Free Surface Effects tn Hull Propeller Interactton 
APPENDIX A 
EXPERIMENTAL PROCEDURES 
All hull and propeller model experiments were conducted in 
the towing tank of the Ship Hydrodynamics Laboratory of the Universi- 
ty of Michigan following essentially standard test procedures, Some 
of the more interesting, but less obvious details are documented here 
for the sake of record. 
A.1. Hull Resistance Test 
The University of Michigan ship model No. UM 1201, built 
out of wood to the shape and size determined by Equations (3) through 
(5), without appendages was used for the hull resistance test. An un- 
usually high freeboard (equal to full draft) was provided to enable test- 
ing at high Froude numbers up to F,, = 0.5. Circular cylindrical studs 
of 1/8 inch diameter and 1/8 inch height were fitted at 5/8 inch spac- 
ing center-to-center along the entire girth of station No. 1 (that is 
0.05 L abaft of the vertical stem) to stimulate turbulence. 
Departing from standard practice, the model was almost ri- 
gidly attached to the towing carriage by means ofa three-point system 
of vertical supporting rods in addition to the usual grasshopper type 
anti-yaw guides at the two ends. This constraint was necessitated by 
the marginal transverse stability of the model and by the desire to 
preclude dynamic trim and sinkage for the ease of comparison with 
theory. The model was correctly weighted before making the connect- 
ions, and static draft, heel and trim were verified before and after 
each test. 
The resistance was measured by means of tare weights and 
a horizontal load cell built into a floating beam arrangement between 
the model and the carriage. Carriage speed was measured from wheel 
contacts and displayed on a calibrated digital counter. The speed 
range was extended up to V,, = 9.75 ft/sec (about Ra 0.45), which 
was the highest attainable within the limitations imposed by tank length, 
model freeboard, and instrumentation, 
A.2. Propeller Performance Test 
The Hamburg Ship Model Basin model propeller No. HSVA 
1222 with a standard nose fairing piece as shown in Fig. 2 was used 
for the propeller performance tests in open water. The propeller ma- 
terial is bronze, 
1883 
