Autoprop ?

[Dockhead]

Originally Posted by a64pilot

Pulling a prop in the water is no big deal, and I would NOT put any heat on that prop when it's out of the water either, especially if it is one of the newer ones that is greased and has rubber seals.
Autoprop sells a special puller that fits that prop perfectly and makes prop pulling very easy, however I am certain that a special puller is not required, just makes it easier is all.
I would never try pulling myself without SCUBA, maybe thirty years ago, but not now.

I agree. Pulling a Brunton prop is very easy with the special puller -- I've done it a couple of times. I guess it's a five maximum 10 minute job for someone with SCUBA.

Concerning the nylon screws: they are nylon to prevent galvanic action. I have 20+ years of experience with these screws and never a problem. You should NEVER reuse them -- replace them with the new ones which come with the new anode. And OBVIOUSLY -- don't overtighten them. Never lost one, never had one break. Might be worth chasing the threads in the prop with a tap, the next time you're out of the water.

The anodes are stupidly designed with a very thin bit of zinc at the screw bosses. So the anodes fall off very quickly if you don't protect the bosses with a bit of prop wax or antifouling. Once you get into the habit of doing this, it's no big deal.

I have a dedicated bag of tools and parts for my quick scrub-off lifts, with a grease gun, special Brunton grease nipple, all the right Allen keys, spare anodes and screws, hull, fridge, thruster, and shaft anodes, and a can of Prop Seal prop wax, for protecting the screw bosses in the Brunton anodes.

With that bag, I can change all my anodes including the Brunton one, grease the prop, check all underwater hardware, check cutless bearing and rudder bearings, in less than 30 minutes. I do this four times a year. Sometimes dry out rather than lift.

[Yachts66]

Some threads never die, I guess this is one of them!

Most folks I know who cruise a lot also like to dive and explore underwater in good anchorages. Hence the cost of dive equipment isn't so bad when you're using it for other things, but to each his own, of course.

[TeddyDiver]

Originally Posted by Tessellate

Something like a screw extractor might work but those are intended to have drilled a pilot hole first, and I can't operate a drill underwater.
I have 2 shaft zincs left that are only 20% wasted. But those don't protect the prop because it's brass?

Get a (compressed) air drill..

[Yachts66]

Congratulations to us! In three days, this thread will celebrate its 11th anniversary! I guess somethings are near immortal, huh?

[frankcilo]

I own a Sun Odyssey 33i with 21hp engine. I had a 3-bladed propeller blade with which I could take all 3600 engine speeds with a 7.5-knot nozzle speed even with a slightly dirty hull. I decided to install a propeller that would give me more sailing speed, and after so many studies I was undecided between Autoprop and Ewol. Eventually I chose Ewol because I was afraid that Autoprop was too complicated. I first mounted a Ewol with a diameter of 15.5, but I was not satisfied, too much cavitation and a little push, then I asked to replace it with a 17 ", paying the difference (Ewol's owner claimed I was the first customer complaining) , Things have improved, but I continue to make half a knot less the maximum speed and when the weather conditions deteriorated, the propeller did not push well, I tried to adjust the pace in all ways, but nothing to do! After a year , I decide to go to Autoprop, and then here's my full test, starting from a test with fairly dirty hull (but with log 100% cleaned and fixed), I did not want to clean it before the test. First tested the Ewol to make a comparison at the same conditions, and at 2500 rpm it took 5.5 knots of speed while clutch could not exceed 6 knots at 3000/3200 rpm (the pitch is set to take 3200 rpm).
Mounted the Autoprop without even using a bottle, all in apnea, I immediately sailed to start the test, the sea in the meantime began to increase due to the intense libeccio, graft the gear and feel a tougher tap than the Ewol, I understand from various subsequent tests that he does not always do so, depends on how the blades are all set apart. Start to accelerate and all smooth without vibration, the acceleration is progressive and, giving the handle, up to 3600 rpm with a speed of 6.5 knots. At 2500 rpm (maximum torque and cruising speeds) the speed stops at 6 knots, rewinds to the handle and rises to 6.6 to 3400 rpm this time, indicating that the propeller has had to reduce the pitch for more favorable marine conditions at that time (and the tenth most node testifies).
Here's the video of this first comparison: https://youtu.be/RJSj2vInJFQ

