Practical_Boat_Owner_-_November_2015_

Got a question? Email [email protected]

Ask the experts

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

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

SEA SAFETY

Will Stephens is

Staff Officer

Operations (Coastal

Safety) at the RNLI

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

chairman of the

BMEA and MD of

Energy Solutions

(UK)

MASTS & RIGS

Mike Coates worked

in the spar and

rigging business for

many years

ENGINES

Pat Manley is

a diesel engine

course instructor

and marine author

SURVEY AND

CORROSION

Colin Brown runs

a marine survey and

consultancy company,

CB Marine Services

BOAT BUYING

David Harding is a

regular contributor

to PBO: his photo

archive is at http://www.

sailingscenes.co.uk

ENGINES ELECTRICS

Going round in circles

Q

While cruising in the Bristol Channel recently in my twin-diesel
1988 Fairline Sunfury I suffered a fuel blockage on my port
engine, which would then only tick over at 7 50rpm, unable to run at
higher revs. I wasn’t worried – with twin engines I’d surely get home
on one no trouble. Except... if I took my starboard engine above
1,200rpm the boat just went in circles, leaving me at about 5 knots
with very little steerage in a large, busy shipping channel with 5-knot
currents. Have you any advice how, with a twin-engine setup, you
should manage on one engine? Perhaps I can make some
modifications to rectify the problem should it arise again (though
hopefully it won’t – I’ve cleaned the tank and changed all the filters).
Rebecca Richards, by email

Rebecca Richards wonders how best to control a twin-engine Fairline
Sunfury like this on only one engine

PAT MANLEY REPLIES: With
only half the normal power
available, your boat will not be
able to get up on the plane, so
maximum speed will be severely
restricted – 8 or 9 knots might be
all you’ll manage. With the dead
engine’s leg in the water, there will
be a lot of drag from both the leg
and the prop, even if the failed
engine is running at 750rpm. The
boat will naturally, then, want to
turn towards the dead engine.
The best thing to do is to raise
the leg of the dead engine to
its highest position, hopefully
completely out of the water, to
eliminate its drag. Then increase
the rpm very slowly on the good

Q

I’m seeking an opinion

on my proposal for

charging batteries on my

7 .6m (25ft) sailing yacht.

I have a split-charge diode

rated at 7 0A, to which is

connected a 50A alternator. In

order to run a peltier coolbox

(as I don’t have room for a

compressor fridge) I intend to

buy two new service batteries

and connect them in parallel

so that I have

approximately 200Ah

of capacity. Would you

recommend that I

connect my solar

panels, two at 10W

each and diode-

protected from reverse

current, in parallel to

the split-charge diode

and, when 230V mains

is available, connect a

25A charger to the same

place? Under normal

circumstances my boat lies

on a swinging mooring so

mains electricity is not

normally available, hence

the solar panels.

Kevin Mullins, by email

PAUL HOLLAND REPLIES:

Connecting the solar panels in

parallel to the input side of the

diode splitter will mean that

both batteries are charged

when the sun shines. However,

the downside is that you get a

voltage drop across a diode,

which will slightly reduce the

voltage that the battery will see.

http://www.boatgear.info

engine, steering as necessary to

keep straight until you are going

as fast as possible and still

running straight ahead. In this

condition, turning the boat

towards the good engine will

require you to reduce rpm first, so

forward planning will be necessary.

To save money, manufacturers

will often fit a power steering

pump on only one engine, so with

the ‘wrong engine’ failed, steering

can be a problem at higher speed.

Next time you are out in your boat,

you could try some single engine

handling practice so that you are

familiar with how your boat

responds at different speeds

and power settings.

A fair system of charges?

You don’t say what voltage the

panels are: if they are nominal

12V panels then they will charge

a battery, but not as effectively

as they would if controlled via a

solar charge regulator. If you

were to use that you could also

operate the two panels in series,

which would ensure charging

continues to happen at lower

light levels.

Without a regulator the output

voltage is dependent on light

levels. When the light level

drops the panel is still capable

of delivering power, but the

voltage is too low to drive

current into the battery. If you

put two panels in series (with

a regulator) the panels will

continue to put useful energy

into the batteries at much lower

light levels. The solar regulator

has an integral DC-DC converter

function that maintains the solar

panels at the best operating

voltage to maximise their

output while (on the battery

side) providing the correct

charging voltage to maintain

your batteries.