THE BEHAVIOUR OF A 

 GROUND EFFECT MACHINE OVER 



SMOOTH WATER AND OVER WAVES 



W. A. Swaan and R. Wahab 



Netherlands Ship Model Basin 

 Wageningen, Netherlands 



ABSTRACT 



The results of tests on the over water behaviour of a flying model of a 

 Ground Effect Machine are given and discussed. Over smooth water 

 the effect of a variation in water depth was investigated. Over waves 

 the variables were the wave length, height and direction, and the rise 

 height. The effect of side wind was also considered. 



INTRODUCTION 



The information presently available on the behaviour of ground effect ma- 

 chines over water is rather limited. See Refs. [1] through [8]. It is based on 

 the experience gained with a few man-carrying prototjrpes and a number of 

 model tests. The model experiments were in general conducted with a fixed 

 model with the object to determine the static forces and the effect of the air 

 cushion on the water surface. 



Additional information has been obtained now with a dynamically scaled free 

 model of the SKMR-I "Hydroskimmer" in a model basin where various wave 

 patterns were simulated. In order to avoid telemeterir^ problems and energy 

 storage in the model a towing carriage was used. The maximum carriage speed 

 in the seakeeping basin of the N.S.M.B. is about 15 ft sec-i. The service speed 

 and size of the SKMR-I is such that a very small model would be required to use 

 this carriage for the whole prototype speed range. In view of these problems it 

 was decided to construct a 5 ft long model of the SKMR-I with a weight of about 

 22 lbs. Equivalent speeds up to 35 knots could be attained with a model of this 

 size. 



The N.S.M.B. was only concerned with the model tests, which have been re- 

 ported in Refs. [9] and [10], and not with the design of SKMR-I itself. In this 

 paper some of the most characteristic data are discussed. 



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