2 blade prop vs 3 blade prop, is it worth changing? - SailNet Community
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post #1 of 15 Old 02-24-2018 Thread Starter
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2 blade prop vs 3 blade prop, is it worth changing?

I am debating to replace my 2 blade prop with a 3 blade prop, and wondering if it's worth the $500 to $600 costs.
On my previous sailboat, I purchased a Max prop feathering prop and I loved it but it costs me $3,000 plus and it is not the type of expense that I want to spend right now and that was a completely different sailboat than what I have now, which is a heavy cutter. In addition, I have several expensive winter projects currently going on (headsail roller furling, re-bedding all the deck hardware, adding (2) winches on the cabin deck, etc...)

To add, the only reason I would be changing from a 2 blade to a 3 blade is more control while docking and better motoring during rough seas. I did find a used prop that would work except I would need to add a bronze reducer bushing to fit my shaft. If I went in the 'used' direction.

Any thoughts?

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post #2 of 15 Old 02-24-2018
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Re: 2 blade prop vs 3 blade prop, is it worth changing?

On a fin keel boat with exposed prop, switching to a three blade will increase drag from the prop significantly. Drag from a prop in the deadwood of a long keel boat with prop in aperture is not much of an issue. You can stop a two blade prop in an aperture in alingment with keel for virtually no prop drag. Haven't seen any direct comparisons of same boat/engine between a 2 and 3 blade prop but it would be interesting if there are any tests out there to look at. Have had mostly two bladed props for lower drag and they've worked fine on some 1 to 3 day powered passages in low/no wind conditions.
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post #3 of 15 Old 02-24-2018
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Re: 2 blade prop vs 3 blade prop, is it worth changing?

I have a fixed 2 blade and have nothing to compare it to... deep fin, propshaft log enclosure and skeg rudder. Performs fine... not much drag... aligns with the keel when sailing.
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post #4 of 15 Old 02-24-2018
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Re: 2 blade prop vs 3 blade prop, is it worth changing?

What problems have you found using your 2-blade?
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post #5 of 15 Old 02-24-2018 Thread Starter
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Re: 2 blade prop vs 3 blade prop, is it worth changing?

Unlike my previous 3-blade props, my 2-blade seems to lack a some power and drive when their is a little chop and I am looking for more control while motoring within close quarters and docking.
I can definitely live with what I have and wondering if this type of sailboat would benefit from this change vs a fin keel sailboat.

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post #6 of 15 Old 02-24-2018
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Re: 2 blade prop vs 3 blade prop, is it worth changing?

Consider a Campbell sailor prop - control and power of a 3-blade with the lesser drag of a 2-blade. It is a bit more expensive, but worth it. Pay attention to the size recommendation they give because it will seem too small, but will perform correctly.

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post #7 of 15 Old 02-25-2018
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Re: 2 blade prop vs 3 blade prop, is it worth changing?

We had a 450 mile beat to get home once on a Catalina 30 with 11hp diesel. The skipper had a diver change our 2 blade folding race prop to a three blade and all powered life, especially motor sailing, became much better. We switched back once home. If you are not going more than 50 or 100 miles, it's probably not worth the trouble.

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post #8 of 15 Old 02-25-2018
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Re: 2 blade prop vs 3 blade prop, is it worth changing?

Two blade propeller is more efficient than a three blade one. It is also efficient for sail if you can hide it behind the keel. It is more difficult to balance two blade than a three blade. If the aperture for the propeller is good enough use a two blade otherwise a three blade. Normally for the same efficiency a two blade should be bigger than a three blade.

These are the facts. If you need more power change your engine.
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post #9 of 15 Old 02-26-2018
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Re: 2 blade prop vs 3 blade prop, is it worth changing?

In my previous 30ft with an Atomic 4 I went from a two blade to a small (specially designed for the A4) 3 blade. My max RPMs increased, cruising speed went up by about 1/2 a knot, prop walk was reduced by a noticeable amount. Stopping power went from oh crap we are going sideways but still moving forward to, well, stopping power. The manufacturer claimed reduced drag under sail, I can't say for sure if this was true but the prop blades where much shorter, albeit there was another one.

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post #10 of 15 Old 02-26-2018
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Re: 2 blade prop vs 3 blade prop, is it worth changing?

The diameter of three blade prop for the same output is smaller than a two blade propeller. Most motor yachts have 4 or 5 blade propellers because the distance to the hull is not enough to house a lesser blade propeller.
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