HDPE pontoons

Discussion in 'Boat Design' started by Chris Chadwick, Jul 19, 2022.

  1. shaun Moir
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    shaun Moir Junior Member

    thank you, Barry,

    the reason I put tidemans was as an example of it being done

    in the USA there are many proofs of vessel that can cope with the weather etc

    Building boats in HDPE is not a new concept in fact they have been building them for many years

    The majority of them as sea-going vessels from small dinghies to large sea-going vessels some with big twin outboard motors

    I have even seen some small ferry vessel

    The size is 40` x 10` and built using 20mm for the base of the boat 15mm for the sides and 12mm for the upper sections

    we actually teamed up with a canal steel boat builder to build the boat we have now as he had the build plans and knowledge to help us

    as for the tantalizing comment i actually never put any negative of HDPE at that present time as I was simple.

    "Let’s explore some of the benefits that polyethylene and other forms of boat plastic can offer"
     
  2. shaun Moir
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    shaun Moir Junior Member

    HPDE (high density polyetylene) is a strong and robust material deviated from petrol. Unlike other polyetylenes, HDPE is heavy and firm. Approximately, 1.75 kg of petrol is used to produce 1 kg of HDPE raw material. HDPE is lighter than water and together with its durability it becomes a preferred material for marine purposes. HDPE boats can be shaped by molding and extrusion methods. It can be processed in workshops and can be welded with special methods. It is difficult to combine with adhesives. HDPE is a very strong material with a density between 150000 – 400000. It's resistant to water and chemicals.

    HDPE’s mechanical composition is extremely strong on impact and tension. Normally the tension resistance is like 225-350 kgf/cm2 and heat resistance is above 100 OC. HDPE is widely used in pressure pipes, gas distribution pipes, liquid containers, machine and home appliance parts, and in insulation. Lately, because of its resistance to water, it is also used in tank and boat manufacturing.

    The advantages of HDPE in the boat building are;

    HDPE Boats' service life is stronger than any boat, made of any other building material: Due to its chemical composition and its very nature HDPE is very durable against aging and corrosion in marine conditions. HDPE boats' minimum measured life is 50 years.

    HDPE Boats are almost maintenance free: HDPE is not a corrosive material. Oxygen, salt and water have no effect on HDPE. There is no need for anti-foiling, painting, wintering, dry docking, etc.

    HDPE Boats are very strong: HDPE is not a breakable material. Its very dense and Tension crack resistance and crack running resistance are high, the impacts remain minimum damage. HDPE boats are almost indestructible.

    HDPE Boats are environmentally friendly: HDPE boats are 100 % recyclable. HDPE boats can be remelted and reshaped for reuse. HDPE boats does not require anti-fouling and therefore do not pose any toxic pollution to nature.

    HDPE Boats are comfortable: HDPE is not a rigid material. Therefore HDPE boats are very comfortable especially in strong weather conditions, sailing on choppy seas in comparison to the rigid conventional boats.
     
  3. clmanges
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    clmanges Senior Member

    Please state units of measure. That number doesn't look like a density measure for anything boats are typically made of and I suspect it refers to a property other than density.
     
  4. clmanges
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    clmanges Senior Member

    This is also a property of non-rigid inflatable boats, which makes them both comfortable and also inefficient to propel. Rigidity is generally valued in boat hulls of this size.
     
  5. shaun Moir
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    shaun Moir Junior Member

    apologies it was a property rather than a density

    The density of HDPE can range from 930 to 970 kg/m3.

    Until recently HDPE was not used for boat building considering the challenges that didn’t have a clear solution. Some of the major challenges we face were avoiding the bending/buckling of the panels, and how to provide equal strength that is given by other materials. Once these obstacles are tackled,
    . Now there are many boat builders around the world started building HDPE boats considering the current demand and the future prospects. Though there is not a straightforward rule book/standard to follow for building these boats, the classification society has come forward to modify their current standards suitable for these boats. I am sure very soon we can expect a separate clause for HDPE boats.

    if I'm right, aluminum, FRP/GRP and Carbon fiber are the most commonly used materials for boat building

    . To give a small comparison of these materials a 7m boat hull would require 4mm thickness for aluminum, 7-9 mm for FRP, and 15-20mm for HDPE. HDPE being just 3 times lighter in weight but 5 times thicker compared to aluminum you can figure out the challenges that come with the overall weight. So if the HDPE boat is heavier why is it preferred over other materials? The reason is when it comes to the commercial market the weight is not the first priority for the owners or builders. The most exciting advantages of HDPE is that its maintenance-free since the surface doesn’t catch barnacles, lighter than water to provide enough buoyancy, exhibits amazing impact strength to provide a smooth ride, recyclable completely to keep the environment safe, and very easy to repair. All these reasons make HDPE the perfect choice for boat owners. Usually once an FRP mold is made it’s not easy to change/customize the design. But with HDPE since it’s a welded panel the design can be modified in every boat. Everything put together HDPE definitely performs better than the other conventional materials in the commercial segment.
     
