An everyday story of sailmaking....

David Glenn's blog

Latest weblogs from the editor of Supersail World

24 June 2009

It's plastic - polyethylene to be precise - but it's stronger than steel, an eighth of the weight and among many other things it's used to moor the world's biggest VLCCs - very large crude carriers. Apparently its lack of stretch in a mooring rope means its backlash characteristics when it breaks render it less dangerous than steel�

Dyneema is indeed a remarkable material but until now its use in fibre form has been limited in the yachting world because it is extremely slippery and doesn't like being glued to anything.

It's been used in running rigging for a while, its weight advantage and low stretch properties making it an ideal material for halyards. But now the world's biggest manufacturers of sailcloth, Dimension Polyant (DP), have found a way of using it in their D4 sail membranes or laminates, sandwiching the load bearing fibres into a matrix.

Although DP make some 40 per cent of the world's sail cloth they reckon they don't often get the glory or the headlines, so to coincide with their Dyneema sail making breakthrough they flew a bunch of journalists to Palma to explain what they do and how they do it.

Rather cruelly they kicked off by sitting us in a hotel lecture room for an afternoon where they bombarded us with chemistry and convoluted facts and figures about sails. They called the press event The Secrets of Sailcloth but when it came to revealing the real detail of how they had configured Dyneema to work in a membrane sail they remained tight lipped. Hmmm�

D4, originally produced in Australia way back in 1996 as an antidote to North's 3DL which was taking the grand prix sailing world by storm, continues to use other materials like Twaron, Kevlar and carbon as the load bearing element of a membrane sail, but Dyneema, DP claim, out performs all these materials in just about all respects and is particularly resistant to being folded, twisted and generally jumped on unlike carbon, for instance, which doesn't like being roughed up.

It is also a particularly stable material in that it doesn't stretch much - it's only out performed by carbon in this instance - so the ability to hold the shape in a sail is exceptional.

It is the combination of being hard wearing and stable that has attracted sail makers who want a 'cloth' that will perform well on the race course as well as aboard a world girlding cruiser. But don't get too excited - there's a price premium and no real weight advantage.

Previous attempts by the D4 loft in Australia to use early forms of Dyneema in sail making failed because it didn't like the high temperatures needed to flow the resin which holds the layers of the sail together. But DP scientists have developed the technology and a period of 'validation' which has involved Dyneema being used in a number of test sails has now satisfied DP that the material can be used in their D4 product.

They have addressed the need for UV protection and have gone some way to eliminate mildew, which still occurs in sails and is still a major cause of delamination. According to DP the only way to stop mildew is to poison it but regulations prevent them using the necessary toxins in cloth making. DP also emphasise that an important feature of their membrane 'construction' is the use of vacuuming to create the bond and then applying rolled pressure of some 6.5 tons.

Relieved that our Palma classroom session was over we were wined and dined before DP took us afloat the following day where we were able to see Dyneema in action onboard the immaculately maintained and professionally run Swan 112 Anemos. While the D4 sails themselves looked like any other white sails typically seen on large yachts, the press corps were being fed the inside story plus sushi and champagne as we sailed gently across the bay of Palma.

Richard Foster the highly experienced skipper of Anemos reckoned if he got four years out of his new sails he would be satisfied, but he anticipated they would eventually be replaced not because they were underperforming but because they would start looking tatty and dirty. Red Sahara dust carried in rain plays havoc with Richard's sails and unlike like his last suit of Cuben fibre, which were totally waterproof and could be hosed down, these sails, like most others, retain some moisture and the red sand that goes with it. So it's on with the sail cover as soon as the sail is furled.

Only time will tell if these sails really are likely to be longer lasting than any others. Surely no laboratory test can replicate how they are handled by a crew, good or bad.

Anemos, owned by a mad keen sailor, is used hard, sailed around the Balearics every week-end, so she would seem, in many respects, to be the ideal testbed for DP. In the meantime this new material will become yet another product available to sail makers who will, in turn, be armed with new facts, figures and performance claims to enlighten and hopefully not confuse their clients.

If all the claims about the use of Dyneema prove to be valid this material could be a winner. Time will tell.

You can wake up now