Good looking new speed contender and correction
23 November 2010
I want to thank John for this lead.
There is a new speed-sailing project, The V-39 Albatross. http://verneyyachts.com/index.htm
This is a great looking project and I wish them all the best. At this time it appears that all the work is via computer simulation and models or prototypes are yet to be done. Comments that I make are based on what I've been able to learn from the website and I expect that there will be changes/refinements/advances made by the time the craft hits the water.
This craft appears to be well thought-out and has the potential for high-speed. There are a couple of points that I have some reservations about. Please refer to their website, the tab "V-39 Albatross", and its subheadings for this discussion.
With reference to "Stability and Control" note the force vector "LW". This is the resultant of the two wings and is the airfoil half of the "squeeze" I've discussed in earlier posts. (5 & 6 May, 6, 7, 9, 20, & 21 Sep. '08). Vector LW has to be opposed by an equal and opposite vector (when looking at the craft from the nose or tail). If we combine the vector forces "LK, LH, & W" it will be possible to get their resultant aligned with LW. The pilot will be in control of this by adjusting the wing positions and the rudder tip hydrofoil position.
When we look at the craft from the side, it gets a bit more complex. The forces will be changing with changing velocities and with the control settings needed to maintain balance. I see a potential problem with weight being used, as shown, to balance the craft. Once the hull is airborne, any increase in velocity will overcome the weight; this is supposed to be handled by force LH in combination with the water's drag, but I suspect that the craft will get "squeezed" up at the keel. This will tend to pitch the craft nose-up and we could have a back-flip such as what happened to Sailrocket.
Naturally, these are speculations on my part, intended only to provide a glimpse of how I view a craft in terms of the forces it generates. What actually happens will be the result of how well all the forces balance and will be controlled to a large degree by the pilot. All the forces have to balance or there will be an acceleration in some direction; the only direction we want an acceleration in speed-sailing is forward. When that forward acceleration is balanced (by drag) we have achieved our top speed (for the conditions).
26 Nov 10 Correction to above:
I had a brief email chat with Tim Clarke of Verney Yachts and he corrected me on my speculation about flipping the V-39 Albatross. Here is his comment:
"The weathervaning nature of the lifting surfaces means that the pitching of the main hull is largely independent of the wing-sail aerodynamics. The CG of the main hull (fore/aft) is placed to give the smallest rudder hydrofoil loads across the speed range. Cheers, Tim"
Sailrocket's cross-arm airfoil was fixed in place, so when the nose pitched-up, the airfoil's angle of attack increased, causing more lift and Paul went flying. On the Albatross, the airfoils are not fixed but align to the airstream, so even if the nose pitches up, the angle of attack and the lift won't change.