Over the past month we have got in two final sails and have been busy tidying up loose ends in advance of the shipping. This has involved a lot of fitting and testing, meaning that the boat came back near dusk, giving some excellent photo opportunities.

Our top priority was the dolphin striker, which didn’t have the clearance we wanted. It acted as a really good reminder of just how much drag a blunt object can produce when dragged through the water. Figuring out just how to modify it to reduce the length by a useful amount proved trickier than anticipated: at its original length the UD carbon striker wire was seeing 14 000 microstrains (with a 1.5 dynamic factor). Also the eyes of the yoke connecting the striker wire to the restraining bolts had yielded slightly and the free edge buckled. We hadn’t been aware of this, and were in no hurry to fold the boat in half after several years work and a month before the regatta. Another factor was that, since the bolts pass through the centreline of our front cross beam, any change in striker wire geometry would mean a pair of new holes in the cross beam for the wire to pass through. These holes would have to be inboard of the attachment bolts, and therefore would create an open section in our previously continuously closed section tube. Torsional rigidity, free edges in compression, stress concentrations at the ends… it’s something we wanted to get right. After much debate, a handful of different concepts and the smell of hot calculator keys, we settled on a similar concept to the original, with the addition of a pair of doublers for the inside and outside of each of the new apertures.

On the day before our last weekend of sailing we were pleased to meet our latest collaborator: Sito Avilés Ramos from BALANCE Arquitectura Naval (http://www.balance-an.com/eng/htm/perfil.htm)

Sito has come up with a new pair of rudders for Invictus, which he laid up himself and flew over from Spain to fit. Our old rudders, while fairly light, were oversized and therefore draggy. However their biggest problem was that they simply had too much area behind the axis of rotation, which made for a heavy helm. The new ones look fantastic and have trailing edges sharp enough to shave with. The moment he arrived, Sito got straight down to the business of fitting and trimming the cassettes and the result is pretty swish. Paul reckons the new rudders had enough authority and a good neutral helm. The boat has never looked better.

Another improvement involved re-extending the “element 2” trailing edge, as our previous extension was lost in the capsize earlier this year.Following this Julien sculpted the shroud fairing whose absence has irked him since the first sail with the MkII wing. The result of exhaustive low Reynolds number CFD, we have dubbed his creation "Sputnik". We finally got hold of a TacTic, and with Sailrocket’s wind instruments and data logger, we have finally set about gathering useful data. Better late than never. With an operation such as ours, where we are frequently pulling a boat out of a trailer, assembling everything, and reversing the process after pretty much every sail, no matter how careful you are, small bumps are inevitable. And a set of hulls as lightweight as ours (200 gsm plainweave carbon over 6 mm core), minor damage accumulates. This simply has to be accepted as part of the package. And so we finished off with a general filling and fairing exercise on the undersides of our hulls, a handful of places on our wing.

Thursday saw Invictus' trailer backed into a container in Southampton. The next time we see her will be in the USA. We’re excited.