Propellor size

[Sailfree]

Can thoroughly recommend Paul Bell of 1st Marine propulsion 023 80 225 944. They do fixed props and all shaft machining etc. In my case I have bought 2 feathering Variprops off him and he has always given me the best price and good service. Came out this week to check the pitch for me and make minor adjustments to suit my personal preference. No charge now thats what I call service!

No connection but feel strongly that we should always support the good guys in our industry to get rid of some of the cowboys!

If I could name the people that Jeanneau employed to fit my still leaking bowthruster and the heater I would name and shame with pleasure.

 

[oldharry]

The pitch is the theoretical distance the propeloor will screw itself forward in 1 full revolution - same as the pitch of the thread of a bolt. As water is fluid, the propellor 'slips' and the amount of slip is expressed as a fixed percentage - as you will have noticed on the various posts. Of course in practice the degree of slip varies, and the slip figures people are quoting are averaged out figures for prop size /speed calculations.

The whole business of prop sizing is well known as one of the dark arts, and you will get many different answers to the same set of boat dimensions depending on who you ask or which calculating programme you use. One of the best ways forward is to contact the boat builder/designer for his recommendations, and then the Owners Association who will certainly have a pool of practical experience.