Mylar Sails

Frank Bethwaite summarizes the history of the Tasar class, and exlains the reasons for the change from dacron to mylar.

At the Darwin World Championships, it became clear that many Tasar sailors world wide were not aware of the steps which had been taken to change from Dacron to Mylar Sails.  I have been asked to summarise the history and reasons behind the change.

Brief History of Tasar Class.
1960 - Decision by a small group to create a new boat for ourselves. We wanted “most fun and highest performance within the strength of man and woman to handle in the water and out”. No existing boat was satisfactory. Most were far too heavy. A prototype was constructed. Many followed. We established broad rules which encouraged experiment, and called the new class ”Northbridge Senior”, later “NS14”
1966 - Development of flexible spars plus ability to adjust sail shape by manual adjustment. This development called for cooperation between the spar maker and the sail maker to achieve the desired range of shapes.
1967 - Development of datum mark system to enable crews to repeat efficient shapes.
1967/9 - Development of flexible wingmasts. This called for a second level of cooperation between spar maker and sail maker.
1969 - Development of fine-entry hull to which the highly developed adjustable wingmast rig was fitted. This boat is recognizable as the genesis of the Tasar.
1972 - Re-rig with larger sails (123 sq ft in place of 100 sq ft). Class called Nova.
1974 - Combined NS14 and Nova fleets (both development classes) exceeded 1000 boats.
1974 - Invitation from Ian Bruce (responsible for the Laser class) to Frank Bethwaite to join with Performance Sailcraft Inc “to produce a 2-person boat for the world market based on the Nova; the boat to be rigidly one-design.”
1974 - Tasar prototype constructed and trialed.
1975 - First production Tasar exhibited at Annapolis Boat show Oct 75; then at London and New York shows in Dec 75 – Jan 76
1976 to1978 - Tasars were produced by Performance Sailcraft Inc in Montreal, Canada; and in Banbury (UK). Fleets were administered and regattas programmed and races managed by Performance Sailcraft Inc (Montreal) or P.S.UK.
1977 - Starboard Products (now Bethwaite Design) started Tasar production in Australia Jan ‘77
1979 - Performance Inc suffered financial difficulties which became terminal. Gifted CEO of PSUK killed in auto accident. Tasar production in Montreal and London ceased. Reason - demand was only 400 per year. Fleet support of Tasar class by Performance Sailcraft ceased in both countries.
1979/80 - Fleets which had relied on Performance’ administration and support, ie those nearest to London in UK, and nearest to the New York-Toronto axis in North America, withered and vanished. Those which had never relied on Performance for support continued to grow, ie the more remote UK clubs; and the Calgary to Vancouver area in the Pacific Northwest. Australia, in particular, continued to grow strongly.
1980 - Designer licensed new builders in UK and North America.
1981 - First Tasar World Championships were held in Canberra. We loaned Tasars to the 20 app overseas entrants.
1983, 85 etc - Subsequent World Championships were held in Vancouver, Sydney, London, Vancouver etc. Entries of up to 120 boats (Sydney and Keppel Bay). Boats were chartered to overseas entrants.
1985 app - First Tasars into Japan.
1992 - First Japanese Worlds at Hayama. The total Tasar fleet in Japan was not numerous enough for local entrants plus surplus to charter to overseas visitors, so for first time overseas entrants shipped boats to regatta and return in containers, and have done so ever since.
1982 to 1996 - The Apparent Wind Revolution. Initially only in Sydney. Explosive development of hulls, wings and rigs of Eighteen foot skiffs. Shift from Dacron to Mylar reinforced warp and weft only, then to Mylar reinforced diagonally, then to beginnings of automatic rig.
1996 - 49er skiff selected as Olympic class. Apparent wind revolution became global.
1998 - 29er apparent wind skiff youth trainer introduced. Immediately licensed to builders world-wide and constructed in seven countries.
1998/99 - Beginnings of class obsolescence trouble for Tasar Class. Global annual demand for Tasars which had been steady at 10 to 15 boats per year for many years began to diminish sharply - down to about 5 per year by 1999.
1999 - First Effort to Revive Class. At the Tasar World Championships at Hamana-ko, Japan, I was asked by the class to experiment to see if a simple asymmetric spinnaker similar to that on the 29er could offer a new and attractive performance level. Experiment, trialing, measurement and analysis revealed that the Tasar design style cannot set enough sail to deliver consistent apparent wind performance across the whole wind speed range. It needs a stronger topmast to carry a bigger, masthead spinnaker. I advised the class that satisfactory apparent wind performance could not be achieved, and terminated the experiment.
2000/02 - Global demand for Tasars diminished to 3, 2, 1 per year.
2001/2 - Second Effort to Revive Class. I offered to build and trial a “Tasar Two”, a Tasar-style boat with 2003 dynamics, an automatic rig, and much higher performance. The proposal was that this new class would be nurtured through its early growth by the existing class. Support was strong, but opposition was so strong that I withdrew the offer rather than damage the social fabric of the class.
2003 - Third Effort to Revive Class. A Melbourne “Future Directions” workshop group headed by Jonathan Ross, Paul Ridgway, and Alistair Murray arranged promotional team-racing in Tasars at and throughout the Melbourne Boat Show together with other associated class promotional activity. The effect of this was so positive that strong local demand (16 in first year) and robust class activity have been restored.
2004 - Fourth Effort to Revive Class. To build on the local momentum already achieved and to promote the Tasar nationally and globally, the workshop group invited the ATC and myself as designer to become involved. They identified “re-imaging” the Tasar as a strong need, and asked me whether as designer I would consider achieving this with a more modern rig which would use Mylar sailcloth.

