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Sail-World.com : Etchells NSW States: Etchells Tuning Guide receives complete overhaul
Etchells NSW States: Etchells Tuning Guide receives complete overhaul
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As the Etchells return to offshore racing for the NSW and national championships, event supporter North Sails has turned their attention to overhauling its Etchells Tuning Guide.
It is quite a few years since class members have focused on event offshore racing. With a return to this type of course area many of the competitors are looking to revive their understanding of its challenges. Along with practice races and coaching sessions planned by event hosts, Royal Prince Alfred Yacht Club, studying the newly updated North Sails Etchells Tuning Guide will be a valuable asset to these competitors.
'Etchells owners have in recent times had the tendency to steer away from offshore sailing. The sailing has been mainly in flatter water and more convenient sailing locations rather than traipsing offshore. As a result there hasn’t really been many major offshore regattas for a number of years, probably 10 years. As class experts we thought we needed to get our heads around rig set-up and tuning and the sails, doing it early in the season so we could be in a position to best advise our market of how they should be setting up their boats and what sails they should be looking for,' Coxon said.
The principal goal for the study was to re-write the guide, taking into account the possible variances in trim and set-up between an inshore and offshore course. It was also recognised that perhaps the guide needed an updated presentation, 'sexing' it up with more information and photos.
The first version of the North Sails Etchells Tuning Guide was written in 1983 by North Sails principle, Michael Coxon. The format has stayed the same over the years, but the content has been regularly tweaked as trends and developments in sail design and rig adjustments have emerged.
What was ultimately achieved through this study of trying to prove why one Etchells was sailing faster than another, was numbers that have been related back to the Tuning Guide and the company’s sail models.
'We actually found a lot of things we already knew were correct, but what this exercise allowed us to do, in a controlled environment, was to find out that what we have trialled over a number of years has been pretty good. But what we have done with this testing is introduce a few more variables,' Coxon said.
The study started back in July when Coxon, aided by North Sails Melbourne loft manager, Noel Drennan, and Brisbane loft manager, Mark Bradford, devised a structured and analytical study of performance variables including sail models, mast and spreaders. The study comprised an intensive two-day on-water exercise followed by the subsequent review of the test outcomes and update of the Tuning Guide.
Ivan Wheen, Tom King, David Edwards, Billy Sykes, Geoff Bonouvrie and Peter Merrington were then co-opted to assist in the on-water testing.
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Launching out of Royal Prince Alfred Yacht Club, the first step was to spend half a day setting up the test boats rigs identically. The two similar keel weight and section, Bashford-built boats, were Coxon’s 940 and Wheen and King’s 925. As the team wanted to test a number of variables, the boats were bought back to basics establishing a level testing platform. The crew weights were evened up using water bottles.
After the morning briefing session the team then went offshore taking with them two identical mains and jibs which were used to establish identical performance across the two test boats. Drennan who came second in the 2011 Etchells World Championship and Tom King, gold medallist in the 470 class at the Sydney Olympics, were the helmsmen.
Once the variable testing commenced, King and Drennan got their boats going, did the nominated test and then swapped over before repeating the test to ensure the steering variable was taken out of the equation. For each test, one boat remained standard.
The conditions for testing were near perfect with very stable winds Coxon said. 'Firstly we focused on mainsails with the goal of setting the respective mainsails up so they flew the same shape checking from onboard and the coach boat, with photos of sectional shapes taken for later cross-reference. We quickly established that the identical mainsails on the same brand of masts set up to the same rig settings indeed didn’t take the same flying shape. As we suspected, the two masts had differences in their pre-bend which we addressed through tuning aft of the straighter masts mast step. Soon we had both mainsails flying shapes looking the same from both on and off the boats. Once this was established the two boat testing evened up to the point where all involved agreed the two boats performance was identical. We were now in a position to test varying sail models.'
The North Sails team then worked through their range of Etchells sail models looking for performance conclusions. They also played quite a bit with jib batten lengths and stiffness analysing the flying shape of the sail. 'We have options of different length and stiffness of battens especially in jibs. There are three batten options you can do in the top of the Etchells jib where you can have a full length batten and you can have a leech batten. They affect the support at the top of the sail which will affect the flying shape of the sail quite dramatically. It gives us options to change the sail shape quite quickly for changing conditions.
'You can also play with different length tabs on the luff of the jibs. Some of our models have single tabs while other models have both single and double tabs. You can make the sail fuller or flatter by playing with these tabs or hanks. We were testing for each jib model wind range and relative overlap; at what point is one faster than the other. At what wind strength did one kick in.'
'All of this has tended to be gut feel development over a period of time. We had not stopped and accurately documented it,' Coxon said.
The second section of the study was to test rig set-up. 'We were looking at its effect on rake, forestay sag and side sag in the mast for different conditions. We then started going one by one through the tuning variables, again leaving one boat constant, making changes to see if the variable was a positive or negative in the performance of this boat.
'There was no problem finding if the change was better or worse, the thing was to start ticking the boxes because we were trying to further develop the tuning guide. We were just as excited to find something was going backwards or forwards.'
A key finding from this testing was that the rig set-up had a significant impact on the boat’s performance. 'You can do so much with the rig that if you get the rig set up the same, the boats will go the same pace. If you get the rig wrong, the boats will go slower very quickly,' Coxon said.
At the conclusion of each test the participants were asked for their opinions. Co-ordinated photography with photos being taken on the boat at the same time as they were being taken by Bradford on the coach boat were added to the test data. Back on shore the sailors were also debriefed.
Coxon confirmed that while this study was prompted by the forthcoming offshore events, a lot of the information in the Tuning Guide applies to both offshore and inshore racing conditions.
'This guide is a work in progress. Even with what we are coming up with now, with the forthcoming offshore regattas, we will continue to learn and continue to update the guide.'
Even last weekend's Etchells Queensland Championship was used to test and fine tune the gudie information with Mark Bradford and Vaughan Prentice taking time out from celebrating Funky Cold Medina's win to record live race data from the two-day light air event to reconfirm or add to the already collected guide data.
The North Sails Etchells Tuning Guide is available for download from www.au.northsails.com
The 2011 Etchells NSW State Championship Notice of Race and Online Entry is available from the event website http://www.rpayc.com.au/etchells-states
The Etchells NSW State Championship is sponsored by Zhik and North Sails.
by Tracey Johnstone
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10:58 PM Tue 1 Nov 2011 GMT
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