America's Cup: what to expect when racing resumes

Oracle Team USA skippered by Jimmy Spithill in action racing against Emirates Team New Zealand helmed by Peter Burling during day 1 of the America's Cup Match. Photo: Getty

It seems like the longest five days ever waiting to get on with racing for the America's Cup.

There has been a lot going on at both Emirates Team NZ and with Oracle Team USA.

ETNZ has been making further modifications to their fairings, both on their hulls and on their wing. Fairings are designed to reduce aerodynamic drag. This is a big deal on these yachts because they travel so quickly. Any reduction in drag is an increase in boat speed. This is all part of the continual improvement approach.

OTUSA have changed mail foil (dagger-board) tips to increase the area and lift they provide. Their intent here is to try and improve acceleration, upwind height and especially tacking. They were back out on the water after only two days (and nights) in the shed and have been doing a lot of tacking practice.

In Races 1 - 4 Oracle was noticeably slower in their tacking with speeds dropping to around 17 knots in each tack.

Team NZ on the other hand bottom out at around 21 knots and are back up to full speed (around 27-28 knots) very quickly. This results in a loss of about 5 seconds per tack to Orcale and so is a major advantage for Team NZ.

With 10-12 tacks per race, the net gain to ETNZ is around a minute! Furthermore, it provides ETNZ with advantages to defend through tacking on Oracle and also advantages should they fall behind and want to attack Oracle in a tacking dual to get separation.

OTUSA have also changed their elevators (winglets) on their rudders and are changing the way they trim their wing. All of this is about catch-up. They have put nothing on their boat which is fundamentally different than what ETNZ already have. The question is will the chaser (OTUSA) have done enough to catch the leader (ETNZ). We will find out tomorrow.

The forecast is very much in the "Goldilocks" zone (not too windy, not too light) for Emirates Team NZ with all PredictWind models showing wind strengths similar to the first two days of racing.

The only major difference is that the wind direction will be south-westerly as opposed to the east - northeast winds from Day 1 and 2. This wind direction tends to get shiftier towards the top of the course and the lead yacht will need to be careful to not get out of phase with the puffs and shifts as they get towards the top third of the race track.