Recommended prop for Volvo MD11C and 110S saildrive

[ruvane]

Hi,

The original prop is a 16x11x2.

Does anyone know what 3 blade prop is recommended?

Are there any advantages to going with a correctly sized 3 blade over the 16x11 2 blade?

TIA,
Ruvane.

 

[rob2]

Probably best to try the Castlemaine calculator with details of your hull and gear ratio. In general, three bladed props are designed for motoring whereas many two-bladed props have much narrower blades to reduce drag whilst sailing. So for a given installation with whatever limitations there are on prop size/tip clearance you can expect to transmit more power through a 3-blade, allowing you to better punch into wind and tide. This applies even with a small engine as the increased blade width can be expected to reduce losses through slippage. The down side is that you will sail a little slower as you drag the more substantial prop through the water.

I believe there are 3-blade folders made for saildrives, but they are quite pricey. It would however overcome the drag problem.

Rob.

 

[Tranona]

3 bladed props are available for saildrives, although the majority use 2 blade. 3 blades are sometimes used where the boat is "heavy" for its size as the advantage is in greater thrust in adverse conditions - the downside being significant additional drag when sailing. Normally 3 blade alternatives are an inch smaller in diameter than a 2 blade for the same boat - but you can check by putting your boat data into the Propcalc programme on www.castlemarine.co.uk

I have tried both 2 and 3 blade props on a saildrive Bavaria and no measurable difference in performance and found a 2 blade folding FlexoFold a good choice. I would only go 3 blade if I wanted a feathering propeller, but not sure that it would justify the cost.

 

[Maxi Windsong]

I've just bought a new Flexofold for our S130 saildrive (delivered yesterday!) and considered 2 blade and 3 blade - as commented above the recommended 2 blade was an inch larger in diameter than the 3 blade. In the end I chose the 3 blade on the basis of better power into wind and sea, and better maneuverability in our marina where we have strong tides running through the pontoons at times. It did cost 1.5 times the cost of the 2 blade though.

Incidentally, for those who know the Flexofold propellers, they have just launched a new version of the 2 blade cruising propeller, with the same large anode that the 3 blade has always had. Much better than the undersized ring anode on the Volvo props that we've struggled with for that past few years!

 

[Tranona]

Although the newer ones have an anode, it is not really necessary on the two blade which does not have such a big mass of stainless in it and simple bronze gears. Mine does not have one. Better quality materials has always been a big selling point of a FlexoFold over a Volvo!

 

[rob2]

It did cost 1.5 times the cost of the 2 blade though.

Somehow that seems fair...