Jump to content

To quote the duke of Wellington, that was a 'Damn close run thing...'

Posted by sailskkf, 17 March 2011 · 317 views

Posted Image

The 2011 single handed round the island race saw a very close duel between the two JS9000's. Using GPS Action Replay we can deconstruct the results...

The race between the two boats ended on a knife edge. Having changed lead twice on the beat, Agattu was able to demolish Bandersnatch's 600m advantage until, level and 500m from the line, Bandersnatch caught a gust and was able to drive down to the finish 30 seconds ahead of her rival.
The two boats are not identical and this helps to account for some of the idiosyncrasies which make for such tight racing. Agattu is the newer boat, built by Admiralty yachts in Singapore she has a larger Jib and a roached main which lend her a larger than standard upwind sail area. She also possesses a suit of 3 asymmetric spinnakers, the smallest of which is the same size as her rivals'. Bandersnatch, on the other hand, built in Australia by the original desinger, John Swarbrick, may well be the lighter of the two hulls. She also has a back-stay which Agattu's roached main forbids. This, I feel, offers a crucial upwind advantage in heavy conditions, despite her smaller sail plan.

Posted Image
For those that aren't familiar with Polar Diagrams they represent the speed of a boat at any given angle to the wind. They are used to identify sail & trim combinations that offer better speed. Obviously, where round-the-cans racing is concerned the angles sailors are most interested in are +/-35 degrees and the angle producing the best Velocity Made Good to the leeward mark. In yachts which sail slower than the wind speed this angle is very often a dead run. For those that sail faster, like Catamarans' and skiffs the angle varies depending on wind-speed and the judgement can often be very difficult.

This years' Round the Island saw almost perfect conditions. A 16 knot breeze from the North. This allowed the yachts to make the South end of the Island in one tack on a near close-hauled course. 3 tacks at the back of the island in a wind convergeance zone and a reach back down the dam to the finish. The only thing that could have gone better would have been more wind on the reach and a shift further North. This came through for those at the back of the fleet but the front runners had moderate to light breeze on the way back.

The peculiarity of the course played into Bandersnatch's hands on the beat. I started at the weather end of the line and worked hard to claw to weather early in the beat. The boat doesn't point as well as the other boats and can struggle on this angle of sail. This tactic paid off as Agattu made efforts to claw to windward at the southern end of the island, Bandersnatch was able to foot off (trying to avoid an anticipated hole) at over a knot greater boatspeed. According to the polars she seems the faster boat on this point of sail. Nevertheless Agattu had taken the lead again by cutting close to the island - the hole hadn't been as bad as I thought!

Coming around the North end of the Island the boats were 80m apart with Bandersnatch in front for the second after a tacking duel behind the island. Difficulties with halliard's saw Agattu (remember there was no-one at the helm) meander to windward of the rhumb line. By the time she was back on course, 1 km from the turn, she was 255m behind.

Agattu, despite the gap, is fast off the wind. Riding gusts is vital in these boats - it's like catching a wave when you watch it happen. And on one of these waves of wind Agattu posted a speed of 16 knots tearing into the gap. At the same time my 13.25 knots on Bandersnatch was feeling very paltry as I watched the meters vanish!

With 500m to go Agattu had actually regained the lead and was 2m ahead. All things being equal as the leeward boat she had the potential to reach into the finish faster on the shallower angle. Just then a gust came through and caught me first. Catching that gust and accelerating from 10 to 13.2 knots, before the same breeze reached Tielman on Agattu, saw me safe across the line ahead of him. Both boats finished just shy of the Pacer 27 1hr 37min record.

April 2017

232425 26 272829

Recent Entries

Recent Comments