The air rudder is back!

The new planing surface is built and fitted. It has the same width as the last one but is shorter and much stronger. Having said that... I thought the last one was pretty strong as well.

I have tucked the rudder under further to give a more neutral helm and increased the gearing. The onboard camera has been set up to look more down the line of the boat to get a better idea of which way the boat is tracking. I have moved the wind instruments forward so that we can reinstall the air rudder.

We are now going at speeds where the air rudder should start to come into effect. During the last run we had apparent wind speeds near 40 knots and wind angles in the low to mid twenties. So far we haven't used or even tried the air rudder. We have installed it just to get used to it being there but so far we haven't been going quick enough.

For the next run I am going to install a stopper so that it can free rotate to a point and then lock in. This way, when the speed builds and the apparent wind moves forward, the rudder will begin to take effect and cause sailrocket to turn away from the beach. Once we establish the effectiveness of this air rudder we can begin to use it in earnest.

I believe that even as the boat was in the last run that we could have had a well controlled fast run if a few things had of been done differently. The aft planing surface broke under alot of force. We looked at all the broken pieces and the quality of the laminate was all good. It only broke because of the choppy water during the start of the run and it wouldn't have happened in flat water. But still it broke and if it had happened at high speed in close to the beach then the boat wouldn't have been making so much spray... it would have been making alot of dust and sand fly up.

I am now wondering about the forward planing surface... although it doesn't have to ride in the wake of another.

So the next run will simply be done with a more gradual sheeting in process so that SAILROCKET has time to accelerate. I need to be more considerate to what is happening in the water. In that last run I sheeted in hard just to make the boat bear away and from then on in the wing dominated proceedings and the foil and rudder struggled to catch up. You can see the battle going on as the boat is bucking and yawing around. I am simply stomping on the left pedal.

Everything we know about this boat and how it behaves says that she should have been trying to bear away...and yet she wasn't. If the wing was stalled as predicted... then why were we doing 38 knots and well over 36 for 200m?

Something strange was going on there that we still have to understand... and definitely have to avoid.

Those of you who windsurf will be familiar with what happens at high speed if your fin loses grip and the board spins out. You can still keep sailing but you are sliding down the course sideways until you either crash or manage to make the fin regain grip. I wonder if we weren't doing something similar on that last run. The rudder kept us from going fully sideways as did the boat geometry. There are a few clues in the video such as the foil lifting out of the water which suggest that the flow isn't properly attached.

Anyway, we have lots to think about.

I am not intimidated bythe boat at all and can't wait to get out there and go again.

We had a taste of what is to come on that last run.

Things are beginning to heat up.

Cheers, Paul.

 

Paul Larsen
Mobile: + 44 (0) 794 684 1929
E-mail: paularsen1@aol.com
www.sailrocket.com