dilemma: 2 or 3 blade prop?

[wragges]

Hi All,

We're considering changing our 17x12 LH 2 bladed prop for a 3 bladed one (Westerly Seahawk with 28hp Volvo 2003).

I know the obvious advantage is more mid-range thrust and it would turn slower thus less noise/vibration. I also know that a 3-blade will cause more drag than a 2 blade thus reduce sailing speed a little.

....but what I really want to know is what people think that have actually made the change. You know the more subjective stuff, was it worth it, would you do it again. Any less obvious benefits/pitfalls etc.

Any help appreciated.

 

[scottie]

the number of blades will not affect the shaft speed
sailing speed will be cut
3 blades will be smoother yes drag will increase but so will stopping power
think about a kiwi prop
if you any passage sailing boat speed is a major consideration
ie six hours sailing at 5knots 30miles six hours sailing at 5.5knots 33miles

 

[themons]

We changed our 17 x 12 2 blade on our Westerly Corsair to a 3 bladed 17 inch Autostream feathering prop.

If we do not feather the Autostream prop, the drag seems to be much worse than the 2 bladed prop. You still get the same whine from the shaft turning.

We are very happy sailing with the Autostream in the feathered position. We can sail faster and point higher. Of course, the problem is the increased initial cost of the feathering prop.

 

[john_morris_uk]

We changed the other way from a three bladed fixed to a feathering and I would NEVER voluntarily go back to the three bladed fixed prop for sailing.

(It was pretty good for motoring though...)

 

[Dalliance]

I have an almost new 3 blade prop which should be perfect for your engine/boat combination which you're welcome to fit and try. If it suits you we can come to some arrangement. PM me if you want give it a go.

 

[PCUK]

The Volvo 3 blade folder is brilliant. 40% more speed at same revs compared with folding 2 blader.

 

[Sans Bateau]

[ QUOTE ]
The Volvo 3 blade folder is brilliant. 40% more speed at same revs compared with folding 2 blader.

[/ QUOTE ]

Please expand on this, what type of boat, engine size etc?

 

[PeterGibbs]

As with all things sailing, the differences in drag are most noticeable at slower wind speeds. Assuming you let the prop rotate freely when sailing in light airs, the loss through drag in going to 3 blades will be circa 1/2 knot. Anywhere but on long passages that is not material - if you want the 1/2 knot back drain something out of the water tank etc.

But on long passages the loss in light airs could be significant.

If this is not your kind of sailing you will appreciate, as I did, that 3 blades will deliver power in both directions that an egg whip will not. Control on entering wave tossed harbours, get you home...etc

There is virtue in simplicity and, with deference to those who have gone to variable props, my 3 blade fixed prop and Ambassador cutter have never let me down.

Technicalitites are interesting, but I find it comes down to style at the end of the day - I recommend you make your choice on this basis.

PWG

 

[ashanta]

get the volvo 3 blade folding prop. Excellent performer foward and astern and when folded gives me improved sailing performance

 

[Gothik29]

On our Westerly storm we originally had a two bladed folding gori, which we changed to a kiwi feathering three blade. This made a massive amount of difference. On various boats, we've had fixed three blade, folding two blade and feathering three blade - in my opinion the feathering three was by far the best.

 

[oilyrag]

If you want the best of both worlds, i.e. max sailing performance and max motoring performance then, and as others have said, there is no better choice than a 3 blade feathering prop. I changed from a 2 blade fixed egg whisk to a 3 blade fixed, which meant I could tow the Queen Mary but lost a good half knot sailing speed up to F4, to a 3 blade Darglow Featherstream which is excellent. Couldn't fit a Kiwi prop due to space restriction but is cheaper than the Darglow/Autoprop etc. otherwise would have.

 

[Paulka]

I had a three blades fixed prop for more than 25 years, and replaced it last spring by a three blades KiwiProp.
I couldn't believe I was sailing the same boat, so big is the difference : speed gain between 1/2 and 1 knot, nearly no weather helm left, boat heeling less, allowing to reef later by nearly one Beaufort.
No significant difference motoring : same speed forward, a little better performance in reverse, but my long keel boat is reluctant to go backward anyway.
Of course, all this lacks scientific rigor, but I am very much happier, with the new prop.
... And even 1/2 a knot makes a huge difference on a 100 miles crossing.