Fortunately in recent years I’ve become used to wearing a wetsuit when I go sailing, but getting dressed in a buoyancy aid that includes body armour, strapping a large diver’s knife to my arm and checking the fit of a helmet that has a flip down, Top Gun style sun visor before being asked whether I had ever used an oxygen breather, provided some clues that I had stepped a long way outside of the normal world of performance sailing.

For me, today was about joining the team for a day’s routine training as they took another step towards the ultimate goal, the America’s Cup. It was also about getting ready for the Portsmouth AC World Series event on 23-26 July while the weather was going to ensure that everyone was pushed to their limits.

Aside from the dress code there were several points in Ben Williams’ (the team’s safety officer), briefing that brought things into a sharper focus.

“If there’s an incident there are two likely scenarios. You’ll either fall off the back of the boat into clear air, or you’ll go forwards and could be trapped underneath the trampoline if the boat capsizes,” he said.

“In the first case, even with the body armour, you’ll be winded after hitting the water – we’ve practiced and it can hurt. But apart from this, if you’re OK I want you to raise your arm and clench your fist. I’ll be looking for six helmets in the water and when I see this you’ll be low priority while I search for the others. Stay calm and eventually someone will come for you.”

I knew I could do that, but didn’t want to dwell on the idea of what hitting the water at speed could do beyond winding me.

“If you’re trapped under the tramp, try pushing it up to get your head above the water to get some air. I’ll be diving underneath to get you, but you may have to hang on for a bit. When I reach you I may push this oxygen breather into your mouth – just breathe normally. To get out I might have to cut your buoyancy aid off you. Don’t try to swim, just let me drag you out.”

If there was any upside to Williams’ chilling yet comprehensive briefing it was that he rattled through it leaving little time for reflections, but just enough for me to confirm I had understood. But there was something else on my mind.

Aside from the serious nature of these new foiling cats, the 25+ knots of breeze outside had showed no signs of dropping with a forecast for conditions to remain much the same for the day. My guess was that this was the top end for these machines, yet I had not yet been stood down and despite some friendly early morning chatter with various team members I hadn’t dared to ask what the most breeze they had sailed in was for fear of their answers confirming my suspicions.

The T1 training boat that they were using for these trials was the modified AC45 that the team has been sailing since last year and a boat they know well. Although she’s mostly the same as the original AC45s that were used for the last ACWS she’s fitted with new l section foils and some fancy powered control systems that allow the dagger boards to be canted inboard and out as well as raked fore and aft in order to mimic the boats that will be used in 2017 come the Cup. As a result, the first generation test boat is a few hundred kilos heavier and therefore slower than the AC45F boats that will be racing in the AC World Series events between now and the Cup.

Outside the harbour as we passed Spitsand fort just off Southsea, I was dressed and ready aboard one of the two 10m Scorpion chase RIBs as Ben and his five man crew settled down on a fetch across the Solent. Traveling at 18 knots on a fetch the boat was up on its foils as the crew settled into position. It was already wet as the waves broke over the side of the RIB and it was easily as windy as forecast. But while the cat was clearly traveling quickly, she looked more balanced than I had expected, riding effortlessly above the churned up surface of the white capped Solent chop.

Perhaps it wasn’t such a punchy call by the team to continue with plans to take me aboard during the day’s training. Perhaps, as is so often the case, I had over thought the issue while under estimating the crew’s skill, confidence and familiarity with their new sophisticated machine. With the likes of Ainslie, Paul Campbell-James, Nick Hutton, David ‘Freddie’ Carr and Andy McClean in the crew you couldn’t be in better hands.

And then all hell broke loose.

I had only glanced down for a moment to check my watch GPS, but in a split second our world had exploded. Instantaneously it seemed there was white water everywhere as the twin 225hp Yamaha outboards trebled their volume and pitch. Suddenly I was grappling to stop myself being launched out of the back of the boat before being hurled forwards two seconds later as we ploughed into the back of a wave. As I looked up I could see no sign of the BAR boat, had there been an accident, were we racing to the scene of a capsize? What had happened in those few seconds?

As I scanned around I found her, steaming ahead and pulling away as Ainslie and his team fired downhill in a white ball of spray. Far from being the earlier steady platform, T1 was now gyrating erratically around her leeward foil as Ainslie worked the helm to keep the wild cat on her feet.

As we drew alongside we were tracking T1 at 35knots while slamming into waves as if they were giant air bags. But there was no slowing down. As we skimmed the next few waves in a cycle that was clearly building we were launched into the air, the twin outboards screaming like a child who’s trapped their finger in a door as the props came clean out of the water.

