A better idea for Congo - a speedy tug and a plastic bag

Discussion in 'Boat Design' started by congoriver, Jul 14, 2010.

  1. kerosene
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    kerosene Senior Member

    the fuel cost upstream can be lowered by slowing down a bit. The way boats are a slight change in speed can make radical reduction in fuel use. Of course with current to beat you can't slow down too much.

    For speed weight is also crucial so the pirogues might bee on the heavy side. Also steel would probably be out for such small boat.
  2. bearflag
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    bearflag Inventor/Fabricator

    If you burn more fuel, you don't loose any time :)

    I would suggest if you are traveling more than a few hundred miles you would want a bigger boat than 30 feet.

    if you use all local materials, and labor is cheap, even a fairly large boat like Gaia's dream (but no need to be as seaworthy) could be built http://www.pacificproa.nl/dream.htm

    A boat in the 60-90 foot size would give you considerably more volume, security, etc. Less likely to be robbed. Safer to sleep on at night. Support larger crew (which you would need to load, unload, protect, maintain watch etc)

    Don't aim for anything fancy, use the simplest techniques, over build, don't worry about race/yacht worthy materials.
  3. kach22i
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    kach22i Architect

    Another option, long cargo canoes. I've seen old photos where they were 80 feet long, this example is only 20 feet.

    I didn't do any math on it, sorry.

    EDIT: Someone on the forum is building their own 20 foot design.

  4. Village_Idiot
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    Village_Idiot Senior Member

    So, the idea would be to keep the boat running at hull speed, but not beyond, for greatest efficiency. I forget the hull length/hull speed formula, but I'm guessing something beyond 20m would be needed. You also want to keep the hulls as narrow as possible to enhance efficiency (like, 10:1 L/W ratio or greater) - this would necessitate the catamaran or trimaran design. Then, figure the HP/thrust you would need to propel the hull at hull speed. Add 5km going downstream and subtract 5km going upstream. You won't need a lot of HP, maybe 20hp with a well-designed prop? I am not a naval architect, so will leave the specific number-crunching to the experts.

    Having done quite a bit of boating on large rivers, I can tell you that water velocity is not constant throughout the river. Fastest flows will follow the thalweg, or main channel, of the river, whereas slack water away from the thalweg will allow faster upriver travel but slower downriver travel. You may even have backwater eddies where the water travels UPSTREAM for a short distance. All this is to say that if your captain knows how to run the river, you can maximize speed and efficiency going downriver and upriver. This, of course, is complicated by navigational hazards (logs, sandbars, shoals), as they are usually more abundant in the slack water, particularly where the thalweg meets the slack water.

    I wonder, if given a constant stream velocity, if a full-planing hull would be almost as (or even more) efficient as a full-dispacement hull when throwing in the time=money factor? A well-planing hull will require some hull width and quite a bit more HP, but much faster running upstream and much less hull draft (if navigational hazards are an issue). Ideally, you might have a full-displacement hull running downriver, and a full-planing hull running upriver. To my knowledge, such a boat does not exist, unless you use hydroplanes.
  5. magwas
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    magwas Senior Member

    You are talking about 500km/72hours=6.94 km/h, less than 4 knots. is it 500 km in the river? I measured that 500 km means somewhere near Lac Tumba, and Mbanda is some 600 km. I did not spot any waterfalls or locks to slow you down, this should also be taken into account.

    This 7 km/h should be easy especially down the river. I made default hull in Freeship, and scaled here and there a bit to have a boat which can make 10 knots good easily.
    I got LOA=48m, beam=3.7m, draft=0.5m. It displaces 22 metric tons. It have 5 kN resistance at 9 knots according to Delft series, and 11 knots according to Kaper.

    Using the more conservative Delft value, we got a bit more than 23kW=32HP=120 person (at 200W).

    I would recommend building a traditional canoe hull, very long, as wide as applicable, and a shallow one, and planting any car motor in it.

    If the design speed is just 4 knots, we got less than 1000 Watt. As an average man can produce 200 watt in a sustainable manner, it is 5 people-power. With 3 shifts we have a boat - and work - for 15 people. Calculate 200 kg for a man, his food and stuff, and you still have 19 tons of cargo. I am thinking about bicycle-like workstations driving the propeller shaft. I do believe that on the shore of the river there are craftsmen who can build a traditional canoe hull, even in this size. Okay, maybe 48m is a bit excessive, but as the design speed is smaller than the motor version, it can be scaled down.
  6. jg451
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    jg451 Junior Member

