Resistance tests of models of three flying-boat hulls with a length-beam ration of 10.5

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Material Information

Title:
Resistance tests of models of three flying-boat hulls with a length-beam ration of 10.5
Alternate Title:
NACA wartime reports
Physical Description:
7, 35 p. : ill. ; 28 cm.
Language:
English
Creator:
Bidwell, Jerold M
Goldenbaum, David M
Langley Aeronautical Laboratory
United States -- National Advisory Committee for Aeronautics
Publisher:
Langley Memorial Aeronautical Laboratory
Place of Publication:
Langley Field, VA
Publication Date:

Subjects

Subjects / Keywords:
Airplanes -- Nacelles   ( lcsh )
Aerodynamics -- Research   ( lcsh )
Genre:
federal government publication   ( marcgt )
technical report   ( marcgt )
non-fiction   ( marcgt )

Notes

Summary:
Summary: Models of three flying-boat hulls, each with a length-beam ratio of 10.5, were tested at the Langley tank no. 1. The lines of these models were derived from the Deutsche Versuchsanstalt für Luftfahrt (DVL) standard series. The three models permitted tests with two depths of step and two angles of dead rise. Resistance, trimming-moment, and wetted-length data were obtained from general fixed-trim and free-to-trim tests at load coefficients ranging up to 4.0. The results showed that these three models had low hydrodynamic resistance at high load coefficients. At the free-to-trim hump, load-resistance ratios of 4.5 and 3.9 were attained at load coefficients of 1.5 and 3.5, respectively. Increasing the angle of dead rise, excluding chine flare, from 20° to 24.5° tended to increase the resistance and trimming moments at planing speeds. Changing the depth of step from 5 to 10 percent beam had little effect on the resistance. With conventional nacelle locations, excessive spray would enter the propellers at load coefficients over 3.0.
Bibliography:
Includes bibliographic references (p. 7).
Statement of Responsibility:
by Jerold M. Bidwell and David M. Goldenbaum.
General Note:
"Report no. L-79."
General Note:
"Originally issued September 1945 as Advance Restricted Report L5G19."
General Note:
"NACA WARTIME REPORTS are reprints of papers originally issued to provide rapid distribution of advance research results to an authorized group requiring them for the war effort. They were previously held under a security status but are now unclassified. Some of these reports were not technically edited. All have been reproduced without change in order to expedite general distribution."

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 003638098
oclc - 71823451
sobekcm - AA00006251_00001
System ID:
AA00006251:00001

Full Text

AR No. LG9
ARE. No. L5G19


NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS





WAtRTIM'IE REPORT
ORIGINALLY ISSUED
September 19145 as
Advance Restricted Report L5G19

RESISTANCE TESTS F CMDELS OF THREE FLYIG-BOAT HULLS
WITH A LEGTH-BEAM RATIO OF 10.5
By Jerold M. Bidwell and David M. Goldenbaum

Langley Memorial Aeronautical Laboratory
Langley Field, Va.













WASHINGTON

NACA WARTIME REPORTS are reprints of papers originally issued to provide rapid distribution of
advance research results to an authorized group requiring them for the war effort. They were pre-
viously held under a security status but are now unclassified. Some of these reports were not tech-
nically edited. All have been reproduced without change in order to expedite general distribution.


L 79


DOCUMENTS DEPARTMENT






































Digitized by the Internet Archive
in 2011 with funding from
University of Florida, George A. Smathers Libraries with support from LYRASIS and the Sloan Foundation


http://www.archive.org/details/resistancetestso001ang









NACA ARR No. L5G19


NATIONaL ADVISORY CO'I.TITTEE FOR AEROIikUPTICS


ADVANCE RESTRICTED REPORT

RESISTANCE TESTS OF MODELS OP THREE FLYING-BOAT HULLS

,VITH A LENGTH-BEA-M RATIO OF 10.5

By Jerold M. Bidwell and David ]!. GOldenbuum


SUC. ARY7


Models of three flying-b:at hulls, each with a
length-beam ratio of 10.5, were tested at the Langley
tank no. 1. The lines of these models were derived from
the Deutsche Versuchsanstalt fur Luftfahrt (DVL) standard
series. The three models permitted tests '.::ith two depths
of step and two angles of dead rise. Resistance, trir.mming-
mo.nent, and wetted-length data aere Tbtatned from general
fixed-trim and free-to-trim tests at load coefficients
ranging up to t.o0.

The results sh' 2d that these three models had low
hydrodynanic resist -.ce at high load coefficients. Lt
the free-to-trim hump', loac.-resistance ratios of" L.5
and 3.9 were attained at load coefficients of 1.5 and 3.5,
respectively. Increasing the an.le of dead rise, excluding
chine flare, from 20o to 24.50 tended to increase the
resistance and triTuming moments at planing speeds.
Changing the depth of step from 5 to 10 percent beam had
little effect on the resistance. Nith conventional
nacelle locations, excessive spray would enter the pro-
pellers at load coefficients over 5.0.


