The Pitch Pole – Some Insight to ETNZ’s Capsize

Emirate’s Team New Zealand capsized (pitched poled) during the starting sequence of race 4 of the Louis Vuitton Challenger Series semi finals against Britain’s Land Rover Ben Ainslie Racing (35th America’s Cup, Bermuda).

Some insights from Andy Claughton – Chief Technology Officer for Britain’s Land Rover Ben Ainslie Racing who was a research and design coordinator in past Cup cycles from 2000 to 2007 with Team New Zealand.

A pitch pole resulting from a bear-away is an unforced error.  I know I’ve had a few bear-aways not go to plan that have sometimes ended up with me joining the swim team.  Ben Ainslie did a great job of putting the Kiwi’s in a tight spot, with the windward starting mark being close-ish.  Is this the tightest bear-away for the wind conditions, we’ve seen from a team in the 35th America’s Cup so far?

Bear-away’s can be tricky.  Key points to a successful bear-away are:

  • Get your boat flat before you initiate it – hike out more, and or easy your sails to remove the heel.
  • Keep it flat during the maneuver – you can use a combination of things to do this:
    • Move your body weight to maintain a near flat heel
    • Ease both sails during the maneuver; the jib should be just of luffing so it has maximum pull while only adding a minimum to the heeling moment.  Easy the main rapidly to allow the jib to pull your boat around/down, but not add anything to the heeling moment that you can’t balance.

sources: America’s Cup Yachting World – Elaine Bunting, Stuff

Gust Response: Dynamic Balance to Windward

Gusts are always a challenge, and often we find our selves reacting.  It shouldn’t be the case, there is a pattern that you can build to be pro-active in the way you act to make the most of gusts.  There is both height and speed to be gained.  The following is provided to give you an insight in to what’s actually happening as a gust is upon you and passes.  From this I hope you can build a patten of action to respond to gusts going to windward.  Its something for you to absorb, ponder, and hopefully apply some actions to your sailing.

Wind TypesKey / Legend

True: The wind you feel when you are standing still
Induced: The wind you feel because you are moving
Apparent: The combination of True and Induced wind.  It’s what you feel while you are sailing.

Knowing how the apparent wind changes can give you clues to how your boat will respond and the actions you can choose to take.

No. 1 – Just Sailing Along…

wind: Steady
speed: Steady
apparent wind: Steady

righting moment: Crew hiking out to balance the sail force created by the combination of the wind strength and angle
heel: Constant / optimal (dinghy – flat)
tiller: Straight – a touch of weather helm (2-4 degrees)
heading: Steady
sail trim: Close hauled

No. 2 – Gust On…

No.2 - Gust Onwind: Stronger – gust on
speed: Steady – about to accelerate from the increased wind strength
apparent wind: Lifted – moved aft as the wind increased

righting moment: Crew hiking out more (pro-actively done as the first thing to counter the extra sail force of the gust)
Any heeling of the boat will naturally assist turning the boat to windward as the hull change shape in the water and the sail force is moved out board (to leeward) from the resistance of the hull in the water.
 Increased due to the increased sail force from the combination of the apparent wind moving back (more side on to the sail) and the wind strengthening
tiller: Actively allow the boat to turn to windward.  The more the boat heels the less you’ll need to do this as it will naturally want to turn to windward.  Make sure you don’t over steer to windward and lose force in the sails as your boat will stall.
heading: Turning to windward
sail trim: Ease as required to match what your righting moment and tiller movement can’t to against the strength of the gust.

No. 3 – Boat Speed Increased

No. 3 - Boat Speed Increasedwind: Strong – gust still on
speed: Going faster now – accelerated from steady
apparent wind: Knocked – moved forward, to be similar to before the gust arrived

righting moment: Crew hiking out more than steady still
heel: Decreasing to back to optimal
tiller: Pressure the same, which allows it to move to windward (turn you away from the wind) as the balance of the boat is influenced by the increase in speed and change in apparent wind. Some extra pressure (pull) may be required to adjust and hold the boat to the optimal apparent wind angle.
heading: Bearing away, turning away from the wind back to steady
sail trim: In close hauled again, and potentially adjusted to balance for the new stronger wind.

No. 4 – Gust Gone

No. 4 - Gust Gonewind: Eased back to how it was before the  gust arrived
speed: Going faster – accelerated from steady to match the gusts wind strength
apparent wind: Knocked – moved forward

heel: Decreases to windward / less then optimal
righting moment: Crew hiking out less than steady to counter act the lack of sail force because the apparent wind has gone so far forward
tiller: For planning boats such as skiffs bear away just a little to keep using that increased apparent wind to hold the boat at a higher speed for a little longer limiting the speed loss.  For displacement boats the closer you are to your hull speed, limit the bearing away by holding course as you’ll find your speed washes off fairly quickly and the gain in height is more valuable.
heading: knocked or steady
sail trim: Tight to squeeze all you can out of the apparent wind that is so far forward.

No. 5 – Boat Speed Decreased

No.5 Apparent Wind To Windwardwind: Back to steady – how it was before the gust
speed: Has dropped back to match the strength of the lighter wind
apparent wind: Has lifted and moved aft (back)
righting moment: Crew hiking out to balance the sail force created by the combination of the wind strength and angle
heel: Constant / optimal (dinghy – flat)
tiller: Straight – a touch of weather helm (2-4 degrees)
heading: Steady
sail trim: Close hauled

Putting it altogether

Apparent Wind - Close Hauled

A gust initial gives a lift and an increase in sail force which can be taken advantage of by gain height and speed if pro-actively balanced.  Hike out as much as possible to gain as much speed as you can.  If you don’t have any more weight to use to balance the boat them take any height you can gain, but be careful not to loose your boat speed or stall the boat.

As a gust passes you’ll notice an apparent knock in the wind due to your boat speed now being greater than normal for the amount of wind there is.  Sheet in tight, and bear away just a little to limit the lose in speed for that bit longer giving you a higher average speed.

With this knowledge the challenge is to go out with your crew and build a coordinated response pattern to maximise how you sail through every gust and thus gain many boat lengths on the others.