Using EPS pontoons sealed in HDPE liner

Discussion in 'Materials' started by Brad Withyman, Oct 4, 2018.

  1. Brad Withyman
    Joined: Oct 2018
    Posts: 4
    Likes: 0, Points: 1
    Location: australia

    Brad Withyman New Member

    I'm designing a floating home (nothing boat about it) and like the idea of using EPS Foam wrapped and sealed in HDPE liner. I've been though all the pros and cons and can't understand why its not used more in place of the usual composite, metal pontoons, concrete, polypipe hulls.

    The Liner (geomembrane) is HD @ 1.6mm and is welded and sealed around edges. Similar to how pontoons and docks are made in Australia.
    The Foam can be cut and shaped to allow for structural beams to be fixed. (A metal keel section can be fixed if needed)

    Buoyancy Cost is approx AUS$165/Ton + any cuts.

    Has anyone seen this method used on floating structures other than floating pontoons/docks?

    Really like to know, because I could be missing something here ;).
     
  2. Mr Efficiency
    Joined: Oct 2010
    Posts: 6,716
    Likes: 173, Points: 63, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    What is giving structural strength here ?
     
  3. Brad Withyman
    Joined: Oct 2018
    Posts: 4
    Likes: 0, Points: 1
    Location: australia

    Brad Withyman New Member

    Alloy C- Section beams 200x75mm running parallel along the topside positioned into rebates and fixed through the core, connecting each beam. Platform frame cross beams welded to C-Sections (top) that also sit in 100mm channels across the top of core.
     
  4. Mr Efficiency
    Joined: Oct 2010
    Posts: 6,716
    Likes: 173, Points: 63, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    Do you have a sketch ? I take it this isn't a thing that will be on the move a lot. Where are you intending to have it ?
     
  5. Brad Withyman
    Joined: Oct 2018
    Posts: 4
    Likes: 0, Points: 1
    Location: australia

    Brad Withyman New Member

    Correct - On a river on mooring or pillions. It'll have its own propulsion, but like 5kts max.
    I don't wanna post the sketchups until I'm 100% on the process. The HDPE liner is 1.6mm thick, so it can be a ***** to fold and weld if not spot on. It needs to be hot when wrapping and welding, otherwise is too rigid. Laying it up in the sun is the trick.

    Here's a pontoon wrap.[​IMG]
     
  6. waikikin
    Joined: Jan 2006
    Posts: 2,250
    Likes: 87, Points: 58, Legacy Rep: 871
    Location: Australia

    waikikin Senior Member

    Hi Brad
    Most of these I've seen have a reinforced concrete deck & assume that is the "structural element" with pile guides and other structural & joining elements tied into into that - often with an extruded aluminium form around the perimeter. Seem to rarely exceed 9M per module but that may be to suit manufacture & handling convenience.
    Just had to pay some reasonable bucks to dispose of some of these(clad in ferro cement skins though), seems the life around 25-30 years.
    Your scheme has some merit if approached sensibly which appears the case.
    What size are you looking at?
    Jeff.
     
  7. Brad Withyman
    Joined: Oct 2018
    Posts: 4
    Likes: 0, Points: 1
    Location: australia

    Brad Withyman New Member

    Hi Jeff,

    I want 2 x 12m pontoons, but the width, either 1.2 or 2.4 m, is dependant on stability and how much load the embedded beams can take from the top structure. One of the cool aspects of working with EPS is the sectional cuts and channels that can be made, which allows the use of rio bar and mesh for a concrete set. So I'm just looking at what beam profiles I can use in parallel that can be set into the concrete channel. The use of HDPE geo-membrane should (as tests have indicated) give the EPS a much longer life 40+years. I think I'll concrete the top, in between the beam channels, which will allow the HDPE to be folded into the channel and sealed down be the concrete. I'll post a profile soon. The alternative was a set of 45ft glass hulls at $25k, that weren't versatile. Its looking like the EPS path will be half that, with options on cross beams and structural design.
     
  8. Barry
    Joined: Mar 2002
    Posts: 963
    Likes: 44, Points: 28, Legacy Rep: 158

    Barry Senior Member

    With solid floatation chambers, you will lose the ability for the chambers/pontoons to hold freshwater, black water and grey water.
    Of course these can be stored above the deck but may mean more plumbing and pumps
    While you say that 2 45 foot hulls in fibreglass cost $25k, by the time that you factor in the cost of the additional attachments, frames etc, to provide the strength/structure that your plan entails, are you still saving a reasonable amount of money. Including the costs to deal with water in all forms noted above.


    Most of the floating homes that I have seen use holding tanks that are pumped into the marina
    sewage lines when full.

    But maybe your mooring area has a different set up
     

  9. fallguy
    Joined: Dec 2016
    Posts: 1,112
    Likes: 40, Points: 48, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    So, let me get this straight.

    A big massive piece of xps is decored and aluminum replaces it for a skeleton, or some such. Then the entire structure is wrapped in hdpe to protect the xps from absorption and the ally from seawater. Right?

    So the potential downside is tearing the hdpe or a construction error and allowing ingress. A pond liner is similar, only a pond liner shows the problem as the water level drops in the pond. Further, the attachment points in a pond liner are none, but certainly attachments are required here.

    The only thing I don't like is ingress is invisible until the vessel? lists at which time haulout and replacement of the hull is likely the only solution.

    I think perception is the reason it is not popular.

    Noone likes a leaky hull and even worse is a core getting wrecked when you are unaware. The 1970s coring nightmares are still in vivid memory, not to mention the use as tanks as mentioned is lost.

    Just my two cents..
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.