 35 - 40 mm too low which resulted in huge roostertails/spray from the engine leg and rotten performance. A quick check with a long straight edge showed that the cav plate of the engine was way below the line of the hull plating by the keel. Progressively raised the engine about 12mm at a time until sharp turning (to port I think it was - it is related to prop rotation direction) induced cavitation. With no other alterations, engine revs increased up towards max revs nominated in the Instruction Manual, speed increased, noise decreased, skipper happy, navigator happy, engine happy.
    Go for "podding" down to and absolutely dead inline with hull plating.
     
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