    To Congoriver,

    Depending on how the poly bag opens, could two frames (one at source, one at delivery point) be provided? The bag is tied in the frame so the opening can be easily accessed from above. The leaves, I'm assuming, are either bagged or baled to man size. A catwalk from frame to shore or perhaps a conveyor or simple roller path would provide transfer. After loading, the bag could then be closed from the frame. The frames to be three sided, source frame open down stream, delivery frame open upstream. Water depth at frame to be such that a man standing in an empty poly shipper would be standing on the river bed for easy stacking of bales.
    Four Problems:
    Configuration of top of bag so as to be easy to rope open for loading and unloading, and yet simple to close and waterseal. Flat bag is recommended as a round one could utimately rest zipper down. The fuel bladder manufacturers would probably be the best to ask regarding new bag(GOOD) or modifying existing bag(BAD). Sufficient waterseal most important.
    Towing configuration. A long tow downstream will probably not work best. A connected tow would be better; ahead, abeam, directly behind. Ahead would probably be best for maneuvering into frame.
    Transport empty. The bag would probably be buoyant in and of itself, but perhaps a wooden pole attached along each side would make it ride more securely. Streaming the bag behind going upstream may work out better.
    Easier to pull the line over the frame and pull it into place for loading.
    Chafing of the bag surface. Quick patching in case of damage. Again Mfg. is the best source. The bags are pretty tough.

    As to running upstream empty, use your imagination. Perishables. People(local Regs. allowing), anything light small loose the BigBoys don't wish to screw with. You'd have transport, others need transport. Depending, towing is strength and power not nessarily weight, downstream haulage is also a possibility. Speaking of which,the tow boat will be a working vessel so strength of members is important. if you're talking in the 40ft(13-14m), the 7/8kph you need should be no problem.

  7. pedalingbiped
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    pedalingbiped Junior Member

    From my understanding, hull speed is the square root of length X 1.5.
    A boat that is full loaded sinks in the water a little bit more increasing the wet line, thus imposing more drag. So you shouldn't slow down too much.

    Buying half your fuel at double = paying out 66,600fc more.
    From above "So income = 475,000 - fuel or 133,000 = 341,666fc net."
    Would make it 475,000 - 199,800 = 275,200

    The numbers are off somewhat, did not calculate the weight of the fuel.
    Gasoline = 737.22 kg/ meter3
    1000 liters = 1 meter3
    1 liter of Gas = .737 kg
    250 liters of gas = 184kg Half of gas will be used going up so,
    125 liters of gas = 92 kg.

    gross profit from above.
    950fc X 500 = 475,000 fc
    950fc X (500-92) 308 = 387,600
    we lose 475,000 - 387,600 = 87,400 income due to fuel weight.
    However we can haul 678 liters of fuel upstream (500kg)
    678 - 250(222+reserve) = 428 liters to sell at 1200fc (profit 600/l)
    428 X 600 = 256,800fc

    387,600 (leaves) + 256,800 (fuel) = 644,400fc a week for one boat.
    1000fc = $1
    $644 is not a bad paycheck for a week, even here in the states.
    Multiply that by 10 boats and you are looking at serious money.
    One thing that is making so many commodities so expensive is their lack of availability. Once you start hauling, the prices will start to come down.

    Use the owner/operator system that many trucking companies use.
    "Lease" a boat to someone and pay them a percentage of the total they haul.
    The lease would be your cost divided by x weeks. At the end of x weeks he owns the boat.

    You are not in the boat business. Your goal is to develop an infrastructure.
    When you are seen as making a good living then more people will jump on board. You don't care.
    More crops will make it to the cities.
    You need to provide safe boats and safe motors.
    Once the small boats (8.5m) start bringing in the money then move on to bigger, better boats.
    You might want to start thinking of starting a boat building yard.
  8. TeddyDiver
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    TeddyDiver Gollywobbler

    Better than a boat yard just get a couple of boat builders to educate around and sell spikes..
  9. Ilan Voyager
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    Ilan Voyager Senior Member

    It's the problem speed versus economy.

    If you want cheap but "slow" a barge or river boat is unbeatable: 300 metric tons with a modest 80 HP but at 3 knots. The big sea freighters are faster because very long, but it's a very different scale...In the middle you have the V type slim boat (with transverse planking for easy construction) which has an interesting ratio investment/speed/payload/economy, a bit similar to the FAO fishing boats or the flat boat. Made in wood with a small diesel it's pretty cheap and easy to maintain. Some small diesels can use vegetable oil...No need of shipyard or special installations, just a beach. A downwind sail may be a plus to grab the further knot or to save fuel, if the system of winds on the river is favorable. It's the old and proven old solution.

    It seems that you have never been on a fast tug. By fast I mean more than 10-12 knots; tugs are rather complicated (engines, transmissions, propellers) and very expensive at the Kg. They are very specialized boats for one job and only one: pushing or pulling another boat, barge or floating object. A fast tug, like the high sea rescue tugs, is a thirsty beast.

    Hovercrafts (the small ones) use very simple technology, common engines and spares coming from cars or trucks, and can be made in a very ordinary shop. It can be maintained and fixed by any car mechanics. It does not need roads, special installations, nor navigable rivers. It can go on the smallest rivers, reaching any village, pass over the sand banks, and has a decent speed with a rather modest power. The thing is to accept 30 knots instead of 50...The exploitation cost is comparable to a similar payload small truck using dirt roads. The initial investment is modest. Spend 80 bucks and look at the plans of Hovercraft Inc. you'll understand... Big drawback it's noisy. It's the middle solution if speed is needed.

