Aussie 18 on hydrofoils!

Note: this material is related to new technology being used in the full size world and its possible application to models. Please do not read if you are not interested in the subject matter.
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Another article in the new Seahorse discusses an Australian 18 footer that has been equipped with hydrofoils. It had been assumed by many that those boats were already so fast that gains would be minimal or non -existent. But the guys chose to do the foils differently than the Moth arrangement discussed in detail under General Discussion and Technology. Thes foils are dual surface piercing foils mounted on the wings of the boat and a rudder T-foil. The advantages the designers list for using these foils are:

“1) They are self regulating in ride height for a constant speed
2) As the boat accelerates the immersed drag is reduced as less foil is needed.
3)The faster the boat goes, the stiffer it gets in heel.
4)With a T-foil rudder, if the flap is adjustable, the ride height and the pitch angle can both be controlled-the latter helping to keep the bow up.”

The downside of this configuration compared to the Moth configuration is the extra wetted surface before the boat flys and the extra air /water interface with a third foil penetrating the surface and ,of course, (on full size boats) the ever present threat of foil ventillation when a foil is lifting close to the surface.
But the real plus for this type-and why those experimenting with model monofoilers should be interested is that these foils do allow an increase in righting moment ramping up the available power quite a bit with no weight penalty. And in models the great nemesis of surface piercing foilers–ventillation-- is not the problem it is on larger boats.
As far as I know there are no model monofoilers currenty being built using this system but the fact that it appears to work so well on an 18 shows that a model might be feasible.
If anybody is interested in discussing the technical details of applying this concept to models I’ll meet you under “Technology”.
UPDATE: In rc sailing several one off multihull SURFACE PIERCING foilers have recently been built in Europe- Biggest advantage is the reduction of complexity compared to an altitude controlled fully submerged foiler.
Doug Lord
–High Technology Sailing/Racing