I clean the hull well, which was really dirty, and text the Autoprop, the current is around the node, so I try at various angles to get a real result, and this time I solved the gps problem that did not work before: speed the maximum reached 7.6 of log and 7.8 of the current with crossover current, the maximum number of engine speed this time is 3200 rpm, a sign that the clean hull really brakes less and the propeller does not need to take all the engine speed (but I do not rule out that it will take them when there are unfavorable sea conditions); The hull speed is still reached smoothly!
Here's the video of the latter test:
https://youtu.be/bRImZ4hOFhs

Finally I sailed it, I was curious to see how the blades were to be oriented, and I tested that even by turning the engine off in neutral, the propeller stops rotating and the blades are pointing to the flag, however, making it unnecessary to engage the march. No visual turbulence at 7 knots the speeds, so I would say this test too good!

Here's the video: https://youtu.be/9If_zQHSW8Q

In maneuver the evolutionary effect seemed to have disappeared, but in reality there is still fortunately, less but there is and for me it's a good thing because in the maneuvers it can be useful.

For long motor transfers just place the throttle lever to the maximum torque speed to get the best ratio between fuel consumption and boat speed without creating unburned deposits that will ruin the engine, the rest will think Autoprop to adjust the continuous pitch if the sea conditions should vary, making you always achieve the highest speed!

This is really the propeller that everyone should have on their own cruise ship

[a64pilot]

I'm going to get some argument here, but no feathering prop can be as efficient as a fixed prop, or an Autoprop when motoring.
The reason is the blades have no aerodynamic profile, or blade twist, they are just flat plates.
However under sail, they have less drag of course than a fixed prop and even less than the Autoprop, as they are of course flat plates and will present less area to the water flow.

[frankcilo]

I've had both folding and autoprop prop, it's true that autoprop has less flat blades, but are independent of each other and free to orientate each one independently! The maxprop and the ewol, on the other hand, the blades are dependent on each other and all three are oriented to achieve as a whole the slightest friction / drag. In the end I think the difference in sailing is imperceptible, certainly with Ewol I had vibrations over 7 knots, with Autoprop no

[frankcilo]

And do not forget to make a difference between Sail Drive and axle line, in the latter the propeller is tilted and therefore the autoprop I think it will give less strength even than a folding propeller

[Dockhead]

Originally Posted by frankcilo

I've had both folding and autoprop prop, it's true that autoprop has less flat blades, but are independent of each other and free to orientate each one independently! The maxprop and the ewol, on the other hand, the blades are dependent on each other and all three are oriented to achieve as a whole the slightest friction / drag. In the end I think the difference in sailing is imperceptible, certainly with Ewol I had vibrations over 7 knots, with Autoprop no

Tests show that drag when sailing is significantly higher with Autoprop, than with other folding or feathering props. Still much better than a fixed prop, but will definitely slow you down while sailing. In my opinion the Autoprop is not suitable for really high performance sailboats, especially ones which are raced. Autoprop's forte is motor-sailing, for which it is just about without any competition at all, at least until you get to Hundested (minimum 150 horsepower) etc.

[a64pilot]

He has a good point about shaft angle though, if not nearly parallel a regular feathering props blades will of course be at the shaft angle, and that could present considerable drag.
The astonishing thing to me was that even on my full keel, heavy "crab crusher" boat the Autoprop gave me almost a knot, and it's not light wind that it's noticed the most, it's higher wind where sailing speeds are higher.

