Captain/Owner Sleeping at the Helm

[Chuckie]

There is no excuse for either incompetence or negligence of a captain responsible for life and property. Tell that person in no uncertain terms there failings and the consequence of failure.... Won't listen then report....dont risk losing you life and that of others because of an idiot (Captain or no Captain)

[Wotname]

Originally Posted by MicHughV

nowhere on this thread do I see any talk about the noise a spinning prop makes...a whining, grinding, irritating, teeth grinding, annoying, vexing, exasperating, maddening and irksome noise enuff to make a person want to open yet another beer....

Because so far we all are in lock step with this description



But wait awhile......, some nutter is sure to love it!

[StuM]

Originally Posted by MicHughV

nowhere on this thread do I see any talk about the noise a spinning prop makes...a whining, grinding, irritating, teeth grinding, annoying, vexing, exasperating, maddening and irksome noise enuff to make a person want to open yet another beer....

The OP was on a cat with saildrives. Very little noise.

[Kelkara]

Originally Posted by Wotname

Not arguing against the general concept here but expanding the conversation.

As long as we realise we are waaay off topic here ... and probably only applicable to people trying to fly a plane with a boat prop, or drive a boat with a plane prop.

The freely rotating prop finds it's own stable rpm for a given stable hull speed and creates a certain amount of swirly water. Put another way, it is allowed to find it's own rpm and the swirly water will be a minimum for the particular prop design.

We have to remember that the only thing stable in our thought experiment is the thrust produced by the wind in the sails ... and that is balanced by the sum of the drag of the hull and the drag of the prop. All the energy of the wind ends up in the water one way or another. I don't see why the system should minimise the prop drag and therefore maximise the hull drag, all we know is that the two of them add up to the force supplied by the sails.

In a free wheeling system, I don't think anyone would argue that it will it would find it's stable rpm where the swirly water was anything but at the minimum for the particular prop design.

I'm not sure whether I'm arguing against that or not ... but if the prop is rotating either faster or slower than its freewheeling speed, it will experience a torque ... the freewheeling rpm will be when the torque provided by the prop equals the frictional torque on the prop-shaft (close to zero for a true freewheel). I'm not sure that you have convinced me that the rpm of zero torque equals the rpm of minimum drag ... I admit that I don't understand it, but at this point I refer you back to the empirical evidence that props can be designed to have either more or less drag when spinning. For the thought experiment to work it has to make me question the validity of the experimental results, and at the moment I don't ... over.

[Wotname]

Originally Posted by Kelkara

.............

I'm not sure whether I'm arguing against that or not ... but if the prop is rotating either faster or slower than its freewheeling speed, it will experience a torque ... the freewheeling rpm will be when the torque provided by the prop equals the frictional torque on the prop-shaft (close to zero for a true freewheel). I'm not sure that you have convinced me that the rpm of zero torque equals the rpm of minimum drag ... I admit that I don't understand it, but at this point I refer you back to the empirical evidence that props can be designed to have either more or less drag when spinning. For the thought experiment to work it has to make me question the validity of the experimental results, and at the moment I don't ... over.

I think you are wise to question the validity of my previous claim of the free wheeling rpm occurring at the minimum drag point. On further thought I am sure I am 100% wrong on this point. I had gone down a rabbit hole and got lost in the warren.

The rpm of the free wheeling prop is surely a function of the velocity of the boat (i.e. the speed of the water pushing against the prop blades) and the frictional load of the shaft plus the swirly water plus smaller losses like the noise etc. The frictional losses might be higher than you give credit too, though. Many sailboat transmissions are of a constant mesh variety so even in neutral, all the gears are connected to the shaft all the time and all are spinning in an oil bath.

Of course when the prop is locked, the frictional loss of the shaft bearing and transmission becomes zero - no rotation = no friction.

If we argue the boat speed decreases when the prop is locked (as I firmly believe), then the energy that is being extracted from boat's momentum is equal to momentum of the swirly water behind the stalled prop plus the stored energy of the torque of the shaft lock.

The water moving against the stationary prop blade is imparting a torque to the shaft and this is equal and opposite to the torque provided by the shaft lock (which is why the shaft is stationary ). The shaft lock is held in place by the hull and as the hull is dynamic, presumably the shaft lock causes a very slight change in the angle of heel.

