Our cal 34 rudder has excessive pulling to starboard with the engine running in forward gear. It does not pull under sail power only. Power is from a 21hp universal diesel with a 2 to 1 reduction turning a two bladed RH 14X16 prop. As power is applied the pull becomes greater. The boat moves at near hull speed at about 2200rpms. Believe the engine is rated at about 3000. Our surveyor suggested that the prop may be over pitched and was causing some of the pull. Any suggestions? Mike Clark 1967 Cal 34 hull #73
- Status
too common a problem
This is not what most people refer to as prop walk. Usuall they are refering to the problems in reverse. You are experincing the torque pressure on the rudder. You do have too much pitch in the prop but im not comvienced it will relieve the problem. My h37 has way to much pressure on the rudder at 6 knots and over. I think this is a design function more than a prop issue but i would consult with a good prop shop or two to compare notes. The reduced Rpm your gettig is something you should probably fix. by resising props any way. to much pitch greatly increases load on the engine, and fuel comsumption the engine can load up foul the exaust and a number of other things. so get it proped to run reccomend max rpm them you will go faster at cruise with better economy. you will probably have better handling and high end too. I dont think it will help the pressure on the helm. but afterall its a sail boat not a motorboat anyway. good luck. PYI should have some expert advise
This is not what most people refer to as prop walk. Usuall they are refering to the problems in reverse. You are experincing the torque pressure on the rudder. You do have too much pitch in the prop but im not comvienced it will relieve the problem. My h37 has way to much pressure on the rudder at 6 knots and over. I think this is a design function more than a prop issue but i would consult with a good prop shop or two to compare notes. The reduced Rpm your gettig is something you should probably fix. by resising props any way. to much pitch greatly increases load on the engine, and fuel comsumption the engine can load up foul the exaust and a number of other things. so get it proped to run reccomend max rpm them you will go faster at cruise with better economy. you will probably have better handling and high end too. I dont think it will help the pressure on the helm. but afterall its a sail boat not a motorboat anyway. good luck. PYI should have some expert advise
Elliptical Rudder
Excessive prop walk in forward is not a design characteristic/quirk of the Cal 34 and probably results from too much pitch in the prop. A few years ago some Cal 40 owners got together and had an eliptical rudder designed that had much better balance. If memory serves, I think it fits the Cal 34 and several of those owners were in on the initial purchase (Could'a been Cal 31. Foss foam Products built the rudders and I believe they still have the molds. It could alleviate some of the prop pressure and would enhance the sailing characterstics of your, albeit an expensive solution. You can find a thorough discussion and contact info in the Sailnet/Cal archives. Use Foss or eliptical as your search parameter.
Excessive prop walk in forward is not a design characteristic/quirk of the Cal 34 and probably results from too much pitch in the prop. A few years ago some Cal 40 owners got together and had an eliptical rudder designed that had much better balance. If memory serves, I think it fits the Cal 34 and several of those owners were in on the initial purchase (Could'a been Cal 31. Foss foam Products built the rudders and I believe they still have the molds. It could alleviate some of the prop pressure and would enhance the sailing characterstics of your, albeit an expensive solution. You can find a thorough discussion and contact info in the Sailnet/Cal archives. Use Foss or eliptical as your search parameter.
To much pitch, my guess
Hello Mike, My guess would be that the propeller is over pitched. The propeller should allow the Rpm’s of the motor to achieve it’s maximum rated amount. If not the result is to few Rpm’s at full throttle as you describe. As a result the Rpm’s and speed at which the vessel is moving could cause the torque problem. Kevin
Hello Mike, My guess would be that the propeller is over pitched. The propeller should allow the Rpm’s of the motor to achieve it’s maximum rated amount. If not the result is to few Rpm’s at full throttle as you describe. As a result the Rpm’s and speed at which the vessel is moving could cause the torque problem. Kevin
I suffered it !!
