Any other owners experienced this? Our recently purchased vessel ( 2002 Hunter 356) seems to pull slightly to startboard when under power in flat seas -when you take your hands of the wheel. Sounds like keel/rudder mis-alignment ? Keith
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prop-walk
Your propeller shaft angles down from the horizontal. As a result, your spinning prop generates some push to the side, not all directly astern. Since the 356's (like many/most sailboats') prop spins clockwise, this push is to port - making the boat react by moving toward the starboard. In reverse gear, your "prop-walk" will be to port. Once you realize how useful it can be in snuggling into/leaving tight slips, you'll understand why many of us say "prop-walk is your friend." The price it carries is the one that you've discovered, and will soon get used to handling. If I ever traded my H36 for a boat with a saildrive and its all-horizontal thrust, I'd sorely miss being able to use prop-walk in docking.
Your propeller shaft angles down from the horizontal. As a result, your spinning prop generates some push to the side, not all directly astern. Since the 356's (like many/most sailboats') prop spins clockwise, this push is to port - making the boat react by moving toward the starboard. In reverse gear, your "prop-walk" will be to port. Once you realize how useful it can be in snuggling into/leaving tight slips, you'll understand why many of us say "prop-walk is your friend." The price it carries is the one that you've discovered, and will soon get used to handling. If I ever traded my H36 for a boat with a saildrive and its all-horizontal thrust, I'd sorely miss being able to use prop-walk in docking.
What would really be neat
Is if the saildrive would turn like the rudder. Can you say "Turn on a dime"
Jim S/V Java
Is if the saildrive would turn like the rudder. Can you say "Turn on a dime"
Jim S/V JavaTurning on a Dime
Jim, Your wish is granted. Volvo Penta IPS is a new drive system that rotates the forward facing, props - replacing prop shaft and rudder. I found a link off the Raymarine autopilot site. What would be really neat is if your remote autopilot could also throttle your engine - would make single handed anchoring a snap. Barry Bear Necessity H33 #128
Jim, Your wish is granted. Volvo Penta IPS is a new drive system that rotates the forward facing, props - replacing prop shaft and rudder. I found a link off the Raymarine autopilot site. What would be really neat is if your remote autopilot could also throttle your engine - would make single handed anchoring a snap. Barry Bear Necessity H33 #128
Turn-on-a-dime with prop-walk
If you know how to use your H356/H36's prop walk, you can easily spin the boat around its keel in a circle with radius less than your boat's length (diameter less than 2 boat lengths). Starboard helm plus a burst of forward throttle starts the process of kicking your stern to port. Then a burst of reverse power kicks the stern further to port while countering the forward motion you previously induced. Repeat this two-step process, and spin the boat around its keel in a clockwise (turning the bow to starboard) circle. I do this to turn around in narrow fairways between rows of closely-spaced slips. This technique works well with any modern fin-keel/spade-rudder design. No saildrive-converted-to-outboard-motor required, nor expensive bow thruster. Think of your prop-walk as a "stern thruster." <g>
If you know how to use your H356/H36's prop walk, you can easily spin the boat around its keel in a circle with radius less than your boat's length (diameter less than 2 boat lengths). Starboard helm plus a burst of forward throttle starts the process of kicking your stern to port. Then a burst of reverse power kicks the stern further to port while countering the forward motion you previously induced. Repeat this two-step process, and spin the boat around its keel in a clockwise (turning the bow to starboard) circle. I do this to turn around in narrow fairways between rows of closely-spaced slips. This technique works well with any modern fin-keel/spade-rudder design. No saildrive-converted-to-outboard-motor required, nor expensive bow thruster. Think of your prop-walk as a "stern thruster." <g>
Thrusters
I have had gas pump hands ask it I have a thruster when I dock to port.I look like a bozzo when I try docking to starboard. I love prop walk as long as there are port tie-ups.
I have had gas pump hands ask it I have a thruster when I dock to port.I look like a bozzo when I try docking to starboard. I love prop walk as long as there are port tie-ups.
Al - s/v Persephone .....How would you
use the prop walk to your advantage when backing out of a slip and attempting to go straight out as the dock finger is on port and next boat is on starboard??? This would be very helpful. George
use the prop walk to your advantage when backing out of a slip and attempting to go straight out as the dock finger is on port and next boat is on starboard??? This would be very helpful. George
sorry....not a prop walk issue
gentlemen; Thanks for your responses, but I was referring to an obvious pull to starboard when powering forward in open water; not docking.
gentlemen; Thanks for your responses, but I was referring to an obvious pull to starboard when powering forward in open water; not docking.
