Practical Boat Owner — January 2018

36 Practical Boat Owner t http://www.pbo.co.uk

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Here’s just a selection of the latest questions from

PBO readers. Email or write to the address on

page 5 and our experts will answer your queries

CORROSION

THE PBO EXPERTS To ask a question email [email protected] and include your address. Pictures are helpful

CRUISING

Stuart Carruthers

is the RYA Cruising

Manager and has

sailed extensively

SAILS

Ian Brown of the

International

OneSails loft group

is an expert on sails

ELECTRICS

Paul Holland is

part-chair of the

BMEEA and MD of

Energy Solutions

(UK)

MASTS & RIGS

Mike Coates worked

in the spar and

rigging business for

many years

ENGINES

Stu Davies has

a background in

engineering in the

coal and oil field

industries

SURVEY AND

CORROSION

Colin Brown runs

a marine survey and

consultancy company,

CB Marine Services

SEA SAFETY

Keith Colwell is

author of the

RYA Sea Survival

Handbook

SEALING AND

BONDING

Gareth Ross is

Sika UK’s Marine

Market Field

Specialist

Q

This is our 12th season
with our Jeanneau Sun
Odyssey 32 which we bought
new in early 2006. We cruise
mainly in the Irish Sea and
western Scotland areas from
a marina berth in Dublin.
The boat has never been out
of the water other than for
annual anode replacement
and antifouling.
We replaced our headsail
and running rigging in the
past two years and I now want
to set the boat up for,
hopefully, a further 12 years
of trouble-free sailing.
What areas I should be
investing in?
Bryan Downey,
by email

COLIN BROWN REPLIES:
After 12 years there are a
number of places where
corrosion could be working
away on your boat. If you’re
considering a refit it might be
helpful to get a local surveyor to
take a look to give you some
specific advice. Choose a
surveyor who is happy to meet
you at the boat after the survey
so you can discuss the findings.
This is too big a subject to
comment on every possible
place where corrosion may be
an issue so I’ll concentrate on
general principles and two
metal types in particular: copper
alloys and stainless steels.
Copper alloys are commonly
found on modern production

boats as brasses and bronzes

in through-hull fittings and

propellers. Components on all

boats built after 1998 have to

comply with the Recreational

Craft Directive which sets

minimum standards for

materials among other things.

With through-hull fittings the

minimum standard requires

them to last for only five years.

In reality many last longer but

at 12 years old all of yours

should get some attention.

All of them should be taken

apart so you can get a really

good look at the nooks and

crannies not normally

accessible. The main danger

sign is a change of colour

caused by selective loss of the

zinc content from the brass.

The pink colour on the copper

left behind is very distinctive as

shown in Figure 1. You can see

it has been leaking by the white

crusting around it. Here the skin

fitting snapped off in my hand

while the boat was afloat – you

can see the bung in the hole in

the background!

If any parts give any cause for

concern then replace them.

The cost is small compared to

the damage that a failure could

cause. Replace with bronze or

dezincification resistant brass

(DZR) which may be marked as

CR for corrosion resistant (see

Figure 2).

All underwater fittings should

be inspected annually and all

valves opened and closed

monthly to stop them getting too

stiff. The same type of corrosion

can affect propellers which are

often made of manganese

bronze – a brass prone to

dezincification unless protected

by a sacrificial anode.

The second and most

common metal type to

consider is stainless steel,

often found on standing

rigging, guard wires, deck

fittings and fasteners.

Stainless steel also has a

specific set of corrosion types

including pitting, crevice

corrosion and stress corrosion

cracking. Wherever there are

enclosed parts such as under

nuts and washers, swages

and complex shapes there is

potential for water to collect

and low oxygen levels in the

water at the bottom of such a

crevice can initiate corrosion

that can be destructive and

not immediately visible. Rust

stains are the most obvious

warning signs and any

components that have rust on

them should be removed and

inspected closely. Bolts, nuts

and other small fittings should

be replaced and sealed to

keep water out as much as

possible. Figure 3 shows bolts

holding a rudder pintle to the

transom with a classic

seawater leak leading to

corrosion in stainless steel.

Standing rigging is a special

case and at 12 years old

yours is getting towards the

end of its lifespan.

Corrosion and fatigue are

not necessarily visible so

rigging gets a lifespan, often

quoted as 10 years but in

coastal cruising 12-15 years

should be considered a

reasonable life. Take the mast

down and have a rigger

inspect all parts of the rig and

plan for replacement in the

next two or three years.

End of life for fittings

Figure 1 Note the pink, coppery

colour where this dezincified

fitting was easily snapped off

Figure 2 CR (corrosion

resistant) marked hose tail

Figure 3 Rust staining on these

rudder pintle bolts – classic

symptoms of corroded stainless