Ainslie, skipper of Britain’s Land Rover-backed BAR team and a former team mate of Spithill, had the edge in three training races between the two this week.
And the British boat is the one to watch in the competition of 45-foot twin-hulled catamarans, the 36-year old Australian said in an interview.
"Ben had the edge and would have won but it was close, we’re right up there. The local guys have a lot of support, which makes a difference," Spithill told Reuters in an interview.
The America’s Cup, known as the ‘Auld Mug’, is the oldest competition in international sport.
The ACWS is a preliminary event and provides an opportunity for teams to carry forward points based on their final ranking into the next stage of the competition, the America's Cup Qualifiers in 2017.
The racing will pit Spithill against Ainslie, who was drafted in as Oracle's tactician during the 34th edition of the Cup two years ago.
He helped them stage one of the most improbable comebacks in sporting history as they won 9-8 after trailing 8-1 to Emirates Team New Zealand.
But the two are also used to racing against each other.
"We used to go head to head inside the team with two boats and have raced each other a lot over the years. Ben has a strong team, good sailors and good structural design and engineers," Spithill said.
Dean Barker, the former skipper of Team New Zealand, is also competing in the event with SoftBank Team Japan in what promises to be a thrilling opening event of the series.
Sweden’s Artemis Racing, Team New Zealand and Groupama Team France are also competing.
"There are no weak teams, anyone could win. The last day of double points leaves it wide open. This is the strongest group of teams ever," Spithill said.
PORTSMOUTH BUZZ
The arrival of the teams and the spectacle of the AC45 yachts, which rise out of the water as they accelerate on a hydrofoil wing, is already causing a buzz in Portsmouth.
The staging of the ACWS on the waters of the Solent, where the Cup began in 1851, and Ainslie’s campaign to bring it back to Britain is expected to boost Portsmouth's marine and maritime industry as well as the local economy.
Ninety thousand spectators have bought tickets to watch the boats compete off Southsea Common in the historic naval town on the south coast of England.
The boats, which can travel at speeds of over 30 knots (55.56 km per hour) in the right conditions, are more like aeroplanes than traditional sailing boats, with vertical wings instead of sails, which are soft to the touch.
As part of his training, Spithill got his pilot's licence and said that controlling the catamaran is like flying.
"Its more like flying a helicopter, you’re doing three things at once, flying, balance and anticipation," he said.
The boats present physical challenges for the sailors, who work at maximum heart rate during relatively short races, pushing their craft to the edge of stability for maximum speed.
"I think British spectators will be blown away, they will love it. It’s like stadium sailing close to the shore and it's fast at around 20 minutes per race. I wouldn’t be surprised if we had a couple of capsizes or flips," Spithill said.
Nick English, who founded Britain’s Bremont Watch Company, timing partner for the 35th America’s Cup in Bermuda in 2017, was on hand to watch the preparations in Portsmouth.
"We are the first British time partner since 1851, which was around the Isle of Wight, now we’re back again in the Solent, which is phenomenal," he said.
(Editing by Alexander Smith and Toby Davis)
Share
