Engine and thrusters performance

[stwendl]

Has anyone measured the ranger tugs models engine bollard thrusts and thrusts of the both bow and stern thrusters?

This numbers are important when manuevering in a windy area. For instance if one has sidewinds that exert greater force than the thrusters are able to create then using them in tight spaces like a marina may mean that entering the tight spaces may be impossible under such wind conditions. Similarly, forward and backward thrusts are important for the same reason.

Of course, one would not go out in such conditions, but what if you had to return in such conditions. Knowing your envelope conditions are an important knowledge for save boating, like knowing what your break distance is on a vehicle.

 

[knotflying]

Trial and error. There are too many variables for a manufacturer to be able to produce tables like they do with planes. Wind, current and then boat characteristics all come into play. Over time you get a feel for your boat's responsiveness in certain situations. My observation is that these boats have thrusters because at slow speed with our small rudders steering is very sluggish. Bursts of power make it more manageable in tight situations. When docking and knowing how your boat handles being prepared for the situation is the best way. Perhaps waiting for wind and or current to subside before docking is the only alternative.

 

[stwendl]

Thanks for your reply.

The part about " When docking and knowing how your boat handles" was my question.

How much wind to the side can one safely overcome with the thrusters. Similarly, how much wind on the nose
or from stern can she handle.

These are basic envelope numbers to watch out for.

 

[Irish Mist]

The bow thruster is able to do more in stronger winds then the stern as The stern thruster has deflectors on it to help it pick up enough water.. And the stern has more mass... I have found if a good wind they are not able to help you much .. The boat has a lot above water to catch the wind and the thrusters are just not that big.. But they are awesome when it is calm 🙂

 

[Levitation]

The real life answer is that from the side, not much.
From the nose and stern, more than you can handle
Well, it was more than I wanted to handle

So extrapolating the probability of docking in a side wind of 10 knots and a current 5 knots with 4 passengers after 3 rounds of drinks at Hooters:
((+2x-5)-(-2x+5+10a)) - (-5a3+4x-2) = 0
hmmm, bout what I thought

And I suspect that this is about as close as you are going to get to 'numbers' :mrgreen:

 

[trailertrawlerkismet]

Denny-O's math seems to be spot on and the other comments are the reality of how our thrusters work. My policy on thrusters is, for me, is to try to always operate the boat as if it does not have thrusters. This way when I get into difficult docking situations the use of the thrusters is secondary to my handling experience and any thruster use becomes marginally helpful much like the reality of how they work in windy, high current conditions. One other suggestion.....when you know you'll most likely have a difficult docking or maneuvering situation ahead of you start your generator and turn your battery charger on. This way you'll be keeping your thruster battery charged up under conditions where you'll be using them more then normal.

Jim F

 

[tlkenyon]

The real answer to the question is "it depends".....how high are the waves, if any? To high and the thrusters pop out of the water and obviously have very limited thrust. How broadside is the wind? Any angle from broadside might be beneficial, but might not, depending on the situation. Is there current, and from which direction? Same as with the wind...might be beneficial, and might not. Are there eddies in either the wind or current? Same thing. Add all these together in their various combinations and you get "it depends".

Every situation is different on the relative effect of the thrusters. You just gotta practice in a lot of conditions and get a feel for it. I do this out and away from obstructions. I use the thrusters even when they are not needed to just gain the feel for how they are going to work in a given situation. I also practice without the thrusters against the time that they either do not work or are ineffectual.

Needless to say, I have picked up a few scratches and have made a lot of second and third approaches....

Sunny Skies and Fair Winds,

TK