junk rig catamaran made from plastic bottles?

Discussion in 'Multihulls' started by RussellEngland, Apr 23, 2011.

  1. RussellEngland
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    RussellEngland New Member

    I've been inspired by the An-tiki and the Plastiki.

    How would you build a junk rig catamaran from plastic bits destined for the tip?

    My first thoughts are:
    • 2 litre bottles for the hulls held together by?
    • Old soil/compost bags for the sails
    • Plastic conduit for the battens
    • Polystyrene for the accommodation on top.

    I'm thinking junk rig because it should be easy to build from bits of plastic?

    For the hull, maybe have some solid plastic sheets with holes the size of the bottles.

    Its just an idea at the minute. But I would be grateful for any suggestions :)

    Thanks, Russ
    Last edited: Apr 23, 2011
  2. peterchech
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    peterchech Senior Member

    Sounds more like an idea for a raft than for a catamaran, i once saw a documentary about this guy who built a floating island out of empty plastic bottles, covered it in dirt and everything.
  3. Petros
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    Petros Senior Member

    I have thought about something similar, but the strength and quality of a hull made from trash and rubbish would be hard to predict.

    Best material for the sails I have found is the semi permeable house wrap called Tyvek. There are other brands, I am sure there is something similar in your part of the world. It is durable, and is filament reinforced so the stretch is low. It can be sewn or assembled with heavy duck tape. It can usually be found in construction site scrap piles when they have to rewarp a building for whatever reason. Or you can buy the excess left over from construction projects. Often you can find heavy plastic sheets the same way, but they are not as durable, but makes good temporary sails. Finding salvaged woven goods in large enough pieces to be usable is very difficult. I have been looking for many years. Best place I have found is second hand stores where someone was getting rid of a roll of fabric left over from a business or other project. Not really recycled but it was surplus, and you have to keep looking since it shows up irregularly.

    Good spinnaker cloth can be gotten from hot-air balloonists, safety regulations require them to replace the air bag after so many hours of use, perfectly good for a recreational sailboat however. It could likely be used for a Junk rig since the loads are much lower on the fabric than conventional sailing rigs.

    It is much easier to build a quality hull from salvaged lumber and "found" timbers washed up on beaches. The only practical way I thing to use plastic bottles is to melt them down and than add some kind of fiber reinforcement and form sheets or even molded parts. Lots of heat and tooling required for that, but I do not see how you can form a structure by bonding bottles together, you would only be using them for flotation, and if you encase them in a hull there is no reason to use the bottles at all.

    I thought you could make a profitable buisness by having municipalities pay to haul off their plastic bottles (they have to pay to put them in land fills anyway, you could save them some expense), and melt them down and make rotation molded kayaks out of them. And than sell the kayaks, or other small boats, at higher prices than normal on the basis that it uses all recycled plastic bottles. It would ease your customers guilt for being born to pay extra for having a kayak made of bottles that would have ended up in a land fill. So you collect money at both ends, helping making the venture profitable.
  4. MastMonkey
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    MastMonkey Junior Member

    I don't believe the plastic bottles were structural in any way on Plastiki. At most the provided some reserve buoyancy.
  5. thedutchtouch
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    thedutchtouch Junior Member

    lived on it for a few years until it was broken apart and destroyed in a hurricane, and then all the garbage floated out to sea i believe.:rolleyes:
  6. RussellEngland
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    RussellEngland New Member

    Hi Peter

    Yes, I saw that while hunting for ideas. He's filled nets with plastic bottles, dredges sand from a local canal and uses mangroves to keep it all together

  7. RussellEngland
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    RussellEngland New Member

    Ah right... I didn't know that...
  8. RussellEngland
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    RussellEngland New Member


    Thank you for some great advice. I had a look at equipment to melt and reshape the plastic but the costs are over 100,000 which kind of defeats the object really.

    Maybe I'll keep it as a concept.... :)
  9. ProtectTheOcean
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    ProtectTheOcean Junior Member

    It was actually built and sailed from LA to Hawaii. The vessel was called "Junk" and the hulls were PET bottles held together with netting, which supported a grid of old aluminum masts that formed a platform, upon which was mounted a C310 aircraft cockpit and fuselage. It was slow, more raft than cat, but if the bundles had been sheeted, it would have been much faster. BTW, the ocean was already unscrewing the caps by the 3rd day out, so they did some resealing with cement on the fly once offshore.

    For more on the Junk, go to http://junkraft.com/home.html
    Last edited: May 18, 2011
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    MAINSTAY Junior Member

    The Bottles

    A soda bottle boat!? How dim-witted! How ugly!
    But, how very green, Russell.
    I don't think we can take the ugly out, but we can make it smart.

