It is very difficult to draw conclusions from anything in America's Cup racing, other than the final nine-race series of the America's Cup itself. Everything up to that point is smoke and mirrors - or is it? It's just so hard to know how much of their hand the teams are showing. You can be pretty sure that the smaller teams are trying their damndest whenever you see them racing in the Louis Vuitton Acts. But as for the ‘Big Four'? We really don't know.

BMW Oracle, Emirates Team New Zealand and Luna Rossa all raced brand new boats in the recent Louis Vuitton Acts that opened the 2006 season, the match racing round robin of Act 10 and the five-heat fleet race of Act 11. What does seem clear is that these new boats - purpose-built to the Version 5 rules as opposed to being Version 4 boats modified to the new rule - are a click faster than their old boats. If they weren't, that would be a real worry. It is worrying enough, however, that they don't appear to be any faster than SUI-75, Alinghi's wonder-boat which stomped all over the 2005 Cup season.

But then we don't really know, firstly how hard the big challengers were pushing their new boats, and secondly how much more speed there is to be gained from their new boats. America's Cup Class yachts take a notoriously long time to work up to full speed - always months and sometimes years - so there could be a lot more potential than we are seeing yet. The two teams that I think are trying their hardest are Luna Rossa and Emirates Team New Zealand. Last year both teams suffered for pace in their 2003-generation boats and both the Italians and Kiwis were itching to get their hands on the new hardware. Alinghi's skipper and tactician Brad Butterworth sees them as from the same family as the Alinghi boats, and he doesn't seem too worried by what he has seen. But then again SUI-64, the Alinghi boat that trounced the Kiwis in the Cup final of 2003, was seen as a very developed evolution of NZL-60, the dominant boat of the 2000 Cup.

Perhaps a good evolutionary step is all that is required to win the Cup in 2007. Clearly BMW Oracle doesn't think so. In my last column I echoed the speculation that perhaps lead designer Bruce Farr and his team had gambled on a twin-keel arrangement below the waterline, anyone who was in Valencia is now less convinced of that. You could take a bit of a peak at underwater shapes as the yachts exited Port America's Cup at midday each day for the 2pm start. Looking down the impressive new Foredeck Club from 10 or 15 metres up, and with the benefit of Valencian sunshine to light the water, it seems that USA-87 is a more conventionally keeled and ruddered boat than was first thought.

However, the American boat's ability to stop and to accelerate at will does point to something unusual going on below the surface. Butterworth believes the Americans' choice to situate their mast around 2 metres further forwards than most Cup boats could be contributing to their ability to accelerate out of tacks and downspeed manoeuvres, but it is not the whole story. While it didn't always show blistering pace in a straight line, USA-87's manoeuvrability certainly offered skipper Chris Dickson some useful tactical options. In the pre-start he was able to snap round inside other boats, and in the most decisive move of the whole of the match racing he used his boat's tight turning circle to turn the match against Luna Rossa in his favour.

This epic match took place in the final flight of races in Act 10. So close were the standings that things were likely to have to be broken on the tiebreak, as they were so often in last year's Acts. The only team still fully in control of its own destiny was Luna Rossa. If the Italians won their final match against BMW Oracle then they would win the Act, no question. Other teams would have to rely on the outcome of other matches going on around them to see if they would win overall.

Luna Rossa's young Australian helmsman James Spithill controlled the start beautifully, forcing Chris Dickson to tack away - unable to match the speed of ITA-86. Just two minutes into the match, the yachts converged and Luna Rossa passed clear ahead - advantage Italy. There was never more than a boatlength's advantage in the Italians' favour - not much, but often sufficient to win a tightly-fought Cup match between two teams that rarely make mistakes.

However, close to the first windward mark, Dickson pulled a masterstroke when he ducked the Italians to claim a late right-hand advantage. He threw the fast-turning USA-87 into an immediate tack, now sitting on the windward hip of the Italians. Spithill believed he had the speed and momentum to tack across the face of the Americans but it was an expensive misjudgement. Dickson was forced to take evading action and the on-the-water Umpires duly awarded a penalty against Spithill. USA-87 rounded the windward mark first and Dickson defended the lead to the finish. By the time Spithill had taken his 270-degree turn penalty, the Americans won by over a minute, and went on to win the Act. The American victory was not down to raw speed - the Italians looked every part as quick as their rivals - but it was Dickson's superior manoeuvrability that played a strong part in their success.

