The following text, kindly supplied by Robert Imhoff, describes the work he has done with the first two Aero-Hydrofoil prototypes and his goals for the third. Should you wish to find out more, here are the inventor's contact details:
Bob Imhoff
2062 Hanscom Drive
South Pasadena
California, USA 91030
telephone / facsimile (1) (323) 256 0152.
I used the term Aero-Hydrofoil to show that my work was derived from Bernard Smith's, and as an acknowledgement to Mr Smith of his incredible work. He probably has done more to stimulate design innovation in sailing than anyone else.
My first prototype has good sailing characteristics on all points of sailing. Unfortunately I never got enough wind while testing to get it up on the foils. It would have exhibited good speed since its foils got passed onto the second prototype which did make some impressive runs (with the wing-sail stuck 3/4 of the way up the mast). Since I neither clocked the wind nor the boat speed I'll make no claims.
These prototypes did verify what I had already learnt earlier from my work with models, that I have succeeded in aligning the forces that drive the boat such that the wind (no matter the strength) cannot flip the boat, with or without anyone aboard. What this means is the wind can't heel it over. It would be possible to hit something - either a solid object or a big wave - and flip the boat, but at this stage I consider that it be a pilot error, not a design flaw.
I am now working with a third prototype. Here are the design goals for this craft:
# It will carry two people.
# The wind can't flip it (as stated above).
# It is lightweight, the current prototype weights about 170lbs.
# It will never be caught "in irons".
# It's fast (since my parts are fairly crude and I'm now only running 100 square
feet of sail, it takes about 15 knots of wind to "lift off"). The sail
area will be increased after I develop the boat further. Incidentally, my second
prototype had about 230 square feet of sail and I'm getting as good or better performance
with my current prototypes.
# It will run in 18 inches of water and through weeds and can be beached
(this depends on the foil configuration being used).
# It is self steering (lock the controls down and it will stay on course relative
to the wind.)
What I am aiming for is a small "hot rod" day sailer that could be produced inexpensively. It would carry two people, weigh less than 200 pounds, easily sail 25-35 knots, be beachable, be set up ready-to-sail and in the water within 10 minutes, and could be converted to a land sailer or iceboat by simply substituting wheels or runners for the hydrofoils.
A scaled-up version would make a fine live-aboard ocean cruiser or racer.
The project has only been hampered by lack of funding, so its progressed rather slowly.
End of extract. All these pictures are
courtesy Bob Imhoff. You can view his patent (number 5,113,775, dated 1992, covering
the Aero-Hydrofoil design) in the Delphion site here.
Special thanks to Andrew Collier of the CPIT for tidying the images in Photoshop.