Tuesday, 27 October 2009

Show Me Your Leaves, Dearie !

Just a reminder that if you find that the wash behind your boat is a different pattern on the water to usual or is making a strange noise, it could be leaves.

At this time of year, the leaves fall off the trees (so that's why the US call it "the fall" ??) and land in the canal (can I say that ?).

The leaves then start to sink and often get wrapped around the leading edges of your propeller as you're cruising, spoiling its hydrodynamics.

This causes a loss of efficiency.

Its worth just putting the gearbox into neutral every now and again whilst travelling and giving the engine a burst in astern, to blow the leaves off.

Obviously, make sure you do this on a straight stretch when no other boats are around.

Its also quite refreshing to see the leaves come to the surface with the reverse thrust, confirming your diagnosis...

The pattern of the wash is generally very telling. Not quite like tea leaves in the bottom of a teacup, but it can indicate things fouling your propeller.

Large objects like mattresses, fleeces, whole tyres, etc have a way of announcing their own arrival - usually by killing your engine as you are approaching a lock entrance with a fair amount of way on.

However, smaller objects like carrier bags, leaves, fishing line, can just affect performance and this is often where wake watching comes in.

Get used to your normal wake pattern for different speeds, so you recognise anything abnormal.

I find the wake has a habit of not flowing directly behind - it goes sideways slightly, which is usually a sign of fouled prop blades, which plays with the thrust.

Something to think about as you are chugging along.

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