332 BeiMandel 
of the towed vessel is so erratic that towing becomes difficult and hazardous. It was for 
these reasons that tests were carried out with the 1/12-scale Aluminaut model in order to 
observe its behavior while being towed on the surface. 
Test Arrangements 
The Aluminaut model was towed about two model lengths behind a model of an Oceano- 
graphic Research ship at the M.I.T. Ship Model Towing Tank. The research ship model was 
in turn towed by the erdinary gravity towing arrangement employed at the M.I.T. tank. Thus, 
the towing vessel was restrained to straight-ahead motion while the towed vessel was unre- 
strained except for the tension on the towing line. 
Several towing arrangements were employed: 
(a) Ahead tow - single tow line attached to a bracket on the centerline of the forward 
deck of the Aluminaut. 
(b) Ahead tow - bridle tow lines attached to the extremeties of a one-foot-wide spanner 
fixed to the forward deck of the Aluminaut. 
(c) Ahead tow - bridle tow line attached to the leading edges of the Aluminaut bilge 
keels. 
(d) Astern tow - single tow line attached to upper rudder of the Aluminaut. 
Tests were conducted with both the small and the large stern planes and rudder 
described in Table 4. During all tests the model was equipped with the wide bilge keels. 
Limited tests were also conducted with the stern fins removed. 
Test Results 
Distinct differences in the behavior of the towed Aluminaut model were observed with 
the different towing arrangements. The Aluminaut model was initially set directly behind 
and in line with the towing model. Upon release and movement of the towing model, the 
following situations could be observed: 
Characterization 
ipti Behavio i 
Jess EE Eee of Behavior 
1. The Aluminaut model would veer off Unsatisfactory 
course and collide with nearest tank 
wall. 
2. The model would initially veer off Unsatisfactory 
course, but return and cross its initial 
position and collide with the opposite 
tank wall. 
3. The model would initially veer off Satisfactory 
slightly to one side, but within the 
length and width of the tank, it would 
tend to return to a stable equilibrium 
position. 