I welcomed this invitation for two reasons –
• The primary reason is that the cost of Dacron has been rising and suitable material is becoming progressively more difficult to source. This trend has already progressed to the point where a 29er Mylar main and jib costs about two thirds of the price of the slightly smaller Tasar Dacron main and jib. In my opinion it is inevitable that the class will be forced to make the change to Mylar before long. This invitation presented me with the opportunity to make the change in a deliberate and unhurried manner in the technical sense and in a time span acceptable to the class.
• The second reason is that I am now in a position to design a better sail.
I advised the class that I would do my best within the brief that the new sails would fit the existing spars.

Forward-Thinking Sailmakers.
Most of the original 1965 to 1975 NS14 and Nova sail development including the sails for the Tasar was by Mike Fletcher who with Ian MacDiarmid then ran the Elvstrom loft. Mike became a coach. Ian set up his own loft.
My younger son Julian, supported by Ian MacDiarmid’s sail development, has been central in the 1982 to 1996 apparent wind revolution which became mainstream with the selection of Julian’s 49er as an Olympic class.
For the 2004 to 2008 Olympiad all sails for both the 49er and the 29er are produced only by the Neil Pryde loft in Hong Kong with which Ian MacDiarmid is associated.

The Dynamic Considerations.
When I designed the Tasar rig in 1974/75 my core beliefs were –
1. That the structure of the typical wind was about 50% lull or “base wind” and about 50% gust about 40% stronger.
2. That the speed within each gust and lull was reasonably steady.
3. That while the period of and the duration between gusts and lulls varied at random, the mean was surprisingly consistent at about 30 seconds gust, 30 seconds lull at all wind speeds.
4. That it was the business of the crew to set the optimum sail shape for the wind of the moment.
5. That it was the business of the rig to hold whatever shape was set until next adjusted. The Tasar rig is a relatively stiff manually adjustable rig which reflects these beliefs.

What I have learned since 1975 is –
6. 1 above is correct.
7. 2 above is wrong. 2 above describes only the steadiest winds. Most winds are more unsteady. In these the speed within both gust and lull can vary by up to 20% every six to eight seconds.
8. 3 above is correct, but again, the overall steadiness of the wind is a factor. In the more frequent and unsteadier winds the boundaries between gusts and lulls tend to become more blurred and are harder to read on the water..
9. 4 above is wrong. We now understand (7 above) that significant wind speed changes occur too quickly for any crew to adjust to.
10. As a result, 5 above is wrong.

More “automatic” rigs which reflect this new knowledge are now proving both easier to sail and to sail substantially faster.
Typical of these modern automatic rigs are say the 49er and 59er. Both are characterized by a small-diameter lower mast held rigid by lower stays, and a topmast flexibility, upper mainsail cut and batten stiffness matched so that in the gust the upper leech opens and flattens first at the top, the opening of the leech and flattening spreads down as the wind speed increases, and the sail ”fills up” from the bottom upwards as the wind speed decreases.
In designing the new Tasar mainsail I could not change the stiffness of the whole mast. But I was able to change the shape and the cut of the upper mainsail. I was able to change the battens, and by playing with the diamond stay tension I was able to control the relative stiffness as between lower and upper mast.
These measures have taken the sail a significant way toward the modern thinking.

Two further points –
In 1975 I did not understand that light air (glassy water surface) implied a linear boundary layer 5 to 6m thick in which a twisted sail will always be faster (except straight downwind). The Tasar Dacron mainsail does not twist readily. We have tried to make the mylar sail twist more easily. It should be easier to handle and therefore faster in drifty conditions.

The Tasar is just short of windward planning capability in stronger winds when it is pointing at a reasonable angle. (Sail a Tasar three up all hiking in a blow and you cannot stop it from windward planing.) I had hoped that by extending the jib foot to the deck and by using a cuff on the mainsail I could improve the ratios sufficiently to make routine windward planning possible for the normal crew. We tried, but it proved to be one step too far.
For this reason I have settled on a simple mainsail which has no cuff. The good news is that the simpler sail is substantially less expensive.

The Design Interpretation
The notes above are what I discussed with Ian MacDiarmid. We agreed the shape of the mainsail leech, and I left the rest to him. The sails you see are his interpretation of my dynamics.

