Using Zodiac style 3.1M RIB as mold for fiberglass boat

Discussion in 'Fiberglass and Composite Boat Building' started by sreyemj, Apr 14, 2016.

  1. sreyemj
    Joined: Apr 2016
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    Location: Washington

    sreyemj New Member

    I have this mostly worn out 3.1m Bombard PVC RIB. It's very similar to this West Marine boat: http://www.westmarine.com/buy/west-...lding-transom-rigid-inflatable-boat--14460885

    The fiberglass bottom is still in good shape and the tubes hold air. I was thinking about trying to use the boat as a male mold for a (very) similar fiberglass dingy. I would put release agent on the tubes, put a layer of fiberglass over the tubes, separate the top and bottom by cutting around the middle inside and out, remove the remains of the tubes, fiberglass the two halves back together with another layer of fiberglass, and attach the former RIB bottom and transom (with new wood).

    Could this actually work? Anyone know of a similar project? Trying to decide if this would be a fun project or something best abandoned in the planning stage!
     
  2. Barry
    Joined: Mar 2002
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    Barry Senior Member

    If you are going to this much trouble, you could fibreglass the outside of the tube up to the upper portion. Then insert say a 1/4 inch ply from this upper point of the tube down to the floor, glass over the ply and attach/glass it to the floor. That way you will get a "D" profile instead of a "O" profile which will increase the overall inside width significantly and maybe even be a little less work.
    The "D" profile will give you all the buoyancy you need if you should fill the boat with water.
    Note the round tube or half round tube, the D does not supply any buoyancy unless the boat is submerged and there is water inside the boat in contact with the water outside of the boat.
    You will often see inflatable ads boasting large diameters as providing more buoyancy but this is only the case with a submerged boat or partially submerged boat with say the cockpit drain open
    That being said, you will get some benefit, righting, buoyancy benefit from the section of tube behind the transom as both sides of this part of the tube is "wet on both sides"
     
  3. sreyemj
    Joined: Apr 2016
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    Location: Washington

    sreyemj New Member

    Only a bit, but good call on the "D" shape. The inside does get a little cramped with these types of boats. Any ideas how many layers of fiberglass I should plan on?
     
  4. Barry
    Joined: Mar 2002
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    Barry Senior Member

    I am not a fibreglass guy but others will respond
     
  5. compo

    compo Previous Member

    has been tried many times and dosent work

    Even with 1.5 psi of air pressure can do strange things and this has been tried and had never been successful !! but you can fill the tubes with expanding foam and that's work !! sort of ! :(
     

  6. Barry
    Joined: Mar 2002
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    Barry Senior Member

    What does not work?
    A fibreglass rigid tubed "inflatable shape copy'?

    I have built half a dozen aluminum "rigid tube" "inflatable shaped tenders with the D profile. Boss boats and Bull Frog
    build them out of roto molded plastic, seem to work pretty well. One could argue that the foam might not expand with change in temperature, ie air pressure change but this is very slight
    I never installed a vent for the aluminum rigid D shaped tubes and never had a problem
    The advantage is a huge increase in the interior dimensions
     
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