Exteding a hull?

Discussion in 'Boat Design' started by Matt.D, Oct 26, 2007.

  1. Matt.D
    Joined: Oct 2007
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    Location: gold coast

    Matt.D Junior Member

    Extending a hull?

    Does anyone have any info on or has done a hull extention ?
    I have a 21ft fly bridge . glass over ply. want to extend it 4ft.
    Thanks Matt
     
  2. kapnD
    Joined: Jan 2003
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    Location: hawaii, usa

    kapnD Senior Member

    Matt, You need to give us more information on the boat. Type of power, planing or displacement, type of use intended and speed, pictures etc. You are talking about a radical change, must proceed carefully. One thing in your favor is theat glass over ply will be easy to work with! Don
     
  3. Matt.D
    Joined: Oct 2007
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    Matt.D Junior Member

    Hi Don. It will have a 225 outboard on a pod bolted to the transom, will do aprox 30 knts, its a fly bridge cruiser mainly for fishing with a v beath up front.and its a planing hull. . Ive searched the net but cant find any info or pic anywhere. Thanks Mate.
     
  4. CDK
    Joined: Aug 2007
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    CDK retired engineer

    I've done something similar 2 years ago. Made the extension in a makeshift mold, laminated aluminium L-profile all around the inside edge and bolted the box to the existing transom after applying a layer of marine sealant (Sikaflex). In my case I needed another ft of engine room for 2 Berkeley jets, so I made holes in the old transom where I needed them, left the rest intact.
    I contemplated laminating directly to the existing hull, but decided not to because I didn't trust the adherence to 25 yrs old laminate, especially the bilge that has been oily for as long as I can remember. Experts told me that it can be done, but the contact area should be 4-5 times the wall thickness.
     
  5. Matt.D
    Joined: Oct 2007
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    Matt.D Junior Member

    Hi CDK, thanks for the reply. so u build an alloy extention tub and bolted it to the exsisting transom? is that correct? i want to extened my hull for extra fishing space. Matt
     
  6. CDK
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    CDK retired engineer

    Replace "alloy' with "GRP" and you've got the picture.
     

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  7. jim lee
    Joined: Feb 2007
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    jim lee Senior Member

    cdk why would you want 2 jet drives?

    -jim lee
     
  8. Matt.D
    Joined: Oct 2007
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    Location: gold coast

    Matt.D Junior Member

    Sweet. i also want to make a pod that will double not only as a outboard mount but a deck extention 1mt long as i want to cut the transom out and extend to the floor thur to the new transom. Was thinking about making it in aluminum for extra strenght.
    Matt
     

  9. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    I surely don´t, but I didn´t know it then....
    See my post on the surface drive sub/forum
     
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