one prop instead of 2

[YuriB]

Hi,
i have twin prop boat, and i'm going to remove right prop and tunnel, leaving only one on the left side. There 2 rudders on the boat.
Some friends of mine don't like the idea and arguments mostly like "this never has been ever done before".
As for me i don't see any proplems. Does anybody else have an experiense riding a big boat on one prop?

[apex1]

Use common sense Yuri and you will see why that is not a good idea.

[YuriB]

Common sense tells me there is no crime in the whole idea.

[gonzo]

The boat will run at an angle and will turn one way fast and little or none the other. If you want one engine, install it in the middle like it should

[mydauphin]

Good ideas if you cruise your boat in a round lake and you can remove prop on side that always needs turning into.

[Stumble]

Yuri,

There are a number of very good reasons not to remove the second prop, unless you want to move the remaining one to the center of the boat. This while possible would demand a redesign of the central framing to carry the loads of the now central engine.

Some of the problems with removing only one engine:

1) Matched engines counter-rotate with props to match. Removing one of them will destroy this balance and cause the boat to want to turn all the time

2) Because the boat wants to travel in a spiral the rudder will have to be turned to counter act this causing increased drag. The increased forces could also lead to premature rudder failure

3) Boats with 2 engines are designed to have that much horsepower. Assuming this is a planing hull, you may eliminate the ability to get up on a plane at all

4) Low speed manuverability will be drastically reduced since you can no longer use opposing engines to spin the boat.


And these are just off the top of my head. Give me a few minutes to think about it and I am sure there are a hundred more.

[YuriB]

Thanks for your notes, Stumble.
No it is not planning boat, it is 90ft GRP minesweeper, that will have new engine.
Distance in between centerline and the prop shaftline is 4ft, so there is not that big turning momentum to the hull. Also, usually on the single prop vessels, the prop drags a hull aside, towards its rotation direction, so that if i arrange rotation of the prop CCW, it will at least compensate the turning momentum.

Yes the first what comes in a mind is that the boat should curcle when goes on one prop, but what i heard from the people which had one of two engines breakdown, the ship goes rather straight. Even though some constant deviation from the curse is normal because it always happen due to the wind, waves, etc. so i would not much worry about rudders.

[masalai]

Just run your twin system at HALF revs and you will get the dreamed of economy and not stuff up everything... and the outcome will be the same speed.... or somewhere in that vicinity...

Otherwise, sell the boat and get one that more appropriately meets your needs....

[YuriB]

masalai
we, humans, got used to change things to meet our needs.
If you have 2 engines running at half revs, you're not only use your boat space in unefficient way, but also abuse your engines, because diesels are designed to run with nominal or higer load.

[masalai]

Likewise the boat was designed and built for 2 engines - would you remove the front right and the rear left wheels on your car?

[FAST FRED]

The largest hassle you will have is the vessel will be harder to control as you accelerate to a speed the rudders will operate at.

Same hassle docking , it may get really strange with one prop attempting to stern walk the boat , and little rudder control,

Underway should be no hassle , although with only one prop wash the steering at lower speeds will take more rudder angle.

FF

[gonzo]

I like mydauphin's idea. There must be some round lakes around there. Otherwise, you could cruise the Mediterranean in whatever direction you boat wants to go.

[apex1]

The black sea is´nt bad either and probably closer to Yuri´s jetty.

[masalai]

Become a politician, then going around in circles will seem normal/appropriate?

[mydauphin]

Remove both propellers and install a center jet drive of whatever size you want, then if you ever change your mind put propellers back.