PET Bottle Floatation

Discussion in 'Boat Design' started by Katoh, Aug 21, 2011.

  1. Jeremy Harris
    Joined: Jun 2009
    Posts: 978
    Likes: 59, Points: 28, Legacy Rep: 711
    Location: Salisbury, UK

    Jeremy Harris Senior Member

    Yes there are plastic balls that are OK for floatation. I bought a large quantity of plastic balls that were intended for use as winter freeze protection for irregular shaped outdoor pools years ago and found they were OK to a depth of around 70ft (as far as we took them, these were the successors to the PET bottles on a work project). They were designed to be immersed in swimming pool water for long periods and withstand exposure to light and cold, so I'd guess they'd be ideal for use in a boat.

    I can't recall the supplier, but do remember that they made them in lots of different sizes, from around ping pong ball size up to maybe 4" in diameter.
     
  2. Katoh
    Joined: May 2010
    Posts: 205
    Likes: 2, Points: 0, Legacy Rep: 58
    Location: A.C.T

    Katoh Senior Member

    Jermy
    That sounds Ideal! If you remember the name or a brand I would like to look into that, My googling has yet to find anything like that.
    With the balls I get them through the hole and into hull, then pump/push them around the hull with air. Surely it is bound to help, if anything better than nothing at all.
    Cheers

    Katoh
     
  3. Katoh
    Joined: May 2010
    Posts: 205
    Likes: 2, Points: 0, Legacy Rep: 58
    Location: A.C.T

    Katoh Senior Member

  4. lewisboats
    Joined: Oct 2002
    Posts: 2,329
    Likes: 126, Points: 0, Legacy Rep: 1603
    Location: Iowa

    lewisboats Obsessed Member

    Just a tip if you use bottles or any seal-able flexible container...put them into the freezer if you can, open so the air inside is the same temp as the freezer. Then close them tight. This gives you the densest air possible in the bottle and they wont collapse in winter when it gets cold out. If temps aren't a problem, then the bottles are pressurized in warmer temperatures and won't be subject to crush damage nearly as much.
     
  5. Mr Efficiency
    Joined: Oct 2010
    Posts: 9,470
    Likes: 768, Points: 113, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

  6. Poida
    Joined: Apr 2006
    Posts: 1,189
    Likes: 51, Points: 48, Legacy Rep: 497
    Location: Australia

    Poida Senior Member

    Depending on where the hole is, the stern would be good, cap the ends of PVC pipe and feed lengths of it through the hole.
     
  7. Village_Idiot
    Joined: Oct 2007
    Posts: 382
    Likes: 14, Points: 18, Legacy Rep: 138
    Location: USA

    Village_Idiot Senior Member

    Find some heavy-duty plastic (garbage?) bags to put down through the access hole first - that may help hold the "contents" together if that part of the hull doesn't get breached too badly, and is pretty cheap insurance. You might even double or triple the bags, use air to inflate them to the contours of the hatch.

    I've heard of people using styrofoam packing peanuts for flotation where hatch access is severely-limited. However, this was for small aluminum boats used in calm inland waters where a hull breach is improbable. Also, I don't know how the peanuts would hold up to extended water-logging or solvents - you could run a few tests on them.
     
  8. Katoh
    Joined: May 2010
    Posts: 205
    Likes: 2, Points: 0, Legacy Rep: 58
    Location: A.C.T

    Katoh Senior Member

    Great Tip.

    Mr Efficiency
    I can see that spheres are not the correct shape to be using due to the volume of voids that they create, a smaller sphere will have less void volume than larger but you really cant go to small. I was thinking of a ball around the 50mm dia which should give 65cm3 of air volume. work on a one to one and should be able to support 65grams of weight. The whole problem is getting these in there, and balls would make it so much easier to do.
    Cheers

    Katoh
     
  9. Mr Efficiency
    Joined: Oct 2010
    Posts: 9,470
    Likes: 768, Points: 113, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    Styrofoam dissolves in petrol, unfortunately.
     
  10. Katoh
    Joined: May 2010
    Posts: 205
    Likes: 2, Points: 0, Legacy Rep: 58
    Location: A.C.T

    Katoh Senior Member

    Poida
    The access hole is midship, I could possible cut another in the cabin but that would be even further forward and in a more difficult position than the first. Your idea had crossed my mind before, I might have to post a photo of the deck and positioning of the holes so you can see the dilemma.

    Village_Idiot
    The idea of the garbage bags is a good one as well, the only concern that I would have with it that it might allow areas were bilge water can congregate and sit, without draining, might be looking down the barrel of corrosion issues in future.

    Cheers

    Katoh
     
  11. Submarine Tom

    Submarine Tom Previous Member

    And how many pounds, kg or Newtons of buoyancy do you require to keep your flooded vessel afloat?

    -Tom
     
  12. Katoh
    Joined: May 2010
    Posts: 205
    Likes: 2, Points: 0, Legacy Rep: 58
    Location: A.C.T

    Katoh Senior Member

    Tom
    I do not have any exact figures and I am basing this on an educated guess. Say motor and leg 450kg, dry hull 900kg, add extras 150kg lets say 1500kg for a 6m-22" vessel.
    Again I dont know if or how much foam is in the hull? As stated in the first post, but I definitely know there is at least a 900mmvoid running along the keel line. My intention is to fill this void with "whatever System" to give some more or some protection. My plan was to keep filling the hull through this access hole till I could fill no further.
    I basically worked out with a 50mm dia ball you could get 10,000 of them to a cubic meter and they would have 740litres of air volume, I am not certain how many I can fit in the hull space, and without totally removing a sealed (welded) floor I could never confidently give a firm answer. At present I personally do not want to go to that extreme.
    Cheers

    Katoh
     
  13. Rick Tyler
    Joined: Aug 2011
    Posts: 18
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Redmond, WA

    Rick Tyler Defenstrator in chief

  14. Submarine Tom

    Submarine Tom Previous Member

    Interesting.

    Now where in the world is A.C.T. and what does that stand for?

    -Tom
     

  15. Village_Idiot
    Joined: Oct 2007
    Posts: 382
    Likes: 14, Points: 18, Legacy Rep: 138
    Location: USA

    Village_Idiot Senior Member

    You might also entertain coating the balls, bottles or whatever in resin to enhance their resistance to solvents. You will have to figure out how to dry them out, though, without them sticking together - or just inject them into the hull immediately after coating (although you won't be able to retrieve them with a shop vac later if need be). Tennis balls might be ideal for holding/gripping the resin.

    (I have some pine trees over my driveway that are dripping lotsa free resin onto my car :eek: - come get all you want :D)

    Alternatives would be glass (fragile, heavy) or wooden (balsa?) balls, albeit both more expensive. Don't know of any aluminum balls...
     
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.