INTRODUCTION


The effect of length-beam ratio on the water resist-
ance of a flying-boat hull has been the subject of many
investigations. Three independent studies (references 1
to 3) have indicated that, within the range of the









2 YC APJ.' To. L5G19


investigations, increaslir: the length-beam ratio results
In ].ower4 .g the water resistance. T.i-'e of the Deutsche
Versuchsr.nstaalt fur Lvftfahrt (DVL) stan:i.ard series (refer-
ence 1) were used in the development of three rmojels,
each with a length-beam ratio of 10.5. Two of these
models differed only in angle of dead rise; the third
model was similar to the moiel with the higher dead rise
but had a depth of step twice as Great.

T'e models :used -:ere furnished to the :IiCA by
Consolidated Vultee Aircraft Corporation.


MODTL7


The models, designated in the Larngley tanks as
maijels -:2I, 185, and 185-A, were derived frm.:, the
DVL series by increasing the station spacin- along the
forebody and afterbody keels and keeping the beam the
same as that of the PVL models (11.81 in.). Two of
th-ese models differed only in an.-le of dead rise (defined
herein as an -Le of dead rise excluding chine flare); the
angle of dead rise was '' for model 184 and 4l.50 for
modl 105. -.' sections of the m oel with the higher
an-l-e of c' e-d i.'se were forined by multiplying the ordi-
nates of t'. lover angle of dead rise by 25/20. TUse of
this factor "-'elda a dead-rise angle of 2L.5 and a
s1'-.y ]f dl>ferent radius of curvature for the chine
fl~: t.An t:it of model 184. Lines of model 135 are
tgvw i. iv. 'f 1. The third riodel (model l.5-A) was
simile;' to 3o el 185 except that the depth of step was
doiried by '- sin. the whole afterbo..y vertically. Sec-
tions .of the t-r-;e models at the step are shown in fig-
ure 2.


APPA.; ,1iS AND PROCEDURE


Th-. tests were made in Langley tan!." no. 1, which is
describi-.1 in reference it.

C:-nc.ral fixed-trim tests were made ty following the
criocedurc described in reference 4. Tn Lddition to the
usual measurements, wetted l-n.thi of bith f-i-.etody and
afte.rbo.--y were observed. CG-n..ral free-to-trim tests were
also :na.Ji- at .p-.cd co'fficients uo to 5.5 (50 fps) or








NACA ARR lio. L5G19


slightly over the htmip speed. The schedule of loads and
speeds used for the fixed-trin tests is given in figure 3
and the free-to-trim schedule is the same except for the
elimination of all speed coefficients above 5.3. Lirnita-
tions in the capacity of the test equipment made it nec-
essary to drop some points from the schedule. These limi-
tations were the resistance (approlx. 60 ib) and the
trimming moment (approx. 180 lb-ft).


RESULTS


The results of the tests were reduced to the usual
coefficients based on Froude's law to make them independ-
ent of size. The nondimensional coefficients are defined
as follows:

CA load coefficient (/.:b3)
CR resistance coefficient (R/wb )

Cv speed coefficient (v/ g)

Cy trimming-moment coefficient (M/wbf)
CW. L. wetted-length coefficient (l/b)

Cd draft coefficient (d/b)
where

A load on water, pounds

w specific weight of water, pounds per cubic foot
(635. for these tests; usually taken as 6' for
sea water)

b beam (0.985 ft)

R resistance, pounds

V speed, feet per second

g acceleration of gravity (32.2 ft/sec2)
M trimming moment, pound-feet (positive moments
tend to increase trim)









NACA ARR :To. L5G19


1. wetted-length, feet

I .r-.ft at main step, feet

Ay consistent system of units may be used. The
moment data are referred to the center of moments shown
in figure 1. Tri. T is the -r.gla between the base line
of the model and the horizontal.

The data obtained from tests of model 185 are given
in fipe,.'rs to 8. Resistance and trimming-moment data
from fi:e3-trim tests are presented in figures 4 and 5,
resnectively. The trimn.ling-moment data are arranged in
a form unlike that used in previous I..CA repror-s. Because
of the large number of load parameters used, the usual
met'ho of presentationn would result in a confusing inter-
.iln ngr of the curves at low speeds. In figure 5, there-
fore, trim T is the par-~meter instead of the conventional
load coefficient CA. Data fror. the free-to-trim test on
this model are given in figure 6. The static properties
are shown in fi',ire 7- Sir'llar data for models 1.6l
and 185-A are not .given because these data differ only
slic-h.t.ly from those for model 185.

.'.tted-le:nth data for model 1P5 are given in fig-
ure 8. Correzo.-ndinng data for model 184 were obtained
but are not presented herein. .To data on ;vetted lengths
were obtained for mo--el 1-.5-1. Observations of wetted
lengths were made whenever practicable 'but, because of
the heavy s-:.r;., the data at heavy loads are not co:..plete.
No wetted lengths on the afterb.jdy keel are given because
of the difficulty of observing them.

Best-trim curves derived from fixed-trim data for
model 15 are given in figure 9. The best-trim data for
models 1:-1 and 185-A are given in figures 10 and 11,
respectively. Photographs of the forebody spray of
model 1`) are shown in figure 12.