    1. BOTTLES
    Empty 2-liter bottles are not very strong as thohe filled with soda. So let's fill them with something, specifically CO2. We need a weight scale for less than a kilogram (2 pounds), some empty bottles, some iron weights, a chunk of dry ice, and gloves.
    Break the solid CO2 in smaller chunks, weigh a piece and seal it in a bottle, write the weight on the label. Repeat for a variety of weights. And then wait for the bottles to return to room temperature.
    The strength of the bottles is not in the plastic or the liquid inside, but the gas. At some pressure we are about to determine, the bottle is adequately prestressed and strongest. At higher pressures, the higher stress in the plastic leaves less capacity to resist other stress. At lower pressures, the loads overcome the internal pressure and the plastic fails in compression.
    Lay the room-temp bottles on their side and pile on weights until the bottle fails. Chart weight of iron vs. weight of CO2. I expect to see the line rise from zero to a peak and then slope down. If your chart only slopes up or only down, adjust the CO2 weight and repeat. The amount of CO2 at the peak is the amount to put in every bottle that goes into the boat.
    Score 3 points! 1 for recycling plastic, 1 for not using additional energy, and 1 for sequestration of carbon dioxide.

    Okay. So somehow you get these bottle assembled into something functioning as a hull. I can see some advantages and some buts.

    1. The hull will never flood, but has no living space.
    2. The bottles have compressive strength, but how are tensile forces transferred from one bottle to the next?
    3. The boat is unsinkable in that most of the individual bottles would have to be punctured, but survivability depends on the integrety of the means the bottles, etc., are held together.

    Any ideas? What's been tried before?

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    MAINSTAY Junior Member

    The Hulls

    A soda bottle boat hull is simply a collection of small parts, like those plastic blocks from Denmark.

    I think stuffing a hull-shape bag or net would work, but without some internal structure, a tear in the bag or net leads to total failure of the hull and a bunch of empty plastic bottles littering distant shores.

    I think binding the 2-liter bottles in groups of 7 into hexagons is a reasonable start. I don't know what will work best to bind them, or what is available to you.

    I saw on TV a boat built with duct tape as the hull surface over a PVC pipe frame. I worked for a while. But duct tape does not work well in wet environments, even when new. Recycled tape might work on your boat since it is binding bottles and not keeping water out

    But what about that clear plastic stick-to-itself sheet stuff they wrap around pallet loads? It's tough, waterproof, available everywhere, free, and even when they cut down one side of the pallet, sheets of a size usable for your boat remain.

    The sheets are wide enough to cover a number (5,6,?) hexagons end to end. That's 42 or 49 bottles in a block. And they have smooth sides for a faster hull.

    The sheet does not have to be waterproof. That's what the bottles are for. Water inside the sheets and between the bottles may actually help the boat to sail better by acting as water ballast when the hull tries to lift out of the water, without adding any weight when it's in the water.

    The sheets could also form a boat-like prow. I tried to imagine how to taper the hexagons at the bow; like dropping the outer ones making a group of 5, the dropping the next column of them and binding the remaining two bottles of that hex to the adjacent hex, untill only one column remained. At each step the necks of the bottles would be securly bound against the water forcing its way between bottles. And the cutwater being a 50mm (2") PVC Sch 40 pipe split and the necks of the lead bottles inserted in the slit.

    Hydrodynamically, it's very messy. But better the soulders than the concave bottom of the bottles. And better yet if covered by any sheet matertal, (including a bed sheet), aluminum or vinyl siding or anything that can be bent around the cutwater and extend back along the taper. It does not have to extend the entire length of the taper, additional unbent siding panels can be used. And it does not have to be sealed at the top or bottom.

    With the siding, the hydrodynamic forces are pressing the bottles together rather than driving them apart. That's good.

    Now aft to the hull.

    The hexes would nest well together in close packing. If a three-in-a-row axis is vertical, then this gives a rather lumpy v-hull cross-section that just might work.

    The wetted-surface shrinks the A/p ratio to near zero, whick means this hull will be slower than most. But the goal is viable sailboat thru recycling.

    As workable as the cross-section may be, there must be a means to connect the bottles longitudinally, a keel or spine, or the deck, or something.

    I suggest 10mm (4") PVC pipes joined into lengthes the same as the boat. Putting 6 2-liter bottles around it to form the hexes, and binding these long hexes together to form the hull has much improved longitudinal strength.

    If both thin wall (Sch40) and thick wall (Sch80) are available, use a thick wall in the bottom hex and the rest in top hexes, and then use thin in the remaining hexes.

    And if you can get the pipe in colors make 3 blue and two green. The blue can be the center of the bottom and two second layer hexes as wate r tanks. The green can be used for black and grey waste water storage in the other hull. A screw cap on both ends would help maintain cleanliness. And you'd still need all the plumbing to get stuff in and out of the tanks.

