My 1980 Cat 30 still seems to have its original propeller, but the 11 hp engine was replaced with a Perma 30 hp diesel. I'm thinking the engine doesn't like never really working very hard just to spin that anemic prop, and so it carbons up even at 2600. Looking for advice on replacing the propeller. I'm just a Chesapeake Bay day sailor, no racing. The motor is only to get out of and into the bay from my river marina.
Overpowered prop?
- Thread starter Dave Alexander
- Start date
I discovered this link to propeller design that is very interesting, by Peter Sewell of NZ.
www.offcenterharbor.com
I have a CampbellSailor designed by WestbyNorth out of Vancouver Island BC. It has been a great improvement on my boat.
Going Fast with One Modest Engine, WHIO's Propeller - OffCenterHarbor.com
When it comes to speed and economy in powerboats, we usually think about hull shape and horsepower first. But what about the propeller? Is there fresh thinking here we ought to be considering?
I have a CampbellSailor designed by WestbyNorth out of Vancouver Island BC. It has been a great improvement on my boat.
A prop is usually sized to the combination of the engine and boat. Your engine dealer should at least be able to provide a starting point on what prop size to use for a 30' sailboat. What is the engine rated limit for RPM? The correct size will be a prop that will allow the engine to reach its top rate RPM with out going over it. Decide between a two or three blade of the same diameter with the corresponding pitch.
jssailem
What a fascinating story. I'm sure the hull of that boat was very efficient, but the speed of its acceleration in the water, and the lack of huge boiling wake was remarkable.
Unfortunately, my Catalina can handle, I believe, no more than a 12" radius propeller.
Thanks for making me aware of that video.
What a fascinating story. I'm sure the hull of that boat was very efficient, but the speed of its acceleration in the water, and the lack of huge boiling wake was remarkable.
Unfortunately, my Catalina can handle, I believe, no more than a 12" radius propeller.
Thanks for making me aware of that video.
What interests me is you might be able to get remarkable thrust out of this prop even in a 12" radius.
If I am understanding the theory, the way that the prop generates thrust is that it is designed to minimize cavitation. Running at a lower RPM and a progressive pitch it optimizes the thrust to move the boat forward.
Looking at my Campbell-Sailor prop, I believe the prop uses similar design traits.
jssailem
Is what's called a "high aspect ratio" airfoil, like on a sailplane, or the U-2. Less drag, thus turbulence, and more thrust (lift). Can't fit anything like that in 12 inches. But I didn't look specifically at Campbell-Sailor prop. Headed there now. Thanks!
Is what's called a "high aspect ratio" airfoil, like on a sailplane, or the U-2. Less drag, thus turbulence, and more thrust (lift). Can't fit anything like that in 12 inches. But I didn't look specifically at Campbell-Sailor prop. Headed there now. Thanks!
My daughter’s previous Cat 30 had the 11hp universal with a 13” x 9” two blade gori folder. In other words the 13” was no problem.
jssailem: That Campbell-Sailor prop design looks like a winner to me. I'm trying to collect the information I need to send for a quote. Don't know how long it will be before $1k+ for a prop will become possible.
Dave. I would suggest that a call to Kelsey at his business office and a discussion with him regarding your boats engine, transmission, design, and purpose for the prop would be valuable to you.
I had a great discussion with him. He helped me select the prop I purchased. Then he engineered the prop to the specifications, and shipped it to me on the schedule he identified. He is a man of his word and I feel a valuable member of the boating community.
I had a great discussion with him. He helped me select the prop I purchased. Then he engineered the prop to the specifications, and shipped it to me on the schedule he identified. He is a man of his word and I feel a valuable member of the boating community.
If you contact a local prop shop they should be able to recommend a pitch change or if a new prop is needed.