prop
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One Blade...
...Prop would be kind of slow and would sake the be-Jesus out of you and your boat. Unless you wanted to mix a 55 gallon drum of martinis.
...Prop would be kind of slow and would sake the be-Jesus out of you and your boat. Unless you wanted to mix a 55 gallon drum of martinis.
2 or 3 ?
Just to be different (almost) and give you a straight answer, We have a stock 3 bladed prop married up to a M25 (21 hp) diesel, that provides everything we need. In this area it is not unusual to encounter a 5 to 6 knot current while transiting some of the local channels/narrows. The additional power of a 3 vice 2 blade prop is more important to us than any possible added drag caused by an additional blade. I guess what I'm saying is that you need to examine your cruising grounds and the type of sailing (ie: racing) you will be engaged in prior to choosing a prop. Just as a side note, the last 2 surveyors we used warned us against the use of folding props. It is their opinion that the vibrations caused by the prop will result in damage to the strut to hull mount. I have no way of verifying this, but the surveyors seemed to be well qualified. EG
Just to be different (almost) and give you a straight answer, We have a stock 3 bladed prop married up to a M25 (21 hp) diesel, that provides everything we need. In this area it is not unusual to encounter a 5 to 6 knot current while transiting some of the local channels/narrows. The additional power of a 3 vice 2 blade prop is more important to us than any possible added drag caused by an additional blade. I guess what I'm saying is that you need to examine your cruising grounds and the type of sailing (ie: racing) you will be engaged in prior to choosing a prop. Just as a side note, the last 2 surveyors we used warned us against the use of folding props. It is their opinion that the vibrations caused by the prop will result in damage to the strut to hull mount. I have no way of verifying this, but the surveyors seemed to be well qualified. EG
suds, yer not reading
the replies! Tell us the HP rating of your engine and the gear ratio of your transmission. A three blade propeller will give you more thrust both forward and back, but if you choose the wrong diameter and pitch you will either overload your engine or not get the efficiency that you are seeking. Suds you have to work with us here to get good answers.
the replies! Tell us the HP rating of your engine and the gear ratio of your transmission. A three blade propeller will give you more thrust both forward and back, but if you choose the wrong diameter and pitch you will either overload your engine or not get the efficiency that you are seeking. Suds you have to work with us here to get good answers.
Had a Cat 30 for 18 years with a Martec 2 blade on my M25 engine. No problems backing or motoring. Vibrations at certain RPMs but all else OK. could motor at 6 - 6.3 knots.
Use the one Blade
Use the one blade, Just split it so you have half on both sides of the shaft. Just messing with ya Suds. Trial and error my friend. The ultimate prop is the one that the boat works best with. There are formulas and equations to determine the closer match but a gazillion factors have to be taken into account as well. When its all said and done I have a feeling your going to have a 2 blade though. What your after ultimatly on the Cat 30 is about 5.5 knots overall with engine at 3/4 throttle on slack tide . You'll be close enough for Government work at that point.
Use the one blade, Just split it so you have half on both sides of the shaft. Just messing with ya Suds. Trial and error my friend. The ultimate prop is the one that the boat works best with. There are formulas and equations to determine the closer match but a gazillion factors have to be taken into account as well. When its all said and done I have a feeling your going to have a 2 blade though. What your after ultimatly on the Cat 30 is about 5.5 knots overall with engine at 3/4 throttle on slack tide . You'll be close enough for Government work at that point.
I have a three blade prop
on a C30 1988 and its ok .I moter at about 43/4 knots at 2400 RPM.The C 30 was made for a A4 gas moter that spins at a faster rpm so you get more speed over the water with a smaller prop .When they changed to the DSL moter they went for the three blade prop becouse there was no room for a larger two blade prop. I was thinking about trying a CDI prop made of some kind of plastic ,the prop has a extention that allows for a larger blade and the plastic changes shape. The blade twists when you power up The blade works harder when it spining slow and pushs less water when spining faster becouse the blade flattens out.They say this prop will push a C30 at 7.6 knots at 3/4 power . Its 300 bucks .Im going to try one. John
on a C30 1988 and its ok .I moter at about 43/4 knots at 2400 RPM.The C 30 was made for a A4 gas moter that spins at a faster rpm so you get more speed over the water with a smaller prop .When they changed to the DSL moter they went for the three blade prop becouse there was no room for a larger two blade prop. I was thinking about trying a CDI prop made of some kind of plastic ,the prop has a extention that allows for a larger blade and the plastic changes shape. The blade twists when you power up The blade works harder when it spining slow and pushs less water when spining faster becouse the blade flattens out.They say this prop will push a C30 at 7.6 knots at 3/4 power . Its 300 bucks .Im going to try one. John
I have a three blade on my 310
Cost me a bit of sailing performance but in tight, windy harbor conditions it can't be beat.
Cost me a bit of sailing performance but in tight, windy harbor conditions it can't be beat.
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