Roto moulded small hull ..good or bad buy?

Discussion in 'Boat Design' started by pistnbroke, Aug 7, 2010.

  1. pistnbroke
    Joined: Jan 2009
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    Unfortunatly having to return to that horrible place the UK due to the world financial crash...so it looks like its canal time and 4 mph rather than 40.
    Could easy build another stitch and glue ..15 ft ish but I saw some rotomoulded boats by the french company fun yak .....4.4m is good value at 1000 pounds ......should have a resale value when I get fed up with 4 mph !!!
    only thing that worries me is attaching accessories to it .....drill a hole and its there for life .....
    Anybody experienced any of these boats /rotomoulded boats in general ....photos below
     

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  2. Landlubber
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    Landlubber Senior Member

    ....yep mate, they have proven themselves to be quite in destructible.....many have tried very hard but they seem to fight back.

    Nylex here made them, still do, and besides being sort of heavy for their size, they work well.....personally they look crap, but they do have a purpose in life....hire boats like them too....guess that says it all.
     
  3. L.DOSSO
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    L.DOSSO Junior Member

    yes there is fun yack,but there is jeanneau brand. "aquapeche" series for anglin dinghy (green polyethylene) and "cap" series (rather white color polyethylene) for boats that can be used at sea.

    one is intermediary between sea/river use. it is Aquapeche 370 .she has an interreting bottom (of hull)with a cutting bow for plannin in small chopped waters (specielly designed for great lakes , in fact).
     
  4. pistnbroke
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    thanks for that ....very poor website that wont give you the information and they seem to be much more expensive than fun yak ...
     
  5. L.DOSSO
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    L.DOSSO Junior Member

    yes a bit more expensive. true the web site is not pleasant.
     
  6. boybland
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    boybland Junior Member

    I have a secondhand rotomoulded X3 from http://www.sailextreme.com/ it's quite heavy for its size but seems to be absolutely indestructible even when you bang into things quite fast.
    It must already be several years old as I have had it a couple and it was by no means new when I bought it, so from a durability point of view rotomould seems pretty good.
     
  7. Jeremy Harris
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    Jeremy Harris Senior Member

    You could look at making your own rotomould and selling any surplus boats to recover your investment. I friend had some rotomoulded fuel tanks made up, to a complex shape, and found that the cost of each moulded part was pretty reasonable. The mould was just made from welded steel plate, with a bolt-together flange and welded on attachments for the rotational machine to hold it. Not a lot of work or cost if you have access to welding gear.

    Jeremy
     
  8. daiquiri
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    Do you perhaps know how did he control or assure the minimum thickness of the finished part?
     
  9. Jeremy Harris
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    Jeremy Harris Senior Member

    I'm pretty sure the moulding company did that as part of the manufacturing service. All he did was make the mould, using some guidance from them on dimensions, weight and the size of the attachments.

    I saw the finished mould and it looked pretty straightforward, just cut, bent and welded steel plate around 4 - 5mm thick, with welded on fittings. The bit that took the time was cleaning up the inside surface, after fabrication, to get a reasonable surface finish on the part. I recall him saying that he wished he'd taken more care to protect the inside surfaces when handling and welding the steel sheet, as it spent a fair while grinding out scratches and getting the surface nice and smooth.

    I had a couple of the tanks he made (they were aircraft wing tanks) and they seemed fine. The plastic was high density polyethylene, I think, and seemed pretty tough. The tanks even had moulded threads on the filler necks and thick bosses where threaded fuel fittings were later fitted.

    Jeremy
     
  10. pistnbroke
    Joined: Jan 2009
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    yes jeremy .....I have not got more money than sense !! I make a 15ft boat with double skin in 6mm plate to rotomould a boat to use on the british canal system ....crazy ..would cost a fortune and where do you store it ....two boats to store and one weighs 3 tonnes......no no No NO.

    found a nice tag welder to build on your endless sphere ..bidding on the capacitor tonight.....thanks for that but DIY Roto NO
     
  11. apex1

    apex1 Guest

    Pistn,

    the drilled hole must not be there forever. HDPE can be "welded" relatively easily.

    Regards
    Richard
     
  12. jonr
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    jonr Senior Member

    I'd say that the red one is about 15% heavier than a similar inflatable. Of course "similar" is very arguable.
     
  13. Landlubber
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    Landlubber Senior Member

    ....I made up a set of moulds for tanks, they were diesel/potable water and sewage waste.

    The thickness, just as a matter of interest is simple, it is the weight of the pellets that covers the surface area of the inner sides of the mould, the makers have details of how thick the pellets melt to per kg/surface area.
    They simply weigh the pellets to determine the end thickness.

    There is a shrinkage factor to be accomodated, and also angles for square sided boxes, but the product makers know EXACTLY the angles to use, so listen to them (I think it was about 5%, but just ask any of them, they all know very well, cos some moulds are made too tight and they hate them. I made mine to suit the fellas that were doing the cooking, so everyone was happy with the result.

    Spend a LOT of time polishing the steel plate BEFORE welding it all together. I had to TIG mine as my stick welding was not so good. If you can do real nice welds, then MIG or STICK doesn't matter. Die gringing smooth radius is not funny.
     
  14. Jeremy Harris
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    Jeremy Harris Senior Member

    What I was thinking was that you could end up with a free, or at least pretty cheap, rotomoulded boat of your own design, rather than accept an off-the-shelf design.

    You could offset the cost of the mould by getting a few more hulls from it and selling them, or even just by selling the mould to someone else after getting you own hull moulded.

    Your right about needing space and time, though, if your happy with the designs you can buy off-the-shelf then it makes sense to go down that route.

    You should find the capacitive discharge welder works well, there are photos of the one I built somewhere on that ES thread.

    Jeremy
     

  15. pistnbroke
    Joined: Jan 2009
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    the queston was good or bad BUY not MAKE
     
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