586 
FOREST AND STREAM. 
[April 9, 1910. 
of displacement hull, the larger the vessel, the 
greater the economy of power per ton of weight. 
I believe that in the hydroplane and also in the 
aeroplane the same law of increase in efficiency 
will follow as in the ordinary boat, but possibly 
not with the same percentage of gain. 
In all kinds of transportation as well as in 
power plants the larger installation shows the 
best efficiency, and it will be a strange exception 
if it is not true with the hydroplane. 
The lifting power of planes depends on the 
speed and the volume or weight of water dis¬ 
placed ; also on the angle of the planes. • 
The volume of water displaced depends on the 
area of the plane, and also its proportions, viz.: 
its length and its breadth. 
The lifting power of a plane also depends not 
only on its area, but the depth at which the plane 
operates. 
The lifting power and efficiency of planes fur¬ 
ther depend on the form of the surface of the 
planes. 
Most school boys know that they can cross a 
stream of water on small broken cakes of ice 
if they step lively. 
This and the skipping stone are crude illus¬ 
trations of the hydroplane principle. 
Take two steel plates, each say 1/16 of an inch, 
one p’ate 1 foot square, the other 2 feet square 
(the latter containing 4 square feet), suspend 
them flatwise in the water, release both at the 
same time, and the small plate will go to the 
bottom much the quickest, although the weight 
per square foot is no more than that of the large 
plate. 
In making this experiment the plates must have 
suitable guides, or they will, of course, shoot to 
one side and go down edgewise. 
This simple experiment demonstrates abso¬ 
lutely that the surface of large area when in 
motion will support more per square foot than 
a surface of smaller area, and it also is evidence 
that flat planes have no stability, and that they 
must be held horizontally by guides, or, in the 
case of the hydroplane, by displacement, or they 
would turn over. • 
The average man may think that the sinking 
plate and a plane under speed are two different 
propositions, but the engineer of course under¬ 
stands that a p’ane moving forward at an angle 
is constantly sinking, but prevented from going 
under by its speed. 
1 he reasons why the large plane has a greater 
sustaining power per square foot than the small 
one is because the volume of water displaced is 
in a great measure in proportion to the areas of 
the surfaces. A plane displaces a volume having 
length, .breadth and depth which, for convenient 
comparison, is sometimes considered as in the 
form of an inverted pyramid—the sides of the 
pyramid having an angle of 4=; degrees with the 
surface of the plane. 
In speaking. of the length and breadth of 
planes—to avoid confusion—it is to be under¬ 
stood that, the length is the dimension in the 
direction in which the boat moves, and the 
breadth is crossways of the boat. 
It is reasonable to assume that the planes for 
a large boat would have some increase in length 
as well as in breadth, consequently the depth and 
the volume of water acted on bv the nlane would 
be m proportion to the size of the boat. 
As this last statement will undoubtedly be ques¬ 
tioned. T wish to explain that my theory is that 
even though the length of plane bearing on the 
water is and shou’d be less than the width, it is 
the perpendicular area of the width of the in¬ 
verted pyramid that should be taken into cal¬ 
culation. This area multiplied by the extreme 
length of all the planes, presuming that the in¬ 
dividual . planes have a length suitable to the 
speed gives the volume of water that may be 
considered as directly acted upon by the planes, 
and a very good basis for making calculations 
and also comparing the probable performance of 
a large boat with a small one. 
The larger the boat the greater the dentil at 
which the. planes must operate, and as each foot 
in depth increases the water pressure 62 pounds 
per #quare foot, this pressure would augment the 
lifting power of the planes enormously. 
I find in discussing the hydroplane problem 
with authorities on marine engineering that 
theories regarding the hydroplane differ con¬ 
siderably. This is to be expected, as it is a sub¬ 
ject that engineers, as a rule, have given little 
thought to, and there is practically no reliable 
data at hand on which one can base an opinion 
as to what the actual performance of hydro¬ 
planes of large size would be. 
Some engineers express a doubt as to whether 
air would even enter beneath planes having a 
draft of several feet. 
This is an extremely important point also for 
consideration, and my conclusions are that the 
depth to which air will go depends on the speed 
of the boat: planing commences and air will 
enter at a speed and to a depth corresponding 
to the theoretical velocity of water flowing from 
a head of pressure equal to the depth of the 
planes. 
This theory, I think, will prove to be a fairly 
accurate answer to Bosun’s statement that “no 
one seems to know at what speed vessels of 200 
feet to 300 feet would plane.” 
Take for example a 200-ton torpedo boat of 
165 feet length and 5 feet 8 inches draft and 
assume that a hydroplane torpedo boat of same 
tonnage would have four feet draft, air would 
enter beneath the planes at a theoretical speed 
of between nine and ten knots, but as the angle 
of the planes and the friction would drag the 
water to a certain extent, a somewhat greater 
speed would be required to get air under the 
planes at the middle and stern of the boat. 
In my experiments with hydroplanes weigh¬ 
ing one ton to one ton and a half, I have found 
that the boat commenced “planing” at a speed 
of five to six knots. 
In my experimental boat of one and a half 
tons, the weight was 31 pounds to the square 
foot of waterline area, whereas in the standard 
torpedo boat the weight is about 2?o pounds per 
sauare foot, but since the carrying power of 
planes multinlies as to the area of the planes 
and the depth at which they operate increases, I 
am convinced that it is thoroughly feasible to 
build hydroplane torpedo boats and even de¬ 
stroyers. 
