By 1970 I had been interested in hydrofoils for some time as a
member of the Amateur Yacht Research Society, and I had made several
successful sailing models. It occurred to me that any high performance
racing dinghy should make a good platform for adding hydrofoils.
I had a moth “Renegade IV” which had been Queensland Champion in 1969. The sail
area at less than 82 sq. ft. was smaller than any sailing hydrofoil that
I know of. (And may still stand as a record if you discount foiled
In adding foils I did not want to modify or ruin the boat so I
utilised existing attachment points for stays and rudder. I did have to
screw the bow foil gantry to the noseblock however.
The configuration I developed was unique – two main lateral
foils, 6′ by about 14″, surface piercing, for lift, stability and
lateral resistance set at about 45deg. dihedral. For steering and pitch
control there were rudders fore and aft with foils. On the aft rudder
was a low-dihedral submerged foil 6″ chord by about 3′ span. The surface
piercing foil on the bow rudder was of somewhat greater span and set at
about 30deg. dihedral. The two rudders were linked so that the lateral
foils were not loaded or unloaded when turning. The linkage could be
adjusted so that (in theory) more or less pressure could be thrown on
the lee foil.
The foils were shaped by hand in the laundry of my Shepparton
unit out of the toughest Australian hardwood I could find. The section
was flat on the bottom with a slight curve up at the leading edge, and
arc of circle on the upper surface. The leading edge was sharp.
Thickness would have been less than 8%.
The first trials at Albert Park Lake and on Lake Glenmaggie were
hopeless (and incidentally everyone who saw the boat strongly affirmed
that foiling would be impossible). The “stick and string” structure was
a bit like a certain brand of collapsible furniture in that nothing held
up until everything was locked in place.
The boat could be launched and sailed off a beach in conventional
mode, then in deep water the foils lowered and the centreboard
Finally in March 1972, at Cabbage Tree Creek near Brisbane,
Queensland, I achieved lift-off in about 15 knots of wind.
The best thing about it was how easy it all was – it was
absolutely controllable and stable with no vices. Any dummy could have
sailed it, though I think only my mate Tony Turbot ever did. It was he
who took the photos with my Box Brownie and his colour camera.
On the foils it was about as fast as the Mark II Moth that was
sailing there at the time. Once, as I remember, I almost managed a gybe
on foils. It came down after the sail came across and just before I
could power up on the new tack. I usually gybed because tacking involved
a stern board.
Off the foils it sailed ok but was slower than a sabot.
Its worst feature was its intolerance of even small waves. They
sucked it down off the foils. I eventually bust the bow foil pushing it
in waves. The hardwood bent like a steel spring before it broke.
Thereafter it would not foil – I could only get it to do half-hearted
ony bought the boat as I was on my way overseas. The boat
eventually cracked up. The foils I never saw again.
All this is true, so help me God.
P. Frank Raisin (11th. Jan. 2008)
Source post http://moth-sailing.org/franks-foiler/