Captain/Owner Sleeping at the Helm

[NorthernMac]

Originally Posted by Kelkara

But ... if you're feathering the prop it isn't fixed blade ... do planes even have the mechanicals to stop a prop without feathering?

It's true for a fixed pitch prop in a plane too.

I've never seen a plane with a prop brake, but in some situations the prop can end up stopped.

[Saleen411]

Originally Posted by Kelkara

But ... if you're feathering the prop it isn't fixed blade ... do planes even have the mechanicals to stop a prop without feathering?

A spinning propellor is much more drag than a feathered prop on an airplane, A spinning propellor is even more drag than a non spinning unfeathered prop on an airplane.

Evidently, a spinning propellor is LESS drag than a stationary prop on a boat. Which is just the opposite. I don't pretend to understand why, but I believe there is published information on this subject.....like from highly regarded institutions such as MIT.

I also don't know what most manufacturers recommend....I've read some say don't let the prop spin and others that say you should.

[robert sailor]

Originally Posted by Kelkara

But ... if you're feathering the prop it isn't fixed blade ... do planes even have the mechanicals to stop a prop without feathering?

No prop brakes if that’s the question on fixed blades however in most cases you can slow the aircraft to stall speed and most props will stop windmilling.

[MicHughV]

on a previous boat the transmission was hydraulic, so the prop could not be locked in position even if you wanted it to, under sail it made a noticeable awful noise......enter the max prop.....one more reason to love my max prop!!!

[KC375]

Originally Posted by robert sailor

... Yes a fixed blade turning is less drag than if it’s locked. Always had difficulty with that as I’m a pilot and if you lose an engine you need to feather the prop quickly because the wind milling prop has so much drag. ...

I think the difference is in a plane the wind milling prop is turning the engine...not so much drag in a tubo prop...a lot in a piston



With a boat the free wheeling prop is with transmission in neutral.

[Crusty Joker]

My rule from experience is to avoid safety issue. Let the Captain deal with operation and equipment damage issues. Not my area of authority.

When I am on watch the vessel is under my immediate command. However it is not my place to deviate from the course or operation unless immediate hazard threatens the vessel.
Then it is my only course of action to avoid danger, save passengers and the vessel, AND inform the captain that I am changing operation for purpose. I inform but do not create "crisis" where there is none. If there is a minor change, why wake up the sleepers. I am capable and I know it.

If there is conflict, I remove myself from the vessel. I have done that when the best course for myself and the captain would have been to remain on board and complete the investigation into my education from the Captain. I am more humble now. I avoid escalating asymmetrical discussions with too much emotion. There is plenty of room in this world to have different opinions about anything or any subject.

Sleeping on watch is a serious issue.

Not looking for hazards in the water and not avoiding land. Keeping an eye on the hundred other things that require monitoring. These are what the WATCH system requires. I know my limits and have been in situations where it is very difficult for ONE set of eyes to clearly determine what is appearing real from what is actually REAL.

If the captain was negligent or not capable, or having a health episode, then I am clearly capable of taking command. That is why he wanted me there.

Some of us seniors should not take others along for the ride. Nor should we be in a position of not having trusted friend(s) to run the boat... years ago after returning to the YC from a short sail, I mentioned to the lady admiral that I enjoyed and appreciated them both, and would be available anytime. I then informed others at their YC that he should always have someone from the club with him that was totally familiar with the boat... That turned out to be prophetic and very good for all concerned. Safety included companionship for many years until he was able to pass doing his favorite activity.

That Captain was always the Captain... I performed for the Admiral's wife as any chief would do... what is best for all and is best for the ship.

Cheery On Brothers!

[OS2Dude]

It surprises me that comments above act like being asleep while On Watch isn't a SAFETY concern. It is not a matter of 'His Boat, His Rules'. It is a COLREGS violation for there to be no one (awake) on watch, not to mention he put everyone's life in danger. There is more to being ON WATCH than keeping the boat on course. The auto-pilot can't make adjustments for unforeseen events or objects in the water.

