HDPE pond liner sheathing for houseboat construction

Discussion in 'Boat Design' started by mariobrothers88, Dec 4, 2021.

  1. mariobrothers88
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    mariobrothers88 Senior Member

    Hey guys, I'm designing a houseboat using marine plywood and fiberglass with two rectangular hulls and a bridgedeck (similar to a catamaran design). Instead of using bottom paint for below the waterline and topcoat paint, I was thinking of just sheathing the hulls in a blue HDPE pond liner. That way I wouldn't have to be putting on new bottom coat every few years. The HDPE should last a pretty long time without requiring much maintenance and should prevent any bottom growth. What do you guys think, would it work? What are some reasons why it wouldn't work? Thanks for any advice or input!!
     
  2. Blueknarr
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    Blueknarr Senior Member

    A--- good luck getting it to adhere to the floats

    B--- any cut and growth will occur inside

    C--- it takes a good flow of water to keep clean

    D--- regular haul outs allow for regular hull inspections that can reveal problems before they become catastrophic. ESPECIALLY PLYWOOD HULLS
     
  3. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    +1 re Blueknarr's observations above.

    It sounds to me that you are trying to possibly save a few dollars and some possible labour, at the expense of all kinds of future problems.
    You might well find that nothing will glue the plastic to the hull so you then have to use mechanical fasteners (screws) to secure it.
    You should still bed it down on a sealant. Maybe something like 5200 might work if you scuff up the plastic well, I don't know.
    But you will spend a small fortune in buying tubes of 5200.
    And every screw going into the plywood is a potential source of water ingress, and subsequent rot.
     
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  4. fallguy
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    fallguy Senior Member

    I think he means instead of paint, not instead of glass sheathing.

    My main concern would be hydraulics.

    Let's say, Ron, you glued it on exceptionally well, but missed bonding a nickel sized section. You know what will happen? The section will get mechanically moved off and on the hull with water pressures and become larger and larger. Depending upon bond strength, rough seas, speeds, the drama can unfold (close to a pun) rather quickly. You could go from launching well adhered to an area of delamination 6' long or more quite quickly from a minor bond failure. The hdpe might also deform under such action and get stretched out, although I don't know the limits of it on this property well.

    Then, a side issue would be drag. The drag from the hdpe liner might be somewhat higher than paint.

    Then, as stated above, what do sea creatures do? If they stick to it; bottom paints break off. HDPE won't. You'll use hard mechanical advantage to scrape and then go back to the delam issue above.

    Now, all that said, you could so a small experiment with it as a wear pad bonded to the hull, but only where the boat would contact beach. If the contact area is large; the boat should get strakes and you could bond the hdpe to the strakes as a test for sacrificial wear skids.
     
  5. Kayakmarathon
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    Kayakmarathon Junior Member

    It was a creative idea. As with most engineering, many mistakes are made before an acceptable solution is found. There may be some use for the material other than the original application.
     
  6. clmanges
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    clmanges Senior Member

    @mariobrothers88 --If you build the hulls and deck out of aluminum, you won't even have to paint it at all. Probably not what you had in mind, though.
     
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  7. fallguy
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    fallguy Senior Member

    It would make decent locker liner..
     
  8. Rumars
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    Rumars Senior Member

    If you like Hdpe why do you want to make the hulls from plywood? Just get a few hdpe sheets and weld the hulls out of it.
     
  9. messabout
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    messabout Senior Member

    The Op said he wanted a Houseboat. If we are thinking in terms of the Seattle permanent dwelling type house boats, then the HDPE, or whatever, can be a simple diaper. It does not need to be attached to the skin of the hull. If or when it wears out, becomes damaged, hopelessly encrusted with marine growth, then replace the diaper.

    If the houseboat is to be a self propelled vehicle, then that is a whole other deal.
     
  10. mariobrothers88
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    mariobrothers88 Senior Member

    Hi guys thanks so much for all the advice and input. Yes this would be just for a stationary houseboat that would never have to move. I would not use any sealant since there are few things that bond to hdpe well. I was planning to encase the entire hulls in the pond liner and use stainless screws at the top. I would cover these screws with another layer of hdpe liner to prevent water ingress. It would essentially be a diaper instead of using bottom paint and topcoat paint. My understanding is that nothing would grow on the hdpe so it should last for many years.

    Rumars- I was originally planning g
    to make the hulls out of hdpe panels but the logistical challenges of sourcing the hdpe panels made me look at other options.
     
  11. fallguy
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    fallguy Senior Member

    How does nothing grow on hdpe?
     
  12. Rumars
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    Rumars Senior Member

    Epoxy still needs paint for UV protection, in case your diaper ruptures. Is there a hdpe shortage right now? Usually you phone around to find someone with the needed stock, fork over the money and the material appears at your door.

    Growth will still form, especially on a stationary object (a problem that the usual powerboat doesn't have). With solid Hdpe you can dive and scrape regularly, not so with a pond liner, it's to thin, you will have to replace it, wich means a haul out. I would use solid thin plates (1/8-1/4) as a liner if structural ones are difficult to obtain. Screw them down into epoxy plugs with bronze screws and weld all seams afterwards. Use only black UV stabilized material.
     
  13. Blueknarr
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    Blueknarr Senior Member

    As stated marine growth will form on hope. BUT like everything else it doesn't stick well.
     
  14. lobsterman
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    lobsterman Junior Member


  15. lobsterman
    Joined: Mar 2004
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    lobsterman Junior Member

    The "pool material" that you are thinking of is not actually HDPE, it is a layered vinyl, and this is about the lowest cost supplier i could find for the material (i use it as a roof fabric on RV sunroom, screenhouses, gazebos, hen houses, etc. ). The adhesive to use bonding pieces of the vinyl material together is called HH-66.
    https://billboardtarps.com/shop/new-vinyl-tarps/new-vinyl-tarp-20oz-white-white/
     
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