  6. Barry
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    Barry Senior Member

    What did your 14 meter boat weight before equipment?
    Is this the first boat that your company has built?
    Is this boat in operation?
     
  7. shaun Moir
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    shaun Moir Junior Member

    hi Barry

    the weight before equipment etc was 6tonne

    yea this is the very first barge that we have made in HDPE and are looking at making more in the future,

    the boat at present isn't in operation but will be in the new year
     
  8. clmanges
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    clmanges Senior Member

    Not once you've installed a propulsion system, it won't. HDPE is less than 3 percent lighter than water. Even without a drive installed, that steel framework will sink it in seconds. You're still going to have to design extra buoyancy into the design as if the hull were steel, fiberglass or aluminum--more, in fact, since the HDPE is heavier.
     
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  9. shaun Moir
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    shaun Moir Junior Member

    thank you @clmanges very good points we have found there are a lot of HDPE larger boats
    (Passenger and ambulance)25m in size that has been made in turkey as I have said the very first one, we did was more of an R&D could actually build it,
    etc and then learn from it for future ones, there are many good points and negative points however I do think using HDPE can be a different choice rather than steel, etc
     
  10. Barry
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    Barry Senior Member

    Any chance of the link to the 25m boat in Turkey?
     
  11. shaun Moir
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    shaun Moir Junior Member

    of course

     
  12. fallguy
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    fallguy Senior Member

    I'm curious as to why steel was chosen over say white oak for the inside structure; especially if trying for weight reduction. Read it quick, sorry if in error.
     
  13. baeckmo
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    baeckmo Hydrodynamics

    Must say that the HDPE is a very interesting material for various applications in the marine environment. In particular, its toughness to rubbing and its "barnacle-fobic" properties has got me thinking about its use for workboats. I have been building one-off workboats in alu for over forty years, and I have noticed that for the first couple of years, the owners stick pretty well to the recommended antifouling painting procedures, but there comes a time when the preparation before painting is done in a haste. From there on, there is a decline resulting in corrosion problems.

    With the experience we have from water supply pipes on the sea-bed here in the archipelago, I am impressed by the service life we have from the ordinary medium-density PE piping. In most cases, the supply pressure is above 10 bars (~100 m water column), and the installation depth varying between 20 to zero meters, ie a constant pressure differential of 8 to 10 bars. One of the main drawbacks often noted for PE as a boatbuilding material is a tendency to creep, but there has been no creeping observed in our supply net, in spite of the constant load, so obviously that can be managed by correct design.

    The design pressures used in hull strength calculations for boats in the 5 to 15 m range are to a great extent based on the required strength to resist local slamming pressures of short duration. Consequently, the global long-term stresses are generally low, which speaks in favour for the kind of "visco-elasic" properties seen in the HDPE. But...when looking at the strength of welding seams done under field conditions, I feel that there is a risk for failures if the material is introduced as an "amateur option".

    Back in the 1983 issue of the DNV "Rules for construction and certification of vessels less than 15 meters", there is a short paragraph covering polyethylene (and ABS). Scantling rules had a speed limit of 15 knots for MDPE; HDPE was not mentioned. Using these rules, and designing a "decent" structure (not just a thick barrel) will result in quite attractive hull weights, and with more HDPE boats on the water, there is now a huge increase of knowledge about the strength and strain limitations, as well as critical design details and how to overcome.

    I'd like to see our NA's chiming in on this topic, particularly regarding the application of design standards and what the class societies are coming up with. Unfortunately, I have no hope that the ISO will produce anything workable on the subject........!
     
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  14. Silverbreeze
    Joined: Feb 2009
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    Silverbreeze Bruno Tideman

    here is an example of a pontoon in PE 629280E4-6A38-4A29-8D87-64BB4FFB9C2C_1_105_c.jpeg
     
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  15. gonzo
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    gonzo Senior Member

    Fiberglass boats pose a problem of too long longevity, so they have to be buried until there is some way to recycle them

    Any material is "breakable" Kayaks and canoes made of this material routinely break and get cuts. It can be welded.

    Comfortable motion is function of shape and weight distribution and not simply stiffness. A deep Vee fiberglass hull is more comfortable at high speeds than an inflatable boat.
     
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