Hi, first post, wanna build a monstrosity....

Discussion in 'Boat Design' started by parkland, Jul 15, 2012.

  1. parkland
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    parkland Senior Member

    How do you figure the trailer will weigh as much as the boat?

    I'm not getting a full deck floored with 3 x 6 lumber.... just a simple I beam frame with enough support for the boat.

    I know a guy that moves farm buildings with an I beam trailer, it is super excessive for a boat my size, and it only weights around 3,000 lbs.

    Just need to take a design like that, and insure the boat is getting supported properly.
     
  2. mydauphin
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    mydauphin Senior Member

    Building a boat this size is more work and money than you realize. Buy a used boat that fits your need and your half way there. Also your weights are off, for the kind of build your talking about your going to be at least 20-25000 lbs ready to go and the trailer will between 8-10000 dollars, triple axle.
     
  3. parkland
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    parkland Senior Member

    I think I haven't provided clear enough information, as I've been told that it will weigh much less than I think, AND much more than I think.

    Once I can find out the prop shaft assemblies that are close to what I'll use, I can finalize the cabin placement and size, and finalize the boat size, and actually start counting the supplies and parts and adding the wieght up.
     
  4. parkland
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    parkland Senior Member

    http://www.flickr.com/photos/79427079@N02/sets/72157630765798472/


    Theres some pictures of my hull design, please note that I didn't bother making a mid section, so it's just the front connected directly to the rear, just to show my proposed angles and cuts.
    I realise not every line is perfectly straight, it is just a rough design.

    I am really happy with the front, the rear probably needs to be changed quite a bit yet, that will be in "stern version 2.0" haha :)
     
  5. parkland
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    parkland Senior Member

    Does 140 lbs sound right for a 4x10 sheet of 5051 ?
    And 9 lbs for a 10 ft long chunk of 3" x 1/4" of 6061 ?

    For a 40 ft boat (of my design);
    I'm guessing 20 sheets of 4x10x 1/4" sheets, @ 140 lbs each = 2800 lbs for the hull, before ribbing.

    Throw in 3" of 1/4" ribbing every 12" bar using 16 ft = 576 lbs...more with lateral ribbing too...

    2x engines @ about 600 lbs each, more like 1000 lbs each with trans & shafts.

    200 lbs of fuel

    500 lbs of water

    200 lbs batteries

    200 lbs generator


    At this early stage, I'm going to just take a stab in the dark at the aluminum for the cabin, @ 1600 lbs, probably a lot of 1/8" aluminum.

    Slowly, I'll figure it out... And I don't want to buy a boat, unless I can find one that is 8'6" and 30-40 ft long.


    With the bulk of the aluminum, and major equipment, looks around 7000 lbs.
    I think fully completed, this sucker could weigh 9000-12000 lbs (4090 kg - 5454 kg)

    So it should end up "just legal" in terms of size, weight, etc.... the biggest cruising boat possible for tow behind use in lakes or protected water.
     
  6. parkland
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    parkland Senior Member

    What about this?

    How about a folding deck design?
     

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  7. parkland
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    parkland Senior Member

    Just thinking this through further yet...

    Why can't the bow section actually be "hinged", and lay on the deck during transport?
    Then while unloading, it folds forward, and gets kept in place with pins or something?
    The hand railings would have to be removable though.

    This would reduce the length of the boat during trailering, or allow an even BIGGER boat to be trailered !!!!

    I'm thinking 36 ft folded up length....
    26 ft from the rear to the extreme rear, would be cabin. 10 ft of open deck in front.

    On that 10 ft of open deck in front, the bow front section would fold on top, giving an incredible 20 ft of front deck!!
    Unfolded total length would be 46 ft!
    Total unfolded width with the pontoon side decks, would be 16 ft or so !

    Has anyone ever seen anything like this?

    Any ideas on the materials needed so I can start guessing weights? :(
     
  8. parkland
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    parkland Senior Member

    And just like so..... :


    PS I don't use cad much lol./ :D
     

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  9. rasorinc
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    rasorinc Senior Member

  10. parkland
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    parkland Senior Member

    That is a little cool, but I don't see the benefit?

    That boat isn't even close to being a challenging size to transport?

    I guess just so it can stack with 20 ft cube containers?
     
  11. SaltOntheBrain
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    SaltOntheBrain Senior Member

    Before you build a barge, study Lullworth. 8'X40', 40mph, only 275 hp.

    Not exactly a monstrosity, though.

    LF
     
  12. parkland
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    parkland Senior Member

    Is there any way to have 2 engines on the same prop shaft, but use either for different times?

    EG, a v8 or larger engine, but then you could leave it in neutral, and use a 2 cyl listeroid engine, for putting around all day?

    But still have the larger engine if you need it?

    I'm worried that an engine is going to die of wet stacking if it's idled all day just putt cruising...
     
  13. FAST FRED
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    FAST FRED Senior Member

    From the thread above,

    "not to thread jack, but how about two engines on one shaft, so.....
    you aren't lugging a big diesel at lower speed, but still got full power with both engines running."

    Ideally, I'd have 6 and 12 cyl engines, so I'd have 3 possible power levels....6, 12 or 18 cyls.
    "
    The past 40 years or so the US Navy has been installing two engines tied to a gear box and single shaft on landing craft.

    My preference would be for a smallish diesel to operate efficiently at 80% power 90% rated RPM for long range cruising, and a stock motor for the times to make a big wake and de-fuel the boat rapidly.

    3-71 and 6-71 or

    80Hp Deere tractor with Intl DT 466 ,,more Modern , might use less fuel

    Engine can be disconnected under way , but requires shut down to engage to reengage either engine.

    No big deal.
     
  14. bpw
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    bpw Senior Member

    Why not?
     

  15. SamSam
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    SamSam Senior Member

    That's too obscure. Nothing comes up on google with two LLs. Do you have anymore information?
     
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