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  1. #1
    Join Date
    Aug 2009
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    Sydney, NSW, Australia
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    Default Small aluminium boat trailer build

    2 projects on the go at the moment one is a large 4x2.5m tray trailer the other one is this aluminium boat trailer for my tinny aluminium i beam is quiet expensive so i tried to use 1 piece for the two sides it has small cuts in the top and bottom than slightly bent in on both sides i plan on reinforcing the bent sections later on once the drawbar is attached to hold it aligned while i fill in the gaps and cuts

    the black trailer is on its last limb its a old 1970's-1980's model home made trailer which has rusted quiet a bit the new aluminium trailer will replace the old girl

    alloy trailer will have a steel plate top and bottom of the front V joint mostly for strength and rigidity plus the only way to attach the safety chains is to weld and they are steel so the drawbar will be steel i also think i will need to use either steel for the spring holder or possibly stainless but that's expensive

    i only see one hurdle and that is welding the i beam top and bottom pieces being 6mm i have never TIG welded that kind of material so thick i looked on the miller calculator i will be maxing out my machine at 180-200amps
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  2. #2
    Join Date
    May 2011
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    Murray Bridge S Aust.
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    I think you'll have some major problems in regards to the steel being bolted to the aluminium, called electrolysis. How to get around that I don't know, I'd be inclined to go down to the boat ramps and have a look at the ally trailers that are parked there, ask the owners if they have any problems at all. Now is the time to get it sorted out before going much further with it.
    Kryn
    To grow old is mandatory, growing up is optional.

  3. #3
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    Default

    Hey KBs up untill around 12 months ago the commercial boat alloy trailers all had steel drawbars i think they couldn't get around the steel safety chain on a alloy drawbar but i have read lately some trailers are being advertised as all aluminium so i don't know how they went about it, over the years it has been talked about using a steel drawbar some people use thin nylon washers to keep the aluminum and gal steel apart to stop any electrolysis from happening but what thicknesses is a guess, i have my toy lathes so i could whizz some up but i would be skeptical of using them due to the clearance unless there is some rigid type of nylon available that won't compress under great forces it may be something i need to look into, some other people suggest using stainless steel as i have read stainless and aluminium will cause the lease electrolysis but i'd imagine a stainless steel drawbar might be costly and than the spring supports would still have to be steel because of the steel spring hangers need to be welded the support can than be bolted to the aluminum frame

  4. #4
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    Nov 2017
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    Geelong, Australia
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    You can use sealant as an interface between the different materials to reduce electrolysis. Also put it on all fasteners that join the materials. In a previous life in aviation maintenance we used 2 part sealants that had a lot of chromates in them, and the parts were always painted first. The concept is to mainly provide electrical insulation between the parts.
    Just make sure you don't use an acid curing silicone as that has issues of its own.
    Duralac is a non-setting anti-corrosive jointing compound that will do a similar thing. I've previously used it between stainless brackets and aluminium masts etc. There will be other brands and any marine shop should have something similar.

    Steve

  5. #5
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    Aug 2009
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    Sydney, NSW, Australia
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    Default

    That is a really good idea i never thought of coating the steel pieces, i often see moored boats with the lower half of there motors painted with anti fouling paint i think this stops crustations growing on the motor but it also stops electrolysis happening from the salt water and the aluminium

    Do u possibly think this would work? anti fouling paint is readily available and easy to apply

    Also i know i am the designer and builder but i also look for guidance and reassurance in my design, for the plate that will attach the V to the drawbar for the upper and lower plate do u think i should go with steel 3mm or rather something in a think aluminium (i don't know how thick i would need)

    Only the rear 1/3rd of the trailer will be submerged in salt water

  6. #6
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    May 2011
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    Murray Bridge S Aust.
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    The plate to attach the V to the drawbar I'd use something like 10 mm ally. Something else that you could do is to make the steel draw bar pivot, this would allow for launching in shallow waters. For the pivot bush you could you use Delrin, I get offcuts of it, should you need it.
    To lock the drawbar in place, a 10 mm plate bent with a slight angle to feather it in, either side of the bar would suffice with a 16 mm bolt to clamp it together.
    Kryn
    To grow old is mandatory, growing up is optional.

  7. #7
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    Awesome thanks KBs that is what i needed to hear

  8. #8
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    Default

    I just picked up a used axle kit from gumtree for $35 came with hubs,bearings,springs,axle a little rusty she should clean up tho will post pics soon

  9. #9
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    Jan 2004
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    Mackay North Qld
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    Here is rust city coastal Mackay rust and its mate electrolysis are major problems.I have found separating noble and ignoble metals using a thin 2mm Delrin sheet to be an effective preventer of electrolysis.I was given my piece of delrin so I am not nor sure of its provenance. I imagine it comes from one of plastics shops we have .

    An alternative may be cheap food cutting boards as sold in woollies. I have used them as electrolytic spacers before and they work ok.

  10. #10
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    Aug 2009
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    Awsome this came up as the same stuff as delrin Acetal – Cut To Size Plastics they are local to me too

    here is what i picked up yesterday, The springs are just a tad bit to wide i need to move them in a little
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