Nydock welded HDPE pontoons?

Discussion in 'Materials' started by Coracular, Nov 19, 2022.

  1. Coracular
    Joined: Nov 2022
    Posts: 8
    Likes: 1, Points: 13
    Location: Alberta

    Coracular Junior Member

    Hi everyone. I'm new in terms of having an account here, but have ended up reading a lot of posts over the years at the end of a google search etc. I am conceptualizing a houseboat, and am wondering what the thoughts of this community are on Nydock welded HDPE pontoons - Pontoons - NyDock Floating Docks & Pontoons PipeFusion in Huntsville, Ontario, Muskoka https://nydock.com/pricing/pontoons/ - or similar products from other suppliers.

    I recently purchased some forested land on a river, near where I grew up. Ultimately we may retire there, but it's currently a good distance from where we live. I'd like to build a houseboat to live on while we visit, and the HDPE is attractive as it will have long periods unattended (low maintenance) and because it can tolerate being frozen in (ice can get quite thick, temperatures occasionally get down to -40, although less often now than when I was growing up).

    Putting aside for the moment the full calculations of what diameter etc I'd need etc, the following questions come to mind:

    1. Given the flexibility of HDPE, I assume some sort of truss structure should be used to make the deck stiff even before the pontoons are attached - does anyone know of any examples of what that would look like (so that I can understand the design constraints it imposes, and also how it handles thermal expansion)? For reasons I won't go into here I'd like the deck / pontoon combination to be structurally independent from the superstructure.
    2. The welded HDPE brackets seem to be the main thing distinguishing them from regular HDPE pipe with end caps welded on (which is substantially cheaper) - are they worth it, or are there alternative brackets etc that you would recommend?
    3. The 18" diameter has 1/2" walls, the 24" says 1/2" but then farther down says 3/4" - the 36" I'm not sure but I have a short section of similar size from an industrial pipe supplier and the walls are 1" - for a houseboat that will not be travelling at high speeds, do you see a need for compartmentalization?
    4. What did I not think to ask, but should have?

  2. Sundevil
    Joined: Jan 2012
    Posts: 47
    Likes: 1, Points: 8, Legacy Rep: 15
    Location: Ohio, USA

    Sundevil Junior Member

    I worked for a company that used this type of plastic for a scientific instrument float, and it has held up just fine over a decade. The side in the water does need to be cleaned off once or twice a year. I will say that it is heavy, but since this was unattended, we got the thicker wall just to make sure a big tree branch wouldn't come along and tear it open.

    Watch out for high wind gusts and waves that might try to flip it.
  3. Barry
    Joined: Mar 2002
    Posts: 1,812
    Likes: 466, Points: 83, Legacy Rep: 158

    Barry Senior Member

    Thermal Expansion Calculator https://www.plasticpipecalculator.com/ThermalExpansion.aspx
    Above is a calculator that you can enter data and have it calculate the amount that the pontoons will expand in length
    I just guessed at some of the parameters without researching the type of HDPE that you have and found that for a 30 foot pontoon, it would expand 4 inches, plus or minus
    from -20F to 100F
    So the deck will need to accommodate this at the interface between the pontoons and the superstructure

    When dealing with such a high coefficient of thermal expansion, you need to accommodate this length change
    One way to halve the amount of change of length is to bolt the middle of the deck to the middle of the pontoon so it does not move wrt to each other.
    This then leaves you 2 inches of expansion to deal with at each end instead of 4. ( ie if you bolted the front of the deck rigidly)

    An attachment bracket will have to be designed to accommodate the expansion. Starting from the middle of the 30 pontoon and deck, half way to the end of the pontoon, the interface will move 1 inch and at the end of the pontoon the interface will move 2 inches.

    Additionally, the expanding bracket will have to be able to support loads that will come from the flexing of the pontoons in waves as well as hold the pontoons stable. Ie permit only
    longitudinal movement while supporting the deck and stabilizing the pontoons.

    The pontoons should be vented to atmosphere to reduce pressure build up or down throughout the temperature range.
    If you have a structure on top, this will be easy to tap into the wall of the pontoon and run a line up several feet into the structure
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