So a couple of guys pulled up for lunch in their boats.

[T2x]

I know it's not the same thing, but when I was running world record trials in RC boats, we could never get the 4 point hydros to run as fast as the 3points. We did have to run with a fin on one of the front sponsons though, to make them go straight.

Same issue in straights for the full size, or was it only because of the turns the Unlimiteds went with 3 points?

Not all hydros are the same...for instance the Switzer 4 point wing featured a fully functional air foil...unlike most other hydros and was considerably faster due to the ground effect management that it featured. The more traditional Power Cat version (see below) from the same era was no where near as fast with the same power......I don't think that 3 points get around turns better than 4 points and in fact some of the best hydros have wider tunnels and "mini pads" at the rear on either side of the center prop shaft. Since Wings have yet to use the turn fins (I just had a set made for mine) as used on most three points today, the question of which design turns better is till open for debate. Certainly no design that is completely airborne can turn at all until it is brought in for a "landing" or utilizes a fin as a turning fulcrum.

As far as scale models are concerned, there are many aspects that do not translate directly with size. For instance water and air density do not correlate to changes in scale speeds. ( Water is harder at 100 mph than at 25 mph with a 1/4 scale model).

By the way I believe that the Power Cat 4 point would have been a LOT faster with full length air traps.

T2x