I have a 1997 H-336 that has an annoying pull to port when motoring that is somehow caused by the prop wash on the rudder. When motoring forward at 2,800-3,000 the boat wants to turn hard to port: so much so that if I took my hands off the wheel we would do an immediate cirlce in that direction. If I take it out of gear, the pull to port immmediately goes away. It is similar in force to significant weather helm. The pull to port intensifies as engine RPM's increase and instantly stops when taken out of gear. My question is whether anyone else has had this problem, heard of a similar issue, and/or knows what to do to fix it. FYI, we have a Yanmar 3GM30F engine, a 16" diameter 2-blade bronze prop with 13" pitch, and the cutlass bearing shows no wear. Further, there is no noticeable vibration when motoring. At the last survey in July 2001, both the fiberglass rudder post and rudder were in good condition. Any ideas about possible causes or solutions would be GREATLY appreciated. I am curious is this is the correct prop for our application. Have you dealt with this in the past???
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R
Richard
Prop walk
Steve, Its called "prop walk" and most everyone has to put up with it to some degree. You can reduce it by reducing the pitch of your prop but this will also decrease forward speed. You could also try a three bladed prop with less pitch. Others have said this helps. Make sure your prop is matched to your motor hp. Find a good prop shop in your area and have them determine the proper pitch and diameter for a 2 and 3 bladed prop for your boat. Check the "props and drive trains" section of this web site. Turning your motor off and sailing more will help too. Good luck
Steve, Its called "prop walk" and most everyone has to put up with it to some degree. You can reduce it by reducing the pitch of your prop but this will also decrease forward speed. You could also try a three bladed prop with less pitch. Others have said this helps. Make sure your prop is matched to your motor hp. Find a good prop shop in your area and have them determine the proper pitch and diameter for a 2 and 3 bladed prop for your boat. Check the "props and drive trains" section of this web site. Turning your motor off and sailing more will help too. Good luck
J
Jeff Bacon
probably not prop walk....
... with that level of severity. However, I had a similar problem that I fixed by buying a new boat. Never did solve the problem, but I have a theory. My rudder was ever so slightly concave on one side, which, I believe, acted like a wing that pulled the rudder in the direction of the non concave side much like a sail. if I did not buy a new boat, I was going to, somehow, fair the concave side to see if that was really my problem. My assumption is that the effect is more noticeable at higher speeds, or when the prop is actively pushing water over the rudder
... with that level of severity. However, I had a similar problem that I fixed by buying a new boat. Never did solve the problem, but I have a theory. My rudder was ever so slightly concave on one side, which, I believe, acted like a wing that pulled the rudder in the direction of the non concave side much like a sail. if I did not buy a new boat, I was going to, somehow, fair the concave side to see if that was really my problem. My assumption is that the effect is more noticeable at higher speeds, or when the prop is actively pushing water over the rudder
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Trevor
Common
Hi Steve - I believe Richard is right; I've had the same problem on just about every sailboat I've motored. You need to hold the wheel or you'll do a donut in a heartbeat. Aren't autopilots great? You may be able to minimize the effect by changing props, but you may suffer prop performance as a result. Ask around the marina and see if you can find owners of the same model and compare notes. Best, Trevor
Hi Steve - I believe Richard is right; I've had the same problem on just about every sailboat I've motored. You need to hold the wheel or you'll do a donut in a heartbeat. Aren't autopilots great? You may be able to minimize the effect by changing props, but you may suffer prop performance as a result. Ask around the marina and see if you can find owners of the same model and compare notes. Best, Trevor
K
Kevin
move the location of the..
