A salute to stern thrusters

[MapisM]

I can't believe I'm writing this, but a friend of mine who is a psychoanalyst tells me that only fools don't change their minds, so heyho...!

Today we had a very small weather window in a whole week of awful weather, and off we went for a spin with the DP.
Since I am by now beginning to have a decent maneuvering confidence, I made a point of not using thrusters.
And I did manage to reverse in my berth without them, which is not a bad result considering also the typical N Adriatic arrangement with poles rather than bow lines, in front of the dock.

Once inside my berth, the couple of folks who were with us took care of the lines attached from the bow to the poles, and I thought that it was pointless not to use a bit of b/t to facilitate them the maneuver.
All well and good so far: even if I survived 17 years of boating with no thrusters and no damages, I always said that a b/t could have had its use, at times.
Otoh, I also teased a bit those who praised stern thrusters, which I always considered completely useless.
In fact, using just short bursts of fwd/rev either side, I was able to move the stern of my old lady sideways, very easily.
But with these blxxdy P boats, no matter for how shortly you engage the gear, the boat jumps forward/astern immediately, even with just one engine. So, by the time prop walk becomes effective in pushing the stern sideways in the desired direction, the boat has already moved a couple of meters longitudinally if not more, aaarumph!
Therefore, eventually I used also the s/t a bit, to facilitate the crew while they were securing all the lines, because I was unable to do the same with props alone without moving the boat also fwd or astern (which would have actually made life harder for the crew).

Bottom line, I hope all those which I teased a bit in the past on this matter will accept my apologies.
Otoh, if among all the P boats experts (of which there's plenty around here!) there's someone who can suggest a trick for moving the boat stern sideways without also jumping forward or astern in the process, I'm interested to learn it! :encouragement:

PS: suggestions along the lines of replacing the shafts with some IPS are politely declined in advance! :ambivalence:

 

[Kawasaki]

Stuff IPS
Stuff bow and stern thrusters
You say you had Crew to handle lines
So therefore
A Decent Chappie on the Helm can move a motorboat about with no problem.
Without thrusters
Get a grip Man
Although I do understand your comment (these blxxdy P boats) and how they 'jump' when put into gear it is a question of finesse to berth a Motorboat
I can learn how to do it
60 quid an hour OK?:
:encouragement:

 

[Montemar]

"So, by the time prop walk becomes effective in pushing the stern sideways in the desired direction, the boat has already moved a couple of meters longitudinally if not more, aaarumph!"

Just what I find, glad I am not on my own on this.

 

[Bouba]

Stuff IPS
Stuff bow and stern thrusters
You say you had Crew to handle lines
So therefore
A Decent Chappie on the Helm can move a motorboat about with no problem.
Without thrusters
Get a grip Man
Although I do understand your comment (these blxxdy P boats) and how they 'jump' when put into gear it is a question of finesse to berth a Motorboat
I can learn how to do it
60 quid an hour OK?:
:encouragement:

You should not say "Get a grip Man" to somebody who is seeing a psychiatrist

 

[markc]

Totally with you MapisM - the bite on the props is so huge it's impossible to make fine adjustments when mooring and the ST & BT are very useful (this boat is the first I have had with a ST). I'm still going to insult those who insist on steering around the marina using their bow & stern thrusters though!

 

[Nick_H]

All boats are different I guess, but fwd on one side and reverse on the other at the same time moves my back end sideways with only a slight creep forward. I could do with a third hand though to operate the b/t at the same time.

I'm sure a sternthruster is more controlled anyway, in instances where you want to hold the stern in a fixed position against the wind, so it would be a nice to have.

 

[MapisM]

A Decent Chappie on the Helm can move a motorboat about with no problem.
Without thrusters

LOL, it's always a pleasure to read your posts Kawa, but you must have missed the bit about 17 years with a boat just a tiny bit smaller than my current one (albeit a heavy D one and less than half power, which means MUCH less reactive upon gear engaging), no thrusters at all, and zero damages upon maneuvering (including some hairy conditions, in several occasions).
On that basis, I'm rather confident that I could also teach a thing or two on this subject.
Coming to think of it, I could even offer a bargain at 60 EUR/hours, if you don't mind a competitor...

 

[MapisM]

You should not say "Get a grip Man" to somebody who is seeing a psychiatrist

Oi, I said he's a good friend of mine, not someone "I'm seeing".
Btw, he's an excellent cook, which for some reason is something that I tend to rate much more than anyone's profession...
Oh, and unless the terms have different meanings in EN (but I don't think so, being latin-derived), psychoanalyst/psychologists are a different bunch from psychiatrists, anyway. :encouragement:

 

[MapisM]

I'm still going to insult those who insist on steering around the marina using their bow & stern thrusters though!

Seconded 100%!

 

[BartW]

All boats are different I guess, but fwd on one side and reverse on the other at the same time moves my back end sideways with only a slight creep forward. I could do with a third hand though to operate the b/t at the same time.

+1,
my heavy boat doesn't move much fwd nor rev when I engage fwd and rev simultaniously,
just missing that third hand very often

 

[MapisM]

All boats are different I guess, but fwd on one side and reverse on the other at the same time moves my back end sideways with only a slight creep forward. I could do with a third hand though to operate the b/t at the same time.

