Yachting Monthly — November 2017

November 2017 http://www.yachtingmonthly.com 21

EXPERT ON BOARD

Nestling under a

weather shore in

Mupe Bay looks

idyllic, but the wind

may not behave quite

as you’d expect

A low spit, such as a gravel bank, provides

the most basic kind of weather shore

protection, serving as a breakwater but

with hardly any wind break effect (Photo

1). Even so, when a strong wind blows

over the low obstruction it will stay fairly

constant in strength and direction, so

that an anchored boat should lie steady,

without excessive sheering around. The

anchorage won’t feel like a cosy haven but

the anchor, provided it is properly set, is

unlikely to be tripped-out by the boat’s

movements.

We might expect a higher land mass to

provide better shelter, but this is where

things get complicated. A vigorous wind

will generally be stronger at high altitude

than at low level, and a mountain peak is

quite likely to interfere with that upper

air flow, encouraging some of it to spill

down the leeward slope (Diagram 1). The

effect can be particularly marked where

that slope follows a smooth profile down

to sea level, so that the strong airstream

then blasts straight off the beach (Photo

2). Whether this is nasty or nice depends

on whether you want peaceful shelter or

swift sailing. The Isle of Man has a

flat plain at its northern end but most

Basic shelter – with strong winds

In the lee of Chesil
Bank, the water is flat
but the wind strength
undiminished Sea

Wind stronger

at high level

Lee slope downdraught from upper wind

Strong airflow

down lee slope

Diagram 1

ALL GRAPHICS: MAXINE HEATH