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We had a 3-blade Maxi-Prop on Easy Reach which meant we had as much thrust in reverse as in forward. To my best recollection spinning in place, or close to it, was easier to port than starboard and impossibel to starboard if there was contrary force,wind or curren. The reverse thrust enabled me to stop the needed forward motion to get steerage before running into an obstacle ahead. It has been over three years since I last handled her as we sold her in October 2010.
Norris Larson
On Sat, 2/22/14, Silverheels <> wrote:Subject: Prop Walk
To:
Date: Saturday, February 22, 2014, 8:11 PMMy boat has a left-handed prop. Maybe
all of us have
that. A left-handed prop will kick the stern to
starboard in reverse, and (minimally) to port in
forward, and so the boat will pivot best to port, i.e.,
counter-clockwise, when you “back & fill.” Silverheels
does this, only a bit more sluggishly than some other
boats because (IMHO) of the prop/rudder distance.
That’s all I was saying. Surely the prop you’re using
will also affect the prop walk on your boat, as will
engine horsepower to some extent, but the prop/rudder
distance remains constant and will surely have a
dampening effect in any case.I wrote about prop walk on request for SAIL’s November
2013 issue, but haven’t gotten around to posting it on
my website yet. I’ll attach it to this email for anyone
interested. I don’t know if this forum’s system will
allow the PDF to pass through.Tor
Silverheels, P-424 #17
http://www.silverheels.us
Hi Tor,
I agree that the prop/rudder relationship has a lot
to do with it. Due to the distance andangle of
the prop you can’t get the prop wash impact against
the rudder to kick the stern around. Ialmost
learned the hard way on my first trip that the
Pearson basically will not maneuver until you have a
bit of headway. Came pretty close totaking out
the paint job on a gold plater in Charleston marina
but managed to pull it out with at least 2′ to
spare.I was speculating that a bit more power and the
ability to reach maneuvering speed in a shorter
distance would help. That was my mainthought
behind considering more power but probably any
improvement would be minimal.I had wondered if I had lost my boat handling skills
since I read a post somewhere about turning a 424
with reverse prop walk and short bursts in forward.
Used to work quite well with my last boat but
couldn’t seem to get it to work with this one.So
in a strange way I’m glad to hear that it’s the boat
and not me.Now for the first time in my life I find myself
thinking about bow thrusters, until I look at the
costs. Plus I don’t like the idea ofthe
turbulence that big hole in the bow would create.
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Mine kicks to starboard when in reverse. It makes it easier to tie-up on starboard side, the side with the midship companionway. I have a left-hand propeller. I would guess everybody does but there may be one or two with a different setup. Here’s a link to propeller walk.
http://en.wikipedia.org/wiki/Propeller_walkMy prop-shaft is offset to port slightly. You’d have to stand behind the boat on the hard and look at the way the shaft aligns with the skeg to notice it. It might be off by a couple of inches. I don’t honestly know if the boat was made this way or if the strut was bent at some time. I did a bit of research and believe she was built this way. I had a link to a practical sailor article on the subject but it is no longer available online. A bit of offset is often used to counter the tendency of the boat to pull to one side when driving forward. I don’t know if all 424’s have this offset. Here’s a discussion from our 323 cousins on the subject.
http://www.pearson323.com/forum/index.php?topic=282.15Rich
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I’d always thought an offset prop shaft was to allow removal without dropping the rudder. (With a skeg it seems like it’d be essential.)
Correcting a boat’s prop walk in forward occurs almost automatically by slightly cocking the rudder angle. You don’t even think about it. It’s the strong effect in reverse that flusters some boaters until they understand, expect and learn to use it.
Tor
Silverheels, P-424 #17
http://www.silverheels.us
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You’re right, Tor. If there is any offset, it’s for removing the shaft.
Boats like Tartans and Sabres have a large offset to port. By large, I
mean almost to the turn of the bilge. That is to offset the prop walk. An
offset of an inch or two isn’t enough to change the handling of a 424.Bob
On Mon, Feb 24, 2014 at 6:36 AM, Silverheels wrote:
Quote:I’d always thought an offset prop shaft was to allow removal without
dropping the rudder. (With a skeg it seems like it’d be essential.)Correcting a boat’s prop walk in forward occurs almost automatically by
slightly cocking the rudder angle. You don’t even think about it. It’s the
strong effect in reverse that flusters some boaters until they understand,
expect and learn to use it.Tor
Silverheels, P-424 #17
http://www.silverheels.us
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When I researched that article for SAIL, I read that
prop effect is actually caused by the angle of the
propeller’s face, however slight, to the vertical.
Don’t ask me how or why. Ergo, you’d negate the effect
by installing the prop shaft perfectly horizontal.
