Building a floating island/raft from PET plastic bottles like Richart Sowa did.

Discussion in 'Boat Design' started by Boucaneer, Sep 26, 2014.

  1. rwatson
    Joined: Aug 2007
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    Location: Tasmania,Australia

    rwatson Senior Member

    Sure sure - imagine PVC standing up to constant wave pounding.

    Build one, and then report back after you have spent a few weeks on it.

    have you ever spent time on a boat in the ocean ????
     
  2. Gump
    Joined: May 2012
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    Location: Tennessee

    Gump Junior Member

    I find your troll replies quite amusing. I would have guessed that somebody who knows it all would know that 15" culvert pipe is very durable HDPE... but I guess not...

    The idea was presented as a concept which "almost" anybody could see would be workable in one form or another. Certainly better than little mesh bags holding bottles..
     
  3. rwatson
    Joined: Aug 2007
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    Location: Tasmania,Australia

    rwatson Senior Member

    Its much easier to call someone a troll than actually support what you are saying, with basic calculations and/or prototypes.

    And yes, "15" culvert pipe is durable HDPE", but it isn't structurally sound for constant, unsupported shocks. It relies on compressed fill to provide its certified use, with strict instructions on the size and placement of surrounding fill. As a docking pier, it has to resist tonnes of lateral water pressure on a constant basis. It wont resist the sideways pressures of the heavy tyres. Having a steel rod will help with structural support, but my bet is it wouldnt last for long. You could use 4 or 5 rods, running inside or outside the pipe, but unless you had them welded into a girder, they would end up distorting and bending in time.

    Likewise, being mere HDPE, I havnt seen your plans for a way to fasten and secure the floats to the platform. Where are your structural attachment points ?

    And, to add to the list of woes for this ill advised concept, how about doing some calculations to show the effects of marine growth on the floats.

    For my own interest, i have run up a basic calculations that you should have done, and based on "off the top of my head" assumptions, calculate that you would get a maximum of 90 Kilos of flotation per 'Cylinder' for 6 tyres.

    Now, you need to design a platform that will hold all these fragile columns together that wont sink them from its weight.

    If a steel platform could be built say 3 x 3 metres, and you used 9 columns, you might get 800 kilos of support in total, ( together with a huge loading from strong sea swells due to protruding 'legs') . Now, for safety, assume half of the bouyancy is held in reserve, that gives you a tiny 400 kilos of buoyancy for the whole platform.

    Compare that to say a 3 x 3 x .5 metre high density foam platform, that already provides a standing structure can support 4,500 kilos ( 2.5 tonnes useful loading )

    You would be better off building a wire cage and filling it with PET bottles. The tyres are an inefficient and polluting element in the design.

    Now, why don't start proving your concept with sound calculations and/or prototypes.

    Hopefully, my comments will prevent unsuspecting enthusiasts from assuming you know what you are talking about, and wasting their time.
     

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  4. Gump
    Joined: May 2012
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    Location: Tennessee

    Gump Junior Member

    Given that the first drawing was a bit off the top of my head, I'll grant you that it's not the optimal version. The second drawing is much more practical I think...

    Based on that drawing, my thumbnail calculations were for 3 tires... each having approximately 1 cubic foot of useable space filled at 80% of capacity with eps scrap foam would yield a net buoyancy of about 180 lbs... of course nobody could know that until they actually did one .... so the value of those calculations are marginal at best.

    The fact that for virtually no cost you have 180 pounds of net buoyancy with a very durable outer covering makes the tires a nice part of the design.

    The biggest weakness of junk floatation is that it needs to be contained and protected from sun, wave action and marine life. The tires provide that.

    So given those parameters perhaps 6 sets would be the right number for an 8' x 8' section of decking. ( Of course that would need to be tested).

    A stack of 3 tires is only about 18" tall.... I don't see the loading problems you suggest.

    A wire basket would soon decay to nothing in a marine environment. The flotation would also degrade at a maximum rate... So I hope no enthusiasts take you up on that suggestion.

    Another benefit you ignore is the ballast effect of the water contained in each stack. That weight of water creates a very stable platform that would be very resistant to tipping over...

