Jet drive Canoe

Discussion in 'Boat Design' started by Robert solo, Oct 8, 2019.

  1. Mr Efficiency
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    Mr Efficiency Senior Member

    haha, the `1000hp 13 ft boat, they were called "temporary (insert nationality)'s at one time.
     
  2. ondarvr
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    ondarvr Senior Member

    You may end up with the capacity to make the ethanol, but you still need the the input to do it.

    And I asked about storing it on the boat, you need tanks large enough to make the trip.

    I’m not sure it’s a “can’t do” aditude, it’s more of a, what’s your plan to overcome these obstacles line of questioning.

    People are suggesting things that will work. You are wanting to combine features that don’t work well together to achieve your desired result/job.
     
    Last edited: Oct 9, 2019
  3. Robert solo
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    Robert solo Junior Member

    I have seen numbers for about 30% efficient props between 2-4 HP per ton for displacement boats AT displacement speed so since i am well below displacement speed 2 HP per ton sounds reasonable and since my "prop" is on the small side say 11" equivalent so lets say my efficiency is 10% , I think it would be better , but lets just say 6 HP per ton , I have about 8 1/2 metric tons 8 1/2 x 6 HP = 51 HP x a specific fuel consumption of say .65 pounds per HP hr (it would be lower but I am thinking worst case) = 33 pounds per hour x 1.27 ( the worst figure I could find for ethanol ) = 42 pounds per hour = 6.36 gallons per hour that is a lot , but not a crazy number and that also is every single number pushed to the worst case , I would like to find some one that can do a more accurate calculation .
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    With the jet canoe, the estimated speed into a head wind, would be two knots backwards, kind of thing, even if by some contrivance you manage to ease the passage of the box through the water, the windage will not be negligible.
     
  5. ondarvr
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    ondarvr Senior Member

    At that burn rate you need over 1,000 gallons of fuel on board.

    This doesn’t include overcoming wind and current, which combined could put you in the negative range of forward progress.
     
  6. Robert solo
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    Robert solo Junior Member

    Those numbers are unreasonably high , I said that , I was just making a point . But lets go with 1000 gallons , 9 oil drums one on the tow boat and 8 in the container with the bottom bungs connected to a electric transfer pump , I would have to make 8 stops to transfer fuel , not impossible and that is worst case fuel consumption of the longest imaginable tow . yes a strong enough head wind would force me to drop anchor and wait , but I suspect that Magellan also had to wait from time to time . You guys can't figure this stuff out yourselves ? I worked 10 years on a boat , but I am sure that I am not the only one on here that can say something similar .
     
  7. Robert solo
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    Robert solo Junior Member

    I have to take my cat to surgery at 6 am at the capitol , so I have to get up at 4 AM , I need to get some sleep , It has been fun .
     
  8. Mr Efficiency
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    Mr Efficiency Senior Member

    Jet drives are notoriously inefficient for low speed lugging tasks, that is the first idea that ought be canned, then you can move on to examining the other issues, but sticking with a jet drive, the whole idea is handicapped.
     
  9. BlueBell
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    BlueBell Ahhhhh...

    I hope everything went well with you cat's surgery.
    That's a tough one, and expensive.

    Look, this is a great idea and I'd like to see you succeed,
    but towing an awash sea container is a huge load at any speed.

    Can you post a link to your obsesion?
    Drawings? Anything?
     
  10. BlueBell
    Joined: May 2017
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    BlueBell Ahhhhh...

    I found your boat, wow, she's a pretty one.
    So, no, sadly you should not mount an engine
    and jet drive capable of towing adrift sea-containers.

    More feasible would be to sail them home...
     
  11. gonzo
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    gonzo Senior Member

    A loaded container is 40 tones. Therefore, at 6HP per ton you need 240 HP. However, those calculations assume a hull of normal shape, which a container is not; it is shaped like a brick. A canoe will not be able to float with the load of a large engine/transmission, enough fuel and all the living arrangements you propose. Further, tugs need to be heavily built to sustain all the impacts and stresses usual on the job.
     
    Last edited: Oct 11, 2019
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  12. JosephT
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    JosephT Senior Member

    Very wise advice indeed. I build some rather large canoes myself (30+ ft) and I can tell you first hand load & balancing of the large canoes is critical. They can roll very easily if they become top heavy or take a wave from abeam. The size of these boxes are just too big, not to mention how they're loaded will play a big role in how they like to balance out. If they're top heavy or leaning to one side you've got a mess on your hands. Best to ship on a stable platform. In my opinion, a catamaran with strong deck and large dual hulls would be both efficient and safe. They can reach pretty shallow water too. A ramp could be placed from deck to shore to move the boxes.

    Definitely ditch the canoe idea...not the proper hull form for this job.
     
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  13. W9GFO
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    W9GFO Senior Member

    What makes you think that a jet is more efficient? A jet drive would be terribly inefficient in this application. I am skeptical that any jet drive is more efficient than a comparable sized propeller except maybe in very specific circumstances.

    One benefit a typical jet drive has is that it shoots the water out the back of the boat above the water line, into air. The thrust comes not from the jet "pushing" against the water, but from the reaction of accelerating the mass of water rearwards. As soon as the jet of water dips below the waterline the thrust drops off dramatically. It is a similar concept to how flat earth buffoons will wrongly argue that rockets cannot work in space because there is no air to push against. Anything the jet has to push through will slow it down and reduce efficiency.

    A design with the jet exiting below the waterline will be horribly inefficient.
     
    Last edited: Oct 18, 2019
  14. fredrosse
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    fredrosse USACE Steam

    Jet propulsion is simply wrong for pushing cargo around at relatively slow speeds. The only potentially practical method would be.... lets look around at marine transport........AH! a big slow rotating propeller like virtually all the cargo ships on the ocean!! Got to that answer pretty easily, with no need for engineering knowledge. The desire for jet propulsion is simply absurd here, has no technical basis, and solid proof of this is all around any ocean transport, so why do you want jet???
     

  15. JosephT
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    JosephT Senior Member

    I can think of one use for a jet drive: A bow thruster. Very limited use for fine positioning around a dock/pier.

    For shallow harbor island hopping a catamaran utility boat is the way to go.
     
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