Earlier in the day in Flight 10, Luna Rossa had been involved in another humdinger of a match, this time against Emirates Team New Zealand. There was nothing between these two boats for the first leg and a half. As they duelled downwind, the Kiwis tried to roll over the top of the Italians who themselves had just made a passing move, but James Spithill engaged Dean Barker in a slow luff. As both boats rounded closer to the wind, the lightly-built spinnakers loaded up, until the red kite of NZL 84 exploded. As the shreds of sailcloth blew across Luna Rossa's rig, the Kiwis' tattered spinnaker had now caused a rules infringement, and the Umpires duly slapped a penalty on Barker. Luna Rossa took a narrow lead through the leeward gate, and led their wounded rivals all the way to the finish.

It was a torn spinnaker during an ambitious gybe that also lost the Kiwis a tightly-contested match against BMW Oracle. Ever since the debacle of the self-destructing boat in the America's Cup Final of 2003, team manager Grant Dalton has sought to re-establish the Kiwi reputation for reliability. When things break, the New Zealanders are very tough on themselves, but again it was breakage that let them down in Act 10, a regatta they most likely would have won but for those two shredded gennakers.

What of the rest, the B division that are struggling so desperately to get on level terms with the big teams? The Spanish team Desafío Español is one that promises so much and yet delivers so little. Karol Jablonski, the polish skipper and his crew, succeeding in taking a major scalp when they beat Luna Rossa. But then they go and lose matches to Areva Challenge - racing one of the oldest boats in the fleet - and Team Shosholoza, one of the most inexperienced crews in the fleet. Such inconsistency is baffling, and yet their 5th place in Act 10 confirms their status as the team still most likely to threaten the big guns. Perhaps their recently launched yacht, ESP-88, will give them the magic they are looking for, but will it help them overcome the team's penchant for picking up penalties for reckless manoeuvres during the pre-start? Unlikely.

For a team that nearly didn't make it through the winter, the Swedish Victory Challenge sailed very respectably in Act 10, being pipped to 5th place by the Spanish in their final-heat showdown. For a team that could do nothing other than trip over its own shoelaces in 2005, the Italian team Mascalzone Latino-Capitalia Team also showed great improvements. Last year was a year of hirings and firings that was reflected in the team's poor performances on the water. After a winter of training and with the appointment of Jes Gram-Hansen as the Danish starting helmsman, Mascalzone look a much sharper unit than before.

While Mascalzone has profited from recruiting outside of Italy, Team Shosholoza has bolstered its afterguard with two Italians, Tommaso Chieffi as primary helmsman and former Mascalzone driver Paolo Cian as a pre-start helmsman. RSA-83, the first Version 5 hull to be launched last season, is showing good bursts of pace and the South Africans are reaching a level where they would probably be disappointed by their 8th overall in the match racing.

For +39 Challenge, merely turning up for the regatta and earning a wage was a bonus. This is a team that has been in dire financial straits, with Iain Percy and his crew working without pay for many months. They have the oldest and widest boat in the fleet, and mainsheet trimmer Rafael Trujillo described the boat as a submarine under 10 knots of breeze. Whether you choose to describe ITA-59 as a submarine, a pig or a dog, it is not quick in light to medium conditions, although Percy remains undaunted. This is a young team with more Olympic medals than any other, and what they lack in raw boatspeed they make up for with massive self-belief, and 9th place was a victory of sorts for this under-resourced team.

At least Areva Challenge - the French team formerly known as K-Challenge - now have the resources to see them through to the end of the Cup but they will have to wait until November before they can start sailing their hull, currently being built. The former Cup winner from 2000, FRA-60, was a shrewd purchase for the team in 2004, but Thierry Peponnet's team will find it hard to move to the next level until they start using more up-to-date hardware. A 10th place will be disappointing for the team.

Jesper Bank makes no secret of his frustration with GER-72, and you get the sense that the double Olympic Champion won't really be able to move on with the programme until he gets his hands on the new boat, GER-89, which they will start trialling in late May but which will not be ready for the final Act of 2006 in late June. As for China Team, well they never came close to beating anyone, but as skipper Pierre Mas points out, the aim is to imbue his young Chinese recruits with America's Cup experience for a more serious assault on the Cup in the future.

The fleet racing continues to excite sailors and spectators more than the match racing, and Louis Vuitton Act 11 was an interesting three days. Victory Challenge, with four-time Olympic medallist Baron Sebastian Coe riding in the 18th man guest spot, dominated the first race as the Big Four struggled to assert their authority in the painfully light and fickle breezes. But when the wind blew stronger for the second day, so too did the cream rise to the top. Alinghi ended up winning three of the five races. Helmsman Ed Baird commented at the conclusion of the fortnight's racing:  "The biggest thing we have learnt in the last couple of Acts is that the new boats have similar speeds in these conditions and we seem to be going at the same sort of speed. We're pretty happy with where we sit and we're pretty happy that the strong teams have spent one of their boats and seem to be going at the same speed as we are." Oh dear!