Occasionally each gust would coincide with an awkward set of waves and the AC45’s bows would pitch down alarmingly while the windward hull would lift. Instantly and intuitively Ainslie would bear away to try to try to keep the boat under the rig as Campbell-James dumped the wing sheet. But a sharp bear away appears to do little to help lift the bows and no sooner had Ainslie borne away than he was spinning her back up towards the breeze as if controlling a motorcycle tank slapper after over cooking the brakes on the entry to a slippery corner.

Occasionally the bows would bury completely as if the boat had decided to dive, dive, dive. Traveling at up to 39.2knots, (their peak speed for the day), I was frequently convinced I was about to witness a spectacular crash. Yet time and again, somehow the bows came up and the boat took off as if someone had placed a brick on the accelerator pedal.

Hanging onto the aft beam as a passenger? Yeah right!

Minutes earlier I had worried about being able to stay aboard the AC45 on the skinny trampoline netting that hangs off the back of the aft beam – it was now clear I had had good reason to do so.

Instead my immediate concern was staying in the RIB. I had not expected Williams’ safety briefing to apply to the chase boat, but at 40mph it was obvious that hitting the water would be as comfortable as falling out of a pickup truck as it charged across a deeply furrowed potato field.

Even just coping with the spray at this speed was an issue. Try poking your head out of a car’s sunroof in the rain at the same speed if you think I’m hamming this up. Wearing sunglasses is cheating.

As we blasted downwind leaving Portsmouth’s Palmerston forts in our distant wake there was more to marvel at as the crew prepared for a gybe. Dropping the windward foil adds drag, spray and action but it also changes the balance of the boat, dramatically. Get the angle of attack of the new board wrong at this speed as its lowered into the water and as the horizontal foil hits the surface the cat will squirm and thrash around as if you’ve tried to grab it by its tail. And this, just at a critical point

Going to leeward to set up the new running backstay is a ballsy but necessary move for ‘Freddie’ the floater on board. In these conditions Cambell-James’ run across the trampoline shortly after the bear away into the gybe has started is another leap of faith. Once on the other side he takes the leeward wing sheet before also grabbing the helm to steer the second part of the manoeuvre allowing Ainslie make his dash for the new windward side.

With the boat still traveling at 25-30 knots this hand over requires the kind of precision and timing you’d need for a cycling slingshot between a pair of offroad unicycles. With the boat on the boil and the potentially dangerous apparent wind building quickly as the boat slows down, the timing and precision of each crew member’s move is crucial.

But time and again they pulled the manoeuvre off. And while it wasn’t always pretty, they made it safely every time.

At the bottom of their dramatic, full-on foam up of a run Ainslie span the boat through the danger zone and onto the breeze. Safely through and back on the wind the frenetic pace slowed down for all of us. Only then did I have a chance to acknowledge that aside from learning to keep the cat up the right way in seriously breezy conditions, this was also a training session where the team was logging and mapping the performance of the boat for a range of different settings.

Ainslie has an F1 style radio helmet fitted comms connection linking him with various people off the boat. As he coasted upwind at a relatively sedate 12-14 knot pace upwind, still foiling mind you, he’s talking over the radio to one of the coaches in our RIB about the run, the data and the setting for the next downwind run. To those of us watching, the previous 10 minutes was an exercise in survival, yet to Ainslie’s team it was another data run.

The day continues like this and gradually even I started to get used to the pace of play. The second half of the day concentrated on practice starts on a simulated ACWS course – another eye opener.

With the breeze still up in the 20s, the top reach into the first mark took just under 10 seconds each time. Admittedly the real leg will be longer, but not by much and in a few days time there will be a fleet of six boats hammering into the mark at 30 knots, neck and neck before they bear away to smoke off downhill.

In the end flat batteries that power the dagger board control systems forced a close of play and the team headed to wards the dock. I had not got aboard and while I remain desperately keen to experience what it’s like to ride an AC45F, for once I was quietly relieved that I hadn’t. At best I would have been holding my clenched fist in the air. At worst doesn’t bear thinking about.

For some, such a leap in Cup boat performance where boat speeds and have more than tripled and the risks kept pace, this is not only nuts and a massive departure from the roots of the America’s Cup, but is outrageous, unsustainable and unsafe.

But they’re wrong and in my next post I explain why.

In the meantime make sure you’re ready to visit, watch or listen to the action next week. There will be live TV on BT Sports, highlights on BBC and I’ll be reporting live from the wet side of the course on Portsmouth Live 93.7FM which will be streamed on line.