I'm sure a sternthruster is more controlled anyway, in instances where you want to hold the stern in a fixed position against the wind, so it would be a nice to have.

Aaah, a suggestion which is right on the money, eventually.
Yes, I forgot to mention it, but this is a method that has its merits.
But as you say, all boats are different. With alternate thrust, the rotation center on my DP is significantly more astern than in my old boat, which almost exactly rotated around its own longitudinal center.
As a result, with say port fwd and stbd rev, the stern does slide towards port, but the bow does much more of the opposite movement.
Which is fine in some occasions, but not when you want to move the stern alone.
And the engines effect is much stronger than thrusters, so even combining (with a third hand...! ) a b/t pull towards port, the bow still slides to stbd.
I suppose that the conclusion might be that I need an even more powerful b/t to avoid using the s/t, but I don't dare thinking what Kawa would have to say on that...

 

[BartW]

I challenge myself when manouvring, to use the bt as less as possible,
to get practice on the inertion and or swing of the boat

I'm considering to install a S/T, not that I ever missed one,
EXCEPT
during that short week when we had to travel and maneuvre with one broken engine,
so as a backup (when missing one engine) I'm considering to install a simple S/T
if not, a problematic engine (or prop, gearbox, ..) could mean a lost summer season

 

[MapisM]

my heavy boat doesn't move much fwd nor rev when I engage fwd and rev simultaniously,
just missing that third hand very often

I fully understand that, B. Can't say that I actually remember it, but it makes perfect sense that BA, due to her sheer size/weight, reacts more smoothly than my DP.

Besides, her max speed is around 26kts, IIRC?
I'm asking because since the operating range of our engines is exactly the same (650-2300), by definition the idle speed has to be somewhat lower (i.e. shorter pitch and/or higher reduction ratio), compared to a 33kts boat.

 

[petem]

Regarding 3rd hand for B/T, I believe some boats have a P/S (eek, I nearly sail L/R then, the shame!) B/T control mounted on the floor.

 

[BartW]

Besides, her max speed is around 26kts, IIRC?
I'm asking because since the operating range of our engines is exactly the same (650-2300), by definition the idle speed has to be somewhat lower (i.e. shorter pitch and/or higher reduction ratio), compared to a 33kts boat.

exactly,
and I feel the difference when rpm is 800-900,

my old hydraulic gear throttle commands have some hysteresis, so that after sailing at >1000rpm, and slowing down,
the rpm sticks at 800..1000rpm,
I have to give the gear levers an extra up / down push to get engines back at 700rpm,
I don't alway's do that and do the maneuvring at higher idle rpm

 

[MapisM]

Regarding 3rd hand for B/T, I believe some boats have a P/S (eek, I nearly sail L/R then, the shame!) B/T control mounted on the floor.

Interesting, I never came across any.
There's actually a more sophisticated, very posh alternative nowadays: the yacht controller remote.
With it, it only takes two fingers of the same hand to control both gearboxes, and on top of using the other hand for holding the thing, you can easily control also thruster(s) with it.
If only its cost wouldn't be ridiculously high... :ambivalence:

 

[Greg2]

Our recently sold boat (Broom 41) had a bowthruster when we bought it, which was a first for me. After a couple of years we added a stern thruster, not because I thought we really needed it but because we were offered it for a good price. Prior to this I had been quite scathing about the use of both and regarded them as entirely unnecessary.

Ended up being a complete convert! Both were very useful in certain circumstances/conditions and particularly the stern thruster even though we could use prop walk without too much forward/backward movement. Of course given my previous views howls of derision were not unusual when I did use them!

 

[MapisM]

the rpm sticks at 800..1000rpm

Careful there, B.
What you are saying is one of the interesting features of separate levers for gear and throttle, which has its merits.
With my old lady, whenever mooring in some crosswind, I needed a tad more than the push at idle (about 600rpm, with her).
So, I left the engines at around 800rpm instead, and continued to use only the g/box levers as usually.
I did check that in advance with a ZF engineer, who confirmed me that the gearbox was designed to engage/disengage up to 850/900 rpm with zero risk of damaging anything.
1000rpm sounds a bit high to me, though.
Don't you hear the g/box yelling at you from the e/r, if you engage the gear at that rpm...? :ambivalence:

 

[SEARANGER ANCASTER]

I tend not to use my ST a lot but as its there anyway , why not. Its better to get a blip now and again anyway . If youve got it , flaunt it !

 

[Firefly625]

wouldn't be without mine. Single screw I can turn in my own length just like twin screw which I had to do only a couple of weeks ago in a space as wide as my boat with an audience drinking beer and waiting for a cock up that didn't occur. Talk about smug zone. Also the ability to move sideways when in a line of boats nice. My Mitchell does have a long keel and does track straight and even responds to the rudder when engine in neutral and so long as wind and tide permit I do approach a berth at a snails pace, nice to cruise to a stop at a berth rather than bang it into reverse I always think... I sometimes even cut the engine as I approach, even got asked if my boat was a hybrid earlier this year by my neighbour who I had moored next to. I do not use thrusters as a matter of course for mooring up as I got to say not keen on the noise a thruster makes, kind of announces your arrival, I prefer to sneak in.