[KP44]

Originally Posted by Phisher

Now,how do we deal with know it all captains?

It shows the need to do some background work before you accept an offer to crew on a crossing. Inexperienced skippers usually are eager to learn from experienced crew. But some people are so inexperienced that they are unaware of their ignorance.

[Kelkara]

Originally Posted by KC375

I think the difference is in a plane the wind milling prop is turning the engine...not so much drag in a tubo prop...a lot in a piston

With a boat the free wheeling prop is with transmission in neutral.

A quick googling has led me to this graph ...
buried in this book: https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/media/00-80t-80.pdf
I haven't read the details, but it seems that props with a higher pitch angle create less drag when spinning, and those with a lower pitch angle create less drag when fixed. The geometry of the blades will determine exactly what pitch the switch-over happens ... I'd guess that boat props are generally built to operate on one side of the switch-over point, and plane props are built to operate on the other side.

[/offtopic]

[NorthernMac]

Originally Posted by KC375

I think the difference is in a plane the wind milling prop is turning the engine...not so much drag in a tubo prop...a lot in a piston



With a boat the free wheeling prop is with transmission in neutral.

It's a ton of drag in a turbine too

Also shy of a major failure seizing the prop stopped, it's much harder to stop the blades on a turbine, especially a free turbine, vs a piston engine.

Having that disc of drag is like leaving the hand brake on in a car lol

[MicHughV]

I've always been interested in this topic for reasons beyond my understanding...but it appears that generally speaking, the projected surface area of the prop, is always considered when talking about drag...but what about the shape of the blade ? Most all blades will generate a low pressure and high pressure side that must also somehow influence whether or not a prop generates drag whether spinning or not, and the pitch angle would certainly influence this ? Yes, no ??
I don't have an opinion on the matter, just asking the question. I know this topic has been beat to death in other threads, and I don't wish to stir the pot, just curious to know from an " expert" point of view, the question above.

[tidalwavenz]

Enter it into the log and leave it at that. Captains call after that.

[KC375]

Originally Posted by Kelkara

A quick googling has led me to this graph ...
buried in this book: https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/media/00-80t-80.pdf
I haven't read the details, but it seems that props with a higher pitch angle create less drag when spinning, and those with a lower pitch angle create less drag when fixed. The geometry of the blades will determine exactly what pitch the switch-over happens ... I'd guess that boat props are generally built to operate on one side of the switch-over point, and plane props are built to operate on the other side.

[/offtopic]

That's a good find, thanks.
The lower pitch angle leading to higher rpm for a given speed and as the revs increase it approaches the drag of a disc..."an increase in parasite drag which may be as great as the parasite drag of the basic airplane"

[jmschmidt]

Maybe for sail-drives, that's why I wouldn't have a boat with one. Some boats may have poorly engineered transmissions that are damaged by placing them in reverse when under sail. These boats usually have, or should have shaft locks to reduce the increased drag due to free-wheeling.

Yeah, yeah, I saw the guy's video with the test rig he built to "prove" that a free- wheeling prop does not create more drag that a locked one. If you have a few hours I could explain it to you, has do do with the fact that his text rig was not under any load so his apparent test results were bogus.

"I can explain it to you, but I can't make you understand" – Author Unknown

[StuM]

Originally Posted by jmschmidt

Yeah, yeah, I saw the guy's video with the test rig he built to "prove" that a free- wheeling prop does not create more drag that a locked one. If you have a few hours I could explain it to you, has do do with the fact that his text rig was not under any load so his apparent test results were bogus.

"I can explain it to you, but I can't make you understand" – Author Unknown

The common meme is actually :
"I can explain it to you, but I can't understand it for you"

Please don't bother trying to explain your misguided theory, it's been proven wrong both in theory and in practice. There's never been a credible empirical demonstration showing your theory as correct but there have been a number showing it is wrong.