Backing out of a slip
George, In that case, prop walk would be something to be avoided until the boat had traveled sufficiently out of the slip that its turning center had emerged past the end of the neighbor's boat. (On my H36. the turning center is between the shrouds and the mid-ship cleats.) To do so, I'd use as short a burst of power as possible until the boat barely had sternway, and then use the boat's momentum to achieve that partial emergence from the slip. (Prop walk can only occur while the prop is under power. No spinning prop = no prop walk.) Keep the helm amidship until sternway has been achieved. Otherwise your rudder isn't a rudder, but a speed brake. Never use heavy throttle. Driving a sailboat like a power boat usually means trouble when single-screw maneuvering in close quarters. At that point, if I wanted to head down the fairway across the end of the finger I'd just left, I'd use prop walk to help swing the stern across the end of the neighbor's boat, while the forward portion of my boat emerged. Then I'd finish a tight turn-in-place at the mouth of the slip by forward power and some port helm augmented by prop walk swinging the stern towards the starboard, and power ahead past the end of the finger and down the fairway. If I had to go out the fairway in the other direction (away from my finger and across my neighbor's bow - like my home slip), I'd just start backing to port as soon as the boat had partially emerged with its stern well past my neighbor's bow, and back out of the fairway. The penalty you pay in having to avoid prop walk in the first part of your scenario is repaid by the assist you can get from prop walk in making a tight turn at the slip exit. My marina is 3nm up-river from the Merrimac river bar (at McKay's Wharf, where his first clippers were built for the Brazil coffee trade). I often have to cross 3-to-5 knots of current in my fairway, so I actually have to crab at an angle down the fairway to/from its exit. I usually back across-river up the fairway and then back up-river into my slip. Prop walk assists my turn into the slip. On exiting my slip, I turn bow-to-starboard as soon as my stern will clear my neighbor's bow, and back out down the fairway to its exit. Otherwise, the current would push me into the close next-down-river line of slips before I could complete a forward turn to port, even with the turning assist of forward prop walk. If I were to try to power out with the current, until I had boat-speed-over-ground greater than the current's, I would have reverse-helm, followed by no-response helm, eventually followed by forward helm at very high speed-over-ground (if I hadn't already been driven into someone by then). By using a bit of reverse power to partly hold back against the current, I'm effectively already steering in reverse while exiting the slip moving forward. Never try to out-power a current. Use your engine against the current to hold the boat floating over a stationary piece of bottom, while you plan and then execute maneuvers. When Persephone is backed into the slip with her stern into the current, even while still tied to the finger my rudder works in reverse, since the boat is effectively going in reverse against the flow of water over the rudder hydrofoil. Standing at the helm, I can swing her stern toward or away from the finger while standing still with no forward momentum. (The fact that the current isn't exactly aligned with the slips adds another factor <g>.) Using currents in maneuvering (and countering them when necessary) is another fun aspect of close-quarters maneuvering. Like prop walk, currents can be your friend. I often use the currents to counter the otherwise nasty effect of cross winds. (Water can push on your under water parts a lot harder than wind pushes on your hull's freeboard.) But that's best left for another thread.