    On the other hand, planes are always expensive; high initial investment, high maintenance and expensive spare parts, not found in the junkyard or in any hardware shop. Add the consumption of special carburants (turbosine or LL100). Expensive pilots and specialised mechanics. Plus the cost of the installations. So a one ton payload plane cheaper to exploit than a one ton payload hovercraft I like to read the detailed ciphers... I almost forgot; a high rate of attrition in "bush" use.

    Do you know the hourly consumption of a one ton payload STOL plane able to use rustic tracks? Something like a bigger Antonov 22?
  10. pedalingbiped
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    pedalingbiped Junior Member

    The purpose of this thread is to get transportation to the masses and not about making a profit. The business ideas are supposed to be about extending this mission.

    A big bag in the river would catch trees, sandbars and every other obstacle in it.
    Your other thread about casting aluminum in the ground to mass produce cheap boats is laudable but not realistic.

    The FAO boats are cheap to make and of wood. This would replace the cast in the earth plan.

    A 8.5 M boat with a 8hp motor is easy to make and operate and can be copied by anyone.

    Going upstream with fuel and coming down with leaves for a $600 profit is doable. But the more I think about it, the less I like it. A slow boat full of fuel is just asking someone to rob you. A farmer makes $37/year or kills you and makes $400/day

    I am leaning more that a hovercraft is what you need to establish an infrastructure.

    The 10 person hovercraft has a payload of 1400 - 1800lbs (635kg - 816kg)
    Even with higher fuel consumption you can still make money, every day instead of once a week.

    It travels at 50-60mph (80-97kph)
    It goes over sandbars and other traps that would stop a boat.
    You don't need to consider the current, just drive the most straight line.

    With enough fuel you could travel the entire length of the river and back in one week.
    The craft is made of wood ribs and stringers covered with plywood.
    and takes 200 to 400 hrs to make.

    the hard part might be the motors. 18-27 hp for lift and 90 hp or more for thrust.

    That's one model the other one is bigger.

    Just like cell phones saves the government the requirement to establish hard wire lines for telephones. Hovercrafts would be the most efficient transportation until it becomes cheap enough to build freeways.

    You could also become a rich man and be influential in future decisions by the government. Quit talking and get going.
  11. bearflag
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    bearflag Inventor/Fabricator

    On the otherhand...

    Having a hovercraft also makes you a perfect target for people who might want a hovercraft to go pirating and killing people.

    I like it though, pretty cool. I'd probably go with a bigger model though. :)
    Last edited: Jul 18, 2010
  12. pedalingbiped
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    pedalingbiped Junior Member

    Anytime your the point man or any time a nail sticks out it gets hit by a hammer.

    I agree. However, the risk of a small, slow boat hauling expensive payload is asking for trouble.

    The fact that the hovercraft is fast makes it less of a target from "every man"

    You can't overcome it if someone makes you an "organized" target.
    The only insurance is make alot of them.

    If congoriver uses the owner/operator model,he won't be the target.
    Once a jig is made, then it would be very fast to make another boat.
    One business model would be to make the boat but make the buyer put in his own motors.
    Don't try to hoard all the profit yourself. Spread it out at let the standard of living be raised. Fuel prices will drop, farmers will make more money and with more money in their pockets, people will come up with more ideas.

    Quit talking and get going.
  13. congoriver
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    congoriver Junior Member

    Again, thanks for the many additional ideas.

    Can those who talked about a slim, long catamaran elaborate a bit? As I understand it they can go quite fast and consume relatively small amounts of fuel.

    What material should such a catamaran be made of? I read something about wood layers reinforced with epoxy. Epoxy will have to be imported, though.
  14. bearflag
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    bearflag Inventor/Fabricator

    Since labor is probably your cheapest variable and you don't want to have to spend a small fortune on metal fittings etc. You should maybe consider a strip plank/cold moulded vessel. I'm not the boat builder expert here (yet), but there is likely to be able indigenous wood that would be more than suitable for your needs. Essentially all the tools except for a table saw are hand tools. The boats can be made without epoxy, and using various glues and varnishes instead, but epoxy is about 10x better. Add much more strength and dimensional stability.

    I think the design you would wan't do go for in a catamaran, is essentially two of those long cargo canoe shaped hulls, and a simple beam-type structure between the hulls, and deck it simply with either just a net or with planks to save weight. You can just have a tarp or hell even a thatched or sheet metal roof covering the cargo if you need to keep it in the shade. No need to be fancy, your boat isn't for winning boat shows or going in the open ocean. Have everything designed to be easily constructed within the materials and local carpentry as possible.

    Strap a car or truck engine to the back of the boat in the middle of the cross beam and have a long shaft hanging out the back with a prop on it.

    Put your emphasis on simple simple simple. Use a little more wood here or there than you need to (but don't over kill it).

  15. TeddyDiver
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    TeddyDiver Gollywobbler

    Or totally glueless ;) nailed strip plank on frames. Propably easiest in remote locations and can be done out of green timber too..
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