Autostream Propellers - feedback?

[Weyalan]

Do any of you have any feedback about Autostream propellers? These are, to my understanding, manufactred by Seahawk - An Australian Company based in Bayswater, Victoria.

I am considering upgrading my old 2 bladed feathering prop (circa 1988 vintage Barrett) to a 3 bladed feathering prop. These guys have given me a fairly competetive quote for a new stainless steel prop....

[Pete the Cat]

I have had a three bladed Autostream bought through Martec here in the US on my Tartan 37 and have about 1500 hours on it and have motored a few thousand miles (from San Francisco to Panama) in the 6 years or so I have had it. I cannot say enough good about it. Compared to others, I think it is superior:

All stainless construction: some will say that bronze is better-- but I have had no pitting or corrosion despite spending time in some "hot" marinas. Stainless is stronger than bronze. Corrosion was the concern I had when I bought it, but it was groundless. They used to say you needed a bronze shaft until that concept was given up for strength. The construction of this prop is very very beefy when you take it apart. It also comes with replaceable delrin bearings, but I have never seen any wear and I had this apart last year.

Externally adjustable: I cannot stress enough buying a prop that you can easily adjust externally for forward AND reverse. Max prop apparently has one you can pay extra for--I would not have a feathering prop without this feature unless I had an extra $1000 to haul the boat a couple times to get the prop pitch matched to the engine output. It took two or three dives to get it perfectly set up, but that is a whole lot better than hauling the whole boat and disassembling the thing to make adjustments. See David Gerr's book for prop pitch vs. engine output. Most production boats are overpitched and this is murder on your diesel. This prop eliminated "walk" in reverse.

I picked up about .6 Knot of sailing speed with the prop and my engine is finally running at 70% of power at cruising speed--the level a diesel should work to ensure the longest life--with the overpitched two blade the engine gave significant black smoke and went too fast at proper RPM--something I have experienced with mosts of the production boats I have delivered (I did this many years ago for a bit).

This prop is also very easy to install and maintain, the instructions are readable and the help from Martec was excellent when I had some questions. The zincs are easy to replace and the lube can be accomplished under water, but I have found it does not need attention between hauls.

It is one of the best investments I made in my boat. By the way, it costs a lot less than a Max prop or the others out there--at least when I priced my situation.

Ray

[Alan Wheeler]

There are many different types of SST. I imagine the material the prop is made from will be the same type boat shafts are made from. Far less susceptable from corrosion and a reasonably bullet proof material as long as anodes remain good. In fact, you would have less issues than having Bronze mounted on SST.
70% of max engine speed is still slightly to low. 80% is better and 85% is optimum. I would try reducing the pitch ever so slightly again and then take not of your performace. That extra 10% in that range you are in will make a startly difference.

[Pete the Cat]

Alan, I think you are right that it could stand somewhat less pitch according to Gerr, but my Westerbeke mechanic gave me the 70% number (this is a 30 year old slower turning engine). I was at 93% of power for 7.4 knots (hull speed for my boat--and all this is assuming my tach and speedo are accurate which I seriously doubt) going through some parts of the Panama Canal trying to make my lock times. I have some concern about fuel efficiency on the cruising I am currently involved in. The original two blade prop on this boat was grossly over pitched as I believe most production boats are. I have also noted that most of my cruising friends seem to run their diesels too slow and too much pitch. I will probably reduce the pitch a bit when I stop the hiway driving I am currently doing.

[Alan Wheeler]

If you drop that last 10% and get it closer to 80%, you will probably find no loss of speed, a slight increase in agility and a slight drop in fuel consumption. That last 10% makes a big difference in bringing all the numbers together.

[Euro Cruiser]

Weyalan:

I considered an Autostream but found they didn't offer quite what I needed without moving me up to a much bigger hub than I wanted. When I dove on a sistership to do a scrub, I was amazed at the difference in prop hub size between his Autostream and my Maxprop. My suggestion is to include the comparing of physical dimensions between your choices when shopping.

Once Martec took on distribution rights for North America, the price of these Autostream products jumped much higher. It's a good piece of equipment but, over here, was going to cost me more than a MaxProp. Enjoy being there!

Jack

[Pete the Cat]

I will give it a try, but it is hard to believe that increasing the RPM at a specific speed would reduce fuel consumption in this range. Can you help me understand the physics of this?