George, In that case, prop walk would be something to be avoided until the boat had traveled sufficiently out of the slip that its turning center had emerged past the end of the neighbor's boat. (On my H36. the turning center is between the shrouds and the mid-ship cleats.) To do so, I'd use as short a burst of power as possible until the boat barely had sternway, and then use the boat's momentum to achieve that partial emergence from the slip. (Prop walk can only occur while the prop is under power. No spinning prop = no prop walk.) Keep the helm amidship until sternway has been achieved. Otherwise your rudder isn't a rudder, but a speed brake. Never use heavy throttle. Driving a sailboat like a power boat usually means trouble when single-screw maneuvering in close quarters. At that point, if I wanted to head down the fairway across the end of the finger I'd just left, I'd use prop walk to help swing the stern across the end of the neighbor's boat, while the forward portion of my boat emerged. Then I'd finish a tight turn-in-place at the mouth of the slip by forward power and some port helm augmented by prop walk swinging the stern towards the starboard, and power ahead past the end of the finger and down the fairway. If I had to go out the fairway in the other direction (away from my finger and across my neighbor's bow - like my home slip), I'd just start backing to port as soon as the boat had partially emerged with its stern well past my neighbor's bow, and back out of the fairway. The penalty you pay in having to avoid prop walk in the first part of your scenario is repaid by the assist you can get from prop walk in making a tight turn at the slip exit. My marina is 3nm up-river from the Merrimac river bar (at McKay's Wharf, where his first clippers were built for the Brazil coffee trade). I often have to cross 3-to-5 knots of current in my fairway, so I actually have to crab at an angle down the fairway to/from its exit. I usually back across-river up the fairway and then back up-river into my slip. Prop walk assists my turn into the slip. On exiting my slip, I turn bow-to-starboard as soon as my stern will clear my neighbor's bow, and back out down the fairway to its exit. Otherwise, the current would push me into the close next-down-river line of slips before I could complete a forward turn to port, even with the turning assist of forward prop walk. If I were to try to power out with the current, until I had boat-speed-over-ground greater than the current's, I would have reverse-helm, followed by no-response helm, eventually followed by forward helm at very high speed-over-ground (if I hadn't already been driven into someone by then). By using a bit of reverse power to partly hold back against the current, I'm effectively already steering in reverse while exiting the slip moving forward. Never try to out-power a current. Use your engine against the current to hold the boat floating over a stationary piece of bottom, while you plan and then execute maneuvers. When Persephone is backed into the slip with her stern into the current, even while still tied to the finger my rudder works in reverse, since the boat is effectively going in reverse against the flow of water over the rudder hydrofoil. Standing at the helm, I can swing her stern toward or away from the finger while standing still with no forward momentum. (The fact that the current isn't exactly aligned with the slips adds another factor <g>.) Using currents in maneuvering (and countering them when necessary) is another fun aspect of close-quarters maneuvering. Like prop walk, currents can be your friend. I often use the currents to counter the otherwise nasty effect of cross winds. (Water can push on your under water parts a lot harder than wind pushes on your hull's freeboard.) But that's best left for another thread.
Prop walk is prop walk - open water or not
Keith, I apologize for spending too many words on the uses of prop walk in close-quarters single-screw maneuvering. The physics is the same no matter how confined or open the waters. If your boat powers forward with a bow-to-starboard steering bias, it's because your stern is being pushed to port due to an imbalance of forces. Some of that will be present from prop walk, but additional forces can come from a helm that indicates rudder-amidship when it isn't quite aligned with the keel. Though easiest on-the-hard, I have aligned my helm/rudder relationship by seeing that the upper tip of the after portion of the rudder blade (seen through still water) is aligned with the little midships split in the chrome strip around the stern. Then remove the steering quadrant cover (which I once lost overboard, but that's another story) to access the adjustment nuts on the Lewmar D-link from pedestal to rudder arm so your wheel is positioned symmetrically. (Use your emergency tiller to hold the rudder amidships when you release the wheel brake to do the alignment.) Then you can put tape around the centered wheel's rim to mark a feelable-in-the-dark helm-amidship indicator. Finally, adjust the little plastic link from the rudder arm to your auto-pilot's rudder sensor so it shows 0 degrees helm. If the pull is more than prop walk should yield (which is less the faster the boatspeed is for a given prop RPM), and you're sure of rudder/helm alignment, you have a serious problem. Have you ever wacked/bent-up one of the wings on the keel?
Keith, I apologize for spending too many words on the uses of prop walk in close-quarters single-screw maneuvering. The physics is the same no matter how confined or open the waters. If your boat powers forward with a bow-to-starboard steering bias, it's because your stern is being pushed to port due to an imbalance of forces. Some of that will be present from prop walk, but additional forces can come from a helm that indicates rudder-amidship when it isn't quite aligned with the keel. Though easiest on-the-hard, I have aligned my helm/rudder relationship by seeing that the upper tip of the after portion of the rudder blade (seen through still water) is aligned with the little midships split in the chrome strip around the stern. Then remove the steering quadrant cover (which I once lost overboard, but that's another story) to access the adjustment nuts on the Lewmar D-link from pedestal to rudder arm so your wheel is positioned symmetrically. (Use your emergency tiller to hold the rudder amidships when you release the wheel brake to do the alignment.) Then you can put tape around the centered wheel's rim to mark a feelable-in-the-dark helm-amidship indicator. Finally, adjust the little plastic link from the rudder arm to your auto-pilot's rudder sensor so it shows 0 degrees helm. If the pull is more than prop walk should yield (which is less the faster the boatspeed is for a given prop RPM), and you're sure of rudder/helm alignment, you have a serious problem. Have you ever wacked/bent-up one of the wings on the keel?
