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Go Back   SailNet Community > On Board > Gear & Maintenance
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  #21  
Old 02-08-2009
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Lat Nov I was returning from a Race south of me in Seattle, was heading north in 20-30 knot winds, full main and 155 up. Heard a thumping sound for a bit, figured out it was the prop, ie my max prop turning. At the time doing upper 6 to low 7 knot water speed. HullSpeed is 6.6 or there abouts, ie 24.5' WL. Put the trans in revers, thumping stopped, soon after gained some .5 to 1 knot speed, within a minute! Eventully as the wind piped up, we were doing low to mid 8's, even in to the 9's!

While I understand the reason for a fixed like Main sail mentioned, crab/lobster pot issues, for many of us, the foler/feathering prop will net some speed, not matter the speed we are going, or wind speed!

Marty
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  #22  
Old 02-08-2009
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Quote:
Originally Posted by Rockter View Post
Next time I am out in light airs I will try to turn the prop in line with the keel, and then perp to the keel, and see if it gets noticed. It should be a good experiment.
It will indeed. The difference was so noticeable in light airs on my fin keeler when I switched to a folder that it went a long way towards persuading me to go to a feathering prop on my full keeler...that and the positive experiences of my friends with equally "primitive" hull shapes!

On the fin keeler, I noticed that the boat would accelerate better in puffs, would continue to ghost in very light airs that used to see it stop, and that going from a 12 x 6 two blade fixed to a 11 x 8 two blade folder dropped my "dead slow" from 2.5 to 1.7 knots in calm air, giving me more options in docking and maneuvering. The only downside was the slight hesitancy as the blades deployed, which I solved by a brief "gunning" of the engine to get the prop spinning.
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  #23  
Old 02-12-2009
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Re: Folding/feathering props.
While it is true that the difference between a folder/featherer and a fixed prop is most apparent in light air and that hull speed is the limiting speed in heavy air, the real advantage lies not in an increase in speed, but in the increase in windward ability.
In most applications this amounts to 3-5 degrees per tack. This is 6-10 degrees improved angle to windward. A peek at a vector diagram will explain this. The wind in the sails produces a huge force roughly perpendicular to the heading of the boat. This force is opposed by the keel or center/dagger board which must operate at a slight angle through the water moving past it (leeway). When closehauled, which is the condition we're talking about, there is very little sail force left over to move the boat forward. Any drag removed is force freed to move the boat in the direction it is heading. This is why a clean bottom is desirable. A fixed 3 blade is roughly the equivalent of towing a peach basket.
I know gentlefolk never sail to windward, but consider the savings in diesel when you can make 5 knots and 5degrees better to windward in conditions in which you would previously have had to motorsail. Another condition worth thinking about is when deep reefed. In this condition any increase in windward ability results in a better ride.
Of course if you are towing a dinghy all thoughts of sailing higher than a beam reach are out the window.
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  #24  
Old 02-13-2009
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Maxprop

My maxprop came with my Pearson 419 bought used in 1992. 16 years of flawless performance with minimal maintenance and top notch customer support from PYI in Seatle (?) . What more can one ask ?
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  #25  
Old 02-13-2009
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If you want the honest truth, PYI is in Lynnwood, about 15 miles north of the city limits.

They are good props.

marty
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  #26  
Old 02-13-2009
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Autoprop vs...

I've had an Autoprop on a IP 40 for 4 years and have found it to be an excellent product. Bought it for it's ability to vary the pitch. Stopping/Reverse are vastly improved over the fixed prop. Boat speed is up about .5 k under sail. After initial install there was some vibration. Did some Speed/RPM tests for Autoprop. Sent it back to their factory they returned a corrected prop.(all on their dime). I know they changed design about 8-10 years ago to a greased bearing from a water lubricated one. Have not heard of blades "falling off" first hand. I did purchased an adapter to hold an off the shelf zinc as the AP Zincs are hard to find and expensive. You will also lose the prop walk, which on a long keel will make reversing at low speeds interesting. I sail Long Island Sound where there are lots of lobster pots. The keel, skeg, rudder setup that's on the IP40 is terriffic. I haven't wrapped up yet.

Bob Fleno
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Old 02-14-2009
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I have an AUTOPROP on my IP 37 (1997) and love it. The prop came with the boat when I bought her 2 years but was interestingly never installed before. The PO had still the fixed 3 blade factory prop on. I had it installed right away and compared with other IP I sailed I like the "no prop walk" and the added .5kts in light air.

The only issue I have is the fairly expensive and IMHO badly engineered special zinc. This zinc is hollow and doesn't hold up at all. I have to find an adapter to switch to a better zinc. It's a shame the manufacturer of such as nice and sophisticated product didn't came up with a decent zinc solution. I can hardly believe the profit out of the zincs is that important (at the end it's not a ink jet printer where the money is in the cartridge). If you can afford it, I think the Auto prop is an excellent choice. I don't want to miss mine.
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  #28  
Old 02-15-2009
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I can't recall the actual design of an Autoprop but if their zincs are rare and/or ridiculously expensive, how hard would it be to simply machine them from zinc bar stock? (Which I am assuming exists!). I just rechecked my chemistry memories and not only does it melt at only 90C more than lead (so it could be cast into molds), it is malleable at just above the boiling point of water, meaning it could be hammered on a small anvil if both were put in a medium heat frying pan!

I have had occasion to hand-work some aluminum bar stock and so on for backing plates, brackets and the like, and it's easier than wood in some ways.

I wouldn't hesitate to make my own prop hub zincs if it came down to tapping a small cone or putting a hole through it for a cotter pin.
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Old 02-15-2009
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Quote:
Originally Posted by Valiente View Post
I can't recall the actual design of an Autoprop but if their zincs are rare and/or ridiculously expensive, how hard would it be to simply machine them from zinc bar stock?
They're not that expensive.

Quote:
Originally Posted by Valiente View Post
I wouldn't hesitate to make my own prop hub zincs if it came down to tapping a small cone or putting a hole through it for a cotter pin.
As previously mentioned in this thread, there is an aftermarket adapter available that lets you mount a standard American-style prop zinc on the Autoprop.
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Old 02-15-2009
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Autoprop Zincs

As with everything, pricing is relative. The price for the Zinc itself with ~$25 seems reasonable, BUT they don't hold up at all.

They are nicely streamlined shaped as a cone, 3 holes for the plastic bolts and all but they are hollow. I have a diver cleaning the bottom/checking the zincs every 4 weeks in the summer and every 6 weeks in the winter. The Autoprop zincs is only good for about 2 month while all other zincs are holding up 6 to 9 months or more.

I guess if they would be more solid there would be more sacrificial material and they would hold up much longer. Compared in regard to the lifespan with other zincs for me the Autoprop zinc is at least 3x more expensive. I heard about bronze adapters available one screws to the back of the prop to be used with shaft zincs.

If anybody has experience with this and has a link for a source it would be greatly appreciated.
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