AUTOMATIC STEERING. 57 
in wide angle yawing of the ship itself, what will we say when we come to take a simulta- 
neous record of the activities of the rudder, as in Fig. 10, Plate6? Here we come face to face 
with the true evils of poor steering in constantly applying large amounts of rudder and 
running up fuel costs while making a poorer showing in headway. Compare the yawing 
angles of this record with the magnified records in Fig. 5, which are on the same scale. 
It should be remembered that each little step on the magnified chart is only 1/6 of a degree. 
Fig. 11, Plate 7, is a very excellent illustration of the difference between the best steer- 
ing that could be done by the quartermaster using the gyro in heavy weather and immediately 
throwing on the automatic. We are still dealing with magnified charts with the chart ampli- 
tude multiplied by 10. No better proof of the value of automatic steering can be asked. 
Since we have been obtaining continuous precision records of the ship’s steering per- 
formance, we have subjected some of them to mathematical investigation with the following 
results. These have been taken under two headings: 
1. Helm angle. 
2: Zigzagging or sinuosity of course. 
Under the first heading the rudder resistance was investigated. The records show that 
when steering by magnetic compass, an average of 6 degrees of helm was held. When 
steering by gyro compass, this average angle was reduced to 1.93 degrees. With the rudder 
at an angle the rudder resistance is represented by the formula 
IR == All? S< sa 0 SK Dy 
where 4 is area of the rudder in square feet, V is speed of the ship in knots per hour plus 
20 per cent allowance for the slip, a is the helm angle, and p is the pressure of the water at 
speed of one knot, equal to 3.19 pounds per square foot. 
Assuming the area of the rudder of the ship whose records were investigated to be 86 
square feet, we have a helm resistance with the magnetic compass of 9,300 pounds, and with 
the gyro 3,000 pounds. 
Turning now to the second heading, which is more important, by using the tangents 
of the angle, period, etc., for check, we find the very considerable extra distance that it is 
necessary to travel between given points, the angles also giving us some components of the 
extra resistance owing to the bad angle of attack and mean extra cross-section area forced 
through the seas. These lead up to results that check fairly well with large and worth- 
while savings of both fuel and time between given ports. The demonstrations repeatedly 
made of the marked shortening of time over best previous performance has led a number of 
the largest ship operators to install complete gyro-compass equipments, thereby availing 
themselves of this latest refinement of automatic steering with its remarkable additional 
contributions. 
The development work on this device first starting in 1913 has recently been mainly in 
the direction of simplification and the embodiment of very necessary reliability and rugged- 
ness so essential in apparatus of this kind which will go into more or less unskilled hands, 
and which must be immune to vicissitudes of weather and sea effects. Sea trials have very 
conclusively indicated that great benefits and economies to be derived from automatic steer- 
ing are now available in ships equipped with gyro compasses. 
