Yachting Monthly - November 2015

TECHNICAL

68 http://www.yachtingmonthly.com NOVEMBER 2015

Membrane sails are built in a

similar, but also slightly different

process to laminates. The

strengthening yarns are laid

in panels, in line with the load

paths specifi c to that sail shape.

A cruiser’s guide to sailcloth

Multi-piece membrane

Single-piece membrane

Those looking to get the absolute

best performance from their

boat need a set of single-piece

custom-made racing sails

with no panel seams on

the sail surface. They

don’t come cheap and

certainly not without compromise

• they have the best shape, but
  longevity suffers. While there is
  no one best sail on the market
  (although manufacturers
  may disagree),
  there are various
  high-performance
  versions from
  each manufacturer
  using either its own
  membrane or a branded
  one. The best-known sails
  made using this technique are 3DL
  and 3DI from North Sails.

How’s it made

The sail shape is calculated

by computer, which moves a

mould into an aerofoil shape. The

manufacturing process is similar

to a laminate sail, but because it

is built and heated while on the

three-dimensional mould (rather

than a fl at surface), the single-

piece sail takes the shape of a

perfect aerofoil from its mould

without any cutting of panels.

Once lain on the mould the sail is

heated to cure it. The membrane

PROS

■ Perfect shape sails for

your boat

■ Sails can be identical,

ideal for racing

■ No stitching across the

sail surface

CONS

■ Ultraviolet light can

damage unprotected sails

■ Expensive

PROS

■ High performance sails

■ Custom made

CONS

■ Expensive

can be coated with Taffeta but

again this also adds weight.

What it’s made of

North’s 3DL is a high-spec sail, so

even the basic material is aramid

(Kevlar), with the higher-spec sails

also using Dyneema and carbon

for better load path resistance.

Best for

Serious racers that want to really

get their boat to the max, and

don’t mind paying for it.

RIGHT: 3DL

have reinforcing

fi bres laid in

three-dimensions

This X40 has membrane sails,

which have proved to be

wonderful for fast cruising

PHOTO ABOVE: GSP LEFT: JEREMY EVANS

PHOTO: NORTH SAILS

PHOTO: NORTH SAILS

PHOTO: GRAHAM SNOOK/YM

A North 3DL sail is being cured,3D sails have near perfect shape

These panels are

laminated using

either a vacuum

or rollers. Once the

panels are joined, the load

paths match up across the seams

running horizontally across the

sail, creating continuous load

paths over a number of different

panels. Because the joints are as

strong as the panels and follow

the load path, there’s no loss of

strength. EPEX sails from Elvstrøm

use vacuum tables and guarantee

against delamination.

How it’s made

Membrane sails start life on a

computer where the load paths

of your sail are calculated. Next,

sheets of Mylar are laid down fl at

and reinforcing yarns are glued to

the Mylar to match the load paths

of that sail design. These cross-

cut panels are trimmed to shape,

then stitched together to make

the fi nal sail ready for fi nishing.

What it’s made of

At this end of the market,

only the best yarns are used:

Spectra for longevity and

strength. The main yarns are

carbon and aramid. A Taffeta

coating can be added to improve

sail life, but also adds weight.

Best for

These appeal to a wide spectrum

of sailors from cruisers to racers

• they make a great combination
  of performance and reliability,
  with cost being the only issue.

LEFT: Taffeta coated

EPEX, part of a multi-

piece membrane sail

Multi-piece membrane sails

have their fi bres laid out in

panels on a fl at table

The carbon fi bres running along the load paths

on Elvstrom’s EPEX sails are clearly visible

PHOTO BELOW: GRAHAMSNOOK.COM