propeller to skeg clearance

[Murflynn]

Another way of looking at the blade tip to skeg clearance question, leaving aside considerations about noise and vibration, is that a gap as small as possible, down to a quarter or half an inch is the least likely to trap bits of wood with any real strength in them, and therefore less chance of doing any damage.

Before anyone dismisses this as just a theory, I'll say right now it isn't, and it was successfully put into practice over a great many years on working boats of different types.

It wasn't done to reduce the chances of damage, but merely in order to swing the biggest possible propeller diameter, which is one of the reasons why working boats out performed most of today's pleasure craft, with around half of the horsepower that is now thought necessary, propelling a small barge or a pair of narrowboats of around three times the tonnage (displacement).

did empty moored boats line the towpath, displaying signs saying 'slow down to tickover', in the days of working boats?

come to think of it, for one of those working boats even tickover would have been too fast for today's grumpies.

Edited August 29, 2015 by Murflynn

[David Mack]

did empty moored boats line the towpath, displaying signs saying 'slow down to tickover', in the days of working boats?

come to think of it, for one of those working boats even tickover would have been too fast for today's grumpies.

A bolinder at full chat is going at lower rpm than today's grumpies' engines do on tickover!

 

Edited for fat finger error.

Edited August 29, 2015 by David Mack

[zenataomm]

Royal Military Police