River Roller! Pontoon Boat that Rolls Across the Water!

Discussion in 'Boat Design' started by Matthew Lee Towne, May 10, 2017.

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Do you think the River Roller will work?

  1. Yes

    1 vote(s)
    2.4%
  2. No

    34 vote(s)
    82.9%
  3. Maybe

    6 vote(s)
    14.6%
  1. Matthew Lee Towne
    Joined: May 2017
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    Matthew Lee Towne Senior Member

    Very reasonable comments PAR though still a bit negative.

    You are comparing props against paddlewheels. What you say all appears to be true. The problem again is you have to compare a hull/prop system against the trantoons WITHOUT a hull. I believe that the trantoon system will be more efficient than a prop and hull.

    I mean the inefficiency of a hull moving through water is obvious right? So why is it so unbelievable that the trantoon system might be more efficient?

    You commented on the load and maintenance issues. The load will be spread across a very large area. If you figure 2 paddles in the water per trantoon times ten trantoons, equals 20 four foot x 3" paddles applying power to the water? I think the loads wont even come close to a single paddlewheel applying power. I figure the paddles will be rubber and applied like a tire to the trantoons. Sealed bearings should be able to handle the loads

     
  2. ondarvr
    Joined: Dec 2005
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    ondarvr Senior Member

    You've mentioned high speed, what is your target?

    Is this the type of performance you're expecting?

    Water reacts differently at these speeds, so while at 40+ mph this works, you can't get from zero to 20 MPH with this type of propulsion.

     
  3. sharpii2
    Joined: May 2004
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    sharpii2 Senior Member

    Ok. Let me try to explain. A boat's Waterline Length (WL) is the length of the whole it makes in the water. With displacement hulls, which do not ride on top of the water, the water must go around the boat. With some types of boats it goes around the sides and under the bottom. With others, it just goes past the straight sides and under the bottom. This is what it will do in the case of your trantoons. When it makes this journey, it creates a wave. At the fastest displacement speed this wave is equal to the length of this waterline. In the case of your trantoons this will be approximately two feet. A wave's speed is proportionate to its length. Longer waves are faster than shorter ones. The speed of a wave is approximately the square root of its length in feet multiplied by the constant 1.34. This formula indicates its speed in knots. So with a 2 ft WL, you get: the square root of 2.0, which is approximately 1.41, multiplied by the constant, 1.34, which gets you 1.90 kts.

    Because your proposed craft is in effect five separate boats, with five separate WL's (because the water goes under and back to the surface with each one), like say five river-tow-boats, in a line, bow to stern, your displacement speed is limited to the speed of each one.

    If, however, you were cut the stern off the first, the bows and sterns off all the middle tow boats, and just the bow off the last, the and join their hulls together to make one continuous surface, the water would make just one trip under, then one trip back to the surface. This would be the length of your new wave. In your case, it would be approximately 20 ft. this would give you a new displacement speed of: (20^0.5)*1.34, or approximately 6.0 knots.

    Eliminating the three pairs of center trantoons, then making the ones on the ends larger, would improve the situation considerably. Then, each would have a larger diameter, giving each a longer WL. And there would most likely be a considerable space between them, which would deal with another one of my objections. The new trantoon diameters would be approximately 3.8 feet, not including the vanes. The new displacement speed would then be: (2. 53^0.5)*1.34, or about 2.13 knots.

    This is hardly an improvement, but if you spun these four trantoons at a high rpm, you may get this thing to climb on top of the water, as you have originally have hoped to. This will work better with two pair rather than five, because this greater distance between them will give the water between then some time to flatten out. In other words, one pair will not be climbing over the hill created by the one directly in front of it.

    But you are going to need a lot of hp to do this, probably at least 100 hp per ton of boat, or in your case around 250 hp, if not more. Otherwise, you will end up with a two knot ship, if even that.

    A good experiment would be to make two models. The first would be of your design as it presently is. The second would be of a scow which would be as long as your boat, minus the diameter of one of your trantoons (including the vanes). The scow would be nothing but a box, with an upward sloping surface at each end, to lead the water under it then back to the surface. The length of these surfaces would be at least twice their depth. This scow will be the same width as your proposed boat too, and will displace exactly as much. Behind it would be a paddle wheel the same diameter as your trantoon, but with no buoyant cylinder. It will be supported instead by a structure on back of the scow, which will hold it so its vanes have the same amount of dip as the ones on your trantoons do, about three scale inches.

    Once these two models are built, you can race them.

    I expect you will be surprised with the results.
     
  4. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    This boat has a hull, in fact several, each making and sharing their volume on the water as a whole, not independently, particularly as speeds increase. The waveforms will merge (read collide) and this is significant in terms of "crawling up", overcoming parasite and frictional resistance. This is why previous paddle approaches have widely separated wheels or a inline set aft. I don't think it has any potential of ever overcoming its initial wave train, just way too much bashing going on to get a good enough grip, let alone climb out. I'll bet the aft end squats so bad, after the forward wheels bash the water to a froth, the aft most paddles fully submerse for lack of grip (they'll be biting moist air mostly). This will place her trim angle too steep to consider rationalizing anything close to full plane mode. This said, if she was able to get a running start on shore, sufficient enough to insure she blasts over her bow wave and you can spin these puppies fast enough, you might be able to get her up and scooting, but the moment you ease the throttles a touch, you'd fall off and sink. As to the negativity, please, you haven't heard anything and this polite conversation could, possibly should offer the likely realities of a venture like this.
     
  5. tspeer
    Joined: Feb 2002
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    tspeer Senior Member

    Perhaps you should reorient your rollers.
     
  6. upchurchmr
    Joined: Feb 2011
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    upchurchmr Senior Member

    Tom,

    You are just baiting him.
     
  7. Matthew Lee Towne
    Joined: May 2017
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    Matthew Lee Towne Senior Member

    That is too cool! Dare I say a little more proof of concept? I would hope for a speed of up to 50mph. I think that this could be faster and possible very stable at higher speeds.

     
  8. Matthew Lee Towne
    Joined: May 2017
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    Matthew Lee Towne Senior Member

    Awesome! Thanx for the education! I had concerns about the space between the trantoons, but didn't really have a good comprehension of what or why. I do now. My idea was to put horizontal flat or slightly curved surfaces, between the trantoons to redirect water off the paddles horizontally and the keep the water flowing under the boat like a conveyor belt. Do you think that this would then keep the waterline the length of the boat instead of the length of the individual trantoons? Now that being said, I have to beg the question of how much of your analysis would apply to this type of design. This design would be of a displacement hull pulling itself through the water. Much different scenario than a displacement hull being pushed through the water. I believe that the analysis below would still apply somehow but not exactly like a standard displacement hull. I think that its possible that will all the trantoons being powered and moving water in the same direction that this in itself might extent the waterline past just the width of the trantoons.

    I think I can easily work you design into my scale test by removing all but the front and back trantoons and replacing it with a hull. I think there may be many surprises when I test this.

     
  9. Matthew Lee Towne
    Joined: May 2017
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    Matthew Lee Towne Senior Member

    Actually I though of this as an option but I didn't think it would be practical or efficient. Hard to believe, right?

     
  10. Dave T
    Joined: Sep 2011
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    Dave T Senior Member

    50 MPH with electric battery power?????
     
  11. Matthew Lee Towne
    Joined: May 2017
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    Matthew Lee Towne Senior Member

    Ok, so I'm seeing your point better now. So your problem with this design is that it won't transition from displacement to plane. I think I see what your saying if most of the trantoons are submerged. I expect only 10" of a 3.5' trantoon to be submerged and thats at max load. So let me ask a the question. Do you think that this would work at some immersion point? I mean if the trantoons are barely submerged surely it would easily transition from displacement to plane no problem.

    BTW most cynics call themselves realists.

     
  12. upchurchmr
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    upchurchmr Senior Member

    Most engineers call themselves realists.
    Some are better than others, but still.

    I just have to ask if you have ever been on a boat?
    Serious question.
     
  13. sharpii2
    Joined: May 2004
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    sharpii2 Senior Member

    I'd like to add that pushing or pulling a hull through water IS NOT inefficient. In fact it is the contrary. It is the least energy intensive way of moving mass on this planet. Near where I live, there is an unfinished canal system, which was intended to cross the base of my state. This was so horses could tow barges instead of wagons. A single horse could tow a barge which was many times as heavy as a wagon, even one with a team of horses. The coming of the railroads killed the project. Moving mass through the water on a boat may be efficient, but this is true only only at displacement speed or less. And remember, displacement speed is tied to the length of the vessel. This is why you see 1,000 ft long oil tankers and container ships. They can move their huge cargoes around at nearly 20 kts while using as little as 1 hp per ton.

    Much above displacement speed, wheeled vehicles are more efficient. Trains routinely move their cargoes around with as little as 2 to 4 hp per ton. Over the road smi-trucks use as little as 7 hp per ton.

    Planing is very inefficient, which is why you never see a planing cargo vessel. Fast ferries use hydroplanes and sometimes forced air cushions, and are only used when speed across the water is a prime requirement. Pure planing boats are used almost exclusively by pleasure boaters and the military, where efficiency is not an issue.
     
  14. Matthew Lee Towne
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    Matthew Lee Towne Senior Member

    No. I'm terrified of the water.

     

  15. Dave T
    Joined: Sep 2011
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    Dave T Senior Member

    The biggest problem with this concept is that it will not work. I know you envision this boat running on top of the water like a car running on a highway this simply will not happen because first of all you must be able to pick a 5000# very inefficient hull up out of the water so you must have minimum downward thrust of 5000# pounds this would take a huge amount of horsepower eliminating the possibility of electric power. The next thing is with paddle wheels with fixed blades as explained by a previous poster will not make hardly any downward thrust because the only downward thrust is from the front paddles pushing down on the water but this is cancelled out by the paddles on the back trying to pull the boat down so the result is no lift. So now all you have is a very inefficient hull being pushed through the water with an relatively inefficient complicated drive system. The next problem was explained by Par is the aeration of the water caused by the spinning of the paddles which gets worse as the speed is increased. This means that the rear drums lose their buoyancy because aerated water is much lighter so the back of the boat sinks lower causing more drag and less speed and more power needed. Being a realist makes me a cynic and I really do wish your concept would work but I just don't see any way that it can.
     
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