Triple Bladed Prop?

[primetime]

Hi all-

This was my first season with my "new" 1980 Catalina 30 tall rig. I'm really enjoying it and am slowly making my way through several projects. I like her responsiveness in light air, although she doesn't seem to point all that well in general (albeit the sails are quite old).

Anyway, my main complaint with the boat is that she's underpowered. I'm aware of all the variables which go into achieving hull speed but the 5411 installed in this boat is by no means enough given wind, tide and hull bottom condition.

SO, my question is can anyone report improvement with the triple bladed prop offered through Catalina direct, or for that matter any other specific prop which offers a little more speed than the original twin blade which is currently installed on the boat. Re-powering is not an option.

Thanks,
Alex K.
Steppingstone, NY

 

[foolproof]

I also have a Catalina 30 Tall Rig, with an 11 hp Yanmar. It is not overly powered, but I sail on a lake with no tides or currents, so it is OK.

You mentioned that your boat doesn't point too well. Just wanted you to know that mine points extremely well, even with old sails. I can sail ijust to the inside of the windex on both tacks, and I can out sail smaller boats like my freinds J24.

Prowl the threads for rig tuning and setup...hopefully you can get the boat set up better. It is very satisfying to out point other boats, especially in light air, given the extra sail area of the tall rig!

 

[Bad Obsession]

My boat doesn't point well. The wing keel is a part of that equation. The other half is that I usually am out cruising and I really don't care to point too high. Heck, if the wind means that I will tack all day in light winds I will fire up the engine for a while because I want to make some progress.

The three blade prop makes a difference on the M25XP engine. Still, I don't push hull speed with my set-up. 5 knots is about what I get.

 

[anchorclanker]

Less blades are more efficient and faster, more blades "can" provide some extra lower speed thrust but give up some top speed. More blades can offer less vibration, caused by the blade tip creating a pressure wave against the hull. Thump thump thump. Some dont mind it, some love it, some will spend a fortune to minimize it.

This is all provided the props are of equal quality and performance. A cheap two blade will get outrun by a good three blade. No three blade could catch a good two blade. Again, the blades being equal quality.

Main Sail wrote a good article on props, and its well worth reading as well as researching "propeller design" online.

Its also very imperative that a prop pitch is correctly matched to the engine. The engine should be able to reach full maximum RPM listed on the data plate, and turn no faster. Slower can overload and slowly destroy your engine. However, a diesel will hit its governed speed and stay there with a lower pitched prop. Carefully watch your knot meter as you very slowly reduce power from full, and note if the boat immediately slows down and rpms immediately drop. If not you likely have a too low pitch of prop for your engine.

But as its a displacement hull, it would take a few more times more horsepower to go much faster than its hull speed.

 

[Bob4203]

When considering a two or three blade prop in my instance, I would settle for the three blade. Let me explain...........My Universal M-18 which produces 14 HP will have to work extra hard when encountering strong currents and tidal fluctuations on the ICW, especially, in Georgia through the Carolina's. Opting for the three blade strictly for the added thrust and control when backing can and will make a difference. If I had the larger M-25 I would not consider the change to a three blade. For cruising, I'll take the three blade. In my case, every little thing helps!

Bob
'88 Mark II

 

[Stu Jackson]

If I had the larger M-25 I would not consider the change to a three blade. For cruising, I'll take the three blade. In my case, every little thing helps!

Bob
'88 Mark II

Our PO took off the two blade and installed a 3 blade. I'm glad he did. We have an M25 21 hp engine in our C34.

 

[steve77]

Our PO took off the two blade and installed a 3 blade. I'm glad he did. We have an M25 21 hp engine in our C34.

Stu, can you tell me why you like the 3 blade? Do you get more thrust? The 1986 C-34 I'm hopefully in the process of buying (the one with the deck moisture issue I posted on the C-34 website forum) also has the M25 engine with a 2 blade prop. It's not a priority but I'm wondering if replacing it with a 3 blade prop should be something to consider.

Steve

 

[jrowan]

We basically have the same boat, as I have a C 30 1980 with the original 5411.
I have also considered switching to a 3 blade prop. My biggest concern was potentially overloading a small engine, that is already 32 years old. My engine runs good, & in calm water will push the boat to about 5 knots, with a clean bottom, maybe a lil' more at full throttle. When I have something running right, I try not to mess with it & create a problem that didn't exist before. Getting a lil more oomph with an extra blade is tempting, but expensive if you get it wrong. I also have to remember that she is after all a SAIL boat, not a power boat. That extra blade may give you half a knot of extra speed, but will cost you just as much in additional drag under sail. From what I know, even the M25 cannot push the boat more then hull speed of course, which is 6.5 knots. If it can't beat physics, with twice the horses, then the extra blade can't either. While I would love the extra horses of the M25, the ol' 5411 will do the job, is super reliable, & also gets good fuel economy to boot. Long story short, I kept the 2 blade, but I hear that Campbell Sailor's Props offer good speed without sacrificing too much drag.

 

[steve77]

If I were to go with a three bladed prop I think I would look into a folding prop, but I haven't researched them at all. On the one hand it seems like a nice idea, on the other hand it seems like one more thing that could break.

 

[anchorclanker]

The only way to overload your engine is to over pitch the prop or have too large diameter prop for that pitch, or both. How many blades it has is irrelevant as long as its pitched correctly and the diameter is correct for that pitch for the available HP at the particular shaft RPM.

 

[primetime]

Thanks everyone for the feedback, I'll probably hold off for now. I'd rather put the money towards newer sails. Thanks again. -PrimeTime

 

[anchorclanker]

If you do some searches you can find a lot of used boat propellers for a fraction the cost of new. If you research what you need/want, and know what you have, you should be able to sell yours and buy something that performs better and not have a lot invested.

 

[captcoho]

Got to have a three-blade prop, never mind the fact that you can cruise/motor-sail better. But when the seas and wind kicks up, and you want to head in the the waves, you'll be extremly happy you have a three-blade prop.
Uless you race, and your trying to get that last tenth of a knot in speed.
You may want to consider a fishing line cutter around the prop shaft as well.