The International Moth Class Association

The First Flying Moth?

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 sailboards?)

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 retracted.

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 "bunny hops".

Tony 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)