Modular Pontoons design

Discussion in 'Boat Design' started by eng.naval, Nov 28, 2012.

  1. TANSL
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    TANSL Senior Member

    Suppose someone tells you a serious design error or gives a very good idea for it. What will you do if the pontoons are already built?. I think the only thing you're going to get is that some of us, willing to help, work needlessly.
    I think we should use these forums responsibly.
    Regards
     
  2. SamSam
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    SamSam Senior Member

    .

    I assume this...

    [​IMG]

    is just to get the idea across and that the finished clearances will be tighter, otherwise as p1 moves up it looks like it will draw the pin out of the bottom of p2. I can't see the need for the double bracket at the top of p1, the brackets of p2 will limit both up and down movement of the joint.

    As to whether they will work... why not? As to whether they will hold up to the stress, please, you have to give specifics such as materials and dimensions and loads and conditions. The weak part is the extended tang on p2 which will need to be heavy to eliminate bending.

    Any looseness or play will only work and wear out and get worse over time.

    I like this system, although it's not totally clear how they are attached together.
    http://www.damentrading.com/eng/vessels/barge/damen-modular-barge-8.html
    I would imagine there is another part like this on the bottom of the pontoon connected by a long bolt and by tightening the bolt as shown in the video, they clamp the pontoons together both vertically and horizontally and every which way but loose.
    [​IMG]

    Here's another type modular barge. I'm guessing the blue things are keyed wedges that are driven in slots and then secured...
    http://www.poseidonbarge.com/poseidon-i/set-up-pictures.html
    [​IMG]

    Here's a design used in the Olympics, no idea how they work, unless big pins are dropped into holes in the studs, sort of like your idea...
    http://www.dsboffshore.com/dsb-offshore-client-references-past-projects.php
    [​IMG]

    I think all these modular things are assemble in calm water and can then be used in pretty rough conditions, as shown in the video on the first site.

    There are more, just put 'modular barges' in google images. There is even one that is assembled and then jacked way up in the air on studs and then used as an oil platform or something.

    .
     
  3. eng.naval
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    eng.naval Junior Member

    Thank you very much for you effort. The comment you made is the discussion that I needed from the start of this thread.

    Actually the clearance between the brackets is as it appears in the drawing (5 cm). It's one of the problems I had. I would make it 5 mm if it made sense, but as from my point of view, the assembly occurs in water, so wind, waves, and weights affect the process even if it's calm water. Having this small clearance between the brackets will make the assembly very hard, if it's not possible.
    Of course, having this relatively big clearance has its own problems as well. One of them is the pin as you said, which can be resolved be lengthening it a little bit more. But that's not what I'm afraid of; the problem is the movement of the pontoons in the vertical direction as I mentioned before in this thread. I couldn't determine what will happen to the bracket during the heaving of the pontoons separately. I know it depends on the scantling of the brackets itself (it's 30 mm thickness and the pin is 75 mm by the way), but the point is I needed something to make this coupling a rigid one and I couldn't figure out how. Some advised me that after the assembly we can weld some plates between the pontoons in the deck. Maybe I will depend on this idea after all.

    As for the double bracket at the top I added it because it helps with the assembly of the pontoons in the water. The man won't be able to see the brackets at the bottom of the pontoons, and the alignment of the brackets will be hard to make the pin slide through the holes. With three brackets at the top, we have 3 points of pin alignment, when the pin is inserted in the top 3 bracket, the pin will be inserted consequentially in the bottom brackets. I don't know if my logic is true or false, but it wouldn't hurt to add it.

    Your assumption of Damen coupling system is correct. As you can see in the picture.
    Damen.jpg
    What I couldn't figure out is how they attach it in the water. The keys at the bottom have to be below the pontoon bottom before they pull the pontoons together. After they are beside each other they pull the pin up with the bottom key, this way it will be inserted in the slot. That's my assumption.

    The Poseidon Barge confused me. It has 8 points of connection along the side!!!!

    The last type you mentioned is similar to one I saw before. It belongs to Flexifloat. The link below has two flash videos in it, it shows how do they assemble the pontoons.
    http://www.flexifloat.com/(S(zuoaiq...odularbargelockingsystem.aspx?PageID=catalog#

    There's another system that I like. It's for a company called Hann-Ocean

    http://www.youtube.com/watch?v=XA1mqh-Tk8k

    I couldn't see how this system lock the movement in the vertical direction.

