Drifter skiff

Discussion in 'Boat Design' started by DriesLaas, Dec 30, 2016.

  1. DriesLaas
    Joined: Aug 2009
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    Location: South Africa

    DriesLaas Weekend Warrior

    For what it is worth, I have loaded some Queen Mackerel on during the winter season here.....
     
  2. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    Thanks for the update.

    You asked about how I'm involved in the composites industry.
    20+ years as a fabricator building just about anything imaginable, and then 20+ years in tech service and sales.
     
  3. DriesLaas
    Joined: Aug 2009
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    Location: South Africa

    DriesLaas Weekend Warrior

    So our gruelling winter is over, no more 25 degree celcius days for us anymore..........The summer fish are starting to arrive, and I have changed some things on the skiff lay-out.
    That silly center console is gone, and I have a better solution now. A center seat that I can straddle, and brace against. So far it has worked pretty well.
    I also made a norwegian tiller extension, that bolts to the outboard, and a remote throttle and gear shift stick (literally.) These changes totally transformed the usability of the boat, I will fish extensively in the next few months and then consider the development done.
    On a side note, there was an indiscretion I committed during building: A portion of the deck is pine plywood, while the rest is marine ply. This stuff is completely unforgiving: You have to completely both saturate with resin and then cover with glass, otherwise the material will start to delaminate. I need to do a small repair on the deck where this happened. I will post some pics when I am working on the boat again, but this weekend is hopefully off to catch some tigerfish........
    Hydrocynus vittatus
     
  4. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    If the pine plywood is delaminating, no amount of resin or sheathing will help, as the glue lines will just continue to separate the veneers. If the sheathing is heavy enough (thickness) it'll help hold the separating veneers for a while, but I'll suspect you'll need to replace this portion before too long. I hope it's not a big piece.
     
  5. DriesLaas
    Joined: Aug 2009
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    Location: South Africa

    DriesLaas Weekend Warrior

    Hi PAR, yes you were absolutely on the money. The pine just keep separating. Thankfully the very vast majority of the boat is built using good marine ply, so I have made peace that I will replace a section at some point.
     
  6. DriesLaas
    Joined: Aug 2009
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    DriesLaas Weekend Warrior

    More hard earned wisdom with small skiffs: You can and will fall of the thing easily. My 79 year old father and myself ended in the drink recently, on a calm day in the harbor. I can still not quite tell you how it happened, but we were lucky to just lose two fishing rigs....
    Bottom line, wear your pfd, and have a kill switch rigged. Otherwise you will come to grief.......
     
  7. Angélique
    Joined: Feb 2009
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    Location: Belgium ⇄ The Netherlands

    Angélique aka Angel (only by name)

    Hi Dries, two men on top could have made the flat bottomed and narrow skiff top-heavy, so possibly she suffered from the ‘‘pontoon effect’’, and as a consequence capsized without much prior warning . . :confused:

    ‘‘ The (pontoon like) vessel is stable and self-righting up to the point that the centre of gravity shifts past the centre of buoyancy of the ship and the vessel rapidly capsizes. ’’

    With two men on top such a flat bottomed and narrow little skiff becomes top-heavy, and as a consequence with that load she'll need only a little heeling angle to reach the point of sudden capsize, I believe.
     
    Last edited: Mar 26, 2018
  8. Angélique
    Joined: Feb 2009
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    Location: Belgium ⇄ The Netherlands

    Angélique aka Angel (only by name)

    Buoyancy - ---> - Static stability - ---> - Ship stability - ---> - Metacentric height - ---> - Thread: Metacentric Height

    [​IMG]

    ‘‘ Illustration of the stability of bottom-heavy (left) and top-heavy (right) ships with respect to the positions of their centers of buoyancy (CB) and gravity (CG). It is to be noted that the CG being located above CB is not the cause of instability. The increasing height of CG decreases stability. CB will move as a vessel rolls, CB appears to pendulum below a point named the metacenter (M) If CG is higher than M then the vessel is unstable. As CB will apply an upward force and CG a downward, so when stable CG is inboard of CB during a roll and a righting arm will lever the vessel upright (left) and when unstable CG is outboard CB and will lever the vessel over (right). ’’
    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

    [​IMG]

    ‘‘ Ship stability diagram showing centre of gravity (G), centre of buoyancy (B), and metacentre (M) with ship upright and heeled over to one side. As long as the load of a ship remains stable, G is fixed. For small angles M can also be considered to be fixed, while B moves as the ship heels. ’’

    For some more info see the above 4th link - ---> - Metacentric height
     
    Last edited: Mar 22, 2018
  9. DriesLaas
    Joined: Aug 2009
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    Location: South Africa

    DriesLaas Weekend Warrior

     
  10. Angélique
    Joined: Feb 2009
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    Location: Belgium ⇄ The Netherlands

    Angélique aka Angel (only by name)

    Hi Dries,

    I'll guess summarized it means when loaded top-heavy it needs only a little heeling angle, caused by a wave or when making a turn or from some movement of the load (the crew), for your flat bottomed and narrow drifter skiff to become prone to the in post #67 mentioned ‘‘pontoon effect’’ . . :eek:

    I'm glad you both survived it well . . :) - - How's the engine doing ?

    Or was it no turtling but a partly capsize a bit below 90°, and did the boat immediately right after she was freed of her top-heavy burden when you two went into the drink ?
     
    Last edited: Mar 26, 2018
  11. DriesLaas
    Joined: Aug 2009
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    Location: South Africa

    DriesLaas Weekend Warrior

    Exactly like you describe. We fell off, thankfully the throttle closed and I could swim after the boat and reach it. Threw a lifejacket to my dad, who at 79 is still strong enough to help himself. (He was busy trying to salvagee as much floating debris as he could at the time ;-) )
    Lessons learned:
    Wear a lifejacket even in the harbour (I previously only did this when crossing into open sea.)
    Keep killswitch attached to wrist with lanyard to make sure engine stops.
    Tie every rod to boat itself with a lanyard when not fishing. Pretty much everything that is not tied to the boat with a bit of string will at some point be lost......except if it floats.Then you have a chance of salvaging it.
    Two grown men is too much for this boat, it is not safe. I am working on a trimaran concept to improve stability and peace of mind, especially when going out to sea, which I do sometimes.
    Provide ample handholds for the crew ( I think the sequence of events started with loss of balance, which could have been prevented by a well placed handhold to use while moving)
     
    Angélique likes this.

  12. Angélique
    Joined: Feb 2009
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    Location: Belgium ⇄ The Netherlands

    Angélique aka Angel (only by name)

    That's the spirit, hats off to to your dad, and to you too for sharing the story and the lessons learned . . :)
     
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