Mylar sails

Report #4 - Brad Stephens
Report on Tasar Trial Rig, March 19, 2005

Frank has put together a trial kit:

Therefore, unlike Shane Guanaria’s test sail, this sail testing session was with the trial kit that Frank supplied.

The Sails

Jib
The jib now has roach ( maximum at top batten ) and three full length battens. The battens are known as “split jib” being half width of a standard batten style and are only 7mm/.25” wide. As a consequence the furler has gone and the jib is now hanked to the forestay with small plastic clips. The clips are a two-part system; one part webbed to each side of the sail and clipped together such that the forestay rides on the webbing. The halyad block was rigged inline with the forestay at the hounds.

The halyard was lead from the head of the jib up through the inline block and returned down the forestay inside the plastic clips. It was then lead through the forestay takeoff on the bow to a floating cleat that Frank had supplied for the trial kit. The cleat had a line attached at the rear which we lashed around the forward top of the dagger board case. This line ran up the bulkhead with the cleat sitting flat on the deck at the mast.

On hoisting the jib we tied a hitch in the line and lead it through the cleat so as to give a 2:1 purchase before cleating.

At least one club member did lament the passing of the furler but it was pointed out that the new jib leech profile required battens to support the roach and that this roach would produce a more responsive leech plus some additional area.

Mainsail
The mainsail now has only 5 battens with the first batten at approximately 25% of the luff length above the boom as opposed to just above the cunningham on the existing sails. Foot length appears to be a little shorter and as evidenced by the first photos of the new rig there is substantially more roach in the upper half.

The mainsail battens featured a threaded leech end fitting that could be turned by hand to change tension with a snap down plastic cover. Very neat.

Mast and Boom
As noted above Frank has put together a test kit including mast. On this rig the diamond wires had initially been set so as to touch the rig at about 30cm/12” above the gooseneck. However, as presented to me the wires had been lashed together around the front of the spar to in Frank’s words “Immobilise the lower mast …” as the initial approach to sailing with the new rig.

We experienced some difficulties with the rotation lever setup ( still standard ) but Frank has corrected this minor problem.

On the water.
The test sailing was conducted on the upper reaches of the Parramatta River, which is the major tributary of Sydney Harbour. Tasar’s sail locally from the Concord and Ryde Sailing Club on a stretch of water that is characterised by wind conditions that are extremely variable in strength and direction. The wind strength changes alone require constant movement from the crew.

A number of regular Tasar sailors from the club sailed with the new rig in the morning and the first impression of all was how flat the lower half of the mainsail was setting up on the trial rig. It was noted that both upper leech’s responded significantly more in the gusts then the standard sails. This was noted both by those onboard and observers in other boats. All appreciated the extra visibility offered.

During the afternoon race time the local Olympic Park site recorded SSE 10 knots wind speed gusting 17 knots for most of the race dropping to SSE 9 knots gusting 15 knots towards the end of race time.
The race course was essentially long upwind, short reach, long run run, short reach, 4 times around.
For the race I sailed with my son Nicholas who combined with me weighed in at 133 kg in measurement trim. In a fleet of 9 for the day we placed 2nd which would have been our typical placing against the fleet.

Given the wind conditions for the afternoon we would typically just manage to stay ahead of the much heavier ( 150kg/330lb + ) crewed 3rd place getter for the day upwind and skip away downwind. To the heavier ( 150kg/330lb + ) crewed 1st place getter of the day we would loose upwind but close up again downwind but with the overall gain during the course of a race being to them.

Overall, we seemed a lot more comfortable upwind in the gusts then usual ( this is centreboard up to the 87% immersed setting for us ) and faster downwind. Overall, our finish was closer to the first placed boat then I would have expected in the conditions.

I know that the above seems a little against the grain of Frank’s stated aim of benefiting the 145kg/320lb + crew weight but the rig as presented to me on the day was well suited to a light crew. I am sure that rig tune will make a huge difference to the potential benefit for the heavier crews.

I had been concerned how as a light crew we would handle the additional sail area but the flatter lower half of the mainsail combined with the more responsive top half of the mainsail and same with the upper jib leech actually provided an easier rig to sail then the existing rig.

As a guide to how flat the mainsail was setting up there was virtually no interaction between the jib and the mainsail all day, even with the jib sheeted on quite firm.
Trim wise with the mainsail I initially sheeted the mainsail in a fairly normal manner and progressed to more vang and looser sheet with the traveller at times ending up fully to windward with the boom on the centreline.

This seemed to provide a good balance of sheet tension and gust response in the upper leech of the mainsail.
We had provided our own shrouds for the test rig and had ended up taking them up a couple of positions but in hindsight could have done more of this as the new jib design seemed to require or would benefit from more rig tension then the existing jib. The other consideration is that with the hanked luff ( there are eight “hanks” with three spread over the luff area where the lower tufts are ) it’s going to look a little different with low luff tension and will tend to sag between the attachment points.

The new jib did seem to fit the tracks a little better with us sheeting off the middle clewboard position but as noted above we had to take our shrouds up a little so that might just have reflected a change in rake!

Concluding Comments
I think that we benefited from an initial rig setup that whilst great for us as a light crew was not suitably tuned for the target 145kg crew. That is, as a starting point for the next sailing session I would change the diamond tension to enable the lower part of the mainsail to set a little deeper.

Brad Stephens
March 21st 2005

With thanks to Frank Bethwaite for letting us play with the new sails, Tony Keevers the Class Captain at CRSC for organising with Frank and all the Tasar sailors at CRSC for their enthusastic involvement.

Posted 2005-03-21

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