You are completely correct Wayne. The farther aft that a horizontal foil is placed the more leverage effect it will have (like putting much less weight on a very high aspect keel and extending it much deeper in the water – it becomes a much lighter displacement boat with greater righting moments), BUT that is not the primary effect that you are trying to achieve from a T foil which moves in relation to the water in an entirely different manner (and T foils ARE true foils acting as a two directional lifting system – both up and down, not merely as a “leverage” plate akin to a cavitation plate on an outboard motor). The foils function is to “guide” the horizontal direction of the hull through the water and in so doing “dampen” the tendency to pitch, not beat it into submission, and as such there is not a great deal of difference in the actual effect of the foil whether you place it forward, up to approx’ 600mm of the transom, or 300mm aft (and any position in between). The leverage effect that you refer to is not of any great gain (or loss) as it only comes into full effect if the boat is not moving forward but instead stationary and pitching bow up then bow down on any wave action. Then the leverage of an extended aft foil will greatly dampen that pitch. Once there is any forward motion that same leverage effect is virtually nullified. I have said this before, you have to visualise the effects of a T foil in a global form and not in a two dimensional form to understand the way in which it is effective. Personally I find it difficult to relate the inclusion of T foils even remotely to any effect of waterline increase. T foils do improve the overall performance of a given hull, but then there are many things that improve a given hulls performance that are never looked at as undesirable. The example that you give I.E fix the T foil to the underside of the hull on a small vertical foil just forward of the transom so that the trailing edge of the foils came level with the transom, is one of the preliminary tests we conducted, and the resulting effects were exactly the same as we have achieved with the foils on the bottom of the rudders, and by doing it that way (attached to the underside of the hull) there could be no argument that there was any hull length increase. The only reasons that we didn’t go with that scenario was “sailer perception”. We found that most sailers would accept the concept of foils on the rudders but not foils attached to the hull.
Still an interesting argument and one that I am sure will continue to be debated into the future.