    Thank you
     
  4. SamSam
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    SamSam Senior Member

    Assembling in calm water would be best.

    If the big spacing is needed in the brackets, after initial assembling, if spacers could be inserted into the space above and below the top tang on p2, that would limit vertical movement.

    Or...

    If the space between the two brackets at the top of p1 had inserts welded in that would leave your 5 mm clearance for the tang of p2, the inserts at the opening where the tang slides in could be beveled so as to leave a big opening to initially guide the tang into place. The tang could also be ground a little on the end to help. As the pontoons were pulled together, the tang would slide into the space with 5mm clearance and then the pin dropped in. I hope that's understandable.
     
  5. SamSam
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    SamSam Senior Member

    To help guide the pin to the bottom bracket, and to strengthen the connection, you might weld some pipe on p1 between the two brackets.

    If you make another bunch of floats, you might consider using pipe for both floats, with a pin inserted to hold them together, sort of like a giant hinge...

    [​IMG]
     
  6. eng.naval
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    eng.naval Junior Member

    "If the big spacing is needed in the brackets, after initial assembling, if spacers could be inserted into the space above and below the top tang on p2, that would limit vertical movement."

    How a spacer can be inserted after the assembly? I don't think this is possible because of the brackets.

    "If the space between the two brackets at the top of p1 had inserts welded in that would leave your 5 mm clearance for the tang of p2"


    I'm sorry, I've tried to visualize this solution but I couldn't. Are the inserts welded at the side of the brackets tunnel, and shaped like a trapezoidal?

    "you might weld some pipe on p1 between the two brackets"

    If I weld a pipe between the brackets, how will the tang in the p2 be inserted between the two brackets during assembly?

    Thank you.
     
  7. SamSam
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    SamSam Senior Member

    [​IMG]

    I'm trying to adapt what you have to eliminate vertical play. The pin will eliminate horizontal play.

    The connection on the left has 3 enclosed (on 3 sides) brackets- an upper, a middle and a lower. The connection on the right has 2 tangs, an upper and a lower.

    The spacers I'm describing would be square pieces, with the pin hole in them, that would fit into the small space that the upper tang slides into. They would be at the top and bottom of that small space and welded in. Their thickness would leave a slot 5mm (or Xmm) bigger than the thickness of the upper tang. The exposed edge of the inserts, at the mouth of the slot, would be beveled (maybe 45 degrees?) so as to leave a wider vertical opening. Once the tang entered the wide mouth of the slot, it would be guided into the narrow part of the slot by the beveled edges as the 2 pontoons were pulled together.

    Looking at the tang from the top, the two corners could be beveled in the same way to give a little horizontal play when aligning the connections.

    The piece of pipe I was describing would be between the middle and lower bracket. Without it, once you have the pin through the top bracket, the top tang and the middle bracket, there will still be enough play where it will be hard to line the pin up at the bottom of the connection. I can imagine the leverage exerted by the pontoon on that short top connection (before the pin gets to the bottom half of the connection) could easily damage the tang or brackets and bind or bend the pin. The pipe will guide it through the bottom bracket (and also strengthen the middle and lower brackets), and then once the bottom tang is aligned it will drop right in.

    Again, I hope that's all understandable.
     
  8. eng.naval
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    eng.naval Junior Member

    Thank you very much. That's really helpful. I'll let you post after the trials.
     
  9. SamSam
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    SamSam Senior Member

    Well, at least I'm not permanently banned like on the Wooden Boat Forum! ;)
     
  10. eng.naval
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    eng.naval Junior Member

    oops!!! Sorry about that. I wanted to say "I'll let you know after the trials" and "I'll post after the trials" and it came out that way!!! :confused:
     
  11. Village_Idiot
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    Village_Idiot Senior Member

    On your next build, try using the cam lock and dowel setup like they use to put furniture together (unless that is patented, too). That should give you a locking connector in all vectors. Tighten them with a huge T-wrench from up on deck, or get fancy with hydraulic tighteners. Either way, would be good to have additional pins set into the cams' rims for safety backup.
     

  12. El_Guero

    El_Guero Previous Member

    Why don't you just buy some used pontoon bridging equipment ....

    :)
     
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