Propulsion Options for a 5t utility barge

Hey Everyone,

Really hoping you can help us out!

We have a pontoon/barge as below, that we'd like to turn into a self-propelled utility barge..cheaply. It will be loaded with about 3t most of the time.



We have been thing about fabricating a version of the system pictured below or something resembling Hydro-Armor.com products, whose systems we've seen and are fantastic but out of our range



Can anyone help with some guidance on what size/HP engine, and designs we should be looking at and what sort of propeller we should be thinking about, to get the barge moving along in most conditions at a pace resembling that of a donkey?

best regards
Nic

 

What is the target speed (1.4 KPH?) and the weather conditions it will operate in? If you could streamline the bow it would help too. To give you an idea, I had an O'Day 27 sailboat that moved well with a 3.5 HP outboard.

 

Thanks, Gonzo,

• Target speed,- 5Knt
• Max wind speed would be 20Knt
• The wind whips the lake into a short chop, which the barge would have to power through from time to time.
• Climate is tropical year-round,

We'll look into how to streamline the bow thanks for the tip!

 

The low length/beam ratio could result in a directionally unstable behaviour, particularly with the round sidehull shape; it goes "sideways just as easily as forwards". Better bow shapes is an improvement for directional stability as well, but the steering deservs some thought.

With the conditions stated above, a rough guess is that you need about 25 to 30 hp for propulsion. First, what engines are available locally in this power range (industrial engines, agricultural variants aso), and what about the fuel pricing? Diesel available/preferred? My first thought is something like a Thai longtail, with engine inboard on a swivel; details depend on available engine and fabrication facilities. More on that when the engine questions are clear.

 

Hi Baeckmo,

Thanks for the reply.

Points noted on directional stability.

Chinese agricultural diesel engines are readily available. Second-hand car engines are also readily available
Diesel and petrol prices are very similar, though we would have a preference for a system that offered lower operating costs.
Fabrication facilities are no issue, a very well-equipped workshop Lathes, cutting, snipping, welding, pressing, is on hand to do the necessary, fitting out.

Thanks for your help.

best
Nic

 

Very good suggestions by above posters. Cones on the two pontoon shapes might help efficiency, decrease fuel consumption, and might help with the slight chop, large prop requiring an engine gearbox, might be helpful with the 5 knots, some possible considerations. Some more information might be helpful. How much freeboard fully loaded (ie. does it drag in the center), what is the height of tallest cargo, will it always be (fully?) loaded with three [(t)ons?] while transporting? Are the transport runs between the same places, along the same route, full in both directions , and how long is the route?

 

Thanks, PortaCruise.

What size would be a large prop? any suggestions on the pitch and number of blades?
We haven't worked with the barge yet, so not entirely sure how it works and haven't done any simulations.
The equipment on the barge will have a height of 4m when at the site and 2m in transit.
The transport load will be about 8 tons
The longest run will be about 50km with no consistency in the route or distance through.

Best
Nic

 

A long tail outboard setup would be the cheapest and easier. It avoids the lower gearcase.

 

The prop would be the last thing to select, after you have built your engine and gearbox, because you need to input all of the specifications of the set up, like RPM, torque, horsepower, least draft, Etc. To get your wish for the lowest fuel consumption at 5 knots, your propeller would have to have the lowest slippage possible, and that usually involves using larger propellers at low RPMs. You can research other barge companies for similar situations to yours, then can get some rough idea by looking at what kind of engine and propeller they use, then find out all their propulsion specifications. That will give you some ideas about what type of locally available engine to use for your homemade engine and gearbox, and eventually the prop. Lots of info available online, including quick prop diameter and pitch calculators, but they may not have inputs for a homemade engine system. Here's a link with general information about propellers, Choosing the Correct Boat Propeller | Crowley Marine https://www.crowleymarine.com/d/tech_article/choosing-the-correct-boat-propeller

Another possible way to get rough idea for your engine specifications and fuel economy is by towing your fully loaded barge with a separate boat at five knots, as your experiment will give you some rough data to work with.

The other questions I asked were about barge stability as you need sufficient platform if the cargo rides High and tippy. The fuel economy is affected depending upon whether you are going short or long distances, consistent load size or not, etc.

I like the simplicity and diminutive weight of long tail Motors, and still use tiny versions for my particular interests at the present time. I started with larger versions imported from Thailand many years ago, never found them to be very fuel efficient. If you have to do some maneuvering to get your cargo on a dock, you might have some difficulty with a long tail, because they are generally not built to run in reverse, so other methods might have to be used when docking.

Hope this helps!
Just my humble experience, all of these things may not be true for everyone!

 

Many thanks Gonzo

 

Many thanks for the input Portacruise

So good information and food for thought.
The link is much appreciated!

 

Great comments so far.

You've got about ~30 tonnes buoyancy in those less-than-half pontoons before your flat bottom hits the water.
Adding four half-cones to the pontoons fore and aft would reduce drag considerably,
improve directional stability, and increase freeboard and roll stability.

Sounds like a small automotive diesel engine on a swivel long-tail might do the trick.

 

Thanks BlueBell.
30 tonnes useful buoyancy is god information to have!

Best
Nic

 

Wow, I'm giving out "god information", good for me!

Any idea what your hull weighs now?
Any photos of it?

I would think of your ~30 tonnes of buoyancy as ~15 tonnes usable, ~15 tonnes reserve.
You really don't want that flat bow slamming into waves.

Any engines you're considering?
Have you researched "long-tails"?

Best, better, bestest,
BB

 

Haha yeah, that's quite a level of information quality to have reached.

We are looking at modifying the existing structure and ending up with something like this:



we've flipped from longtails to trying to get at least 80Hp split between 2 late 90's Yamaha outboards on the back ( though they do look really out of proportion), as they are reliable and functional, and it's an easier way to get where we want to be.

We are planning on putting the V in to help with hydrodynamics, locating the drill rig in the center of the barge, and helping a little bit with the handling of the piles.



Not sure of how much the existing structure weighs but we suspect about 5t

Best
Nic