The

[Pete the Cat]

Autostream is a somewhat bigger, clunkier--looking hub. I think you might compare the guts of each prop and see which set of gears you would feel most comfortable with when you run down a crab pot or piece of polypro line at night. At least that was my thinking when compared them. Also, the pitch screws are easy to adjust even when free diving in the water, but are not sexy looking at all. My thought was that there was probably a bit more drag with the slightly larger and clunkier-looking hub, but that it was a tradeoff for the increased beefiness, service access and adjustability. I do not recall Practical Sailor ever comparing these.

[fstbttms]

Originally Posted by Pete the Cat

I would not have a feathering prop without this feature unless I had an extra $1000 to haul the boat a couple times to get the prop pitch matched to the engine output. It took two or three dives to get it perfectly set up, but that is a whole lot better than hauling the whole boat and disassembling the thing to make adjustments.

At the risk of repeating myself and for the benefit of those with "non-adjustable" feathering props; any feathering prop can be adjusted while the boat is in the water. Don't let the prop shop or the yard tell you otherwise. I'm sure they'd love to sell you a haulout, but an experienced hull diver can perform, underwater, virtually any service on a feathering prop that can be done on the hard. Pitch adjustments included.

[Alan Wheeler]

Good question Ray. It has a really big answer, but I will keep it concise.
Firstly the prop. The faster the propellor turns and the faster the water flow into the propellor (both are required) the more efficient a prop becomes. So the greatest efficiency is at max RPM and forward boat speed.
The next is the efficiency of the engine. A diesel engine reaches greatest efficiency at about 75% of max RPM. This is the point where in most situations, torque and Hp is working together.
Hp is developed toward the upper end of the rev range. Torque is usually int he lower range. But there is a common point at where both cross each other and it could be said that the engine is delivery it's maximum energy. It is a combination of those two efforts. The cross over point differs between engine types. It's dependant on many aspects of design.
so bringin all the three points together, Max prop efficiency, max engine efficiency and max power available, the point at which all that comes together is about 80-85% of max engine RPM. Now please don't get me wrong, I am certainly not saying you want to be reving you motor out to max adn I am also not suggesting you continousley run at even 80%. You may find the 70% still provides the same speed. Infact in every case I know, that is exactly what does happen. And added to that, the engine developing it's power at the correct RPM sent to the prop working at it's greatest efficiency ends up in a boat becoming very much more responsive in fwd and rev motions. With the combined working power of the engine, the fuel tends to be burn't at it's best, or said another way, it burns the cleanest, thus giving the greates power as well. So all in all, the whole lot comes together in harmony.
I hope that was easy to understand and helpful.

[Elation]

As Arte Johnson would say, "Verrry insterating!" I'm currently being offered feathering props in 3 and 4 bladed (Variprop) designs. What experience has the Forum had With KIWI vs. Variprop vs Hydralign vs Autostream(Martec)? These appear to be the only ones that will fit the restricted prop aperture in reasonable diameters without excessive cavitation.

We are concerned over the reports of heavy "clunking" when going into reverse, and damage through electolysis. Plastic blades and CRES have old world charm!

Lay it on!

Elation

[Alan Wheeler]

Can't comment on the different props you have noted, but Kiwi props are limited to 50Hp. Does that place it out or in the range you are looking at?

[Pete the Cat]

I have had my Autostream on my Tartan for about 10 years in the water (California and Central America) and no evidence of corrosion. Does make a noise when going to reverse, but I am not sure if that is the transmission or the prop. I cannot remember what it was like before.

Alan--I adjusted the prop as you suggested. Not sure of results yet.

[fstbttms]

Originally Posted by Pete the Cat

I have had my Autostream on my Tartan for about 10 years in the water (California and Central America) and no evidence of corrosion. Does make a noise when going to reverse, but I am not sure if that is the transmission or the prop. I cannot remember what it was like before.

I installed a new 3-blade Autostream on a Beneteau 423 last week. It had a heavy plastic pad that mounted under the blades to cushion the hub from the impact of the blades opening. It also had plastic inserts between the blade stems and hub ears to reduce friction and wear at those points. I imagine that prop is fairly quiet as compared to uncushioned folding props like Martecs.

[Schapera]

Any updates to info on the Autostream? Im looking to fit one to a 45ft Shearwater, replacing a 3blade fixed prop, 17"x9". Looking for strong performance in a Med seaway (strong wind, short chop), and good performance in astern (stern-to mooring). Thoughts? Ive considered Max Prop, Autostream, Flexofold, Varifold, Variprop....and retaining my fixed! I am TOTALLY confused!