The Mighty Mekong expedition boat

Discussion in 'Boat Design' started by greginlaos, Nov 14, 2010.

  1. greginlaos
    Joined: Nov 2010
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    Location: Luang Prabang Lao PDR

    greginlaos GreginLaos

    Thank you ....I am a bit overwhelmed by your generosity...

    I think I have mislead you...I meant a boat less than 7 meters. I hope this does not blunt your enthusiasm. The reason for this is the small size and shallow depth of the waters that we want to navigate. I got the >< the wrong way around sorry.

    See answers below

    Dear George, (Greg)

    Can I have the answers to the following questions

    1. You preferred steel. (this is because it is almost impossible to imagine a trip without running into something, also this is fresh water so very limited problems with rust):

    Can you verify the quality of steel?

    (Not really, it is delivered here from china and Vietnam by questionable merchants who buy it wholesale and dump it off at my door. We build many things from steel here, we use several tons every month and I know that the quality is variable. However I can source some from the BHP plant in Ho Chi Mihn City which is above average quality):

    Basically structural quality steel will do but tell the dealer to give you the plate from the later part of the batch. That way you will get low sulphur and phosphorus percentage - good for low corrosion over the years.

    (I think we are just going to have to live with this, is very cheap to build things here and there are many simple steel boats that last for decades)

    2. Good that you have a good team. What kind of welding machines and how many do you have ?

    (We use basic stick welders, there are three of them and 4 experienced welders, they can successfully weld 2 mm plate with this primitive gear. We cant get argon or other gasses here so MIGs etc are out of the question. These guys can really weld tho...)

    3. Minimum draft in the area u will be plying.

    (effectively 0mm :) the draft will limit the range of the boat as these river run for hundreds of Km into the mountains and just sort of peter out. In a practical sense 300mm would be good... )

    4. How many passengers?

    (For this boat and for shorter trips say up to 100 Km up to 6 people. For longer trips just 2 or 4 of us. If we were to work out how to produce these boats we would set them up for much shorter trips with a maximum of passengers on bench seats for trips to the market or school etc. Basically for villagers these bouts would be teh equivelant of a mini bus or larger family car.)

    5. Duration/length of trip?

    (As long as we can, I think the reality is that we should design for up to 200 km if possible between refueling which is why I am looking at a small boat with an small efficient engine. With this boat we plan to just travel as far as we can up some of the larger tributaries, the Nam Ou , Nam Kahn etc. These wind up into the mountains for a very long way. Fuel will be teh limiting factor in most cases. )

    6. Do u need a toilet / pantry on board?

    (basic toilet is good, sometimes access to the shore is difficult. We can store food in lockers, there are village markets along the river banks, lots of fish, would be good to have a very simple galley, just a one burner gas stove to prepare food)

    5. What is the comfort level?

    (I suppose comfortable camping is how to express it. Ok, so remember we are in the tropics, very hot sometimes and never gets colder than the need for long sleeves. Not much need for walls, just canvas sides to allow some privacy. We would need a double bunk and head room if possible. The main issue is insects that need to be screened out.

    6. still water speed Desired? (> 6 knots)

    7. What is the tide current? (The Mekong flows at about 3 knots, but to get upstream you can stick close to the banks where the current drops to very low speeds, the smaller tributaries are variable, but small boats with simple 5 Hp gasoline engines and inefficient propellers can make effective headway. )

    8. can you get a propeller made there if I send you the drawing?

    (Yes there are good foundries in Thailand which I can access.)

    9. Give details of the engine , whatever you have or can get.

    (I cant work out how to attach files that are not from the net so I am afraid that I will have to ask you to look this up yourself ..

    The 14 HP is the one I prefer as I already have two of them and can easily get parts etc, they are a fantastic little engine)

    What i am thinking of is a catamaran hull with single direction curveture.
    why? (I think after my admission of stupidity you may wish to revise this. I have run out of internet time so will continue tomorrow)

    1. cat hull will give you very high stability. Tourists hate a boat that rolls. A dolphin pops up and all the tourists crowd to one side can cause a catastrophe in a single hull.
    2. The passage between hulls allows float sum to pass by.
    3. Rudders/props are wider spaced - giving you more maneuverability.
    4 A lot of underdeck storage space.
  2. kach22i
    Joined: Feb 2005
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    kach22i Architect

  3. Boston

    Boston Previous Member

    I would have thought a Dory style would do the trick nicely
  4. MatthewDS
    Joined: Mar 2010
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    Location: Juneau, Alaska

    MatthewDS Senior Member

    We seem to see a handful of folks looking for robust and simple craft for third world rivers, it seems to me that a traditional stern wheeler would be best for this purpose. Before dismissing the idea as an anachronism, consider the following:

    They have very shallow draft, as they were designed to operate in the same conditions the OP is looking at. It should also be noted that the draft on the ship in the picture is 3'-6" fully loaded, quite a feat for a 237' boat.

    They are simple mechanically, you don't need fancy props, or shafts or underwater hull penetrations

    Any engine will do, as long as you can run a drive belt off it somehow.

    They are designed to haul a very flexible mix of passengers and freight, exactly like you would need in a developing nation. Take a look at the booms in the attached picture, that's a working boat.

    The wood hulls are easily built. I figure that if you could build them on the banks of the Yukon during the gold rush, anybody could build them. Although to be fair, the Nenana was built in Seattle.

    I realize that the OP wanted a 21 ft boat, but I think that the hull shape and propulsion on a stern wheeler would be worth considering.

    Attached Files:

  5. ExileMoon
    Joined: Oct 2009
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    Location: Shanghai

    ExileMoon Junior Member

    I think you need is a rubber dinghy. Like this:

    Length of 7 meters, manned 20. Draft 300mm.