Whether the heel angle is increased or decreased would be determined by the direction of potential rotation (RH or LH prop) and whichever tack the boat is on but either way, it's value would be the same.

....over

[betwys1]

Originally Posted by StuM

So you think it was a good idea to slow the boat and risked potential damage to the engines by locking the props contrary to the skippers wishes and the manufacturer's instructions?



Now how do we deal with know it all crew?


Advisory Number: MSA08-003:

DATE February 8, 2008 Dealers and OEMs
TO: All Marine Distributors
SUBJECT: Gear in Neutral While Sailing All MODELS:

All Sailboat Engines

We continue to get questions regarding the correct gear position while sailing with the engine OFF. This advisory is issued as a reminder; Yanmar requires that if sailing with the engine OFF (not running) the transmission shifter must be in the neutral position or internal damage to the gear or sail-drive will result. This damage will not be covered by Yanmar’s Limited Warranty. Please instruct customers and dealers who deliver the sailboat to the customer, of the correct (Neutral) position for the marine gear while sailing.

So you think that locking a prop slows the boat?

In aircraft, It is well known that a stopped prop provides less drag than a wind-milling prop. I would be rather surprised if water-screws differed in that respect.
So what was that snip about know-it-all crew again?

[Chotu]

Oy. Anyone who thinks a locked prop has less resistance than a spinning prop:

Try it on your boat!

[Cabo 38]

Why is it when folks crew they think they need to expound great wisdom? If you were assisting in the delivery of a vehicle would you behave the same way? Turn here, slow down, speed up, your air pressure is low/high.
If I found the “watch” asleep, there would definitely be a discussion, with respect, but certainly not to exhibit my experience over his. I promise you the situation would have been handled. As a matter of fact, one can tell the experience of a crew member by how little they say. The owner told you he was aware of the vibration but you insisted, only to stroke your ego, at the expense of the transmission.
Very hard to sail with folks like you. Your posting this only proves my point. I would have left you at the closest port. I have had crew like you and it is absolutely awful. Life is short, enjoy. Quit whining.

[aeronautic1]

“So you think it was a good idea to slow the boat and risked potential damage to the engines by locking the props contrary to the skippers wishes and the manufacturer's instructions? Now how do we deal with know it all crew?”

Treat them no different than know-it-all internet posters? It’s a known FACT that a free-wheeling spinning propeller creates more DRAG than a stationary propeller. Ask any pilot or flight instructor.

[aeronautic1]

As a delivery captain and USCG veteran, night time watches are managed one of two ways:

1. With six crew aboard, two crew members on watch rotation of 4/8.
2. When running solo watches with crew of three, rotation at night, 3/6.

I find that 4 hour solo watches leads to more dozing watchstanders than 3 hour rotations.

[Poche]

You should have grabbed a boat hook or something and smacked him in the head.

[CarlF]

Here’s a good link to freewheeling boat propeller drag measurements. It contains MainSail’s in-water test that is pretty convincing. It found a locked propeller has 292% the drag of a freewheeling one.

Propeller Drag under sail, Article

And the Yanmar bulletin prohibits locking the transmission on BOTH sail drive and fixed shaft engines. This superseded previous recommendations. Of course, a hydraulic transmission always freewheels when the engine is off regardless of where you put the lever.

[Bmorgan562]

His chattering boat just didn’t bother him. You can’t save him from himself, his boat from him or his wife for that matter. If you see something. Say something. That will never hurt. ( in my book) Provide the information for “normal” person to make Their own rational decision and be on your way. Get off and don’t sail with him again(obviously). Get your own boat and chalk this up to one experience in your indices of Rolodex cards. You sound like a prudent knowledgeable sailor! Cheers

[betwys1]

Originally Posted by betwys1

So you think that locking a prop slows the boat?

In aircraft, It is well known that a stopped prop provides less drag than a wind-milling prop. I would be rather surprised if water-screws differed in that respect.
So what was that snip about know-it-all crew again?

Not helicoptor rotor and not feathering prop, but fixed pitch air props. But I read the actual experimental studies and I reversed my view on boat props: Locked = more draggy.

[CaptBobR]

Sleeping on watch is gross negligence