jim west wrote:

On the step around 20 to 30 MPH, the problem is pushing the beast up on

the step. You

could lift off at 60 to 65 MPH with 125 HP

Paul wrote:

Perhaps pumping air under there with a two cycle engine as suggested by
Howard is the way to go. If the hull is four feet wide and the contact
area is four feet long with a gross weight  of 2400 pounds that is about

one psi.

snip>

Strong side skirts about 1/4 inch long would
help trap the air and perhaps live through a crabbed landing.

Paul Lamar

I've seen video on TV of experiments done by either NASA or the military
on exactly that. It's pretty ugly to watch. For all practical purposes,
there's no directional control at all on the ground; I can't remember if
I saw them try it off water. By the way, it took a lot more than 1/4"
skirts. It looked like the plane was sitting on a hovercraft (because it
in effect WAS).

How about this as an alternative. Several years ago I had this
'brilliant, original' idea for an amphib hull shaped for perfect airflow
without a water step. Use a retractable, inverted 'T' shaped hydrofoil
to lift the hull out of the water for t/o & landing. While reading
through a collection of 20 year old aviation magazines, I ran across an
article about NASA experiments using 2 different hydrofoil designs on a
Lake Amphibian. According to the article, the Lake got on step (the
hydrofoil) much faster, had less trouble unsticking on t/o, and it
increased the max safe wave height by something like 18". The better
performing foil shape was a thin wedge like hydrofoil boats use. The
article implied that there weren't any down sides to the technique
(other than the obvious complexity issue).

I assume that we never saw it for the standard reasons we almost never
see anything new in general aviation: resistance by the FAA and pilots
to anything new.

Charlie

Flying RV-4 (Lyc)

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