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Oct 18, '07 9:09 PM
by robert_l_gothenburg for everyone

Hello,

PROPELLER CHOICE

I am next month changing my old Volvo MD7A to a new Yanmar 3YM20, 21 hp motor.

Now it is time to decide for having a 2 or 3 blade folding propellor (brand: probably Danish Flex-o-fold). The 3 blade is about double as expensive as the other (I now have a 2 blade folding). You may think then that 3 is better....

There are tests that in many ways say that 2 blade are better (www.flexofold.com) in many respects, but not all.

* Has anyone experience about this choice, or knowledge about which is best on a Ballad?

My main aim is to get maximum pull / strength when motoring against large waves and strong winds, and like going on a river in very streamy waters (the Rhine for example). Second aim is good speed, third is one the has little drag (=smallest possible breaking of the speed).

Thanks for any comments.

Robert

"Albatross", #1390

Gothenburg, Sweden

Tags: general

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8 CommentsChronological Reverse Threaded

msn-ballad775 wrote on Oct 19, '07

Hi Robert,

As I've stated elsewhere I have a two blade Flex-O-Fold prop, and it works extremely well on Gancia Girl. My MD7A will push GG along at 6.5 knots at 3/4 revs quite happily, and motors well two windward in a bit of a chop.

I haven't had the need to push into strong wind and waves so far, but I feel that the way the prop copes generally that it would perform pretty well in strong conditions.

Obviously a three blade prop will give greater acceleration, and stronger pushing power against wind and waves, but it will probably require higher revs to give the same top speed as the two blade, also there will be a little more drag when sailing, there is always a trade off when choosing propellers.

Maybe it would be worth contacting Flex-O-Fold to see what they suggest for the Ballad, it might be that the difference in performance is not relevant for a boat like ours.

I'm sure others would be interested in your findings.

Tim

msn-hepne wrote on Oct 21, '07

GORI has patented a new type of folding propeller which is claimed to be very efficient also in reverse.

http://www.gori-propeller.dk/

John J

jespermilling wrote on Oct 22, '07

While at the Gori Website, don't forget to click the VIDEO, and youl see how the propeller turns the blades around in reverse. It'd genious.

Jesper.

msn-b1144 wrote on Oct 28, '07

I have a Max-Prop 2 blades in combination with a Volvo Md 2020C since 10 years. You can vary the pitch and turning direction ( clockwise or anti) if you like, when you are out of the water.. Mine is leftturning. I like the starbord wall. In reverse it just as strong as forward because of the symmetric profile of the blades. Here comes the minus point of the Max-prop. In forward the propulsion is less then a fixed propellor. A friend of mine , also with a Ballad and with a 2blades fixed propellor and the same engine made 7 knots with his cockpit half full of water. My ballad made 6.6 knots at the most. However I am very content with my Max-prop. No problems against rough waves.

Gerard
B1144 Mallejan

msn-gem2martin wrote on Oct 28, '07

I am re-engining my Ballad with a Yanmar 12MY15 and plan to use a feathering (3 Blade) Kiwiprop. David Steven re-proped his Ballad with a Volvo MD2020 and reported great success especially in reverse. I believe my Kiwiprop will cost about US$1300. My dream is sell the old Gori on craigslist.

Jerry Martin
gem2@ix.netcom.com
Alte Liebe #1266

msn-frenzb9782 wrote on Oct 29, '07

This message has been deleted by the author.

msn-frenzb9782 wrote on Oct 29, '07

I have to make a decision too about this subject. This year I have replaced Aemilia’s – hull number 978- old MD6A with a Beta Marine BD722 - 3 cylinder, naturally aspirated, diesel propulsion engine developing 20 bhp at 3,600 rpm. The gearbox is the TMC 40 1:2.

The engine is great and very powerful. However I have taken too little time to choose the right folding prop and ended up with a 13x9 Radice twoblade folding prop. The good thing was that it is relatively cheap at 275,- euro’s. However it’s not performing very well as it seems not very well balanced as well as the reverse performance is quite poor. Also I need too many rev’s to get to the hullspeed of 6,5 knots (about 3.000 rpm) I have considered the Kiwiprop. However at Aemilia’s homewaters (IJselmeer, The Netherlands)we have serious problems with seaweed and waterplants, especially in the summer. My experience is that the Vane props are great weed catchers, so I am back to the folding prop’s again.

I have ask both Gori and Flexofold for their advice and they both advised me to go for a twoblade prop (Gori with a 14x9,5 and Flexofold with a 14x9). They both said that the 3-blade wasn’t worth the extra investment based on the details I gave them about the Ballad in general and my engine specifically. So I am probably going to choose between these two options.

jespermilling wrote on Oct 29, '07

Is it wrong to assume that a 3 bladed propeller might be more powerfull, but not more efficient than a 2 bladed?

And that as long as there is room enough for an equally powerfull 2-bladed it is a better and less expensive choice?

Jesper Milling

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