AERONAUTICS IN RELATION TO NAVAL ARCHITECTURE. 45 
Having considered the special conditions which affect aeroplane floats, as dis- 
tinguished from those affecting displacement forms, let us now consider what is 
required of aeroplane floats. 
When adrift the floats must provide buoyancy and have sufficient reserve of 
buoyancy to provide against loss due to a damaged compartment. 
Sufficient water-line inertia and freeboard are required to provide initial and 
reserve stability in a strong wind in the open sea. This problem is unusually diffi- 
cult, because of the unusually high position of the center of gravity and of the re- 
quirement of keeping the wings and propellers well clear of the surface, and of 
keeping the center of gravity close to the center of lift. Those inclinations produce 
a rapid movement of the center of gravity, which must be exceeded sufficiently by 
the resultant change in the center of buoyancy. Sufficient initial stability must exist 
to provide against the force of the wind on the extended wings, which may be rolled 
to strong lifting angles. 
When drifting it is desirable that the aeroplane should head into the wind. 
This is difficult to attain by control of form and may require the use of a sea anchor. 
Under way at moderate speeds the aeroplane must steer readily in all directions 
and be able to maneuver in close quarters so as to get alongside the ship. 
Water rudders are not always successful on such short floats as are usual, and 
are objectionable from handling and stowage points of view. If the water rudder 
is a part of the air rudder, action becomes confused in a cross wind, and sharp han- 
dling is necessary when the water rudder breaks clear of the surface. 
Under way at high speed, particularly near the get-away speed or landing 
speed, the bow must have sufficient bearing power to prevent nosing under in a 
rough sea or a badly judged landing. The form must also be such as to avoid 
undue pounding and the throwing of spray into the propellers. 
In order to avoid the requirement of excessive power to drive the floats, plan- 
ing should begin at moderate speeds—in the neighborhood of 25 miles an hour in a 
calm. Planing is readily attained by the use of large areas of planing bottom, but too 
rapid planing is not desirable, and a compromise is required because of the different 
water speeds involved when getting away in a calm or when heading up or down 
wind. If too much planing is present, the aeroplane may be tossed off rough water 
at less than flying speed, or before the air controls become effective. This always 
results in severe pounding and may cause the aeroplane to return to the surface in a 
dangerous attitude. If after planing is attained the attitude of the float relative to 
the surface can be modified, the wing lift can also be modified, and the actual get- 
away becomes controllable within limits. This latter feature is very desirable. 
When getting away or landing it is extremely desirable that the forces acting 
on the floats should be moderate and act with small moment arms about the center of 
gravity, so as to introduce moderate disturbing forces and require a minimum use 
of the air controls and maintain the proper attitude of the aeroplane. 
In the air the floats should present a minimum resistance and interfere as little 
as possible with the flow of air to the supporting surfaces and the air controls. 
