Mylar Sails

Report #5 - Ray Martin

On Easter Sunday, March 27, 2005, during the recent NSW state titles, Frank Bethwaite brought the proposed new mylar sails to Wangi sailing club for the assembled fleet to view. For we Victorians and South Australians, it was a valuable opportunity to see for the first time how this project is developing.

The program was to rig the sails in front of the club, while Frank showed the relevant features of them on shore. Craig McPhee, and Kevin Kellow would then helm Code Flag Z, while I sailed Too Dry Martinis with the new sails. Nicole Douglass was my crew. Half way through the sail we would swap boats and compared performance again. The time available to sail was limited due to the start of Heat 4 of the state titles.

Frank provided the sails, and supervised their rigging on Too Dry Martinis. Rigging was straight forward, with no changes to the mainsail. The new jib is pulled up on a halyard, which has a number of advantages. The hanks were a new experience, but not difficult. Frank pointed out that the luff tension was adjusted using the halyard, and that the tension made quite a difference to the sail shape in light airs. One obvious advantage of the halyard is that at a regatta, you could drop the new sails overnight without having to drop the entire rig. This will be some consolation to those that love their furlers. More on that later.

The Jib was fitted with three very light battens, which provided the jib with a small amount of roach (!). This roach puts the leech of the jib in exactly the right position relative to the mainsail, even when the jib is twisted open.
Both the jib and main are made out of a light grade of very flexible Mylar, with carbon fibre re-inforcing. The fabric appears to be lighter than the grade used in the 29er. Over all the sails are slightly larger than the standard sails.
Before launching, we tipped the boat on it’s side, and had a play with the various controls. Compared to the standard sails, the luff tension had quite a marked effect on bending the top section, and flattening the upper sail, without hooking the leech.

Out on the water, the wind was very light, mostly 4-6 knots, but with the odd puff to about 9 knots.
Upwind in the lighter airs, there was no speed difference between the two rigs. However, I did notice that I needed to pay attention to the mainsheet tension through the minor wind fluctuations to ensure that the leech did not either hook in the lulls, or blow too open in the gusts. This is similar to the behaviour of the standard sails, but exaggerated.

During the few significant gusts (9 knots), the new sails were noticeably quicker. With me hiking slightly, and Nicole sitting on the side tanks, the upper leech opened up, and the new sails pointed higher, and went faster. A similar puffs after the crews had been swapped, confirmed the result.
We didn’t have the opportunity to do any reaching. While running, we couldn’t detect any difference, whichever crew was sailing the new sails. However, I expect that the high roach will require care on a windy run to prevent the leech blowing forward of the mast, and causing windward capsizes.
My feeling is that despite the slight increase in sail area, the new sails are much more forgiving to sail. However, in light puffy breezes, to get the very best from the sail will involve careful attention to the mainsheet tension.

How the boat would behave in a blow remains to be seen, but I believe that upwind, the upper rig will blade out completely flat, leaving the crew to power up the lower sections. This would help to improve the upwind planing ratios that Frank is aiming for.

Concerns that the new rig will be more powerful and brutal are completely wrong. In fact, for an experienced Tasar sailor, the rig feels too soft. If I was to start using the sails as they stand now, I would begin the tuning process by tightening the diamonds to make the rig stiffer. The new design is that effective at de-powering.

A recent experience was illuminating for me. I sailed a 29er for the first time last weekend. To experience the properties of a rig similar to the proposed Tasar rig, in a hot puffy northerly wind off Mordialloc was illuminating. Two observations are relevant – Firstly, the loose leech rig was incredibly forgiving of the gusts. In fact, being a skipper with the crew playing mainsheet, I was almost unable to detect when we went through a puff, beyond the increase in speed that resulted. Our pointing angles were low compared with the Tasars, but our VMG was much better (our pointing improved significantly as I developed a better feel for the boat). The challenge in sailing a 29er comes from the narrow hull, not the rig. The rig actually tames a very unstable and difficult hull shape.

Secondly, I think that it will indeed be possible to drop the jib between races, and not have the jib blow overboard. This was possible even on the very narrow bow of a 29er. Further testing is required, but I think it will work. This is good news for those of us who love getting rid of the jib between races.

Back to my sail at Wangi. The clear Mylar is fantastic to sail with. An unexpected effect was that while I got used to the clear sails very quickly, stepping back into the standard Tasar left me with a definite feeling of claustrophobia for a few minutes. All that mass of solid white cloth blocking my view everywhere I looked!!.

Overall, I was very impressed with the new sails. I think the new rig will achieve the double, of being not only slightly faster, but much more forgiving. The new rig won’t make it any easier to sail well, but will make it easier to stay upright when you don’t sail as well as you would like.

In many ways, the new sails behave just like a Tasar, but more so. In other ways, they are light years ahead.

Posted 2005-04-06

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