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S&S Swan General - Propeller for swan 44 |
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Join Date: 12 March 2013
Posts: 24 |
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Propeller for swan 44
Regarding the last 2 months question about the propeler for my swan 44, which one will best for crusing and racing, here is the information about ratio and engine : engine yanmar : 4jh3g-te1 reduction 2.7 N°E157557 Tk u and fairwinds, César |
Join Date: 02 January 2008
Posts: 1547 |
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Dear Cesar Thank you for the engine type information and reduction ratio. Your powerful engine would benefit from a bigger propeller, but the diameter is probably restricted to about 17" on this model. It would be worthwhile checking the maximum diameter that can be fitted, but some clearance is also needed. The choice of propeller depends on what is important for you - maximum thrust in a strong headwind, good cruising performance, or small resistance under sail? As pointed out recently on the Forum there is no single propeller providing the best of all these, compromising is necessary. If maximum thrust is important the suggestion with restricted diameter is to choose a 4-bladed propeller for maximum blade area, for cruising speeds a 3-bladed, and for small resistance a 2-bladed. In order to give you an idea of the differences, a 4-bladed would provide about 16% more thrust than the 3-bladed, and a 2-bladed 20% less. The Forum post dated 8 May 2010 discusses various aspects of propellers, and it is recommended that you read it in this connection. If you could check the maximum diameter, and indicate the preferred number of blades and type of propeller a proposal can be worked out. Kind regards Lars
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Join Date: 12 March 2013
Posts: 24 |
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tk u lars, i will have a look on the forum, probably going to chose a flexofold 3 blades. Fair winds, César |
Join Date: 15 April 2011
Posts: 395 |
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Dear Professor, I just read the thread dated may 8, 2010 which describes in clear and thoughtful detail propellers, propeller tests and comparisons of propellers by use; e.g., flat blades vs. curved blades. Thank you. I continue to learn everytime I read something you write! One question: would the diameter of a 4-blade prop necessarily be smaller than a 3-bladed prop? Chris |
Join Date: 02 January 2008
Posts: 1547 |
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Dear Chris
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Join Date: 15 April 2011
Posts: 395 |
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Dear Lars, Yes, that answers my question very clearly and, as usual, there is more to the answer than I anticipated. Thank you. Chris |
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