Best propeller for more speed in a Lagoon 42

[patolega]

Hi everyone,

I’m trying to choose a reliable propeller that will increase the speed when motoring on my Lagoon 42 catamaran, with a Yanmar 57 and SD60 saildrive, and would really appreciate input from fellow cruisers—especially other multihull sailors.

We usually do long raids of 6 to 8 hours mainly on motor.

I have been looking for options like Gori and Bruntons.

What would you choose again (or avoid)?

With or without ropecutter?

Thanks in advance for any help or experiences you’re willing to share!

Fair winds,
Patolega

[Montanan]

Of keen issue is whether one wants the Lagoon to be a powercat, or a sailedcat.

If you wish to primarily power then look at the propulsion systems of the Lagoon power cat vessels for guidance as to engine, transmission, propeller, etc.

Or just purchase a power cat.

[oceancrossing]

If you motor extensively, and sail infrequently, you will be hard pressed to beat properly sized 3-blade fixed props. It has the advantage of also being a less expensive option. The additional cost of two feathering props might exceed $10k.

Line cutter utility really depends on where and how you sail. At night, and/or in areas with lots of fish traps raise the value of these.

[Montanan]

The line cutters become invaluable if one gets tangled, but they will degrade somewhat the performance of the propeller that is located downstream of the turbulent flow of the cutter blades.

One is unlikely to have doubly bad luck to get lines tangled around both of your widely separated, twin sail drives of catamaran and one can operate with just one propulsion system operating until you can untangle at a place of convenience.

[Montanan]

A bit dated cutter test article. There are likely some new versions on the market given ten years has passed.

https://www.yachtingmonthly.com/gear/propeller-rope-cutter-test-30012

[dlymn]

People talking about getting more speed always reminds me of the Wikipedia article about the history of PT boats. They were often powered by 3 engines generating about 1000 kW and went at around 30 knots. In boats I think that the power to speed graph is exponential. To double your speed might need more than 4 times the current power and massive propellers.

[oceancrossing]

Originally Posted by dlymn

People talking about getting more speed always reminds me of the Wikipedia article about the history of PT boats. They were often powered by 3 engines generating about 1000 kW and went at around 30 knots. In boats I think that the power to speed graph is exponential. To double your speed might need more than 4 times the current power and massive propellers.

Of course they want to go fast! They bought a catamaran. All catamarans sail fast! Having left a lot of floating condos in my wake, I guess I understand the need for motor generated speed.

And you information on the performance of PT boat is quite inaccurate. 40 knots was more like it. You can read real information, accurately researched here:
https://loosecannon.substack.com/p/fascinating-history-design-and-development.

Wikipedia is yesterday’s AI mistake generator. We now can make more mistakes faster with humans being involved at all!

[Loredo]

The OP asked a simple question, six worthless replies thus far...
I'll give it a try. For me the Autoprop by Bruntons works. Better speed, 30% less fuel consumption. The prop really shines when motor-sailing. I couldn't ask for more. They're pricey but you get what you pay for. Maybe this helps a bit?

[Montanan]

References:

Yachting World

Folding and feathering propeller test

Emrhys Barrell March 24, 2015

Which is the best folding or feathering propeller for your boat? Emrhys Barrell compares 15 props in a test of speed, thrust, drag, stopping speed and propwalk

https://www.yachtingmonthly.com/gear/folding-and-feathering-propeller-test-29807



https://forums.ybw.com/threads/is-a-bruntons-autoprop-the-only-propeller-to-do-what-it-does.449173/

[Tupaia]

Originally Posted by Loredo

The OP asked a simple question, six worthless replies thus far...
I'll give it a try. For me the Autoprop by Bruntons works. Better speed, 30% less fuel consumption. The prop really shines when motor-sailing. I couldn't ask for more. They're pricey but you get what you pay for. Maybe this helps a bit?

I looked at these in the past and they have a good reputation although there are maintenance issues. The big problem is they are not good when "sailing" in excess of 8 knots. Lagoons are not fast sailors so maybe Autoprop would be an option.


They might work for the OP but no information about whether they just motor or also sail.

[Loredo]

I have no problem with the Autoprop sailing (only sails) above 8 Kn. Also, motoring around 8 Kn no problem. Motorsailing in very light winds is a pure joy often exceeding 8 Kn. Important though, the prop needs to be NOT spinning while sailing. Otherwise it drags a LOT. It is true that the Autoprop needs to be greased so that's one (more) thing to do during haul-out. Needs also to be said, a simple folding prop or maxprop have less drag than an Autoprop. The Autoprop still has a lot less drag than a fixed prop though. Of course, the fuel savings with this prop will never pay back. On the other side of the coin, the range on the same fuel is increased by roughly 30%. That for me matters.

[Tin Tin]

The Gori props have an overdrive function that may suit your situation. We had Flexofolds on Lagoon which were fine, we have another boat now with Goris and have used the overdrive function, it does work but speed difference is marginal say 0.5Kn but I did not do a reliable testing regime it is more complicated than the the flexofold.

[MicHughV]

The simple answer is here:

"The Propellor Handbook" authored by Dave Gerr.

Props, engines, hulls, and many more factors are involved, and simply changing props is NOT going to provide some or other miracle improvement performance.

[barnakiel]

You will be limited by how the boat is designed. A fixed 3 or 4 blade would be most efficient ... but likely not what you can have.


I would not buy a Brunton as my friends had a bad accident with one.


There are 3 and 4 blade Goris that have an overdrive ability. Try these. I used a 3 blade overdrive on a HR and it worked very well. I also had one on an Oyster where it kind of worked.


https://gori-propeller.com/product/3...ive-propeller/


TRY if there is a 4 blade model. More surface better.


barnakiel

[AiniA]

I am impressed with Flex-O-Fold.