Autoprop ?

[chala]

Originally Posted by osirissail

sort of hiding it behind the keel while sailing.

Not too many mariners are that kind of having their boat propeller hiding behind the keel at every half revolution.

[chala]

Originally Posted by seasilk

The prop had been cleaned and inspected no less than 6 times in the 9 month period.

Greasing of the prop is important and must be done with care, It cannot be done satisfactorily under water (sorry ftbsbttms) When greasing it is important to notice if water is coming off from the propeller which is very difficult to notice underwater also the colour of the grease coming out is an indication that the older grease is getting replaced all around the bearings.

Originally Posted by Pete the Cat

I wonder what the diesel mechanics say about obtaining cruising speed at just above idle. My thought is that this is nice for noise and fuel economy and a disaster for the life of your engine. Or am I missing something?

At low rpm an autoprop will load more the engine which is better for a diesel engine, much better than

Originally Posted by chala

36%

for a conventional prop.

[fstbttms]

Originally Posted by chala

Greasing of the prop is important and must be done with care, It cannot be done satisfactorily under water (sorry ftbsbttms) When greasing it is important to notice if water is coming off from the propeller which is very difficult to notice underwater also the colour of the grease coming out is an indication that the older grease is getting replaced all around the bearings.

No need to apologize. I don't believe I ever mentioned lubricating an Autoprop underwater. I certainly have never been asked to do it.

[GALAWA]

AUTOPROPS have one advantage over any other low drag prop, whether folding or feathering :Autoprops can drive a shaft alternator while sailing, and very effectivelly so :
The shaft alternator is driven by a belt and a pulley mounted on the exit of the gearbox. Leave it in neutral and the shaft spins and drives the alternator.

I heard from an AMEL SUPERMARAMU owner that when crossing the atlantic he needed to run his shaft alternator only 3 hours per day to meet all power requirement of his ship

I believe this high efficiency results from the proper positionning of the prop blades i.e. The intrados ( or concave face) of the blades face forward as when powering astern, whereas a fixed prop, the only other kind of prop which can drive a shaft alternator, keeps the extrados facing the flow of water.
This is an important application of Autoprops: More contributions to this issues would be welcome

[Astrid]

Here is an interesting article on the subject:

Tow Generator

[chala]

Originally Posted by GALAWA

The shaft alternator is driven by a belt and a pulley mounted on the exit of the gearbox. Leave it in neutral and the shaft spins and drives the alternator.

For what I have seen, Amel use a properly engineered gearbox with a dedicated take off for the alternator. Also if my memory is correct, to pitch the propeller in such a way that it drives the alternator when sailing, the engine is started then put in reverse, then in neutral and switched off.

[deckofficer]

Originally Posted by GALAWA

AUTOPROPS have one advantage over any other low drag prop, whether folding or feathering :Autoprops can drive a shaft alternator while sailing, and very effectivelly so :
The shaft alternator is driven by a belt and a pulley mounted on the exit of the gearbox. Leave it in neutral and the shaft spins and drives the alternator.

I heard from an AMEL SUPERMARAMU owner that when crossing the atlantic he needed to run his shaft alternator only 3 hours per day to meet all power requirement of his ship

I believe this high efficiency results from the proper positionning of the prop blades i.e. The intrados ( or concave face) of the blades face forward as when powering astern, whereas a fixed prop, the only other kind of prop which can drive a shaft alternator, keeps the extrados facing the flow of water.
This is an important application of Autoprops: More contributions to this issues would be welcome

This is a great topic, and as we adopt to hybrid drives we will get huge regen capabilities. Also, heavy regen from both drive motors could replace using a drogue for controlling speed. Below, this was brought up by me on a maxprop thread......

Will this prop still pitch for astern propulsion for setting the hook with some real grunt? Also, I'm sure it feathers if it was last used in ahead propulsion, but will it stay locked in astern propulsion if you power up with the sails? The reason I ask this is the old one would, and on an old boat I had I used this feature to charge batteries underway. Once charged, I'd fire up the diesel and push for forward, this would pitch for forward, then would feather, cut out all the noise and increase sailing speed after losing the drag.

Answered my own question, if you shut down the engine in astern it will, like the older ones, stay pitched 180*, thus allowing charging while sailing. The owner's manual even now mentions the charging ability if you have your shaft set up for engine disconnect and gear up pulleys to an alternator.

Back to me live, Galawa, great minds think alike. The water medium has the same ability of receiving power from your aux, to transmitting power for the spinning of the motor.

[hellosailor]

How well does it drive the shaft alternator if a blade falls off?

Which is apparently still a topic of debate, either they fall off too frequently or they've never fallen off on this planet, depending on who's post you read.

[fstbttms]

Originally Posted by hellosailor

How well does it drive the shaft alternator if a blade falls off?

[Yachts66]

About 2/3's as well?? LOL

[chala]

Originally Posted by hellosailor

How well does it drive the shaft alternator if a blade falls off?

Which is apparently still a topic of debate, either they fall off too frequently or they've never fallen off on this planet, depending on who's post you read.

How long will a diesel engine last if the engine is only cleaned but the oil is never replaced?

Originally Posted by fstbttms

I don't believe I ever mentioned lubricating an Autoprop underwater. I certainly have never been asked to do it.

[hellosailor]

chala, I don't think any of the mfr/rep responses to the blades indicated any "You should have greased it" point of view. It seemed more like "Well that's never happened on this planet before, gollee gee willikers!" Yeah, that helps.

The one Autoprop manual I've seen makes the greasing seem like no big deal, every 1200~ hours of use OR whenever you have for antifouling. That could be every 2nd or 3rd year for some boaters. Maybe they need to ship with a big red "Remove and grease before flight" ribbon stuck on them if the greasing is just as critical as engine oiling? Just a simple line of bold text in the manual that says IF IT ISN'T GREASED IT WILL BREAK.

Or maybe their reps just need to be made aware that's an issue, if indeed that's something that can cause a blade to fail. After all, how many boaters would remember "I need to grease my prop" ? (Stick that on a little label next to the engine oil fill, that could help.)

[GALAWA]

Unlike a maxprop blade, an autoprop blade is assymetrical . If the shaft is stopped , either by brake or by engaging the gearbox in reverse, the autoprop blade positions itself in the flow of water with some 10 or 15° of incidence. Release the brake or disengage the gear box and the autoprop should start spinning the shaft immediatly. Il will do so with the intrados of the blade facing forward. Apply a resisting torque such as caused by a shaft alternator and the autoprop will drive it very efficiently.
There should no need to spin the shaft with the engine backward or forward to 'lock' the autoprop in any position. The blades rotate freely and cannot be locked anyway.
I hope we shall get contributions to this forum thread from sailors with first hand experience of running shaft alternators with autoprops

[Yachts66]

Aren't shaft generators a tremendous source of drag? You loose a knot or so in speed, which is a lot on a long voyage. I remember reading that somewhere, sometime.

Thomas

[msponer]

Originally Posted by Yachts66

Aren't shaft generators a tremendous source of drag? You loose a knot or so in speed, which is a lot on a long voyage.

I had a towing generator, not a shaft generator, and lost about 1 knot in light air, but barely anything (1/4 knot?) once we were up in the 6's (with hull speed on that 40' boat around 7.5). I think once the boat is going fast there is already so much drive from the sails, or drag from the hull, that the additional drag from the prop isn't that much more.

My particular installation was very noisy, so we did not leave it running very often. It was bolted to the stern over an empty part of the lazarette, and made a sort of guitar box where the spinning sound amplified. It made an absolute ton of electricity when we were going fast, though.