A Brief Investigation of the Effect of Waves on the Take-Off Resistance of a Seaplane Page: 5 of 19
This report is part of the collection entitled: National Advisory Committee for Aeronautics Collection and was provided to UNT Digital Library by the UNT Libraries Government Documents Department.
Extracted Text
The following text was automatically extracted from the image on this page using optical character recognition software:
NACA RM L56B09
The average resistance was obtained from the records by direct meas-
urement without the need for any averaging process because the spring
tension remained essentially constant. This was so because of the low
spring constant, which resulted in the application through the dynamometer
of a nearly constant towing force; the fluctuations in resistance caused
by waves were overcome mostly by the inertia of the model. The trim and
rise, however, fluctuated greatly, and the averages of these were obtained
by dividing T dt and r dt (obtained by mechanical integration of
the records) by the elapsed time t.
RESULTS AND DISCUSSION
The results are presented in the form of plots defining the variation
of average total-resistance coefficient, average trim, and average rise
coefficients caused by changes in speed, elevator deflection, wave height
and length, center-of-gravity location, dead rise, and loading. These
data are presented in figures 3 to 8.
The average total resistance, trim, and rise in smooth water and in
waves of various heights are shown plotted against speed coefficient in
figure 5. At low speeds the influence of the waves was small because the
model followed the wave contours with little angular or vertical motion
relative to the water surface. At the higher speeds the wave impacts and
rebounds caused the average values of resistance, trim, and rise to be
higher than for smooth water and to increase progressively with wave
height. The average rise. coefficient in waves continued to increase to
getaway, but the greatest effects on average resistance coefficient and
trim occurred at intermediate planing speeds where it was observed that
the most severe impacts and rebounds occurred. At a speed coefficient
of 10.1 0.7 G) the increase in resistance due to waves was 40 percent
for the 2-foot waves and 65 percent for the 6-foot waves. Near getaway
speed the observed severity of the motions and the average resistance
decreased because the model was nearly airborne and only contacted the
wave crests occasionally. Near getaway speed, the resistance in waves
actually became smaller than in smooth water, probably because afterbody
wetting in waves exists for only a short interval during each wave
encounter.
The effect of elevator deflection on average resistance, trim, and
rise in smooth water and in waves at a speed coefficient 'of 10.1, which
is in the range of maximum wave effect, is shown in figure 4. In smooth
water, porpoising occurred, causing the tests to be limited to the ele-
vator range from -15 to 100; but, in waves, elevator settings beyondCONFIDENTIAL
CONFIDENTIAL
Upcoming Pages
Here’s what’s next.
Search Inside
This report can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Report.
Mottard, Elmo J. A Brief Investigation of the Effect of Waves on the Take-Off Resistance of a Seaplane, report, April 24, 1956; (https://digital.library.unt.edu/ark:/67531/metadc62263/m1/5/: accessed May 2, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.