Using my boat as a trailer

Discussion in 'Boat Design' started by rasorinc, Feb 10, 2015.

  1. rasorinc
    Joined: Nov 2007
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    rasorinc Senior Member

    Using my boat as a trailer
    My current build is 7' x 16' to be used in river exploration and in lakes.
    the aft 7' is a flat dory hull then a shallow V hull 14*up to the bow.
    I wish to design a pair of wheels with an axle that attach to the transom and are able to be lifted up out of the water similar to this http://boatloader.com/wheels.html 1 want to mount a pair of 13" road wheels through an axle with 2 braces that bolt over the axle. I believe I need some sort of shock installed at each brace maybe 2 small air shocks. I will use a rod and hook to lift them out of the water.
    Loaded, the boat will weigh about 1500 pounds and I will travel on highways at speeds up to 60 MPH. The bow piece I know how to do and support. I may or may not need brakes depending on the vehicle tow car.
    Any and all comments much appreciated. Thank you, Stan
     
  2. messabout
    Joined: Jan 2006
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    messabout Senior Member

    That arrangement will put a lot of load on the boat itself. If it is to weigh 1500 pounds more or less, then half or more of that weight will be carried by the hitch. That means that the boat will endure a beam load of considerable amplitude along with dynamic loads from highway dips and bumps. That also implies that the boat will need to be heavily reinforced, which means that it will be a beastly heavy boat, which means that it will need more power, which means even more weight........and so on.

    Best use a trailer and keep the boat as light as good practice allows.
     
  3. Poida
    Joined: Apr 2006
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    Poida Senior Member

    Do not know what your laws are, but here, to tow something on the road it has to be registered and to do that you need an endorsement from an engineer that the structure is suitable.

    People who design trailers normally do not design boats.

    A boat trailer for a small boat would be easier to tow and better for launching as the stern of the boat is further in the water in relation to the wheels.

    Poida
     
  4. NavalSArtichoke
    Joined: Oct 2013
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    NavalSArtichoke Senior Member

    Also, and most important, shock absorbers are not the same as springs. You need springs to help cushion against all the imperfections in the roads you'll be traveling on.

    There's a reason people don't use their boats as trailers, and it's not because of a conspiracy by trailer manufacturers to sell you a trailer.

    A boat's hull is designed to take a load which is spread out over the bottom. As has been pointed out a few posts back, a trailer-boat is going to see high loads at the hitch and at the wheels. Without any buoyant loads on the bottom to help support this beast, it may just jack-knife and fold up, especially if you hit a big bump. Verrry embarrassing and potentially dangerous to any nearby motorists.
     
  5. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Repeatedly, folks have tried to make things serve multiple roles. The Amphicar is a classic example, with the Aeromobile possibly a close second. The same is true of most anything that has attempted to be more then it is. The Amphicar was a lousy car and a worse boat. The Aeromobile was a piece of crap car with a barely adequate flying platform dragged behind. This "theme" is true of every example of this type of thinking.

    The engineering compromises go up exponentially with these sort of combo products. So, the short answer is, yep, you can sure do it, but you should ask yourself how much are you willing to accept and pay for, to have this on the surface, convenient contrivance.
     
  6. myark
    Joined: Oct 2012
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    myark Senior Member

    If you start a new boat build flat dory it is very easy to place a aluminium box into the hull for the plug in torsions suspension which float off when in water.
    This suits flat bottom Dory and would be low to the ground and light to tow, it does not need boat ramps and can be launched and retrieved on surf beaches or remote water ways such as a rivers edge.
    The torsions if want can fit in boot of car when boat in water.
    One set of torsions suspension can carry on average 2000 KG.
    For example a picture shows a 8.5 m Myark trailer barge with two 25 hp outboards doing about 30 knots.
    No extra weight in water and a pleasure to tow with a small car, is structurally stronger than a traditional style trailer, cost less and less weight to tow = gas saving less strain on car
     

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  7. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    How can adding structural members and a suspension system to a boat produce "no extra weight"?
     
  8. myark
    Joined: Oct 2012
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    myark Senior Member

    Make the aluminium box inserts part of structure design which is anchored onto the top floor stringers, then add the removable Titanium torsions bar, leg and axle that also has titanium hubs, stubs and nuts with 440c stainless bearings. The aluminium casing that comes apart for DIY replaceable rubber cords that cost $2 each cord, a grease nipple at the back of the axle so can not be damaged and keep water out of bearings.
    The Titanium and aluminium torsion are stronger and 3 x lighter than conventional torsions that can not have the cords replaced and will rust also the trailer structure is stronger than a conventional trailer that twist under stress.
    Teflon is used as liners for the box inserts to make sure torsion's slide with ease as aluminium on aluminium can grab.
    This small Myark trailer barge has 750kg load torsion suspension.
     

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  9. whitepointer23

    whitepointer23 Previous Member

    So he has to stand in the water each time to remove the wheels and axles. He might not want to get wet every time he goes out. Especially if the water is very cold.
     
  10. whitepointer23

    whitepointer23 Previous Member

    You keep throwing around the word titanium. How much does it cost.
     
  11. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    He claims they make the boat lighter. Also, there is going to be some serious galvanic action between titanium and aluminum. According to a study by NASA called CORROSION PROBLEMS ASSOCIATED WITH THE USE OF TITANIUM FASTENERS
    "Because of the high solution potential between titanium and alumi-
    num alloys (Table II) , considerable galvanic corrosion occurred on the
    bare aluminum panels adjacent to the titanium fasteners in this study."
     
  12. myark
    Joined: Oct 2012
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    myark Senior Member

    Read again :rolleyes: I said "No extra weight in water" also naturally the boat is lighter in trailer form on road if no heavy trailer added in towing mood, the titanium torsions suspension are light which by can be floated off while in boat so you do not get feet wet.

    The titanium torsion bar do not touch the aluminium as the rubber cords are in between and act as insulation ;)
     

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  13. whitepointer23

    whitepointer23 Previous Member

    How expensive is the titanium.
     
  14. myark
    Joined: Oct 2012
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    myark Senior Member

    A Myark proto type 12' X 8' tinny that towed opened or shut that was self trailered and made from 2mm aluminium with two 15hp out boards.
    It is a smooth ride through the surf and when towed closed all the equipment was locked up like a large suitcase.
    This picture was taken on a clam day in surf and can handle a lot larger surf with ease that the life saver boats would not dare
     

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  15. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    The density of titanium and the rest of the metal structure is denser than water, so it will have weight in the water. Also, there is no need to have a heavy trailer; a light one will do.
     
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