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  1. #1
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    Dec 2004
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    Default Filling a rubber dinghy with foam?

    I have had an idea!

    I have a very nice Avon Dinghy, although 15 years old it has no patches etc but it is still too nice to leave chained to a Pontoon 24/7.

    Rather than bringing the dinghy back and forth from home every trip I need something to "float" across a very sheltered harbour and be able to leave on the mooring and chained to a pontoon 24/7.

    For a previous boat I had a very cheap plywood pram dinghy which did the job, but I sold this with the last boat (and kept the Avon!) - the only problem with the pram dinghy was that after many years with Avons I did find it rather a tippy b#gger, I never fell in, but I had my "moments"!!

    My options are:-

    1) Another cheap pram type dinghy - too "tippy"

    2) A plastic dinghy with built in buoyancy - hard to get cheap S/H

    3) A cheap s/h inflatable - they require frequesnt (ish) pumping up (especially cheap s/h ones!) and keeping them afloat 24/7 doesn't do them a lot of good.

    My idea is to get a very very cheap small s/h inflatable dinghy, doesn't matter if it only holds air for less than 5 minutes and has more patches than a quilt or more holes than a sieve, because...............I am going to fill it full of foam!

    My questions are, has anyone done this? Would the usual expanding foam react with the Dinghy "rubber" (ie does it contain chemicals that would "eat" the rubber?). I was also thinking of coating the Dinghy with some form of Epoxy or similar (on the basis that anything I buy will probably not be water (air!) tight, and I know you gotta keep the foam dry).

    I am not sure whether I patch the dinghy first, then coat it with epoxy and then fill with expanding foam (i figure this was way would give me a bit of "leeway" in case I over fill it!). Or fill it with expanding foam first, then epoxy it.

    Perhaps this is not the cheapest route and the resulting "creation" may not win any beaty contests, but as long as it does the job I will put any resulting ugliness down to a cunning anti theft device!

    Any thoughts / words of wisdom (I have not used epoxy or expanding foam before).
    Waiting for Dan to put me out of your misery since 17 Feb (2010 ).

  2. #2
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    Jan 2003
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    Default Re: Filling a rubber dinghy with foam?

    Good idea, might work, but could be very messy if you use too much foam. Why not cover the filled dinghy in GRP? Be sure to have a vidio running when you fill it!

  3. #3
    tazzle's Avatar
    tazzle is offline
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    Default Re: Filling a rubber dinghy with foam?

    I'm open to correction, but I have a feeling that standard Polyurethane builder's foam is not closed-cell - i.e. it will absorb water if the skin is punctured. Could be wrong.
    If we wish to preserve a free society, it is essential that we recognize that the desirability of a particular object is not sufficient justification for the use of coercion - Hayek

  4. #4
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    Default Re: Filling a rubber dinghy with foam?

    [ QUOTE ]
    Why not cover the filled dinghy in GRP?

    [/ QUOTE ] - I was rather hoping to get away with just "painting on" a coat (or two) of epoxy, rather than doing any laminating. Of course epoxy is not cheap, maybe I could get away with just the resin stuff that is used to "make" GRP???


    [ QUOTE ]
    Be sure to have a vidio running when you fill it!

    [/ QUOTE ]

    Actually that is not a bad idea, might pay for a proper dinghy!
    Waiting for Dan to put me out of your misery since 17 Feb (2010 ).

  5. #5
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    Default Re: Filling a rubber dinghy with foam?

    [ QUOTE ]
    I'm open to correction, but I have a feeling that standard Polyurethane builder's foam is not closed-cell - i.e. it will absorb water if the skin is punctured. Could be wrong.

    [/ QUOTE ]

    I was assuming that this was the case, hence the covering of epoxy - but I didn't realise you could get any other sort. Anyone know? - cos it might save me messing around with coating it with epoxy (or similar) to make 100% sure it was waterproof.

    BTW I will post up photos of the finished "creation"!!!
    Waiting for Dan to put me out of your misery since 17 Feb (2010 ).

  6. #6
    Stemar's Avatar
    Stemar is offline Registered User
    Location : Home - London, Boat - Gosport
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    Default Re: Filling a rubber dinghy with foam?

    I don't think the covering with epoxy bit would work, 'cos the whole advantage of a rubber duck is that it's flexible. Epoxy isn't. At least, not compared to a rubber duck which, even when filled with foam is still going to stretch in the sun and bend with waves and bumps against the pontoon or your boat.

    Sheathing the beast in grp isn't such a daft idea as it sounds at first. I've seen an aluminium "rib" which, allegedly, adds rigidity and puncture resistance to the advantages of the rib. Cost and time would probably make it a non-starter unless you have nothing better to do for a few weeks and an unlimited supply of glass cloth and resin. If you have, please let me know when I can come and pick up a load [img]/forums/images/graemlins/smile.gif[/img]

    I wouldn't trust builder's foam, but Mr Sadler and M Etap seem to have found some stuff that might work. I think I'd want to know more about how it would stand up over time to the flexing of the boat before I spent much time or money on it though.
    Steve
    Never believe anything until it has been officially denied.

  7. #7
    Talbot's Avatar
    Talbot is offline Registered User
    Location : Stavanger, Norway
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    Default Re: Filling a rubber dinghy with foam?

    This has been done, and IIRC there was an article on PBO- as a means of extending the life of a dead inflatable.
    "Be wary of strong drink. It can make you shoot at tax collectors - and miss."
    Robert A Heinlein

  8. #8
    VicS is offline Registered User
    Location : Home: Kent. Boat: Chichester
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    Default Re: Filling a rubber dinghy with foam?

    The builders foam works by reacting with moisture in the air, I believe, so it may not work in large confined spaces. The resulting foam is not "closed cell" so could absorb water. Closed cell foams are produced with a two component system. It should be possible to get them from glassfibre suppliers especially one that supplies materials for making canoes.

    In either case it will be difficult to judge the quantity required to fill the compartments and impossible to actually get the mixture in unless you cut big holes in place of the valves.

    IMHO your best bet is to find a tatty old fibreglass dinghy which is more stable than your old one. It'll probably be cheaper and last a lot longer.
    Sea Wych Owners Association: www.Seawych.org

  9. #9
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    Default Re: Filling a rubber dinghy with foam?


    i think it's a great idea, please let me know what foam should be used !

    just make sure you never want to roll it up again :-))

  10. #10
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    Default Re: Filling a rubber dinghy with foam?

    I have seen this done to a quite large RIB,sheathed comprehensively in grp..
    The owner said it was a bir er heavier and a b--ger when it rubbed up against his topsides!
    Using 2 part foam? Why not,it will prob cost you 100 in foam though-and if you dont get enough in there it wil be,er,lumpy?saggy?..I think the video and using too much foam is the way to go,.Hey at worst
    you will get a bigger dinghy than when you started!
    There was a short thread on here about 10 years ago where someone asked if it was possible to construct an inflatable dinghy from a kit or a set of plans....It ended with the one response''Are you mad?"
    How about a forum whip round,say a pound a pop to ensure you buy enough foam for this enterprise,could be fun
    Why argue with a nautical wall? I just read the graffiti these days.

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