Accordingly, sail drives should produce no prop walk,
though I can’t personally confirm it either way.Considering this, I don’t see any value in offsetting a
prop shaft to port or starboard. Seems like that might
relieve some of the effect in one gear, but exacerbate
it in the other. Or not.Tor
Silverheels, P-424 #17
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Having just replaced my prop shaft, there is, the 1 or 2 degree offset from
the centerline which I thought was for clearance to pass the skeg, but when
I pulled the shaft if came free of the strut just before getting to the
skeg. Hmmm.Ken
On Mon, Feb 24, 2014 at 6:36 AM, Silverheels wrote:
Quote:I’d always thought an offset prop shaft was to allow removal without
dropping the rudder. (With a skeg it seems like it’d be essential.)Correcting a boat’s prop walk in forward occurs almost automatically by
slightly cocking the rudder angle. You don’t even think about it. It’s the
strong effect in reverse that flusters some boaters until they understand,
expect and learn to use it.Tor
Silverheels, P-424 #17
http://www.silverheels.us
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…and by the way, I cashed in the old shaft at the scrap yard and did get
enough for 3 cone.prop zincs including shipping!On Mon, Feb 24, 2014 at 8:29 AM, Ken Page wrote:
Quote:Having just replaced my prop shaft, there is, the 1 or 2 degree offset
from the centerline which I thought was for clearance to pass the skeg, but
when I pulled the shaft if came free of the strut just before getting to
the skeg. Hmmm.Ken
On Mon, Feb 24, 2014 at 6:36 AM, Silverheels wrote:
Quote:I’d always thought an offset prop shaft was to allow removal without
dropping the rudder. (With a skeg it seems like it’d be essential.)Correcting a boat’s prop walk in forward occurs almost automatically by
slightly cocking the rudder angle. You don’t even think about it. It’s the
strong effect in reverse that flusters some boaters until they understand,
expect and learn to use it.Tor
Silverheels, P-424 #17
http://www.silverheels.us
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Tor
While offsetting the shaft to make removal easier might be a good idea. it could be removed by sliding it under the skeg. It clears the skeg with no problem. I’ll try and send a photo of the shaft and skeg when I get a chance.You’re right that you can compensate for the tendency of the boat to pull to port by slightly turning the wheel, it’s a bit of a pain to always be pushing the wheel to port to correct for prop-walk when driving. It also pulls on the autopilot making it work harder. In fact, with a lot of throttle, prop-walk can be strong enough to overcome the autopilot even with the shaft offset to compensate.
I prefer tying up on starboard side because the boat walks this way when set in reverse. I’ve never been comfortable depending on this behavior however. I sometimes think the boat has a mind of her own when backing. I’m on a mooring, not in a slip. I don’t have to deal with maneuvering in tight quarters often. You folks that have inside slips down narrow fairways get my respect.
Rich
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An interesting notion point, Rich. Perhaps our boats have an offset shaft specifically to reduce prop walk in forward gear in order to lessen the need to compensate with the rudder.
Tor
Silverheels, P-424 #17
http://www.silverheels.us
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There’s not enough offset in our boats to affect the steering. It’s not
even close to the amount of vertical offset from the V-drive. When a
designer is trying to minimize walk or torque during powered operation, the
prop is offset a foot or more from centerline.Bob
On Mon, Feb 24, 2014 at 3:24 PM, Silverheels wrote:
Quote:An interesting notion point, Rich. Perhaps our boats have an offset shaft
specifically to reduce prop walk in forward gear in order to lessen the
need to compensate with the rudder.Tor
Silverheels, P-424 #17
http://www.silverheels.us
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Wow, a foot or more from center line… that sounds like a bow thruster
or stern thruster as the case may be.For me, the zen of the spring line is where it’s at. We now have the
first slip inside a T-head with another similar slip opposite and have
to turn right into the slip when returning to it. So Jill steps off
with the bow line and we spring off the end piling until the boat points
down the slip. An aft spring on the dock side becomes are parking brake
while we tie off the other lines. Spring from the boat with a looped
line to get out easily. (I think Tor taught me)Pete
On 2/24/2014 5:18 PM, Robert Fine wrote:
Quote:Nah, just been under a lot of boats, and then asked why the props aren’t
anywhere near they’re supposed to be.On Mon, Feb 24, 2014 at 5:13 PM, Silverheels wrote:
Quote:Damn, you’re smart.Thanks.
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Back and fill, indeed. Maybe that Beta 50 just does the pulsing better
than the W58… and plenty of patience.On 2/24/2014 6:58 PM, Silverheels wrote:
Quote:Spring lines are awesome tools, Pete, but when you have
to maneuver – spin the boat, etc – in the absence of
docks or pilings you still have to deal with prop walk,
don’t you?Quote:
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