Andres Lepp's tow hook

Lepp's tow hook

This drawing appeared during 1973 in Free Flight News and then in the NFFS Symposium for that year.
Click the image for an enlargement

Andres Lepp's idea of combining circle tow with zoom launch was the master stroke. Circle tow per se is purely a thermal hunting technique and, by itself, didn't change much except to make really big wings impractical. Without VIT and wigglers a high span wing is a real handful to circle tow in anything except really calm conditions. However, it was the zoom launch height gain that, as the NFFS Symposium said when Lepp's hook was made the 1973 F1A Model of the Year, made the search for performance from really high aspect ratio models obsolete. Very large span models don't roll fast enough for a good zoom launch pattern. With a high zoom launch a good all-round model could usually beat a high aspect ratio model which could only manage little or no height gain, so the latter went out of favour because suitable conditions for them were so rare.

The result was that nobody much flew this type of model until Makarov & Kochkarev put it all together (carbon wing, wiggler, bunt) and removed the requirement for a fast roll rate after launch. A few people, notably Chop, Isaenko and Lepp, had big zoom models: their glides were great, but the height gain on launch was pretty small and they were only used in flat calm or dire emergency, such as Lepp's predicament in round 7 at the 1981 World Champs in Burgos. In this very windy contest all his other models had been damaged or stolen, so he was forced to fly his large AL-33 in the last round. After a masterly display of towing he made the final max. Few others could have flown that model at all in those conditions.