Maxi-props?

[CaptainK]

Gord.

You sure have a way with words!!

I would never have come up with even half of the ones you've mentioned on this forum?

Thanks GORD. I have found that to be the best way to sort through the sales pitches.

[Jon D]

I have had multiple MaxProps on different boats over 20 yrs. Absolutely swear by them never any issues or problems. Currently have a 3 blade non adjustable pitch version on the boat.

The question on feathering vs folding from a drag perspective only a study done a while ago at MIT I think showed that for a cruising boat perspective its six of one half dozen of the other. At the extreme end of it a folding prop has slightly less drag but we don't have racing bottoms so it really does not matter.

On the question of the adjustable pitch vs the take it apart traditional version - had a conversation with the owner a number of years ago and he talked me out of the adjustable pitch one for a cruising sailboat - reason being that even if you get it wrong the first time on the next haul you adjust the pitch up or down and it is far cheaper than the delta between the two.

If I had a trawler where I was shutting down an engine to save fuel or going long distances on one, he then recommended the adjustable one as you could over pitch on purpose for range and then readjust when in a more conventional running environment. This is BTW why I originally was going to buy the adjustable pitch one figuring I could reset the pitch to meet a cruising requirement.

On the zinc issue I currently average about 1 zinc per year and have never had one wear to the point it falls off.

[R2boat]

We have one and love it. There will be noticeable improvement in reverse...the down side is having to haul the boat to do anything to it. It comes apart in very small pieces, maybe the newer ones do not and forget keeping zincs on it...we added another zinc to the shaft and said the hell with it. Several times the zinc would shear the S.S. that held it on.....you can also send the prop back and have them serviced and the company is good about taking them back towards the purchase on another one.

[btrayfors]

In 1990 I fitted a 17" 3-blade MaxProp in Ft. Liquordale to my 27K lb displacement sloop. I had come down the ICW from Washington, DC with a fixed 3-blade prop the previous fall. This was the year (1989) of absolutely TERRIBLE weather along the East Coast of the U.S. The worst day of all was south of St. Augustine in Florida: blowing a full gale, 26 degrees F (well below freezing), a horrific hail storm followed by an incredible ice storm. Interstate 95 was CLOSED FOR TWO DAYS in Florida due to the ice!

So, when I reached Ft. L. I had a pretty good idea of the performance of my boat with a fixed 3-blade prop.

Fitted the MaxProp, and 16 years later have never looked back. The MaxProp has been absolutely flawless for all these years. Much better power and control in reverse. Forward power is about the same as with the fixed prop. I believe that sailing performance has been enhanced with the MaxProp, having spent 11 years in the Eastern Caribbean and sailed the boat everywhere from Grenada to Maine. After fitting the MaxProp, my average days run crept up noticeably, and average boatspeed seems also to have perceptively increased.

The MaxProp gets my unqualified vote. It's worth whatever it costs these days.

Bill

[fstbttms]

Sorry to revive an old thread (and with my first post, no less), but after reading the first couple of pages I had to dispel a common misconception about Max-Props. There is no model of Max-Prop, be it 2 or 3-bladed, variable pitch or otherwise, that cannot be removed, re-installed, re-pitched or lubricated while the prop is underwater. In fact, this is true for every folding or feathering prop made. If it can be done on the hard, it can be done under water. All that is required is an experienced diver with the right tools. Regarding Max-Prop, call PYI in Washington and they will happily refer you to a competent diver in your area who can do it.

PYI- 800.523.7558

[Charlie]

Originally Posted by S/V Elusive

2divers

Reverse is very good, with light to moderate, but consistant prop walk until there is enough flow across the rudder. Anyone who doesn't like (or know how to use prop walk) hasn't tried to manuver a larger boat with a full to partial cutaway keel - I don't need no stinking bow thruster.

Thomas does the pitch make a difference how much prop walk you get when reversing. I had a problem with backing my Sceptre 41 (yes it has a Max Prop) the boat turned hard to port when backing out of my slip (I wanted to go straight back) and then trying to back into another slip in Roche Harbor the boat turned hard to port.

[Alan Wheeler]

Charlie, in a nut shell, No. Prop walk has nothing to do with Pitch, diameter, No of blades, material it's made from, colour, No of fish in the water, tide height or the abilities or lack there of of a the skipper. Well OK, a good skipper is one that knows how to use prop walk to their advantage so lets forget the last part of that one.
Prop walk is caused by the angle in which the prop shaft enters the water. Having the prop fixed (hopefully) to the end of that shaft means that the blade is also on a angle. (The reference plane of that angle is the horizontal plane of the water surface.) As the propellor rotates, the boat moves and the blades are actually taking a longer path through the water as they go to the bottom of the cycle than they are going to the top of the cycle. Because of this difference in path length, resistance against the blades rotation (water creating the resistance) is different between the top going cycle and the bottom going cycle of each blade. This causes the boat to want to "slide off" to one side. The problem occurs in both forward and reverse directions. But the problem tends to have it's greatest affect when trying to reverse. This is because there is no or little water flow over the rudder to help with steering. When going forward, the prop wash is rushing over the rudder and the affect is not so great. Plus a deeper hull tends to cause the water to flow into the prop at a slightly altered angle. So the result is that the forward rotating prop does not tend to have as great an influence. So the boats with the greates down angle of the shaft and flatter hulls tend to have the greater issues with prop walk.

[GordMay]

As Alan correctly indicated & explained, Prop’ Walk is primarily determined by the attack angle(s) of your propeller blades, and to a lesser degree, the amount of tip to hull clearance, and appendage interference (from keel & rudder). The more the shaft is angled (horizontally and/or vertically), and the less clearance you have, the more walk you experience.
However, since both diameter and pitch affect the angle of attack, I would expect an increase in either to increase the asymmetric thrust effect.

[swagman]

We've had a Maxi Prop on last boat and IMHO it was the best performing prop we've ever had. We have a Flex o Fold on the new boat and whilst OK driving forward or under sail, is nothing compared with Maxi Prop in reverse.
Dependent on the size of the boat you buy you could also research the relatively new Kiwi Prop. I've several pals who fitted them (understand only good up to approx 38 foot) and they all rave about performance - plus due to composite blades, they are not only a lot better value than a Maxi Prop, but the pitch can be easily adjusted in or out of the water, and the reduction in metal surface area also extends anode life.
Good luck with whatever you decide.
JOHN

[Alan Wheeler]

I forgot to add, the reason why these feather props tend to "feel" like they give less propwalk, is ONLY because they are a little more efficient in reverse. So they get the water moving much faster. The actuall sideways effort is not different no matter what prop you use, but being able to get the water flowing over rudder and the boat moving in a shorter time all help to lesson the affect of propwalk.
Gord, good point, but from all that I have studied, all suggestions so far is that the diameter and pitch have no affect. However, if you can find anything to the contrary, please let me know. In know you will ;-)

[Charlie]

Thanks Wheels and Gord:

I guess what I really need is more practice. Its hard to get a crew to help you when they know that all you are going to do is practice docking. I guess I could mix it up with a sailing trip. Then I could get some volunteers.

[S/V Elusive]

To add (very little to the already excellent commentary), I find I can mitigate the reverse prop walk by keep revs low, and the helm centered or just SLIGHTLY opposite the direction of prop walk. As your speed in reverse increases, you have more helm, less walk, and you can increase revs, if necessary (such as for a longer run to back out of a tight situation or chase).

[never monday]

The best way i've found to counter reverse walk is to use bursts of power. Power on then off and adjusting steering between. Charlie, try a power boat for prop walk, I don't even need a bow thruster.