    The flexibility of rubber boats can be difficult to ensure that crashed through the rocky area. If the inflatable sac filled foam, you can guarantee it will not sink even crashed through (but not be folded.)

    The entire rotation of the side of the plug-in engine ensures that there is enough rapids maneuverability.

    Attached Files:

  6. Boston

    Boston Previous Member

    hey Mathew that is the coolest picture

  7. michael pierzga
    Joined: Dec 2008
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    Location: spain

    michael pierzga Senior Member

    My sister was a school teacher over there and used to Kayak the Mekong. If your looking for a real " cruiser " why no go miltary surplus DUK ? Chop here, chop there...little bit of this and that and presto !! all terrain Mekong cruiser !!

    Attached Files:

  8. kach22i
    Joined: Feb 2005
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    kach22i Architect

    What type of foam would this be?
  9. hoytedow
    Joined: Sep 2009
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    hoytedow Wood Butcher

    It was very useful in un-civilized North America.
  10. cthippo
    Joined: Sep 2010
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    cthippo Senior Member

    When I was doing the research for my surf sled I came up with a supplier for two part expanding foam, which is USCG rated for flotation (i.e. closed cell) and when fully expanded weighs only 2 lbs per cubic foot.

    Something like that seems like it would work perfectly in a RIB
  11. Milan
    Joined: Apr 2005
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    Location: The Netherlands

    Milan Senior Member

    After reading about expected usage of the boat, (number of passengers, length and duration of the trips, operational economy ...), I think that it would be mistake to limit length to just 7 meters. To pack everything in such a short boat will make it quite bulky.

    You need a low resistance, trim hull. Length / beam ratio around 1 / 5. Such a boat will go upstream much better, with a lower fuel consumption.

    (Length alone is quite cheap, just a little bit more steel plate and paint, quickly earned back with a less fuel burned).
  12. apex1

    apex1 Guest

    I´ll second that. Especially in the light of passenger transport with some sort of rest room and the (for me not clear) demand in a double bunk. Which both is simply not feasible below 7 meters.

    To the original question about propulsion.

    The Kubota´s mentioned are very reliable and good engines, there will be hardly any better around.
    When there is a higher power demand "Shanghai Diesel" is available in all countries around, they should be in Laos too. (not on the night market)

  13. greginlaos
    Joined: Nov 2010
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    Location: Luang Prabang Lao PDR

    greginlaos GreginLaos

    OK so maybe I was dreaming or half joking about he bed and toilet although some sort of on-board head would not be a bad idea if possible.

    The length restriction has little to do with cost. Its mostly about maneuverability and access and also the fact that if I need to truck it somewhere this is a practical sort of length with the vehicles easily available here and also with the state of most river access points where it is only possible to get a medium sized vehicle anywhere near the water.

    I could stretch it to 28 feet ..but that would be the practical limit.
    But lets deal with some other things first:

    Hover craft and inflatable boats are both outside the technology envelope here. Remember that I would like to transfer this design to common use here if possible. Outside of my workshop there is not a single competent motorcycle mechanic in this province... and only two that I know of in country....really, not one, let alone someone who can effectively maintain either the drive gear for a hovercraft or an outboard motor.

    The trajectory for most machinery here is "purchase... no service...break down (minor)… discard and use as livestock dwelling" ...

    In fact anyone with some spare cash could make a fortune here rescuing the hundreds of broken down earth movers and other machinery that is rotting in fields because of some very minor mechanical failure or because parts are impossible to get. This really is the back woods and I am trying to design something for everyday use.

    This is one reason for sticking with the low powered Kubota engine, because they have a well established supply chain here that reaches into the hills. They run training courses and have good spare parts back up.

    Also because they are such a tested and self contained unit and cheap..$1000 USD for the 14 hp model. Affordable for reasonably well off locals. If I need more power I think I will opt for two of them with two screws.

    The stern wheel idea I will look into as I have never though / heard / imagined such a thing.

    Also people here are profoundly conservative so the catamaran idea would be treated with deep sceptically. Also it would produce a wide hull that would make manoeuvring in many of these streams difficult.

    I think what it comes down to is a long narrow, relatively flat bottomed displacement hull as suggested. This is the design that local people use but usually with some horrible, noisy Japanese car motor and a propeller that acts as water spraying device. These hulls are made of light steel, so perhaps I should stick to what is locally used.

    The longer boat (8.4M) that is shown in the FAO Fishing Technical paper 134 might be simular to what you are suggesting….The paper does provide a way of expanding the beam by 20% (from 1.8 to 2.2 M). ( I’m sorry but either I am stupid or I have a bug in my system because when I try to attach a file the browser just opens a new blank page )….so if you want a look you will have to go to :

    and click on Designs (P7). For the info about the beam modification go to page 15.

    My questions are:

    Could I build this hull or something simular in steel or would the weight be too great?

    Would a 14 Hp engine power such a boat or would I need more horsepower?
  14. apex1

    apex1 Guest

    Yes to both questions!

    These Gulbrandsson designs are easy to make, cheap, and fit your minimal requirements roughly.

    I would recommend doing them in wood though! Of course I am aware of your metal skills, and that this would be you first choice, but timber sure is cheaper, and you must not redesign anything. Forget about Teak, you can even use Yemane in this case.
    A perfect boat would be a different animal, but thats not what xou need anyway.


    does Mae´s restaurant still exist? where you had to cook your meal yourself?

  15. Milan
    Joined: Apr 2005
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    Milan Senior Member

    Yes. For river use they could be further simplified, using flat bottom.
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