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Old 18-11-2014, 13:53   #31
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Re: Autostream Propellers - feedback?

I love my Autostream.
Went from a two blade folding to the autostream and cannot believe the difference in maneuvering. Better thrust for stopping, its great.
I noticed I only need to replace my prop anode every two years on a Volvo sail drive and kept in a marina.
We have ours propspeeded at each haulout and it looks great. Its now 7 years old.
Derek
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Old 19-11-2014, 08:18   #32
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Re: Autostream Propellers - feedback?

I have had my Autostream for 17 years and probably 25k miles and have only good to say about it. It gave me about .6 knot increase in sailing speed and the ability to easily externally adjust the pitch in forward and reverse to get it perfect with two different engines/drive trains. No corrosion, but I keep it in zincs--my usage varies depending on where I am moored. I get a couple years out of one on the mooring, but I used to have to replace them annually when I was in a hot marina. The folks at Martec were very helpful when I installed it myself. Straightforward unit, beefier construction than MaxProp IMHO. I have no relationship with the company other than a being a customer.

I believe that MIT did a study that demonstrated that there was no significant advantage to curved blades below something like 17 knots through the water as I recall. I will see if I can find it.

I can attest to the the sturdy construction of the prop: I once picked up a hunk of 1" polypro line that sheared the bolts in my coupling and did nothing to the prop. I have hit lumber and wound a number of lobster traps over the years (I now live in Maine) and I just checked the prop this fall and it is still running true.

As a former delivery skipper, I did not like those "self adjusting" props that vary pitch by centrifugal force; I will disagree with Dockhead that it is a good thing to be maximizing torque at less than full throttle for two reasons: 1. Try picking up a mooring when the slowest you can get the boat to move is 3 or 4 knots because you prop has automatically pitched up to maximize the torque available. and 2. Getting maximum torque out of an engine at low speed is hard on it: like driving a care around at 15mph in 4th gear. Diesels like to work hard, but the modern ones do not like low speed lugging. In my experience, it seemed to me that many production boat manufacturers overpitch the stock propellers on their boats for some reason. An externally adjustable prop is a huge, money saving advantage for getting things right.

FWIW
Ray
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Old 19-11-2014, 09:08   #33
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Re: Autostream Propellers - feedback?

No,
Dockhead is correct, if it's possible a prop that can vary pitch due to conditions is best for the engine and most efficient, it's why automobiles have transmissions and why you are seeing more and more CVT's.

I'd be interested in seeing the MIT report if you find it
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Old 20-01-2015, 23:02   #34
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Re: Autostream Propellers - feedback?

I've found an interesting piece of trivia regarding the autostream, I currently have a worn out max prop and I'm reviewing alternatives.
A limiting factor with the autostream prop is the maximum shaft size it can be fitted to is 1.5 inch ( which is what I have) although after talking to the boss at Seahawk they say that even 1.5 inches is too big because the prop hub has to be machined out too much for safety ( 1 1/8 is the next best size) . Also maximum end nut size is 1 inch UNC, most 1.5 inch shafts have larger thread diameter. Plus anyone that needs to swing a prop larger than 20 inches diameter is out of luck as this is their maximum size. Unfortunate as their pricing is good and they are Australian based ( good for me anyway) .
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Old 02-01-2016, 00:28   #35
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Re: Autostream Propellers - feedback?

I lost my 15 year old autostream between Langkawi and Penang. I miss it very much. Luckily I still had my old fixed prop. The difference in performance under sail and power is marked. Pounding through tide rips with the fixed was slow but the autostream would have pushed right through. I have a major decision to make. I found that I can swing a 20 inch prop where the old was 18 inches. Is therr a good reason to increase the diameter of a prop?
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Old 02-01-2016, 16:06   #36
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Re: Autostream Propellers - feedback?

I think that you want to swing the largest prop you can for efficiency's sake. I think this is especially true with a feathering prop where drag when sailing is less important than with a fixed prop of a bigger size. You do want to have clearance of a couple inches between the blade tips and the hull as you can get some uncomfortable vibration if the tips are really close. If you are in the US, Gary at Martec (who sells AutoStream) can help you. Also, I think there is an AutoStream site that has some information on clearance if I recall correctly.
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