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Aluminium C channel stiffener process

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  • Aluminium C channel stiffener process

    Houseboat trailer
    I have a 35' aluminium boat trailer that is flexing .
    I want to stiffen it up
    The channel I want to stiffen up is a 10 "x 3.5" x 3/8 " c channel
    The channel is flexing about 3/8 " w the boat on it . I have not check yet w out the load to see if it will come back or it is bending
    Some of the internet sites for steel suggest welding a flat plate on top and bottom .
    At first I was just going to weld a 6" i beam on the bottom but that will drag w launching boat . Adding anything to the in side and or top on the c channel is out w out cutting some supports off.
    Any suggestions and or will welding a plate on bottom weaken the channel?

  • #2
    My first question is if the trailer was designed to haul that boat, and who designed it to do so, and why do you think the flex is not supposed to be there.

    It could be that, yes, you need to address the flexing, but I would be making sure first.


    • #3
      I have seen so many aluminum trailers that have been built too light duty. They use the same thickness of aluminum as a steel frame would be built and then the problems start...Bob
      Bob Wright


      • #4
        I called the manufacturer and they said no it should not flex . They also said I should fix/stiffen it. The trailer is 9 years old and the builder ( McLain trailers )
        said they only built one , that was custom for my boat . They also could not tell me how to fix it.


        • #5
          Plate the sides , try the outsides first, then the insides if that doesnt do it. Top and bottom don't matter as much. If you cap the c it will stiffin it more for the same weight of material, but a lot more work.


          • #6
            Every structure flexes. Presumably this trailer is over 40' in length. 3/8" flex in 40' ain't much.
            When structures don't flex or are stiffen to prevent flex (with no fore thought or understanding
            of the dynamics of structure loading)....that creates more cracking, bending, permanent deformation.
            Yes, structures can and should be stiffened in some cases--but each one is an individual deal
            and not seat of the pants 'weld 'er up and shut up', hip shootin' decision.

            You haven't provided any pics or relevant info on location/measurement of this 'flex' (which may
            be permanent deformation) it's all a big guess on too much flex.

            You need to examine the welds on/to the channel from other frame members for cracks.
            The presence and location of any cracks sez volumes to 'what's going on'...'too much flex'...
            'not enough flex'....etc.