D4® – Custom Load Path Sail Laminate

May 4, 2011

Dolphin are now producing sails in D4® membrane

Dimension Polyant has added the first commercially available customized membrane sailcloth to its product line. D4® membranes cover the full range of applications, with a history covering boats of all sizes in Grand Prix and Club Race, Cruise and Mega Yachts. Different fibres and blends thereof combined with several surface options allow us to create a custom product directed specifically to the customer’s needs. Sail shape designs are created by Dolphin.

Yarn densities and trajectories are varied throughout the membrane to ensure the optimal amount and direction of yarn for the predicted loads. Complementary yarn layouts are standard for the reefs, cunningham and tack. For the cruising sail, additional passes addressing loads from roller furling can be added to ensure proper thread support for partially furled sails. The result of this advanced threadline construction with curved yarns is minimum weight for maximum shape retention, longevity and performance of any type of sail. When the D4® kit arrives at the loft we complete the construction of the panelled sail. The result is an extremely smooth, durable and lasting sail that will perform over a wide range of conditions.

Frequently Asked Questions

What is D4®?
D4® is Dimension Polyant’s brand name for custom sail membranes. Rather than being made from standard rolled sail cloth or a sailcloth laminate, a D4® membrane is custom made for the intended use from fibre through to finished sail.

How is D4® made?
The D4® sail process begins with a sail design. The production process begins with large flat sections made from polyester films (or films and taffeta). A computer controlled machine then lays the fibres in accurate curved arrays, and depending upon the complexity of the design this can comprise a number of layers. Once this process is complete the top film is placed and the lamination is formed using extreme pressure and controlled heat to bond the films and fibres. After curing the sections are placed on a large x-y plotter where the panel edge shaping including luff, leech and foot curves are drawn. We assemble the D4® sections and complete the sail.

Who designs the sail?
Dolphin Sails. The 3D shape of the sail is defined in the normal way using our sail design software.

How are D4® membranes shaped?
D4® is shaped through its horizontal broadseams.

Can all kinds of sails be made with D4®?
There are no limitations with regards to the kind of sails that can be made with D4® membranes. Mainsails, genoas and headsails can be constructed from D4® components.

Are there limitations in sail sizes with D4® membranes?
D4® membranes can be manufactured for all today’s sail sizes – from 30 footers to mega yachts. The sectional configuration of D4® membranes allows even the largest sails to be made from D4®.

Are D4® membranes fit for use with roller furling systems?
Yes. D4® laminates are fit for furling and reefing. D4® membranes can also incorporate custom reef furling trajectories, where supporting fibres are laid to support new loads when the sail is partially furled.

How reliable is the D4® technology?
As early as 1996 the first D4® sails were tested under race conditions. Since then thousands of D4® membranes for yachts from 30 to 150 feet have excelled even under the toughest conditions and won lots of silverware.

Sails recently developed include:

Stewart 36

Sigma 38

Prima 38 

Dufour 45e


Oyster 46 / 54/ 56 / 655  

‘Oystercatcher XXV’ Winner of the Rolex RYS race around the Isle of Wight.
EAORA Ralph Herring Class 1
EAORA Pattinson Cup Class 1
North Sea Race Class 0

Gironde’ IMX 40 2nd IMX Cowes week, 1st EAORA week
‘Jalapeno’ J109 – 2nd Dartmouth Week
Oyster 53 – 3rd Class 2 Cowes Oyster Regatta
X99 3rd overall Icelandic Championships
‘The Geek’ Stewart 30

Dehler 36
HOD 35
First 31.7