Roy,
Doug has shared with us the design tradeoffs that he and Graham played with such as whether to use a gybing daggerboard or a forward rudder, where to position the daggerboard, the design considerations of winches to drive the canting ballast strut, the power consuption, the tradeoff between canting ballast and trapeeze based shifting ballast just to name a few. I’m sure more will be forthcoming including pictures of the design process. I’m not sure if he plans to publish the plans as those are probably proprietary.
I am well aware of the history of winged keels on RC boats. I have talked to quite a few guys who have tried them. In general, they were attempting to replicate the function of wings on full sized boats which is to reduce the induced drag of the keel. However, given the relatively deep draft of RC boats on a scale basis compared with their full sized counterparts, the keels of RC boats are already quite low in induced drag and the induced drag reduction of wings is offset by the increased drag of wetted surface area. given the very low reynolds numbers of RC boat keels, this is completely predictable.
However, my idea is not to use the wings to reduce the induced drag of the keel but rather to provide lateral resistance with the boat at say a 60 degree heel. One could imagine that with that extreme heel angle, the keel will tend to want to just slip sideways. So by adding wings to the keel you introduce a foil that is better angled to produce lateral resistance. They are not being added to improve the balance but rather to counteract the sideslip. I will pay a drag penalty off the wind, but I am hoping that the lighter weight weill allow me to plane sooner than the other boats and make up for the extra wetted surface area.
The only canting rig boats that I am aware of in any class is Hal Robinson’s US1M and Dario Valenza’s M class “Phie”. I have talked with both gentlemen about their desings and have discussed my theories with them. Generally their responses were positive. Hal even indicated he would try it on his boat. I’m not sure if I misread Gregs last post. did he indicate that Jim Lavine also has a canting rig boat? If so, that makes 3 that I am aware of. My concept is closest to Phie. To Quote from their website:
“Phie is beyond doubt faster than any it has yet sailed against. The catch is that it is incredibly touchy to sail. It is difficult to tack downspeed if overpressed with the rig centred and it is impossible to sail with the rig on the wrong side. Canting the rig at the right time is critical as the boat is easily overpowered with the mast centred. Balance seems to be reasonable but will improve with experimentation of lead values. Balance shifts subtly as the boat heels.”
"Surprisingly, it is on a reach that the most dramatic bursts of speed are observed, regularly sailing around an entire race fleet. Upwind in light winds performance is marginally but consistently greater than the top boats. Downwind the acceleration is more dramatic due to reduced displacement. The boat accelerates instead of trimming down and nose-diving when overpressed. Acceleration out of tacks is phenomenal if the mast is canted during the tack. "
Dario expressly states that he has chosen to go with lower displacement and take advantage of off the wind speed and greater stability in moderate to high winds. This is my goal for the US1M.
I am not 100% sold that the wings will make the boat faster. I am being open minded about it. But based on what I have gleaned from others i think there is a possibility that it could fix some of the apparent pproblems with heeling the hull to such extreme angles.
I chose the US1M because the club that I belong to has a fleet of these (9 boats on a good day - 2 or 3 most days) and the class rules seem to allow for canting rigs. I think the performance advantages of a canting rig system would be greater in a fleet with a higher displacement to sail area ratio where minimum displacement was not controlled by the class rules. I have looked at many of the other classes and the M class is a possibility although it does not have as high of a displacement to SA ratio as I would like.
For the US1M, I am banking on being able to plane in lower wind speeds and carry the full sized rig up into higher wind speeds. In order to do this, boat weight must be reduced for a given sail area. This puts a premium on light weight hulls, and components. I am already at a disadvantage due to the additional weight of the canting mast mechanism. But I still feel I can put a boat in the water with 1 to 1.5 lbs less displacement than a typical boat. It will require substantial use of carbon fiber/foam laminates but I think it can be done.
I am not using any VPP programs in my design work. I am focussing on getting a mechanical system that works well and then I will experiment with positioning of the keel, rig, etc. I am buying a hull (most likely a Venom based on some recommendations) and sails, so my job is to build and perfect all the mechanical bits. As such, I am wrestling with similar design issues that Doug has been talking about.
For example, I have chosen to use a cam system like Hal Robinson’s to cant the mast (as opposed to the pulley system Dario uses for Phie). This system has the advantage of “locking off” the mast into the full cant positions such that the torque on the servo is zero. That will allow me to use a much smaller battery (saving weight) and sail longer on a single charge (Dario talkes on his website about power consumption). I will also use a swing arm sail servo that does the same thing (locking off the sheets to reduce torque on the servo).
I will probably drag my leeward rail in moderate to high wind, so having a clean faired deck will be key. The mast will be unstayed, so that will eliminate some of the deck clutter.
Like Dario, I will probably end up experimenting with different bulb weights and keel positions (for balance). I will also sail with and without the wings. I expect to be doing a bit of development once I get the boat in the water and am specifically designing certain features to be adjustalbe (mast position, keel position, etc).
It will be next spring at the earliest before my boat hits the water (the water gets sort of hard around here in the winter). And given my serious lack of free time lately, it may not happen until next year. But I will let you know how it turns out.
Will Gorgen
DSC00639.JPG
DSC00626.JPG