    Regarding marine growth I would also suggest that your wire basket version would be much more of a problem than tires.
     
  5. rwatson
    Joined: Aug 2007
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    Location: Tasmania,Australia

    rwatson Senior Member

    beside the point that I wasn't recommending baskets, just comparing them for volume, here is some references to marine grade mesh

    http://www.sakura-tech.net/english/product_02_01.html


    I await your definitive testing
     
  6. Gump
    Joined: May 2012
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    Location: Tennessee

    Gump Junior Member

    how much would the marine grade basket cost ?..... Isn't the whole premise of the exercise to make the least expensive but practical design ? Just the block of polystyrene for the concrete idea will cost in the neighborhood of $500. add to that the cost of concrete and connection points and you could just about buy boats and tie them together.

    Are you offering to also test your concrete idea ?
     
  7. Gump
    Joined: May 2012
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    Location: Tennessee

    Gump Junior Member

    I reviewed your calculations and find them lacking as well. Your rate of fill per tire is light because you are not utilizing the center open area when the tires are stacked together afforded by the metal plate / threaded rod idea.

    Your net buoyancy figure also ignores the weight of the tires which obviously must be accounted for in some way. So I feel I must warn unsuspecting enthusiasts to avoid that piece of work.

    While I like the tire idea for a more durable "free" design option, the other way would be to use the construction method found on the photos of the boats I showed on page 3.

    Individual pontoons are constructed like a roll of lifesavers. Outer covering is made from sewn indoor outdoor carpet, which functions like a very fine mesh. It allows water to filter right through it. It lasts for decades in sun and weather. Several boats I've made are over 6 years old and have never required replacement or repairs.

    Junk floatation is managed in individual mesh bags. Stacked like lifesavers within the outer cover.
     
  8. Boucaneer
    Joined: Sep 2014
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    Boucaneer Junior Member

    Ooh, what's been going on here then. Lol

    I have decided to use a 1/3 Portland cement and sand mix for my polystyrene heconagional blocks. I have a question please, had anyone had any good experience or knowledge and knows the best mix ratio for boat hills and acrylic mix please?

    I'm seeing a lot of sculptor ferrocement info, which isn't helping me, but I'm using the 1/3 Portland cement/sand ratio from a water tank design.

    Any advice you guys can help with regarding the mix ratios/recipes would be most appreciated.

    Now, no arguing chaps while I am away. :)

    Thank you all for your good advice as positive attitude.

    Have a great week.
     
  9. rwatson
    Joined: Aug 2007
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    Location: Tasmania,Australia

    rwatson Senior Member

    Some good videos available.

    This one may be helpfull, with mentions of mix ratios



    You did buy those recommended ferrocement building books - didn't you ?? :confused:
     
  10. Boucaneer
    Joined: Sep 2014
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    Location: Far far away.

    Boucaneer Junior Member

    Great, yes I see now they put that extra ballast mix in as the weight of the water. Interesting. So I am going to buy some acrylic but how much would you think I should add to help with adding to the waterproof resistance?

    I'm pretty set on the cement and sand mix, it's just the acrylic that confusing me.

    Thanks.
     
  11. rwatson
    Joined: Aug 2007
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    Location: Tasmania,Australia

    rwatson Senior Member

    You seriously need to contact some cement experts in you area, and buy some info.

    I am not an expect on concrete, very few people are.

    If you are serious about this project, do the homework and dont be lazy.
     

  12. Boucaneer
    Joined: Sep 2014
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    Location: Far far away.

    Boucaneer Junior Member

    All the people in my area mate are Pakistani shop owners. Lol
    I will seek advice in England, I just have to find the right people.

    People charge good money for free advice in the U.K, I'm just trying to find the information out using this modern technology of Internet by boat enthusiasts and DIY builders.

    I'm sure somebody can advise on acrylic mix tips, I've seen 6oz mentioned in a 5 gallon cement/sand mix.

    Just looking for confirmation or experience. Maybe best to start a reinforced ferrocement thread instead, that might collate the information that people may need in the future.

    Thank you for your advice, it's put me in the right track.

    Cheers.
     
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