Australian Trialing
I no longer sail at competitive level, so asked others to evaluate the new sails.
For about two months, I loaned the sails up and down the coast and to Victoria to all who asked, on condition that they reported. Reports were published globally. Early reports and pics are on www.tasar.org. All subsequent reports went onto tasarsailors@yahoogroups.com. Broadly speaking, nobody sailed slower, but these “one day stands” were insufficient for either the crews to develop any familiarity or for any clear difference to develop.

For the next two months Graham Hanna and Liz Kemmis offered to use the sails regularly in the pre-worlds practice racing programmed by Balmoral Sailing Club. Their reports are on tasarsailors@yahoogroups.com and www.tasar.org.
With this opportunity to become increasingly familiar with the sails, and with regular high-level competition from Rob and Nicole Douglass a pattern developed –
• If they started last (to begin with Ghaham let the standard boats go and followed), they sailed through the fleet (usually 10 or 11 Tasars) and finished second to Rob and Nicole.
• Later. they usually started well and almost always won, and this was true from drift to 20 knots.
• I encouraged him to tighten his diamonds “to make the topmast do more of the work”. The sails stopped feeling “springy” and sailed slower. When he slackened his diamonds to his “standard” (able to pinch to the mast 30mm above the whisker pole attach fitting) the springy feeling and speed were restored.
• Because of their springiness (upper leech more mobile) the sails are easier to handle in unsteady conditions than the dacron sails. (A number of early reports by lighter crews comment on the unexpected ease of handling).
• They appear always to be faster on the broad reach.
• Another unexpected factor is that because the leech of the jib is visible, crews are able to be certain of jib trim and will probably trim jibs better in future.

At a late stage I extended the length of a whisker pole 100mm. The length of the jib foot is a little longer and this extension restores the geometry.
We advised sailors world-wide that Graham would have the sails in Darwin for overseas sailors to look at and sail with as opportunity offered.

Global Trialing
Following Darwin, I loaned the sails to Fumio Kaneko to use and show in Japan, and arranged for two further pre-production suits to be made and sent, one to Richard Spencer in Vancouver / Seattle and the other to Mandy Stock in Lymington. There will be no further pre-production sails.

In Vancouver, a pattern broadly similar to that which developed in Sydney seems to have repeated. Richard Spencer advises that he sailed for four or five days with different crews and sensed no performance difference. Then came a day with four races, and in every race he was first at the first mark and went on to extend his lead. He has now loaned his sails to Jay and Lisa Renehan in Seattle, who will make them available to the fleets in Seattle and Portland.

I have encouraged Mandy to loan her sails to Egbert Gerlich in Germany. We await reports from Fumio and Mandy Stock.

Summary
I think that the above summarises what we know at present. The new sails –

• Re-Image the Tasar by giving it a more modern look. This will extend the life of the class by ten years at least, probably fifteen.
• Are easier to handle and sail at best about 5 per cent faster.

The Formal Adoption - The Three Key Requirements.
Prior to the World Council meeting at Darwin I described the prototype sails to the ISAF Technical Manager, received “in principle” approval for what ISAF regard as a specification change, and advised the World Council..
At the Darwin Tasar World Council meeting, the council voted to approve the use of mylar sails. With this vote, two of the three key requirements for adoption were put in place -
• Approval by the designer,
• Approval of the change by the class.
- and with these the class adopted Mylar sails.
• Following this approval, full manufacturing specifications have now been developed by the sailmaker and loft, and on 12th Aug 05 I filed a copy of these with ISAF, who very reasonably ask for complete specifications, which they hold as the final evidence in event of any dispute about conformity. With this lodgement we have completed the three key steps. Confirmation of approval by ISAF is expected in due course.

The Final Steps.
What remains to be done -
1. For the Class through the World Council to initiate and carry through the minor rule changes re forestay without furlers, jib halyard arrangements and longer whisker pole, which will make the new sails convenient to use.
2. For the class to decide how the change should be implemented.

I have no doubt that you will hear from the Exec Sec before long re the rule changes and the implementation.

Practical Matters.
Source. All sails will be made at the Neil Pryde loft near Hong Kong, with which Ian MacDiarmid is associated. This will give uniform quality world-wide, together with a substantial reduction in price and generally uniform prices world-wide.

Availability. It is expected that the test production sails from the Pryde loft will be in Sydney within a week or so. Initial batches will be delivered in late November or December.

Price. The prices below are indicative. Final price will not be known for a few days, but will be very close. If mylar sails were available now at the indicative price, we would sell them in Australia, and understand that our licensees will sell at similar prices world-wide at -

Class Royalty. The class did not respond to my enquiry about this, so Julian and I have included in the above price a $US15 per sail royalty.
• Of this $10 will find its way back to the class.
• Bethwaite Design will administer the other $5 in class promotion eg regattas, trophies etc.

I compliment the class on their vision in initiating this change, and thank them for their support.

Frank Bethwaite,
Designer
Posted 2005-08-18

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