Not prop walk
If Keith’s bow is swinging to starboard, it is not due to prop walk, if he has a right hand fixed prop. The effect of unequal blade thrust or prop walk will kick the stern to port in reverse and to starboard in forward. The natural tendency, therefore, is that the bow will turn to port in forward. The opposite of what Keith is experiencing. I agree with Al, the first step is to make sure that when Keith thinks the wheel is centered, the rudder is as well.
If Keith’s bow is swinging to starboard, it is not due to prop walk, if he has a right hand fixed prop. The effect of unequal blade thrust or prop walk will kick the stern to port in reverse and to starboard in forward. The natural tendency, therefore, is that the bow will turn to port in forward. The opposite of what Keith is experiencing. I agree with Al, the first step is to make sure that when Keith thinks the wheel is centered, the rudder is as well.
Let me present another theory here
How about this: The natural tendency for a RH prop in forward is to swing the stern to starboard and hence the bow to port. In order to counter that you turn the wheel so as to steer to starboard and the prop thrust off the rudder accentuates that causing the pull to starboard. Sound logical?
How about this: The natural tendency for a RH prop in forward is to swing the stern to starboard and hence the bow to port. In order to counter that you turn the wheel so as to steer to starboard and the prop thrust off the rudder accentuates that causing the pull to starboard. Sound logical?
Not steering with prop walk
Richard, I thought I'd respond; your answer is logical. Unfortunately, my boat (a 290) doesn't agree. Turning the wheel would make sense if you're moving, where the rudder will have some effect on direction. The prop walk we experience is at the lowest speeds; hence the movement occurs because of the direction of the prop turning and prior to sufficient movement to counteract by steering. Once we get moving, then steering is the right way to offset the movement. Sorry, doesn't help the answer but thought I'd add to the mystery.
Richard, I thought I'd respond; your answer is logical. Unfortunately, my boat (a 290) doesn't agree. Turning the wheel would make sense if you're moving, where the rudder will have some effect on direction. The prop walk we experience is at the lowest speeds; hence the movement occurs because of the direction of the prop turning and prior to sufficient movement to counteract by steering. Once we get moving, then steering is the right way to offset the movement. Sorry, doesn't help the answer but thought I'd add to the mystery.
Keith - it's the same thing
The answer(s) Al gave about the natural tendency of the boat to turn (i.e., prop walk)is the same thing that's causing the pull on your helm. Even though nearly all of his discussion was in regard to maneuvering the boat the same forces that apply also apply when you're motoring along at 6 knots. My friends older C&C 36 has the engine and drive trane installed at an angle to centerline so at cruise speed it has minimal pull on the helm. However, most boat manufacturers have their drive tranes in line with the centerline of the boat. For all Al's discussion on the why's and where for's of this phenomenon I'd like to publicly give him an Atta-boy. I think he put a heck of a lot of effort into his responses. I also see the prop-walk phenomon as an advantage, not a detriment. Also, I'd like to make a comment to PHitchcox - in your second sentence "Turning the wheel would make sense if you're moving, where the rudder will have some effect on direction" - if your boat is an inboard and the prop is forward of the rudder, the prop wash, even if the boat isn't moving, will be deflected by the rudder which will cause an effect like a bow thruster or a jet in a jetted tub. This effect, with a turned rudder, will cause the boat to turn one way or another. I don't know what effect this has on your discussion - just thought I'd mention it, for what it's worth.
The answer(s) Al gave about the natural tendency of the boat to turn (i.e., prop walk)is the same thing that's causing the pull on your helm. Even though nearly all of his discussion was in regard to maneuvering the boat the same forces that apply also apply when you're motoring along at 6 knots. My friends older C&C 36 has the engine and drive trane installed at an angle to centerline so at cruise speed it has minimal pull on the helm. However, most boat manufacturers have their drive tranes in line with the centerline of the boat. For all Al's discussion on the why's and where for's of this phenomenon I'd like to publicly give him an Atta-boy. I think he put a heck of a lot of effort into his responses. I also see the prop-walk phenomon as an advantage, not a detriment. Also, I'd like to make a comment to PHitchcox - in your second sentence "Turning the wheel would make sense if you're moving, where the rudder will have some effect on direction" - if your boat is an inboard and the prop is forward of the rudder, the prop wash, even if the boat isn't moving, will be deflected by the rudder which will cause an effect like a bow thruster or a jet in a jetted tub. This effect, with a turned rudder, will cause the boat to turn one way or another. I don't know what effect this has on your discussion - just thought I'd mention it, for what it's worth.
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