Nautical
Well-Known Member
Looking at that picture Bart, you have an issue with the AP there for sure, shouldn't have any squirrelly line in the prop wash if AP set up right.
Semi displacement / planing, fuel prices
- Thread starter henryf
- Start date
BartW
Well-Known Member
since Henry doesn't mind, I think we are simply talking about A/P gain control adjustment Bart. Had the same issue on my Cetrek a/p because the setup menu is so retarded and unintuitive that I accidentaly managed to max out the value on this. Result was much worse than what you describe, but trying to fix it I passed from this stage you're facing and eventually minimised it (and I'm talking D speeds since my one turbo was stuck...)
There's another complimentary value that has to be tuned as well, sure MM will come and correct me soon
V.
if I remember well, I had a similar intuition, and tried to lower gain, but that was already in its lowest position. (more gain made it worse)
and also remember about a second parameter which was also at its lowest value.
In the brochure I found a hand written drawing, giving some clues, but none of it was an improvement.
some more testing to be done when experienced ap specialists are onboard
MapisM
Well-Known Member
Geez Bart, GNBN time, I reckon.
Good news is, if the steering equipment of BA (a/p, leverages, pump, rudders, the whole lot) lasted till now working like that, which is probably 3 times what they should normally do, if not more, they're definitely built to last!
Bad news is of course that surely there is something which is not working properly.
Didn't GC highlight this in his survey? The excess of rudder hunting is too obvious to be missed. Or maybe you had some rough sea during the sea trial?
Anyway, let's try to better focus the problem, before even think about any sort of troubleshooting.
When you say that it takes 2-3 seconds before the boat reacts to the A/P, you mean that:
1) you see either the port or stbd arrow appearing on the upper part of the display below (which shows the port arrow, in this case), AND
2) only after 2-3 seconds the boat steers in that direction?
If I misunderstood anything, please correct me. But if the above is correct, I have a couple of questions:
First of all, what happens during those 2-3 seconds, does the arrow stay on, or does it disappear before the boat starts reacting?
Secondly, while the arrow is on, you might see also a few LCD segments in the horizontal scale at the bottom, in the same direction where the boat is steering.
Did you notice if and how many of those segments appear, every time the a/p is operating?
Oh, and did you notice, while steering manually, if on average the corrections vs. the neutral rudder position which you must introduce are more to port or to stbd (or neither)?
In other words, when you keep a straight course manually (I assume you can! If not, pls specify), would you say that those LCD segments at the bottom appear more frequently on one side, or isn't there any obvious difference between port and stbd?
Anyway, we can definitely check a few things when we'll meet, even without moving the boat.
But at the moment, the thing which is more difficult to understand is the reason for the delayed reaction of the boat.
At P speed, 2-3 seconds are a helluva lot of time. Even considering that BA certainly isn't a light sportboat, she should react much faster than that.
It's simply impossible that it takes her so long to steer after the rudders are actually moved.
Therefore, you might be correct in thinking that the problem is elsewhere - e.g. a weak pump, or whatever.
In which case there's no calibration on earth which can improve the performance of the poor A/P, of course.
And that's one thing which is difficult to check without moving the boat, because unless there's a delay in the rudders movements even without any pressure on them (which would be the worst case, but at least useful for troubleshooting), it's necessary to check the rudders operation while cruising at speed, in order to understand what's what.
Interesting problem, anyway.
It's surprising to hear that the previous owner didn't seem to bother too much about it.
I am lazy enough to leave happily with my grey teak (sorry jfm), but I'd go nuts for a thing like that.
Your pic alone is enough to make me nervous...!
Elessar
Well-Known Member
The nordy I brought to Antibes had 6 fuel tanks. Well 7 actually but the 7th is a part of the day tank. The day tank is the only one that can feed the engines. Any of the other tanks can be selected to the day tank, and they are gravity fed no pumping required.
Tank 7 is a tiny tank above the day tank, with a sight gauge. Shut off inlets to this to do a consumption check, which will of course check the total consumption of engines/gennies.
So of the 5 storage tanks, any tank can be routed to any tank, via a pump and a big racor filter. The filter is easy to access if it clogs. This is fuel polishing surely?
