Amazon river, Loadum up

[Chris Ostlind]

Originally Posted by apex1

Sorry mates, but a Cat is the worse choice for a violent river. And common sense tells easily why.

Hi Apex,

Have you used a catamaran for this application and your comments are from experience? If so, could you tell us as to the type of boat, it's design particulars, etc.?

You are certainly entitled to your opinion, but perhaps you could tell us how this remains supportable when measured against the use of big, inflatable catamarans for extreme whitewater applications?

Class V and VI rivers are routinely run with catamaran style craft and some very experienced river runners actually prefer the inherent stability over a monohulled variant.

That kind of violent river?

Chris apples and apples please............
These rafts are not really what we call catamarans, and they are designed (and fit well) to handle the violent rapids, but not the extremely different conditions on the amazon river. And no, I used RIB´s on the Amazon and have never seen a CAT there.

Regards
Richard

[Chris Ostlind]

Hi Richard,

With all due respect, you did not define the apples. It was simply, "but a Cat is the worse choice for a violent river. And common sense tells easily why"

That's a mighty broad pair of statements.

Common sense says that the guys who are using the mentioned catamarans on big, violent rivers are getting quite good results. And they really are catamarans the way that I see it. Two hulls held together by a structural bridgework. Is there another way to describe a catamaran? Some of them are quite big and totally powered by outboard engines. Please describe the problem if they were to be made from a suitable material, such as wood, or aluminum.

Cats can be made in all kinds of sizes, from all kinds of materials, for all kinds of purposes. What is it about the genre that you find as the "worst choice for a violent river."

I'm not looking to engage you in an argument of the hostile type. I'm just looking to discover the reasons for your statement in this regard.

Hello Chris,
yes technically these large Hypalon hoses are catamarans and they do what they have to do, they stay afloat even if damaged or if they capsize (what they sometimes do). And I´m not shure if that sort of vessel would really be "the worst" choice on the Amazon (they just never have occured to me), if I think of it in deep. Windage would be a real disadvantage on a wide open river btw. and I doubt they are economical to operate.
But my statement was made with the common, usually lightweight cat in mind. A vessel that would have to be of a very rigid design or a reinforced type to stand the uneven loads that occur regularily. This would sacrifice some of the economical advantages of the cat. The need for a second engine is another point against a cat. More disadvantages have already been posted here (Manoeuvring in weed must be very interesting too.).
Cost is a factor not mentioned by now but another point to add to the list.
And I did not feel your approach to be of a hostile manner, we are fortunately able to change our opinion if we are tought better.

Regards
Richard

[rasorinc]

I would think that no matter what you would want 2 engines on the Amazon River. I would not venture on the that river with out a back up. I've only seen pics and videos of it but I would not want to just be adrift. A back up engine for emergencys should be a safety requirment along with 120% flotation of total boat and engine weight. Plus a damn good radio. My 2 bits.
Best, Stan PS If your going against current then you need Hi Thrust engines which I posted way back. High HP is not the answer because you then have high speed at a time when you do not want it.

[TeddyDiver]

Loosing thrust is not so serious as I've allrady said earlier.. There's allways a town downstream, not Niagara
2 engines.. "not cost effective"..

[ancient kayaker]

The value of life, like the cost of fuel, varies from place to place.

[Chris Ostlind]

Originally Posted by apex1

... my statement was made with the common, usually lightweight cat in mind. A vessel that would have to be of a very rigid design or a reinforced type to stand the uneven loads that occur regularily.

I do not see a problem with the need to design a cat that is structurally rigid, as well as reasonably light in weight. A cat will actually handle uneven loads better than will a monohull, simply because the buoyancy form is at the widest possible beam ends of the craft, making for a much more stable design.

Capsizing a cat is as frequent an occurrence as the sinking of a monohull, which is fairly rare. This issue does not happen nearly as often as people seem to think it does.

Originally Posted by apex1

This would sacrifice some of the economical advantages of the cat. The need for a second engine is another point against a cat. More disadvantages have already been posted here (Manoeuvring in weed must be very interesting too.)

The slightly higher cost to build is more than compensated by the much lower cost of operation. This reality is, of course, dependent on the service life of the vessel, but for an average life span, the cat is considerably less expensive to operate and the added cost to build is quickly amortized. The world over, ferry craft are switching to more efficient cat hulled designs for this very reason.

A cat does not necessarily need a second engine to operate properly. Secondarily... even if you do choose to install a second engine, one on the transom of each hull, the cost to purchase two 30 hp outboards, is pretty much the same as buying one 60 hp engine. Advantages with twin engines are that the load is spread evenly across the stern of the boat and it is highly unlikely that both engines will fail at the same time, providing a backup that can still propel the boat, albeit at a slower pace.

A breakdown with a single engined boat is not just a loss of propulsion, it is also a loss of steerage, because the boat will then be moving at the speed of the current. That means you will go wherever the river decides for you to go and you can make little difference in the reality. Miss the next town because you can't get their attention and now the customers on board are a very long way from their destination. That will likely mean an added expense to get them back to the proper drop-off point.

Maneuvering in weed is not any different than with a monohulled design. In fact, with a twin engined cat, you could have even better steerage control as you can reverse either engine while keeping the other in forward.

[TeddyDiver]

Originally Posted by Chris Ostlind

Miss the next town because you can't get their attention and now the customers on board are a very long way from their destination.

A paddle perhaps ? It's not an ocean
and he's driving aid personel in to jungle, not tourists

[TeddyDiver]

A cat might find some turns a bit tight..

[Chris Ostlind]

Paddles... in the plural form, depending on current speed, weight of boat and skills of the Aid Personnel on board.

So, what is the speed of the current (I realize it varies seasonally, so just an average, is fine)

One way or another, time is money to everyone, Teddy. Aid workers have schedules too. If the boat malfunctions and there is no way to have one's schedule met, or the situation adjusted, then it won't be a functioning enterprise for long.

Twin engines... I see many benefits involved with the same cash outlay.

[Chris Ostlind]

Originally Posted by TeddyDiver

A cat might find some turns a bit tight..

A cat driver reverses one engine with the other driving forward. A skilled driver can make the boat spin on a.... well, not a dime, but a whole lot better than a monohull with a single engine in the center.

[TeddyDiver]

And if time were the main issue they would use a helicopter, but reckon, having $20000 they don't own a coca plantas..

[TeddyDiver]

Originally Posted by Chris Ostlind

So, what is the speed of the current (I realize it varies seasonally, so just an average, is fine.

I'd say avarage current speed about 3kn, and a slim hull(s), cat or mono, can be paddled about half of that. But it doesn't matter if you have a map to see which side of the river the next town is and get to the same side in time..

[ecflyer]

You need only a larger Evinrude or Johnson Motor, lets say approx 110 hp, 2 stroke, 4 cylinder. The yamaha is giving you 2 mpg. You should get double that from an Evinrude if you run it at 75% power. Efficiency comes from the larger prop and Evinrudes pattened cruise-throttle system. I had a 140 hp Evinrude--top speed was 38mph in a heavy boat and I ran at 28 mph to get amazing fuel economy.
Have a Great Day!
Earl