Propeller for a swan 44
Dear all and the professor,

I m looking to buy a new propeller for my swan 44, my engine is a yanmar 4jh3g 75 hp, program is cruise and racing.
Tk u for helping me,
Fair winds,
Cesar

We have a three bladed one of these on our 441 (Cant remember the size, but we have 50hp Beta so wouldn't be directly comparable)

http://www.darglow.co.uk/Propellers/FeatherStream/index.html

Been on two years and very happy with it.  Very favourable price compared to the maxi-prop which was the final desider!

Happy sailing

Adrian

Dear Cesar
Would appreciate some information for evaluation of your installation.
Do you have a technical leaflet for your engine? It appears there are many versions
What is the reduction ratio in forward and reverse?
Is it the original propeller shaft and shaft strut?
What propeller is there now, type, size, number of blades?
Present top speed and rpm, cruising speed and rpm?
Are there vibration and noise problems?
Kind regards
Lars

thank for your answer i will have a look on the link

Dear Lars, tk u for you quick answer, technical docs is on boat, and unfortunatly i m not on it.The engine is 5 years, i have also a 5 years normal propeller with 3 blades. Cruising speed is 6.1 at 3400 rmp. I want to gain some speed when i m sailing and looking for propeller like maxprop or any other similar models.
Should be able to give you more details in 20 days for the ratio... when i will enjoy my boat.
fair winds

Is there a prop on the market that can be "switched" between FOLDING /racing mode and feathering cruising mode at all?
Its just that the folding props have great advantages obviously when racing....making time..but when going astern or when needed in a critical situation/high current are not as efficient as a fixed /feathering prop.

Thank You
Florence

Dear Cesar
Thank you for the information.
No wonder that you consider a change, the present combination of engine and propeller can be described as extremely inefficient.
At 6.1 knots the propeller uses about 15 hp, and if the engine has a maximum rpm of 3800 then at this rpm the propeller absorbs about 21 hp, a fraction of the available engine power.
Considerable improvement should be possible.
Kind regards
Lars


Dear Florence
Most sailing yacht propellers are either folding or feathering, and you probably mean one providing minimum resistance under sail and still providing high thrust under power?
Such an animal is not available, unfortunately the laws of physics require that propeller blade area is increased in proportion to engine power. This means that bigger diameter and/or more blades are required with more power in order to have an efficient propeller.
It has been pointed out earlier on this forum that good folding propellers can perform better than fixed or feathering ones, suggest you look up the thread dated 8 May 2010. One important thing is how accurately the propeller has been manufactured.
Kind regards
Lars

Dear Florence
Referring to your question about folding versus feathering I would like to ask what type propeller you have now, and how it performs in the mentioned situations?
Kind regards
Lars