Advice on changing to a folding prop

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europe172

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Hi All
Looking for advice re changing from a three bladed fixed prop to a two bladed folding, my current prop whichs suits the boat and engine well is a three bladed 14" with 11" pitch, changing to a two bladed folding my choice is 15" 10" pitch or 15" with 12" pitch.
Has anyone out there got experance of replacing a fixed three bladed with folding two blade and the differances that sixe and pitch make?
 
You'd probably be better off talking to the suppliers you have in mind for your new prop, the main ones have probably got experience of your particular installation.
 
europe172 said:
Hi All
Looking for advice re changing from a three bladed fixed prop to a two bladed folding, my current prop whichs suits the boat and engine well is a three bladed 14" with 11" pitch, changing to a two bladed folding my choice is 15" 10" pitch or 15" with 12" pitch.
Has anyone out there got experance of replacing a fixed three bladed with folding two blade and the differances that sixe and pitch make?
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I have done the opposite, to great advantage.
 
europe172 said:
Hi All
Looking for advice re changing from a three bladed fixed prop to a two bladed folding, my current prop whichs suits the boat and engine well is a three bladed 14" with 11" pitch, changing to a two bladed folding my choice is 15" 10" pitch or 15" with 12" pitch.
Has anyone out there got experance of replacing a fixed three bladed with folding two blade and the differances that sixe and pitch make?
Click to expand...

You may be disappointed with the reverse thrust from a 2 blade folder after using a 3 blade fixed. A 3 blade folded is considerably better than 2.
 
johnphilip said:
Presumably performance under power is more important than sailing speed then.
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Mine was on a Folkboat, which I built. I installed an MD1 with a two bladed prop, and would lock the prop with the blades inline with the stern-post when sailing. It was fine when sailing, but performance under power was quite poor, particularly if there was any sea or wind on the nose. As an experiment, I tried a three bladed prop, of approx the same dimensions. It was a long time ago, and I cant remember the precise sizes. The three-bladed prop didn't seem to have any noticeable detrimental effect under sail, but was very much better under power, so I stayed with the three blades.
 
We went from two bladed fixed to three bladed folding. One of the best additions we have made to the boat, it now motors better in a seaway but also now will stop and go asturn. To get the old prop off we had to heat it with a blow torch and then hit the prop from each side with 2 mash hammers and it flew off.
 
europe172 said:
Hi All
Looking for advice re changing from a three bladed fixed prop to a two bladed folding, my current prop whichs suits the boat and engine well is a three bladed 14" with 11" pitch, changing to a two bladed folding my choice is 15" 10" pitch or 15" with 12" pitch.
Has anyone out there got experance of replacing a fixed three bladed with folding two blade and the differances that sixe and pitch make?
Click to expand...
There is a big difference between those two sizes if they are both the same make of folding prop. If one works, the other won't and of course neither might be the right choice, although they are in the right ball park compared with your current prop. If you are buying new, provide your boat details to the supplier and take their recommendation. If you want a quick check on the most suitable size then put your boats details into the Propcalc programme on www.castlemarine.co.uk
 
I switched from a fixed three blade to a three blade feathering prop on a 27" Cheverton crusader.
Very pleased with the results. Much improved sailing performance. And beter under motor also.
Check out darglow great helpful company based near Bournemouth.
http://www.darglow.co.uk
 
I swapped from a 13 x 9 'skinny' 2 blade fixed prop to a 14 x 8 2 blade folding prop with slightly bigger blades. My maximum engine revs dropped by a couple of hundred RPM but the boat will still go to hull speed under power and the sailing speed has increased by maybe half a knot.
In your case the 15 x 10 is closer to your old prop but as others have said check with your prospective suppliers.
 
Gone sailing said:
I switched from a fixed three blade to a three blade feathering prop on a 27" Cheverton crusader.
Very pleased with the results. Much improved sailing performance. And beter under motor also.
Check out darglow great helpful company based near Bournemouth.
http://www.darglow.co.uk
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Over this winter season I've removed my 3-blade fixed and I'll replace it with a 3-blade flex-o-fold from Darglow. I'd also endorse their helpfulness but I'd add the warning to sit down before they mention the cost. I hope the things lives up to its expectations!
 
I went from two bladed folding to two blades fixed...back to folder and then back to fixed and preffered the fixed blade for manouvering which is when I used the engine. Sailing there was no noticeable difference. But I was not racing or looking for half a knot. Generally when cruising I don't think you often have the boat set up for max speed so drag was not of that much importance. We also towed an Aquair generator most of the time when sailing. I liked the reverse grunt of the fixed and the fact that there was no delay in power coming on.
 
Several years ago, we fitted a Brunton's Varifold 3 blade prop via First Marine Propulsion at Shamrock Quay. They advised on the dimensions of the prop given engine power and reduction ratio of the transmission.
Having made a typo in the spec we were overpropped, limiting revs and speed under power, and inducing a lot of black smoke.
Having diagnosed the problem, Ist marine were very helpful, arranging the supply of replacement blades from Bruntons at minimal cost. This would not have been have been possible had we given the wrong spec of a fixed blade prop!
The prop then gave us excellent service until we sold the boat 6 years later.
 
I have also had good results from a Flex 0 Fold three blade folder, and Darglow are helpful on sizing. They are expensive but they are well made. Mine seems as new after three seasons: I take it apart and clean it every year. The only slight downside is the price of the small anode, about £40 a pop and they only last a year on my boat for some reason.
 
I also think you may be disappointed with the performance of a two blade folding prop compared to a three blade fixed one. I swapped my fixed two blade for a Volvo three blade folding prop and was very pleased with the result both with the original Volvo 2030 and now with the replacement D1-30. I estimate about a half a knot extra when sailing and there's plenty of grunt in both forward and reverse with very little if any lag. I chose the Volvo as it was considerably cheaper then some of the alternatives such as the Brunton, but it does not have the "overdrive" facility when motor sailing which some of the more expensive props enjoy as I motor sail very little.

The point about anodes is well made, I have just replaced mine again for the second time since last April; they certainly do not last a season and should, in my humble opinion, be bigger.
 
Thanks to all who have taken the time to reply.
Due to my budget I am going to go to two bladed, I know these are not as good as three, but I just can't go the extra.
The castle marine software is a good start, When I insert my boat details for three bladed it gives 13.7 by 11.2 (I know 14 by 11 works well) so would seem to validate the calculations. for a two bladed it gives 14.8 by 11.3,-
So still in the same position, anyone else fitted a two bladed folding prop on a westerly centaur?
 
I have read with interest the outboard debate, but having to use petrol (and a lot of it) would make me stick to an inboard, try motorsailing for eight hours with an outboard then tell me its a good idea :)
 
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