I'm just pondering over a 2 blade or 3 blade folding prop, any opinions please?

C

cliffdale

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I have left a deposit for a flexofold. It would be around £500 more for 3 blades.

Boat is Dufour Classic 36 saildrive.

Sailing is fair weather but have occasionally been caught out on channel crossings. Choppy seas and headwinds.

I'm thinking put the saving towards a cruising chute.

Anyone here with similar boats use a 3 blade folding?

Thanks

Cliff
 
cliffdale said:
I have left a deposit for a flexofold. It would be around £500 more for 3 blades.

Boat is Dufour Classic 36 saildrive.

Sailing is fair weather but have occasionally been caught out on channel crossings. Choppy seas and headwinds.

I'm thinking put the saving towards a cruising chute.

Anyone here with similar boats use a 3 blade folding?

Thanks

Cliff
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Prvious 2 boats (Dehler 34s) had Gori 2-blade folders, The second one had a 3-blade fixed which was so poor that it must have been a mistake. The 2-blade folder was much better :confused:

Current Dehler 35 has a Volvo 3-blade folder. Superb. Definitely better than 2-blade folder.
 
cliffdale said:
I have left a deposit for a flexofold. It would be around £500 more for 3 blades.

Boat is Dufour Classic 36 saildrive.

Sailing is fair weather but have occasionally been caught out on channel crossings. Choppy seas and headwinds.

I'm thinking put the saving towards a cruising chute.

Anyone here with similar boats use a 3 blade folding?

Thanks

Cliff
Click to expand...
Don't have the three blade, but think maybe your starting point is whether you are satisfied with the performance of your current 2 blade. Think you have the same engine as me in a very similar boat and the two blade Flexofold is just about indistinguishable from the fixed 2 blade. The potential advantage of the three blade is in perhaps better performance in adverse conditions. 3 bladed fixed are often fitted to saildrives with more powerful engines because you can't get the diameter to swing a 2 blade (usually for obvious reasons, larger heavier boats) so a 3 blade folder is required to maintain performance.

Sometimes a 3 blade is fitted (either fixed or folding) if the performance with a 2 blade is considered inadequate, but don't think your boat would be criticised for inadequate motoring performance in its standard form. Longwinded way of saying 2 blade is fine, save the £500.
 
cliffdale said:
Yep, I'm going with 2 blade. Most of my sailing is local and fair weather. I'm thinking I will put the saving towards a cruising chute.

Cliff
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Think carefully before you go for 2 blade. I had 2 B folder, Ok ahead unless heavy seas, very very poor in astern. Changed to 3 B folder, better ahead at lower revs, much much better astern. It will be expensive if the 2 blade does not fulfill you dream.
 
Stork_III said:
Think carefully before you go for 2 blade. I had 2 B folder, Ok ahead unless heavy seas, very very poor in astern. Changed to 3 B folder, better ahead at lower revs, much much better astern. It will be expensive if the 2 blade does not fulfill you dream.
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Don't think he will have that experience with the prop he is buying. Identical to mine on the same engine/drive and as I have posted previously, as good as the fixed prop in astern except for the slight (manageable) delay as you drop it into reverse at tickover.
 
There is little difference between 2 and 3 bladed motoring in calm conditions, where you will see an advantage is motoring in rougher conditions where there is a chop. However usually in those conditions there is enough wind to sail unless it's on the nose.

BUT (that's a big but) With our 2 bladed fixed I've had a number of times when motoring out of a harbour, or though a channel where cross tacking would be too tiring for the two of us, going into a head sea. Even giving the engine beans we were still only making around 2 knots over the ground away from a lee shore trying to get the experience over with asap.

A 3 bladed prop gives more grip in the water. Most of the time you'll be happy with a 2 bladed prop, but you will have time you're glad you wend for the 3 bladed.

We're upgrading to a folding 3 bladed soon :)
 
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prop calculation

I have had both 2- and 3-blade foldings, currently a 3-blade.

If one is just comparing on equal terms 2 and 3 blades, 2 blades are more efficient, theoretically - and most likely in practice as well.
Do not compare 20 year old 2-blades with new 3-blades, the blade design has improved over the years!

With almost all engineering issues there are different limiting factors. On most sailboats space is a limiting factor - not only should there be room for the prop blades, but also some nice clearance.
A 3-blade is usually dimensioned 1" smaller diameter than a 2-blade (boats and engines of this size). This is most often the reason why 3-blades are experienced as giving a better grip.

It is usually said that 3-blades are only meaningful with engines > 25 hp.

A 3-blade is a more complex design, will require more maintenance, and is certainly more expensive.

As pointed out earlier, if one has a 2-blade which works reasonably well, then there is no reason to change to a 3-blade. A new 2-blade will probably be slightly better than the old one.

It is a good idea to make a proper prop calculation before ordering. The major suppliers have some calculation services on their home pages, there are also some free programs available on internet, test some few - it is worth to get the optimal propeller.

Now, having advocated for 2-blades, why do I have a 3-blade? Space, of course. There was too little clearance between blades and hull with the 2-blade (Gori), resulting is some noise and not as powerful as it should be.

/J
 
As long as you have a reasonable bhp/ton ratio, 2 blades will serve just fine. I have a pair of flexofold 2-bladers and I can stop the boat in her own length from 10 knots.
 
Forget the cruising chute

Spend the money on a 3 blade and you wont regret it and just be thankful when your in a head sea you made the right choice.
Had same issue and opted for 3 blade.
 
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