    Such boat-length tanks have a nasty characteristic
    when partially full, and the green will always be partially full. The liquid runs to the lower end of the tank as the boat goes over waves and chop. This shifts the center of gravity of the boat a greater amount than the same liquid in a normal tank. However, the normal tank would be located higher, perhaps on deck, which increases the impact of the normal tank by the level arm of height. So the effect may not so difference between the two systems. But something to check the numbers.

    The pipes not used for storage could be stiffened with internal pressure like the bottles. And I suggest testing on short lengths as before, starting at 3x the CO2 per liter. But since these pipes are more structural than floatation, I might go with a valve and air pressure. If the CO2 leaked, there's no way to restore the stiffness without disassembly. With a valve the pressure can be checked and restored if needs be.

    It's late. Good Night. And we don't have a means to attach deck, standing or running rigging, or steerage.(You do want to carry poor immigrants, right?)
  12. mungus
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    mungus New Member

    Beer Can Regatta, Darwin, Australia

    Hi Russell,

    There is a fun event in Darwin, Australia, called the beer can regatta, for which participants build a vessel using aluminium beer cans and race it around a course. Some of the vessels have become very sophisticated over the years, carrying rowing crews of up to 20 people and also others which have mounted outboard engines of considerable horsepower.

    I helped one team which was disqualified for cheating because we used PET bottles instead of beer cans. (No penalties were ever imposed on the winning team which didn't use beer cans either, they used Coke cans because they remembered that 'things go better with Coke').

    But I digress - the PET bottles stuck together excellently using Sikaflex polyurethane adhesive, it's not cheap but is very durable and not noticeably affected by UV degradation.

    Before that we tried cheaper industrial adhesives like liquid nails and most didn't work well and some damaged the PET.

    We also glued the caps onto the bottles. We staggered the bottles a bit like building a brick wall, overlapping them lengthwise improved the structure considerably.

    Ours was about 24ft (7.5m) long and 3m wide, the width was the widest which could be towed on the road without a police escort/permit.

    It was entirely made from PET bottles because they proved quite strong enough for the six crew to walk around and sit on for paddling although it is just a one day event so we weren't worried about any damage to the 'deck'. If you wanted it to last longer you could just add a ply deck painted with epoxy paint - glue it on with Sika as well. incidentally the Sika cost us more than $1000 (about 700GBP) but then Darwin is a very expensive place, if you bought it by the case it would be perhaps half that.

    It would be easy enough to embed some timber in appropriate places to act as chainplates for your rig and a mast step.

    The PET copes quite well with UV but it wouldn't hurt to provide some protection for the outer bottles - a cheap paint perhaps (test for damage to the PET).

    The boat won't last long if left in the water unless you use a lightweight filler to block up all the passages between the bottles because it will become home to every kind of hull fouling and the extra weight will take it down and then more critters and even more weight etc.

    Incidentally a PET boat isn't light!

    After the regatta we couldn't break ours apart, the Sika works well! So it went to the tip in one piece and even the tip bulldozer had a fair battle with it before it finally succumbed.

    One poster's idea about using dry ice to pressurize the bottles sounds like a good one but if you don't keep the dry ice moving while it vaporises it will weaken the PET where it sits on it.

    Idea - search for cheap plywood and build a boat that way...

    Have fun,

  13. troy2000
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    troy2000 Senior Member

    This thread gives the term 'junk rig' a whole new meaning... :)
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    MAINSTAY Junior Member

    Plastic Bug

    A soda bottle boat? Russ, I've been infected with the plastic bottle bug! Help! I can't stop.

    You have not said how you are going to use the boat. If you want a day sailer, then Mungus has a proven method. And by the effort needed to destroy it, it may be blue water capable.

    The Plastiki was 60-ft OAL and had a half circle (Max diameter near center and decreasing fore and aft) of plastic bottles below the waterline (perhaps 8,000 or 10,000), and additional bottles by rank and file above. The rest of the boat is fairly standard fiberglas and aluminum boat construction. If you want something like the
    Plastiki or Junk, then my suggestions are inadequate. The PVC pipes are too flexible
    for that length.

    My suggestions were more toward a 10m sailing catamaran with accommodations on the bridge with maximum reuse/recycle, with minimum new material, min. added energy, min. greenhouse gases, and perhaps low tech and low cost.

    Then I added, a boat that works well enough that others may want to build and sail, thereby recycling multiples of the materials out of the tips and dumps, improving our planet, and having a little sport at the same time.

    So. what do you think? Are you still in this project?


  15. MastMonkey
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    MastMonkey Junior Member

    Another consideration is that since you intend to use a junk rig it will be necessary to design a system in each hull that will support the free standing mast. I would be skeptical that a hull made of plastic bottles and some sheeting material alone would do so.
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