I suffered it !! (OCEANIS 381) I understand you, I think (see the article I posted months ago, more or less TURNING RIGHT WITH THE ENGINE) !! Actually I solved the problem. First I change the prop for another with opposite sense of turning (the gear-inversor allowed it). This, and the next, was enough to get a "normal" reaction of the rudder and the boat indeed. Any way I´m keep trying to get the "proper" prop, what I consider almost imposible, or very expensive ... in my former boat (Dufour 31) it tooks me (really to the dealer) 5 differents props after a change of engine, and I never felt as I if I have the "right one"... Back to the 381, when I change the prop. I did some compro-bations and I find out that the acelerator was limited for the former owner (only 2.500 rpm, when the estándar was 3.700 rpm), the boat was a charter unit and I think the owner changed the prop for another overpitched, so the boat could get more or less the standard speed ... avoiding abu-ses for the "renters". The prop I fixed (one lost in the mechanic store ...) was one inch less of diameter and two inches less of pitch, then the boat get the same speed and the estándar rpm. But when the sea becomes "no flat" the boat looses more sped than I think he should. And also I feel as if the prop would be too small, that boat gets the speed "slowly" and looks like as if there isn´t close relationship between the gas (or the engine rpm) and the reactions or speed of the boat. I was told (this seems to be a generally accepted subject) that if is a right prop fitted the engine looses a 10% of the rpm from the max. estándar when is with all the acelera-tor-gas (whitout black gasses). With all these scenario I order a new prop with the same diameter but with two inches less of pitch than the "original", I´ll try it in 10 or 15 days. If you want to know the results of this new prop let me know I´d be very please helping. Really sorry about my english ... Nicolas Soler
I suffered it !! (OCEANIS 381) I understand you, I think (see the article I posted months ago, more or less TURNING RIGHT WITH THE ENGINE) !! Actually I solved the problem. First I change the prop for another with opposite sense of turning (the gear-inversor allowed it). This, and the next, was enough to get a "normal" reaction of the rudder and the boat indeed. Any way I´m keep trying to get the "proper" prop, what I consider almost imposible, or very expensive ... in my former boat (Dufour 31) it tooks me (really to the dealer) 5 differents props after a change of engine, and I never felt as I if I have the "right one"... Back to the 381, when I change the prop. I did some compro-bations and I find out that the acelerator was limited for the former owner (only 2.500 rpm, when the estándar was 3.700 rpm), the boat was a charter unit and I think the owner changed the prop for another overpitched, so the boat could get more or less the standard speed ... avoiding abu-ses for the "renters". The prop I fixed (one lost in the mechanic store ...) was one inch less of diameter and two inches less of pitch, then the boat get the same speed and the estándar rpm. But when the sea becomes "no flat" the boat looses more sped than I think he should. And also I feel as if the prop would be too small, that boat gets the speed "slowly" and looks like as if there isn´t close relationship between the gas (or the engine rpm) and the reactions or speed of the boat. I was told (this seems to be a generally accepted subject) that if is a right prop fitted the engine looses a 10% of the rpm from the max. estándar when is with all the acelera-tor-gas (whitout black gasses). With all these scenario I order a new prop with the same diameter but with two inches less of pitch than the "original", I´ll try it in 10 or 15 days. If you want to know the results of this new prop let me know I´d be very please helping. Really sorry about my english ... Nicolas Soler
Prop rotation
Hello Mike, I think I’m understanding Mr. Solar’s comments and if I understand it correctly he is talking about using a LH rotation propeller on a RH, in forward, rotating transmission. This will force him to run the transmission in reverse to move forward. This could be VERY devastating to the transmission. So much so that it could destroy it in a matter of a few continues running hours. If I’m not mistaken the Kazaki transmission, attached to the Yanmar motor, does not use a sump lubrication system but a pump system. I believe in talking to some Yanmar dealers the pump is inactive in reverse and that some models of transmissions can only be operated minimal hours before you have to run it in forward to get some lubrication going. Hope you can fix your problem but I would be very shy of running the trans full time in reverse. Kevin
Hello Mike, I think I’m understanding Mr. Solar’s comments and if I understand it correctly he is talking about using a LH rotation propeller on a RH, in forward, rotating transmission. This will force him to run the transmission in reverse to move forward. This could be VERY devastating to the transmission. So much so that it could destroy it in a matter of a few continues running hours. If I’m not mistaken the Kazaki transmission, attached to the Yanmar motor, does not use a sump lubrication system but a pump system. I believe in talking to some Yanmar dealers the pump is inactive in reverse and that some models of transmissions can only be operated minimal hours before you have to run it in forward to get some lubrication going. Hope you can fix your problem but I would be very shy of running the trans full time in reverse. Kevin
- Status