Here it may be well to mention that the one 
and a half ton boat will plane with a load very 
much in excess of 31 pounds per square foot. 
The additional load would increase the draft 
and the speed required to commence planing 
would be slightly more, and as per the rule 
mentioned for calculating the velocity of water 
having a certain head. 
Having made the statement that the efficiency 
of planes depends on the form of the planes, 
it is important to present the reasons. 
In this instance I will consider only the dis¬ 
position of the surface of the plane crosswise 
of the boat. ■ 
Primarily there may be three kinds of planes, 
viz.: flat, concave and convex. 
The designer of the fast boat of the ordinary 
type of hull seeks to get lines offering the least 
resistance. The designer or a propeller blade 
wants a form of surface that will give the great¬ 
est thrust. 
A hydroplane surface and a propeller blade are 
identical in the sense that the greatest thrust or 
resistance are desirable. 
No one would consider for a moment making 
the rear surface of a propeller blade convex. 
There are many believers in flat blades (true 
pitch), but in my experience for hydroplane work 
the concave blade or increasing pitch propeller 
is much the most effective. If this is true in 
propellers, it ; s well to consider the reasons and 
their applicability to planes. 
The efficiency of a plane depends not only on 
the volume of water acted upon, but the direc¬ 
tion in which this volume of water is thrown. 
A plane in movement thrusts the water in a 
direction at right angles to its surface. 
Water radiating, so to speak, from the surface 
of a plane of convex cross section finds less re¬ 
sistance in the area, which rapidly increases 
about a convex surface. 
For this reason p’anes having the rounded 
form of the ordinarv boat would be verv ineffi¬ 
cient; also for the further reason that they de¬ 
flect the water sidewise rather than downward, 
in which the water displaced would meet the 
greatest resistance. 
Of the three forms of planes—flat, convex and 
concave—the convex, in cross section, displaces 
the least volume of water; the concave, the 
greatest for the same width and radius of sur¬ 
face, this difference being equal to the difference 
in area between the arc of the convex surface 
and that of the concave. 
Water requires force to move it quickly, and 
as more power is necessary to drive it into a 
contracted zone against resistance, and when 
complex motion must be created, as in the cast 
of concave planes, it means that the concave 
plane has superior efficiency per horsepower. _ 
My experiments and studies on this question 
have forced me to the conclusion that neither the 
flat, the concave or convex plane in their simple 
forms are practical. 
In boats of 150 feet or more in length it will 
undoubtedly be necessary to employ a number 
of planes, as two planes having one step near 
the middle would not perceptibly decrease the 
amount of surface friction. 
If a number of planes of flat cross section 
were to be used, they would, in a boat of such 
length, drag the water, so that the stern would 
not rise at all, and if it was possible to make 
the stern rise so that the displacement would 
be considerably reduced, the boat would not have 
stability. 
The lack of stability in the flat plane is very 
well demonstrated by the steel plate experiment, 
and this want of stability is probably explained 
by the theory that the pressure beneath a plane 
is greatest in the center, the water escaping more 
freely around the edges. 
If the application of the hydroplane principle 
to large boats presents the difficulties that I have 
mentioned above, apparently the only practical 
way of overcoming them is to provide such ar¬ 
rangement of planes that the dragging or “wake” 
will be minimized. Whether this can be done 
along the lines I have been working on, or 
whether it will be accomplished in some other 
manner is one of the features to be 1 cleared up. 
In the hydroplane the two principal elements 
of resistance are the angles and the friction of 
the wetted surface. 
The resistance of the angles can be calculated 
with reasonable accuracy, but the friction resist¬ 
ance is more complicated, because of the diffi¬ 
culty of determining in advance the amount of 
wetted surface. 
Estimating from the basis of known experi¬ 
ments and using Froude’s rule for the friction 
of short surfaces, 22 horsepower per ton would 
apparently be the maximum power required for 
a torpedo boat of 200 tons at 26 knots. 
Considering 'that a 26 knot torpedo boat of 
200 tons has about 18 horsepower per ton, and 
that the angle of 1 to 17 may be reduced with¬ 
out a proportional augmentation of friction 
area, and further that the co-efficient of friction 
(.41) may be high for such large boats, there 
is very good ground for the belief that existing 
high speed torpedo boats and destroyers might, 
with their present power and some practical form 
of hydroplane hull, show a substantial increase 
of speed. 
In hydroplane vessels it is possible to modify 
the shape of the stern in a manner to counter¬ 
act to a considerable extent the resistance of the 
angles of the planes. 
In a sense I regard the hydroplane problem 
much as the steam turbine, and believe that with 
refinements in the principles and the construc¬ 
tion, extraordinary results can be obtained. 
However, in order to form an opinion as to 
whether a 200-ton torpedo boat will plane or 
not, it is unnecessary to enter into complicated 
calculations dealing with the lifting power and 
areas of planes and the dynamic action of water. 
It is an easy matter to calculate the draft of the 
planes when the boat is at rest. 
[to be concluded.] 
The Forest and Stream may he obtained from 
any nezvsdcaler on order. Ask your dealer to 
supply you regularly. 
