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aluminum frame to handle 8000lbs of pull

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  • aluminum frame to handle 8000lbs of pull

    Customer Is trying to build a pontoon boat to haul logs across a river. He wants me to design and fabricate a frame that can with stand 8000 lbs of torque to mount a big winch on. I have never had anyone give me such a precise strength without a print. I was thinking 3"x3"x1/2" angle for the perimeter of the frame and 3"x1/4" for the braces across. Dose this sound strong enough? I've never had to get strength out of alum like this before and I'm not familiar with its capabilities. Anyone have any ideas. Design wise that may strengthen it?

  • #2
    Which is it? 8000 Lbs. of pulling force, or 8000 Ft. Lbs. of torque? I would think it is pulling force more than torque. He probably has a specific winch in mind he is wanting to use for this. It looks like you may have additional work from this customer that he doesn't know about yet. He will be needing to anchor this boat to something SOLID to use that much pull on a log, in which case, he is going to be pulling the boat apart somewhere else. So then you will get to fix that problem too, then do a bunch of reinforcing there too.
    You could just make the winch mount from steel, as you are most likely more familiar with the strength available from it. He's just thinking to make it from aluminum since that is what the rest of the boat is made from and to keep it light weight.
    For this purpose, there is going to need to be more thought processes than just mounting a winch to a pontoon boat.


    • #3
      Call up Shelby Stenga. He sinks a boat or whatever you might call that contraption at least once a year.
      Dynasty 280DX
      Bobcat 250
      Spool gun
      Twentieth Century 295
      Twentieth Century 295 AC
      Marquette spot welder
      Smith torches


      • #4
        Here's the other part of this thread on welding discussions.

        I would like to see this rig when completed. Sounds like it is something from Swamp Loggers.


        • #5
          Bistineau, I have to agree with you, he needs to give us a lot more info, What is he going to anchor the pontoon too, Pontoons are good for about 2500 lbs or so.

          Try putting 15 people on say a 24' twin toon and your bringing water up over the floor with a small wave.

          A 28' triple toon. you might be good for a maximum of 18-20 before your getting water over the deck.

          Figure 20 people at 175 lbs. each and we are talking 3,500 lbs. so its pretty safe to assume he's not lifting that much.


          • #6
            I don't think he wants to lift it, so much as pulling it free from the suction of the mud for salvage purposes. Which means he will have to tie to a tree on the bank to hold the boat in place while the winching is going on. I believe the guy is trying to salvage sunken logs(cypress most likely) from the river bottom, to sell. Watch an episode or two of "Swamp Loggers" on History Channel and you will see a couple of guys doing this with a pontoon boat. But yeah, some more info on what the intended purpose is would help to narrow down what is expected of this project.

            I think we need to wait for the OP to check in with more info on this project and what is expected of it.
            I don't even have any idea what equipment Dent welder has to use on this build. Bailing wire/ duct tape drill & Bolt, MIG, TIG, stick, O/A? . What do you have to use on this?
            Last edited by Bistineau; 04-09-2014, 07:42 PM.


            • #7
              two pieces of 3x3x1/2 aluminum will hold 8000 pounds in tension easily. The next question is will the force always be applied in tension, or at what angle, and will the attachment of the angle to the boat support the load.

              If horizontal pull I'm sure the boat would have to be anchored to pull 8000 pounds towards the boat instead of pulling the boat to the load. To prevent pulling the boat apart the anchor should be attached to the winch mount itself and that would prevent the winch from getting ripped off the boat also. If pulling off the bottom of the lake the boat won't move but there is no way to anchor the winch mount straight up so the attachment to the boat would need to be strong enough to do the job.


              • #8
                if possible I would put a 1/2 doubler plate on the deck and make sure it is atleast a 1' wider than the winch mount. I weld 1/2" padeyes to slickline boxes and we test pull them to 10k the boxes are 3/8 thick I'm sure that pontoon is around a 1/4 or less so go as big as you can with a doubler.


                • #9
                  Has this project made any progress since this thread was started? If so what is going on with it? Have not heard anything from the OP lately about this. Got any pix of the boat this is supposed to be mounted to?