[frankcilo]

The resistance tests are carried in tanks, not in real condition! I believe that in reality the Autoprop gives less drag max prop or ewol, especially if you have axis line because the paddles are true that they are not flat as ewole Maxprop but are independent and free to steer at best, while with maxprop and ewol the 3 blades are oriented so that all three together are the least strength, but then you understand that an axis line or a tilted boat is the flussonon Linear. Certainly for racing boat the best prop is FoF race 2 blades

[Sputnik]

To remove a plastic screw that has sheared off flush/below the surface either use a Left hand drill (readily available on line or good tool suppliers) in a mandrel of some sort (you can grind flats on the chuck end and use a screwdriver handle to put it in) , or of course in a cordless drill if the boat is out of the water.

You can also fashion an extractor from a flat end screw driver:
Grind the tip to provide a sharp flat end.
Heat the tip to red hot and use pliers to twist the end so that it will bite into the end of the plastic in a counter-clockwise direction.
Quench the tip to harden it again.

Push the modified screwdriver or drill hard against the end of the plastic bolt as you turn it, it will cut into the plastic and allow it to be unscrewed without damaging the threads.
Before fitting the new plastic bolts run a tap down the thread to clean it and apply vaseline to lubricate it. (Only a small amount on the thread of the bolt so as to ensure you don't get a hydraulic lock in the housing when the bolt is fully home )

I would like to try plastic bolts on my SD20 saildrive, as I am sure the stainless bolts help erode the anode.

I would like an Autoprop, but need to justify it to myself (SWMBO is ok with it )

Great discussion here......I think I would go with the AP, it seems a very elegant design, not withstanding all the caveats aired in this thread. I am fortunate in that I am local to Bruntons and have a Hunter 356 bilge keel so can dry out on the hard at Brightlingsea or any friendly beach.

I am yet to enter into contact with Bruntons, but would welcome anyone with info' regarding my installation. ( Yanmar 3GM30F on a SD20 saildrive. )

Thank you everyone for your input...I have spent the whole morning working through this thread!

[Sputnik]

Not meaning to drift this thread, but on the subject of loading the engine at the "wrong" rpm......

If you are making hull speed or the maximum you can into weather/seas it is pointless to advance the "throttle" beyond the minimum you need to achieve that speed, all it does is overfuel the engine and create excess heat and carbon buildup.

Interestingly for shut down Yanmar instruct owners of their GM30 engines (not sure about other models or manufacturers) to allow the engine temperatures to stabilise after heavy load and then run them up to "rated" rpm (I assume this to be max' governed speed) and then shut down via the fuel cut-off.

This procedure should not be used on Turbo-charged engines, as the Turbo would be accelerated up to working speed and then starved of lubrication as it would still be spinning after the engine has stopped and the oil pressure lost.

On every trip out in the boat once the engine is up to temperature and conditions allow I run mine to max' rpm for a couple of minutes to clear it out.

Neil

[Sputnik]

Originally Posted by a64pilot

I'm going to get some argument here, but no feathering prop can be as efficient as a fixed prop, or an Autoprop when motoring.
The reason is the blades have no aerodynamic profile, or blade twist, they are just flat plates.
However under sail, they have less drag of course than a fixed prop and even less than the Autoprop, as they are of course flat plates and will present less area to the water flow.

The Bruntons Autoprop and quite a few of the others have profiled blades with the twist they require, they are not flat.....therefore just as efficient as a fixed blade prop', but in both directions, which a fixed prop' isn't.

Have a look at: https://www.ab-marine.com/feathering/auto-prop/

[Raggedglory]

Originally Posted by Sputnik

The Bruntons Autoprop and quite a few of the others have profiled blades with the twist they require, they are not flat.....therefore just as efficient as a fixed blade prop', but in both directions, which a fixed prop' isn't.

Have a look at: https://www.ab-marine.com/feathering/auto-prop/

I do not know this Bruntons prop but have just taken off a Variprop and replaced it with a fixed 3 blade prop.
I find both going forward and astern to be easier and more precise.
I believe that the center gear housing takes up much valuable prop space in effect reducing the actual prop to water area and thus efficiency.
Ill pay for the drag when sailing gladly as i do not race.
Just my thoughts.