Yachts & Yachting – August 2019

line from that point to the clew of

your jib and with a permanent pen

mark the nal 10cm (4in) by the clew.

e starting point for a powerful

sheeting angle is when the jibsheet

is a continuation of that pen line. If

you are trying to encourage ow over

the sail because it’s light or get rid of

ow because it’s windy, then move

the car back from that angle (to open

your jib leech); if you are looking for

more power, go forward of that mark

(to close or tighten the jib leech).

A telltale on the jib leech, a hand

width underneath the top batten, or if

you have no batten, about a quarter of

the way down the leech is a sail-tuning

must. is telltale shows the ow of

air on the exit of your sail. If it is ying

horizontally you have ow, if it is curling

behind the jib, the wind is stalling.

Foredeck marks give you a visual

aid as to the depth of your jib. If you

are new to the boat, guring out the

right place for this can be hard. My

best advice is go and have a look at

someone who is fast and copy what

they have! If that isn’t an option, thread

some twine through the bottom forestay

xing point to the shroud and mark a

10cm line where the middle of the jib

foot would sit. In the 470 you would

make two further parallel lines at 5cm

intervals towards the gunwale, but the

exact measurements may dier for

other classes – ask your sailmaker.

Put a mark on the jibsheet and some

calibration marks on the deck that the

jibsheet runs past. is is just for quick

visual reference, out of manoeuvres,

showing that you are near the right place.

IN SIMPLISTIC TERMS:

A deep jib with a tight leech adds

power, until you go too far.

A at jib is less powerful but creates

an easy shape for light wind to travel

across, again until you go too far.

An open leech gets rid of power.

ese visual aids will show you what

you need to do with the jib, but you

need to decide how to achieve it: with

jibsheet or jib car? For example, if the

leech telltale is wrapped around the back

of the sail, you need to open the jib:

You need to ease more jibsheet out to

get the telltale ying more, but as you

do that you are losing drive from your

jib (the front starts caving in slightly),

as it is just too far out on the sheet.

So, go forward on your car setting,

which makes your leech tighter, but ease

the jibsheet to get the telltale ying.

So, the base of your jib is still pulling,

but you have opened up the top.

When you are on the water

consider the wind strength, sea state

and the feeling in the boat when

sailing in a straight line and discuss

what you need from your jib:

Above left

Jib control system

in the 470 with

a fore & aft jib

car and dierent

settings marked on

the boat and line

Below left

Jib control system

in a Fireball with

a sideways jib

car and piston

(equivalent of a

fore & aft jib car)

Below

A telltale on the

jib leech is a

sail-tuning must

UPWIND SPEED

Jib set-up

Even though the jib is the small

relation to the mainsail, it makes a

large contribution to your performance

upwind. As the crew, it is your domain.

e jib’s main job is to accelerate wind

on to the leeward side of your mainsail

and you need to set the jib slot to get

the optimum power from the wind.

In under-powered conditions you are

trying to squeeze as much energy from

the wind without making the gap so

hard to get through that the wind just

doesn’t bother. When you are over-

powered, you are trying to lose and spill

wind from the leech of the jib because

the wind strength is too much for the

boat to cope with. And in between

those two states is ‘max power’ when

your jib leech is set at it’s tightest.

Control of the jib leech is a combination

of two main elements: the jibsheet and

jib car position. You might not have an

adjustable jib car in your boat, if so, you

would use the windward / lazy jibsheet

instead. To understand the eect of the

sheet and car, rig up the jib in 6-7 knots

of wind and look how the two elements

aect the sail. If you pull only jibsheet,

the leech will be straight; using jib car

(or the windward jibsheet) puts a curve

in the jib leech. Look at the shape the

foot of the jib is making on the foredeck:

using jibsheet makes a straight line (a at

jib); and jib car makes a semi-circle (a

deep jib). Look how much movement of

jibsheet or jib car it takes to change the

shape. e object is to mirror the shape

of the mainsail as you look at the boat

from behind, but as a crew you don’t have

that viewing perspective when racing.

ree visual tools to get you in the

ballpark of correct jib set-up are:

Have a look at the diagram opposite

on page 49. Make a small mark halfway

down the lu of your jib (either measure

it or fold it in half ). Draw an imaginary

HOW TO WIN STRAIGHT-LINE SPEED

PHOTO: THOM TOUW

48 Yachts & Yachting August 2019 yachtsandyachting.co.uk