DISCA331 ON


Thi ?rray -nd resistance characteristics observed
were similar on all three models, sorne relatively minor
effects on the resistance .er: produced by the change in
ar.;le f de- d rise a i- d'pth of step. Relatively high








rACA A LR Ho. L5G19


load-resistance ratios were maintained at very high-load
coefficients br each of the three iodeels.

Effect of angle of dead rise.- The effect of changing
the angle of dead rise from 20'-' to 2L..5' on the load-
resistance ratio at hump speed snd at high speeds is
shown in figure 13. The model with the lower angle of
dead rise shows slightly lower resistance at both hump
and high speeds. Trimming moments are less positive for
the model with the lower angle of dead rise at best trim
beyond the hurmp. Below hump -peed &he effect of the
change in angle of dead rise was nc eligible. These
results are in agreement with those, for conventional
length-beam ratios reported in reference 5.

Effect of denth of step.- The effect on the resist-
ance of changing the depth of step from 5 to 10 percent
beam is indicated in figure 11, by a comparison of load-
resistance ratios under several conditions of trim and
speed. The effect is small, the trend for the mojel
with the deeper step being toward higher resistance at
hunp speed and lower resistance at high speed and light
loads. Greater positive trimrzing r.moments were observed
on the model with the deep step than on the iiodel with
the shallow step. These results are similar to thoc'e
for conventional length-beam ratios of reference 6. On
a hull of the form of model 165, if a step as oeep as
10 percent beam is required to attain good landing sta-
bility, no marked increase in take-off time may be
expected over that for a hull with a shallow step.

Forebody spray.- Photographs of the forebody spray
of model 1U5 -re given In figure 12. Tne model is shovn
running free to trim at several load coefficients and at
several speeds. The effect of the change in angle of
dead rise on the soray was imperceptible, and therefore
no photographs of the model with low angle of dead rise
are given. The criterion for forebody loading (refer-
ence 7) is given as Co = k -] where Lf is the
length of the forebody and k is an empirical coeffi-
cient. The following CA0 values have been computed
for this model having a forebody length-beam ratio
of 5.8:








NACA ARR No. L5G19


k Co

0.119 4..0
.0975 (excessive) 5.23
.0825 (heavy) 2.77
.0675 (satisfactory) 2.27
.0525 (light) 1.76
From this table, model 185 would be expected to produce
extremely heavy forebody spray at a load coefficient
of 4.0. lie spray actually observed and shown in fig-
ure 12 verifies this expectation. With nacelles and wing
located accor:'.ng to current design practice, a flying
boat having a hull similar to model 184 or 185 would have
an excessive amount of spray in its propellers when oper-
ating at load coefficients ver 3.0.


COUCLUSI ONS

1. The three models tested maintained relatively
high load-resistance ratios to'bhigher load ciefficients
than do models of conventional le-gth-beam ratio. At
the free-to-trim hump, load-resistance ratios of 4.5
and 3.9 were attained at load coefficients of 1.5
and 3.5, respectively.

2. Chsaning the angle of dead rise (excluding chine
flare) and the depth of step on these models had the
same effect on their resistance as similar changes made
on models of conventional length-Oeam ratio.

3. Excessive spray was shown for the three models
tested at conventional propeller locations with load
coefficients greater than 3.0.

Langley Memorial Aeronautical Laboratory
National Advisory Committee for Aeronautics
Langley Field, Va.








IAC.G ARR :'. L5019


REFERENCES

1. Sottorf, YV.. The Design of Ploats. UNC TA rINo. 160,
1938.

2. Bell, Joe W., Garrison, Charlie C., and Zeck. Howard:
Effect of Length-Be.am Ratio on Resistance and Spray
of Three F1 models of Flying-Poat Hulls. !IMC.C ARR
No. 5J25, 19 r.

5. Davidson, Kenneth S. ". and Locke, F. '. Jr.:
General Tank Tests on the Hydrodynarai c Character-
istics -f Four Flying-SBot Hull !.idsels of Differing
Length-Beam Rat.o. iNACI AFR To. Fl., 1.)"+.

4. Truscott, Starr: The Er'arged J.A.C.A. Tank, and Some
of Its Jorli. NI.Ca TI. N-o. 918, 1959.

5. Bell, Joe WV., and ,i'llis, Jolin ;.1., Jr.: The Effects
of Angle of Dead Rise and Anjle of afterbody Keel
on the Resistance of a Model of a Flying-Boat :lull.
NACA ARR. Feb. 154' .

6. Bell, Joe ;.: The Effect of Depth of Step on the
Water Perfomance Df a Flying-Boat Hull ;idel -
H.A.C.A. F'odel 11-C. NCA Ti: Ho. 535, 19 5.

7. Parkinson, John B.: Design Criterions for the Di.raien-
sions of the Foreoody :,f a Long-Range Flying Boat.
NACA ARR No. ;KCS. 1945.








NACA ARR No. L5G19


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NACA ARR No. L5G19


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Model 186
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NATIONAL ADVISORY
COMMITTEE FOR AERONAUTICS


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NACA ARR No. L5G19


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