Hello Steve, If the pull does not happen as you remove prop load we could assume that the prop is the culprit. I would not reduce the pitch to the current unit because what you help to solve will only create other problems, mainly obtainable speed. If you change to a three blade you will see a reduction of pitch but because the three blade is more efficient then a two the problem could still and will most likely be there. I have been involved with other boat owners that have had similar problems and it was fixed by increasing the length of the shaft and placing the propeller closer to the rudder. What may be happening is that the disturbed moving water that is being thrown of the face of the propeller is striking the rubber very hard to one side. By changing the proximity of the propeller to the rudder you will change the point and area the disturbed water makes impact. It can be done by moving the propeller aft or forward, which ever direction allows you the least pain and expense. I would not jump out yet and buy a new shaft though. I would first start be using a spacer that can be fitted between the coupling halves. Sailboatowners.com sells a flexible unit that when installed will place the propeller aft by 1.3”. Spurs Marine sells a metallic unit that pushes the prop aft by apx. 1”. 1” does not sound like much but in flow it makes a huge difference. Either of the above will run apx. $100 and can be installed by the end user in the water. And if it does not work take it out and send them back. A side note, don’t fret the shafts added length aft of the cutlass bearing in the strut. The strut bearing is capable of handling 1.5X the diameter of shaft in unsupported length taking into consideration the shaft length is at its maximum lengths. Your shaft length is well below the maximums so the unsupported length aft of the bearing can increase. Good luck and please keep me posted I like the challenging ones. Kevin kwoody@pyiinc.com
Hello Steve, If the pull does not happen as you remove prop load we could assume that the prop is the culprit. I would not reduce the pitch to the current unit because what you help to solve will only create other problems, mainly obtainable speed. If you change to a three blade you will see a reduction of pitch but because the three blade is more efficient then a two the problem could still and will most likely be there. I have been involved with other boat owners that have had similar problems and it was fixed by increasing the length of the shaft and placing the propeller closer to the rudder. What may be happening is that the disturbed moving water that is being thrown of the face of the propeller is striking the rubber very hard to one side. By changing the proximity of the propeller to the rudder you will change the point and area the disturbed water makes impact. It can be done by moving the propeller aft or forward, which ever direction allows you the least pain and expense. I would not jump out yet and buy a new shaft though. I would first start be using a spacer that can be fitted between the coupling halves. Sailboatowners.com sells a flexible unit that when installed will place the propeller aft by 1.3”. Spurs Marine sells a metallic unit that pushes the prop aft by apx. 1”. 1” does not sound like much but in flow it makes a huge difference. Either of the above will run apx. $100 and can be installed by the end user in the water. And if it does not work take it out and send them back. A side note, don’t fret the shafts added length aft of the cutlass bearing in the strut. The strut bearing is capable of handling 1.5X the diameter of shaft in unsupported length taking into consideration the shaft length is at its maximum lengths. Your shaft length is well below the maximums so the unsupported length aft of the bearing can increase. Good luck and please keep me posted I like the challenging ones. Kevin kwoody@pyiinc.com
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Mike DiMario
Just Some Ideas
Steve, The fact that it happens in gear and immediately stops upon shifting to neutral is interesting. I think that prop wash is a combination of forces that causes "side walk". If you have a right hand prop, the prop walk would cause the stern to push starboard in forward gear and direct the boat in a left handed turn. The fact that other boats do not share this issue to this degree, leads me to believe it is a combination of different causes and effects. It would be interesting to poll the boat owners with the props that are angled horizontally by design. The answer, as in most cases, hinges on how much time and money you want to throw at the problem. Since it is likely a combination of forces, you may want to try a small adjustable tail on the rudder to cancel out some of the force. This may neutralize the forces enough to end up as a compromise to satisfy you. Like Jeff stated in his reply, his rudder was asymmetrical. You might do something, even temporarily, as a test. Maybe create a bulge on the port side of the rudder to create more resistance. Use 3M 5200 and a piece of stainless. Another science experiment would be to make a shroud around the prop similar to the one that is offered for an outboard (see link). This would seem to eliminate a large amount of prop walk. Also, if it were slightly adjustable laterally, it would control the direction of the prop’s stream over the rudder. It would seem that hull design, general boat design, engine H.P., rudder configuration, etc, etc, all contribute to a boat’s handling characteristics. So finally, the most expensive solution is to hire someone qualified to evaluate the problem and propose a solution that might work! Good luck, Mike D
Steve, The fact that it happens in gear and immediately stops upon shifting to neutral is interesting. I think that prop wash is a combination of forces that causes "side walk". If you have a right hand prop, the prop walk would cause the stern to push starboard in forward gear and direct the boat in a left handed turn. The fact that other boats do not share this issue to this degree, leads me to believe it is a combination of different causes and effects. It would be interesting to poll the boat owners with the props that are angled horizontally by design. The answer, as in most cases, hinges on how much time and money you want to throw at the problem. Since it is likely a combination of forces, you may want to try a small adjustable tail on the rudder to cancel out some of the force. This may neutralize the forces enough to end up as a compromise to satisfy you. Like Jeff stated in his reply, his rudder was asymmetrical. You might do something, even temporarily, as a test. Maybe create a bulge on the port side of the rudder to create more resistance. Use 3M 5200 and a piece of stainless. Another science experiment would be to make a shroud around the prop similar to the one that is offered for an outboard (see link). This would seem to eliminate a large amount of prop walk. Also, if it were slightly adjustable laterally, it would control the direction of the prop’s stream over the rudder. It would seem that hull design, general boat design, engine H.P., rudder configuration, etc, etc, all contribute to a boat’s handling characteristics. So finally, the most expensive solution is to hire someone qualified to evaluate the problem and propose a solution that might work! Good luck, Mike D
A
Al
try the brake
Every sailboat has the same problem, i just tighten down alittle on the brake handle and it holds the rudder straight, then you can open a beverage or eat a sandwich. It's not so tight that you can't manuverthe wheel. Try it it next time your out.