The main engines are fed by a lifeboat style double filter system with changeover for hot swapping and vacuum gauges.
The only possible criticism I had was that the aft most 2 tanks, which were outboard of the engine room, had no fuel gauges, only sight gauges.
Well thought out and executed IMHO. 9000 litres capacity too.
grumpy_o_g
Well-Known Member
Does the rudder induce roll? I always thought it was the change in heading that induced the roll because of the CofG or the hydrodynamic thingie that makes planing boats heel into the turn?
BartW
Well-Known Member
Thinking about it afterwards, the sea trial and testing the navigation stuff during the survey, didn’t get the same attention like the hull.
I even had the impression that GC didn’t pay close to no attention to this. He sayed something in the line like, on a 20yo boat, you can not expect the navigation electronics to be impeccable.
Nevertheless I remain with respect for GC for the thorough work he did on the hull and the superstructure. Actually some of the work we are doing right now, is payed from a price reduction he achieved from the survey.
Now to your ap operational questions:
YES and YES
It disappears
what happens during those 2-3 seconds, does the arrow stay on, or does it disappear before the boat starts reacting?
That I don’t remember, that’s the part from the display which is difficult to read
I don’t remember as I don’t operate it like that,
after switching the ap “on” I correct the course (on the ap) until the boat is heading in the right direction on the gps. I don’t remember if the correction is to P or SB
Don’t know, don’t look at a/p during manual steering
I can add to that; also during manual steering you have to get used to the slow reaction time,
Eacht time when I have someone else at the wheel, they make a terrible zig zag due to the slow reaction time.
Ones I had a 14yo girl on the wheel, after a short explaination she was the best guest shipper I ever had; Meaning, when correcting course, you have to give the wheel lets say a half a turn, and then wait several seconds before something happens, and then course is slowly changing.
Cant blaim Alf for that, he is a good first line problem solver, and most of all a good cook which you will hopefully experience yourself very soon, but he has no technical background, he can’t make a correct analysis. He believes that it’s a problem related to the hull, which I don’t take as you might guess
Now thinking about it, I should have noticed and questioned this issue much earlier, but pls realize; Before I started helming BA,
- I had zero experience with ap’s
- The biggest boat I ever operated was a 29ft Karnic
- And actually it took a long while before I started using the ap, as I never did before, and I didn’t like it’s behavior, ....aha !
And most of all, It gave a good feeling operating the wheel of such a large vessel.
I have the impression that we are close to a point where we can improve efficiency (straight course) by another teaspoon
Most probably by installing a new hydraulic system.
Don’t mention a combined stab – rudder computer
thanks a lot MapisM for digging in to this !
MapisM
Well-Known Member
Ok, unfortunately that is the most critical point of the troubleshooting, so I think we must postpone any further evaluation to when we'll meet.
Just FYI, this is the reason why I'm saying this:
When either the port or stbd arrow appears, it means that the A/P is instructing the rudders to steer to port or stbd respectively.
For as long as one of these arrows stays on, the A/P is continuing to steer.
But this does not tell you how quickly, and by how many degrees, the rudders actually respond.
It's the horizontal bar at the bottom, i.e. the rudder angle indicator, which tells you that: each of the LCD segments which can appear either to the left/right of the "0" position means a 2 degrees angle to port/stbd.
Therefore, assuming that you are on a straight course and the rudders are centered, what should happen if the A/P senses the need for a correction, let's say to port, is that the port arrow appears for a moment, and immediately after that you should see a few (at P speed and on a flat sea, probably just one) LCD segment to the left of the "0" position.
That segment should stay on till you will see the stbd arrow appear for a second, returning (again, immediately) the rudders to their centered position.
The trick is that the arrows and the horizontal bar are driven by different events: the arrow appears whenever the A/P sends an instruction to the pump for steering, whilst the rudder angle is sensed by what Furuno calls the "rudder reference unit", a component directly connected to the rudders, which therefore shows an X degrees angle only if and when the rudders are actually rotated.
If in between there is a weak pump, or any other faulty component which leads to a delay in the actual rudder response to the A/P instruction to steer, you should see the arrow first, whilst the LCD segment(s) would follow only after a while.
