[FONT=arial]Some adjustments to the foil arrangement. In order to get a reasonable angle on the foils in the rotated position the angle of the axis of rotation had to be increased:
Rotated (foiling) position:
Vertical position:
Side view:
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A step forward and a step back on this boat. To begin with I realised that I had unnecessarily complicated the foil arrangement. The revised arrangement is shown below:
I also replaced the conventional wing with a mast aft wing sail. Testing of this revised configuration is shown below
The boat behaved quite nicely, but didn’t foil. It also didn’t point very high, or tack particularly well.
I decided that I needed to take a step back and understand the boat/sail behaviour with a simple keel and rudder. I will describe this in the next post.
I stripped the boat right back to the hulls and rebuilt it in a very simple arrangement. For the keel and mast I used the type of rc helicopter blades often used on RG65s. The setup allows for the sail and keel positions to be easily adjusted. The boat now only needs two servos (as opposed to 3 in the previous configuration, and 4 in the configuration before that). The camber on the wing adjusts with the degree of sheeting, as described in my “mast aft wing sail” thread. Some footage of testing in light winds below:
The boat behaved well, to the point where I was able to appreciate the quirks of this type of sail. To begin with, I found that the boat seemed to point higher with the sail sheeted out somewhat and a significant angle between the front element and the flaps, much more than I am used to with more conventional wings. I wonder if this has something to do with the small aspect ratio of the sail and the thickness of the chord? Secondly, the boat seems to tack in a very strange manner. It is a bit hard to describe, and I’ not sure that the clip adequately displays it, but it is as if the “sucked” rather than “driven” through the tack. Once again, the boat seems to tack better with the sail sheeted out somewhat. Perhaps prematurely, I compared the performance to a fleet of Lasers on a course, and to be honest, it didn’t match up very well. It was competitive down-wind, but miles behind up wind (although I hadn’t really worked out how to maximise its performance up wind by that stage). It is a bit early to draw too many conclusions regarding this boat/sail/keel configuration, as it is going to take some time to learn how to sail this boat. Over the next couple of weeks I’m hoping to test it under a range of wind conditions to see how it performs and work out how it can be optimised.