Reached hull speed with 3 blades propeller Hunter 356

That's Great Serb!!
It's all been worthwhile!!
A Happy Skipper, Wife and Kids to Enjoy!!
Cheers

PS..Have you sold the Tasman 26?

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Serb1980 said..
Today, I have installed a new 3 blades propeller 16x11HR instead of original 2 blades 16x11. The difference is amazing. On 2900 rpm I have achieved 7 knots, instead of 4.4 with old propeller. Boat is so quite that on 1500 rpm you are asking your self if engine is working or not. What an improvement. very very happy.

It's the "little engine that could" all over again,, thumbs up.

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BeamReach said..
That's Great Serb!!
It's all been worthwhile!!
A Happy Skipper, Wife and Kids to Enjoy!!
Cheers

PS..Have you sold the Tasman 26?

Not yet. Few offers but nothing fair.

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jbarnes85 said..
I need to replace my two blade. Was thinking of getting a three blade. Did you swap it under water?

I've removed and replaced a prop underwater, so it certainly can be done. It would be a lot more fun to do it with scuba gear! :-)

Three blade fixed props cost a LOT of speed under sail; half a knot to one knot, or about 20% of speed.

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jbarnes85 said..

Serb1980 said..

jbarnes85 said..
I need to replace my two blade. Was thinking of getting a three blade. Did you swap it under water?

Yes Pablo was the man. Underwater.com he is in Sydney

Do you have his contact details? That web site doesnt work.

Google Pablo Canestro Underwater Dive Services

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Chris 249 said..
I've removed and replaced a prop underwater, so it certainly can be done. It would be a lot more fun to do it with scuba gear! :-)

Three blade fixed props cost a LOT of speed under sail; half a knot to one knot, or about 20% of speed.

I've also done an underwater prop remove/refit and it was not a big deal, although it had only been removed and refitted on the hard a few months before. A prop that hadn't been touched for years might be a struggle as you can't use impact or heat.

Cheers, Graeme

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Magpieuser said..

Chris 249 said..

jbarnes85 said..
I need to replace my two blade. Was thinking of getting a three blade. Did you swap it under water?

I've removed and replaced a prop underwater, so it certainly can be done. It would be a lot more fun to do it with scuba gear! :-)

Three blade fixed props cost a LOT of speed under sail; half a knot to one knot, or about 20% of speed.

If this is the case then my Magpie is a speed machine. 6.5 to 7 knots under sail, with a clean bum and 15 knots of breeze.

Thats a real boat speed not some random SOG grab from the instruments.

So with fresh sails and a folding prop I'm going to see 8.5 to 9 knots ??

(Assuming my prop is costing me a knot and my old sails another?)

I think my fixed three blade that is free wheeling is costing me closer to .3 to .4 of a knot.

Thoughts?

I'm getting the information from a Yachting Monthy test, which for some reason I can't link to, and other sources.

I was thinking of a non-spinning prop because until I checked this evening, I hadn't realised that apparently modern gearboxes can take a spinning prop without damage; my understanding was that old ones didn't (which is why many years ago we had a complete PITA with a broken shaft lock and a fixed prop on a passage to Noumea). About the same time the family cat had fixed props and was stuck in gear to stop them spinning - so when it surfed down a wave apparently the diesels push started!

Another Yachting Monthly test towed fixed and spinning props and said that "To put these results in context, towing a 10in diameter bucket produced just 10 per cent more drag than locked prop."

We know how fast the best Magpies are; Joubert's own one was very succesful and as fast as other good 3/4 Ton IOR racer/cruisers of the same age. After looking at the ORC charts of speeds for boats like the Magpie, your estimate of .3 to .4 could be right, the estimate of 0.5 to 1 could be right; we don't know without more information about exactly what your speed is and your configuration.

I didn't say old sails cost a knot and wouldn't expect them to. Old sails well trimmed only cost a small fraction of a knot in one design classes in my experience.

We've got a feathering 3 blader a previous owner fitted. It's a Kiwiprop which didn't perform well in the Yachting Monthly test, and I'm seriously thinking of going to a 2-bladed folding prop; the YM test showed that a surprising number of 2 bladers pushed the test boat faster than 3 blades.

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Chris 249 said..

Magpieuser said..

Chris 249 said..

jbarnes85 said..
I need to replace my two blade. Was thinking of getting a three blade. Did you swap it under water?

I've removed and replaced a prop underwater, so it certainly can be done. It would be a lot more fun to do it with scuba gear! :-)

Three blade fixed props cost a LOT of speed under sail; half a knot to one knot, or about 20% of speed.

If this is the case then my Magpie is a speed machine. 6.5 to 7 knots under sail, with a clean bum and 15 knots of breeze.

Thats a real boat speed not some random SOG grab from the instruments.

So with fresh sails and a folding prop I'm going to see 8.5 to 9 knots ??

(Assuming my prop is costing me a knot and my old sails another?)

I think my fixed three blade that is free wheeling is costing me closer to .3 to .4 of a knot.

Thoughts?

I'm getting the information from a Yachting Monthy test, which for some reason I can't link to, and other sources.

I was thinking of a non-spinning prop because until I checked this evening, I hadn't realised that apparently modern gearboxes can take a spinning prop without damage; my understanding was that old ones didn't (which is why many years ago we had a complete PITA with a broken shaft lock and a fixed prop on a passage to Noumea). About the same time the family cat had fixed props and was stuck in gear to stop them spinning - so when it surfed down a wave apparently the diesels push started!

Another Yachting Monthly test towed fixed and spinning props and said that "To put these results in context, towing a 10in diameter bucket produced just 10 per cent more drag than locked prop."

We know how fast the best Magpies are; Joubert's own one was very succesful and as fast as other good 3/4 Ton IOR racer/cruisers of the same age. After looking at the ORC charts of speeds for boats like the Magpie, your estimate of .3 to .4 could be right, the estimate of 0.5 to 1 could be right; we don't know without more information about exactly what your speed is and your configuration.

I didn't say old sails cost a knot and wouldn't expect them to. Old sails well trimmed only cost a small fraction of a knot in one design classes in my experience.

We've got a feathering 3 blader a previous owner fitted. It's a Kiwiprop which didn't perform well in the Yachting Monthly test, and I'm seriously thinking of going to a 2-bladed folding prop; the YM test showed that a surprising number of 2 bladers pushed the test boat faster than 3 blades.

Nah It wasn't you that suggested fresh sails are worth 1 knot but plenty have told me that over the years.

The Yachting Monthly test was the one I had read back when I changed the prop (well plus a minus a year, I can't remember) and either decided I had done the right thing or was about to.

I just wanted a reliable solution and a prop that matched the hull and engine and it does. Yes I'm costing myself 20 odd minutes at the end of everyday or thereabouts but I wasn't up for either fixing my worn out 2 blade folding prop nor spending 3 - 5k on a new folding one.

I have whatever the matching g box attached to the 3GM30 and so far so good with it spinning, as per the previous owners I guess.

As far as I recall the South Coast 36 was built in the vicinity of Wollongong.

Q to the panel,
sort of related (2 blade folders, 3gm30).


Does a prop for a saildrive fit both the Volvo Pentas and the others. that is non-Volvo SD20 (fitted to Yanmar / Kubota ) drives?

thanks