Flawed assumptions revealed... but it's all good.

Sooooo... we're still here!
We decided to stick around for a bit longer to have one more go at getting to the bottom of the Sailrocket puzzle.
We have made great progress with the overall handling of the boat and the new skeg has shown... so-far, that it dampens the boats evil traits down nicely.
Other issues have arisen with the huge amounts of leeway that have been discovered thanks to the onboard instrumentation and Pi research data collection system (literally, the 'black-box').
On Friday night we went around for a Braii (BBQ) at a local friends house. Besides being a commercial pilot and Namibian speed sailing record holder at over 40 knots... frank also builds the most amazing remote controlled jets to a degree of detail that is staggering. He's a pretty 'cluey' guy to have about and put on a Braii that made our simple affairs back home in Oz just look like a source of heat to stand around whilst we get mashed! Which, come to think of it, makes me wonder why I just put off going home!!!

During the smoking of the 'Angel fish' on the indoor braii (indoor... I told you these guys were advanced) I went through the problems we were encountering with leeway and what the possible causes could be.
Frank called up the following morning and said he had had a revelation. He came around to the container and explained it. He touched on many of the points we had already been considering and were aware of but he also went back to basics of the angle of the main foil. It should be mentioned that an assymetric foil can be very difficult to 'eyeball'. they often look crooked when they aren't. Whilst we have a simple jig to measure this (which we had a couple of times), Frank used another simple method of taping a staight edge to the Leading edge of the main foil and one to the trailing edge. The alignment of these two points represents the centre line of the foil and therefore... in many ways, the true centreline of the boat. when we sighted down this transit it became obvious that the foil was crooked. Now this wasn't so critical when we had a free floating rudder which would just align itself with whatever direction the main foil was going in and steer accordingly... but it matters alot now that we have a fixed skeg on the back. (Other aspects of sailrocket are also affected such as the beam/wing angle and the apparent wind angle information as these are all alligned to the boats centreline... when they should be to the foils centreline as this determines the direction that the boat is actually travelling in.)

After Frank left us with that little bombshell I went over and over Sailrocket trying to work out where we were crooked. No matter where I measured I couldn't find any flaws. Everything was straight as you like... but the foil was crooked. The problem came down to the pitch of the tapered centre board case. Whilst the chord of the centreboard is horizontal in relation to the boat... the centre-board case is angled at 4 degrees nose up to match the angle of the forward planing surface. as the centre-board case is angled to around 40 degrees to allow for the various adjustable angles of the main foil this means that the Leading edge of the foil touches the case further down towards the centreline of Sailrocket than the trailing edge. As our flat jig/template is also on a 4 degree pitch angle, it looks straight when it is held against the planing surface... but is actually crooked if it is held horizontally i.e. in the true orientation of the boat through the water.

This is quite a 'biggy'.

So we also recalibrated the instruments and the Pi research 'black-box' and found a few degrees discrepency. This all explained away about 7-8 degrees of the leeway. One big thing it didn't explain was the fact that for all 'normal' purposes, Sailrocket should have been bearing away hard every time it took off as the fixed-skeg was straight ahead whilst the main foil was pointing to leeward by 5 degrees. So why was the boat riding along nose high towards the beach making around 12-15 degrees of leeway... in a stable state? The only answer can only be that the foils are fully stalled and possibly ventilated. The boat is not hooked into the water yet.

Anyway, we have been going nuts over this all weekend and Malcolm has been going hard at modelling our new understandings and working through the solutions, implications and so on. The good news is that we have discovered a problem and have already dealt with it before anything serious has happened. We have come to understand the boats behaviour in the real world alot better. Whilst we are yet to get the boat working properly, the project itself is beginning to come on strong and one by one we are resolving issues. One by one we will get it right and bit by bit we will climb our way to 50 knots.

So once again I had to disappoint friends and family to sell my soul to speed sailing. I'm not going back to Oz for the high-school reunion this weekend. Some of my longest friends will be there. Old 'best-mates' whom I haven't seen for over twenty years. People who I first experienced the joys of wind and water with on small dams and ponds in the country. Oh well, this job simply can't be left unfinished... and it won't be.

Hopefully we can get out tomorrow as the afternoon high-tides are coming back around.
The main foil is now totally alligned on all axis and we will see what that does. This thing is going to kick-off one day or another. All the information is at our fingertips, the data, the pilot sensations, the audio, the video and the stills. In amongst all that is the worlds fastest boat.
Now let's start seeing it.

Cheers, Paul.