ONR Hydrofoil Boat XCH-6 231 
Marshall P. Tulin 
We should all thank Mr. Lang of the Naval Ordnance Test Station for presenting us with 
his recently obtained experimental information on base- and side-ventilated foils. Work of 
this kind is most important to continue. I might perhaps mention at this time that the idea 
of using a fully-wetted but base-ventilated hydrofoil for high-speed operation was, to the 
best of my knowledge, originated at the Langley Laboratory of the NASA by Mr. Virgil E. 
Johnson, Jr. These foils are very promising in certain respects, but are also probably very 
sensitive, cavitation wise, to angle of attack. As was mentioned in the paper, we believe 
that supercavitating foils intended for use on seagoing boats must be capable of operating 
without cavitation under a reasonable range of design angles of attack; that range may be 
larger than is possible with fully-wetted, base-ventilated, parabolic foils. 
W. Graff (Versuchsanstalt fiir Binnenschiffbau, Duisburg, Germany) 
The project of a full-cavitating hydrofoil is a proposal of mine made 24 years ago. 
About 12 years ago J constructed and tested such a boat. The boat was driven by an air- 
screw of 800 hp. The system of foil was somewhat similar to that shown by Mr. Wennagel 
and had forward foils piercing the surface and a full-submerged foil aft. The trials of the 
boat raised serious difficulties. Running on smooth water with full-cavitating foils we got 
self-excited heaving and pitching oscillations, known as porpoising, such that it was 
impossible to reach the full speed. Unfortunately, I could not finish these trials. The cal- 
culations made on this matter seemed to show that the distance of the foils on high speed 
was the most important factor in this problem. It was of interest to hear that Mr. Wennagel 
also observed these phenomena and that he was able to eliminate them. 