Every sailboat has the same problem, i just tighten down alittle on the brake handle and it holds the rudder straight, then you can open a beverage or eat a sandwich. It's not so tight that you can't manuverthe wheel. Try it it next time your out.
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Les Blackwell
It may not be prop walk. You need to do a test.
Our H380 pulled exceedingly hard to starboard when we first got her. All my crew noticed it and the boat would pull to the right even under sail albeit, a bit less. We bought a Max Prop and some of the so-called prop walk dissapeared, however, in hauling the boat to put on the prop a friend measured my rudder and we found that is was not symetrical. It actually had a curve that would turn the rudder and make the boat go to the right. Take a straight edge and a piece of cardboard and measure your rudder. You should be able to cut the cardboard at one spot and move it across to the other side and place it on the rudder and it should be the same. If not, you may have a problem. You may need a new rudder or you may need just to feather it with a glass like material.
Our H380 pulled exceedingly hard to starboard when we first got her. All my crew noticed it and the boat would pull to the right even under sail albeit, a bit less. We bought a Max Prop and some of the so-called prop walk dissapeared, however, in hauling the boat to put on the prop a friend measured my rudder and we found that is was not symetrical. It actually had a curve that would turn the rudder and make the boat go to the right. Take a straight edge and a piece of cardboard and measure your rudder. You should be able to cut the cardboard at one spot and move it across to the other side and place it on the rudder and it should be the same. If not, you may have a problem. You may need a new rudder or you may need just to feather it with a glass like material.
C
Clyde
This problem has been discussed before
All sailboats with a clock-wise rotating propeller (right hand prop) will have a slight pull to port while motoring forward. When motoring in reverse or counter-clock-wise rotating propeller, the bow will move to starboard and the stern will move to port. Since the problem only occurs during motoring and not while sailing, I don't think it's an asymmetrical rudder problem because you would have this hard pull to port while sailing if your rudder was asymmetrical. This problem has been discussed before on other Hunters models. A previous post in the archives suggested that Hunter uses a semi-balance rudder which is rake to allow better helm control while sailing, but may cause the prop wash of the propeller to affect the rudder while motoring. I think he is right about the rake rudder configuration affecting the prop wash on the rudder. The older Catalina 34s and 36s had this same problem before Catalina replaced the older style rudders with an elliptical rudder. This problem has occurred in Hunter 37, Hunter 37-cutter and Hunter 340 if you check the archives, but no one has ever posted that they had found a solution to this problem. I hope you find a solution. Fair Winds. Clyde
All sailboats with a clock-wise rotating propeller (right hand prop) will have a slight pull to port while motoring forward. When motoring in reverse or counter-clock-wise rotating propeller, the bow will move to starboard and the stern will move to port. Since the problem only occurs during motoring and not while sailing, I don't think it's an asymmetrical rudder problem because you would have this hard pull to port while sailing if your rudder was asymmetrical. This problem has been discussed before on other Hunters models. A previous post in the archives suggested that Hunter uses a semi-balance rudder which is rake to allow better helm control while sailing, but may cause the prop wash of the propeller to affect the rudder while motoring. I think he is right about the rake rudder configuration affecting the prop wash on the rudder. The older Catalina 34s and 36s had this same problem before Catalina replaced the older style rudders with an elliptical rudder. This problem has occurred in Hunter 37, Hunter 37-cutter and Hunter 340 if you check the archives, but no one has ever posted that they had found a solution to this problem. I hope you find a solution. Fair Winds. Clyde
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