Anyway, we'll look at that. As I previously mentioned, it could be that the delay is perceivable also without moving the boat, in which case we would have probably already found the reason for the boat behaviour.
Otoh, if there would be no delay at rest, the system should still be checked at sea, because the pressure against the rudders is close to nothing when the boat is moored, whilst is quite significant at 20kts or so.
vas
Well-Known Member
long shot, so don't shoot me...
So, we are talking about some non compressible (sp?) liquid, i.e. the red steering oil, we have lots of pipework two controllers and one actuator.
Now, the delay in response MIGHT be that there's air in the circuit that compresses and the instruction IS given, the pump DOES work, the oil is pressing and compressing the air in the circuit for some time before it eventually slowly manages to push the rudder to where we want (By which time it's overdone it and we're back in the opposite move...)
I'm thinking of the equivalent of spongy brake pedal when there's air in the circuit.
how far off am I doc?
V.
So, we are talking about some non compressible (sp?) liquid, i.e. the red steering oil, we have lots of pipework two controllers and one actuator.
Now, the delay in response MIGHT be that there's air in the circuit that compresses and the instruction IS given, the pump DOES work, the oil is pressing and compressing the air in the circuit for some time before it eventually slowly manages to push the rudder to where we want (By which time it's overdone it and we're back in the opposite move...)
I'm thinking of the equivalent of spongy brake pedal when there's air in the circuit.
how far off am I doc?
V.
MapisM
Well-Known Member
Naaah, why should we?
I didn't even think of that, since Bart said that the boat always behaved like that, and it would be amazing if the previous owner never tried just bleeding the circuit...
You might well be right, though. As Dr.Lecter would say, first principles, Clarice: simplicity
I'll meet Bart in a couple of week on BA, we'll have a look at that too, thanks for the hint.
kashurst
Well-Known Member
another long shot but simple to check - is there any loose joints in the steering mechanism. It looks like the AP system is hunting so either too much gain or underdamped or a non-linearity - posh word for something loose.
MapisM
Well-Known Member
Yep, that's another possibility.
Though at the moment we're not yet sure that the delay in the boat response is due to a delay between the A/P impulse and the actual rudders movement.
I would be really surprised if it's instead a matter of delayed hull response to the rudders movements, but we can't rule that out completely yet.
The boat is pretty heavy, hence inherently stable (she also has a keel, IIRC?), and the rudders might be a bit small.
Just guessing of course, but if that would be the reason, the solution (if achievable) should be looked only in the A/P calibration.
Though at the moment we're not yet sure that the delay in the boat response is due to a delay between the A/P impulse and the actual rudders movement.
I would be really surprised if it's instead a matter of delayed hull response to the rudders movements, but we can't rule that out completely yet.
The boat is pretty heavy, hence inherently stable (she also has a keel, IIRC?), and the rudders might be a bit small.
Just guessing of course, but if that would be the reason, the solution (if achievable) should be looked only in the A/P calibration.
BartW
Well-Known Member
yes, I've been thinking of the this also Vas, while writing my previous post,
Alf an I have been bleeding the hydraulic throttle system a few times,
and we have been looking at hydraulic fluid levels in Throttle system, rudder hydraulic system and paserelle hydraulic pump
he never bothered about leaking the rudder hydraulics, so I gues he isn't aware if or where to do that and neither am I.
I don't think there is really something loose in the sense of "broken"
as it has alway's been working like that, or at least for a very long time.
thank you guy's for the sugestions, and Henryf for the discussion platform
We will leave this here and postpone any further evaluation until I'm there,
soon I will meet up on the boat, with a mate who has something to say about Rudders and ap's
BartW
Well-Known Member
no keel MapisM !
and fairly flattish bottom,
the rudders seem indeed quite small (?)
but let's first investigate the rudders response to the ap impuls
MapisM
Well-Known Member
Whoops. God knows why I thought BA had one.
Must have mixed up with some other P boat of the same vintage wihch I've seen.
In the good old days, keels were not so unusual also on P hulls.
BartW
Well-Known Member
would have been nice though,
because then the change to a D boat would be more smooth for me
