Section 25.535

14 CFR Ch. I (1-1-19 Edition)

VS1 = seaplane stalling speed at the design
water takeoff weight with flaps extended
in the appropriate takeoff position; and
b = angle of dead rise at appropriate station.

The area over which these pressures
are applied must simulate pressures occurring during high localized impacts
on the hull or float, but need not extend over an area that would induce
critical stresses in the frames or in the
overall structure.
(c) Distributed pressures. For the design of the frames, keel, and chine
structure, the following pressure distributions apply:
(1) Symmetrical pressures are computed as follows:

K 2 VS 0 2
tan 

2

(2) The unsymmetrical pressure distribution consists of the pressures prescribed in paragraph (c)(1) of this section on one side of the hull or main
float centerline and one-half of that
pressure on the other side of the hull or
main float centerline, in accordance
with figure 3 of appendix B.
These pressures are uniform and must
be applied simultaneously over the entire hull or main float bottom. The
loads obtained must be carried into the
sidewall structure of the hull proper,
but need not be transmitted in a fore
and aft direction as shear and bending
loads.

spaschal on DSK3GDR082PROD with CFR

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25-23, 35 FR 5673, Apr. 8,
1970]

Section 25.535 Auxiliary float loads.
(a) General. Auxiliary floats and their
attachments and supporting structures

L =

C5 VS 2 W 3
0

2

(

tan 3  s 1 + ry

)

2

2 3

where - 
L = limit load (lbs.);
C5 = 0.0053;
VS0 = seaplane stalling speed (knots) with
landing flaps extended in the appropriate
position and with no slipstream effect;
W = seaplane design landing weight in
pounds;
bS = angle of dead rise at a station 3-4 of the
distance from the bow to the step, but
need not be less than 15 degrees; and
ry = ratio of the lateral distance between the
center of gravity and the plane of symmetry of the float to the radius of gyration in roll.

(c) Bow loading. The resultant limit
load must be applied in the plane of
symmetry of the float at a point onefourth of the distance from the bow to
the step and must be perpendicular to
the tangent to the keel line at that
point. The magnitude of the resultant
load is that specified in paragraph (b)
of this section.
(d) Unsymmetrical step loading. The resultant water load consists of a component equal to 0.75 times the load specified in paragraph (a) of this section and
a side component equal to 3.25 tan b
times the load specified in paragraph
(b) of this section. The side load must
be applied perpendicularly to the plane
of symmetry of the float at a point
midway between the keel and the
chine.

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EC28SE91.042</MATH>

where - 
P = pressure (p.s.i.);
C4 = 0.078 C1 (with C1 computed under
Section 25.527);
K2 = hull station weighing factor, determined in accordance with figure 2 of appendix B;
VS0 = seaplane stalling speed (Knots) with
landing flaps extended in the appropriate
position and with no slipstream effect;
and
VS0 = seaplane stalling speed with landing
flaps extended in the appropriate position and with no slipstream effect; and b
= angle of dead rise at appropriate station.

EC28SE91.041</MATH>

P = C4 

must be designed for the conditions
prescribed in this section. In the cases
specified in paragraphs (b) through (e)
of this section, the prescribed water
loads may be distributed over the float
bottom to avoid excessive local loads,
using bottom pressures not less than
those prescribed in paragraph (g) of
this section.
(b) Step loading. The resultant water
load must be applied in the plane of
symmetry of the float at a point threefourths of the distance from the bow to
the step and must be perpendicular to
the keel. The resultant limit load is
computed as follows, except that the
value of L need not exceed three times
the weight of the displaced water when
the float is completely submerged: