A model support system used to support a model in a wind tunnel test section is described. The model comprises a metric, or measured, half-span supported by a nonmetric, or nonmeasured half-span which is connected to a sting support. Moments and forces acting on the metric half-span are measured without interference from the support system during a wind tunnel test

Dollyhigh, S. M.

Jackson, C. M., Jr.

Shaw, D. S.

English

NASA Technical Reports Server

United States Patent [I91 
Jackson, Jr. et al. 
[54] METRIC HALF-SPAN MODEL SUPPORT 
SYSTEM 
[75] Inventors: Charlie M. Jackson, Jr., Yorktown; 
Samuel M. Dollyhigh; David S. Shaw, 
both of Newport News, all of Va. 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
[73] Assignee: The United States of America as 
[21] Appl. No.: 145,210 
[22] Filed: Apr. 30, 1980 
[51] Int. c1.3 .............................................. GOlM 9/00 
[52] U.S. C1. ...................................................... 73/147 
[58] Field of Search .............................. 73/147, 862.04 
[561 References Cited 
U.S. PATENT DOCUMENTS 
2,582,814 1/1952 Beman ................................... 73/147 
2,909,061 10/1959 Gelbach ................................ 73/147 
2,910,866 11/1959 Czerwinski ........................... 73/147 
3,005,339 10/1961 Loftin .................................... 73/147 
11 11 4,327,581 
[451 May 4, 1982 
3,233,452 2/1966 Jones ..................................... 73/147 
3,276,251 10/1966 Reed ..................................... 73/147 
4,107,986 8/1978 Jones ..................................... 73/147 
FOREIGN PATENT DOCUMENTS 
128308 7/1959 U.S.S.R. ................................ 73/147 
Primary Examiner-Kyle L. Howell 
Assistant Examiner-Denis E. Corr 
Attorney, Agent, or Firm-Wallace J. Nelson; John R. 
Manning; Howard J. Osborn 
[571 ABSTRACT 
The invention relates to a model support system used to 
support a model in a wind tunnel test section. The 
model comprises a metric, or measured, half-span 12 
supported by a nonmetric, or nonmeasured half-span 11 
which is connected to a sting support 13. Moments and 
forces acting on the metric half-span 12 are measured 
without interference from the support system during a 
wind tunnel test. 
3 Claims, 5 Drawing Figures 
14’ 19’ 4 
https://ntrs.nasa.gov/search.jsp?R=19820015380 2020-03-21T16:28:12+00:00Z
U.S. Patent May 4,1982 Sheet 1 of 2 
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METRIC HALF-SPAN MODEL SUPPORT SYSTEM 
ORIGIN OF T H E  INVENTION 
The invention described herein was made by employ- 
ees of the U S .  Government and may be manufactured 
and used by or for the Government for governmental 
purposes without the payment of any royalties thereon 
or therefor. 
BACKGROUND O F  T H E  INVENTION 
Wind tunnel studies provide solutions to a wide range 
of aerodynamic problems, including the effect of drag, 
aircraft lifting characteristics, static stability, pressure 
distributions, and flutter characteristics. Data are usu- 
ally acquired through the measurement of forces and 
moments acting upon a model and by changes produced 
in the airstream by the model. The fundamental instru- 
mentation approach for detecting and measuring these 
effects is based upon providing a supporting structure 
for the model in which reactive forces and moments are 
generated in maintaining the model virtually motionless 
with respect to the wind tunnel structure. The reactions 
to yaw, pitch, roll, lift, side and drag components can 
then be effectively isolated from each other and sepa- 
rately detected. 
T o  guarantee the accuracy of the measurements, it is 
essential to reduce any collateral effects resulting from 
interference caused by the supporting structure. For 
example, if the support attached to the model interferes 
with the normal flow of air around the model, this inter- 
ference will create an error in the measurement of data. 
Similarly, if the supporting structure causes a distortion 
of the configuration geometry of the model, the accu- 
racy of the determination of reacting moments and 
forces will be reduced. 
PRIOR A R T  
Previous systems for supporting a model in a wind 
tunnel include two major categories: symmetric sting/- 
balance supports and half-span splitter plate supports. 
With a sting/balance support, a balance, or force and 
moment transducer, is attached to a model either exter- 
nally or internally. For example, a rear sting mount is 
used to obtain the aerodynamic effects on the forebo- 
dy/wing combination and a forward blade mount is 
used to obtain the effects on an afterbody/tail combina- 
tion. However, a sting mounting system inevitably re- 
sults in some distortion of the model configuration or, 
depending upon the position of the sting model support, 
some unwanted effect on the air flow around the model. 
The prior art half-span splitter plate method uses the 
concept of a reflection plate parallel to the wind stream 
and located at the model plane of symmetry to provide 
support for one-half of the model. The reflection plate, 
however, changes the airflow causing aerodynamic 
interference effects. 
SUMMARY OF T H E  INVENTION 
Thus, a need continues to exist for a wind tunnel 
model support system which does not interfere with the 
accuracy of the measurement of data. 
Accordingly, it is an object of this invention to pro- 
vide a system for supporting a model in a wind tunnel 
which does not interfere with the aerodynamic flow of 
air around a model. 
It is another object of this invention to provide a 
system for supporting a model in a wind tunnel which 
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does not distort the configuration geometry of the 
model. 
These and other objects are accomplished by the 
present invention by providing a model support system 
utilizing a nonmeasured, or nonmetric, half-span to 
support a measured, or metric, half-span. The two half- 
spans are symmetrical and connected at the plane of 
symmetry of the model by an enclosed airtight seal. A 
symmetrical balance is located at the center of the 
model and a sting support is attached to the wing tip of 
the nonmetric, or support, half-span. The forces and 
moments acting on the metric half-span are measured 
free from unnatural interference from the nonmetric 
support half. 
BRIEF DESCRIPTION O F  T H E  DRAWINGS 
A more complete appreciation of the invention and 
many of the attendant advantages thereof will be 
readily attained as the same becomes better understood 
by reference to the following detailed description when 
considered in connection with the accompanying draw- 
ings, wherein: 
FIG. 1 is a perspective of the entire model of the 
present invention with parts broken away and parts in 
section; 
FIG. 2 is a top view of the assembled model half- 
spans, shown in FIG. 1; 
FIG. 3 is a side view of the nonmetric model half- 
span and sting support as seen along line 3-3 of FIG. 2; 
FIG. 4 is a sectional view of the assembled model 
halves taken along line 4-4 of FIG. 1; and 
FIG. 5 is a sectional view of the assembled model 
halves taken along line 5-5 of FIG. 1. 
DETAILED DESCRIPTION OF T H E  
INVENTION 
Referring now more particularly to FIG. 1, there is 
shown an illustration of a model 10 according to the 
present invention used in wind tunnel investigations. 
Symmetric model 10 comprises metric half-span 12 and 
nonmetric half-span 11. Strain gauge balance 15 is posi- 
tioned between metric half-span 12 and nonmetric half- 
span 11. In the preferred embodiment of the present 
invention, strain gauge balance 15 is rectangular and 
constructed of a stiff metallic material such as, for exam- 
ple, stainless steel. The beams 19 of balance 15 are sepa- 
rated by a relatively long length in order to maintain 
pitch measurement fidelity without encountering signif- 
icant deflection of the apparatus during testing. In other 
respects, balance 15 is a conventional strain gauge bal- 
ance constructed according to principles well known in 
the art. Half-spans 11 and 12 are connected to balance 
15 by means of bolts 50 (FIG. 5) extending horizontally 
through bolt holes 30 and by bolts 40 (FIG. 4) extending 
vertically into balance 15 from the bottom of model 10. 
A sealing gasket 14 is positioned in grooves (not desig- 
nated) which extend along the inside perimeters of met- 
ric half-span 12 and nonmetric half-span 11. Gasket 14 is 
formed of a suitable compliant or elastomeric material 
such as, for example, neoprene or silicon rubber. In the 
preferred embodiment, a soft 3/16 inch diameter neo- 
prene seal was utilized. When metric half-span 12 and 
nonmetric half-span 11 are connected to balance 15, the 
pressure forcing the two half-spans together, achieved 
by tightening bolts 50 (FIG. 5), creates an airtight seal 
between half-spans 11 and 12. Gasket 14 is positioned 
between half-spans 11 and 12 near the model surface at 
balance 15 relative to model 10. Bolt holes 30 and beams 
19 are more clearly shown in this figure. 
Referring now to FIG. 4, a sectional view of model 
10 taken along line 4-4 of FIG. 1 is shown. As shown 
therein sealing gasket 14 extends completely around the 
interior of model halves 11 and 12 and is used to main- 
tain an airtight seal between metric half-span 12 and 
nonmetric half-span 11. Balance 15 can be seen to be 
symmetrical relative to metric half-span 12 and nonmet- 
ric half-span 11. 
Referring now to FIG. 5, a view of model 10 taken 
along line 5-5 of FIG. 1 is shown. Typically, bolt 
access passageways 51 are filled after bolts 50 are tight- 
ened. 
The filling of bolt access passageway 51 provides a 
smooth aerodynamic surface to the exterior of the 
model halves. MetaVsolder, wood putty or any other 
conventional filler material may be employed for clos- 
ing access passageways 51 with any excess filler being 
removed by machining, sanding, polishing or the like, 
to give a faired surface to model 10. 
OPERATION 
The operation of the invention is now believed appar- 
ent. The support for the metric half-span 12 is provided 
by nonmetric half-span 11 in conjunction with sting 
support 13. Because the support of metric half-span 12 is 
located on the plane of symmetry of model 10, there is 
no distortion of the geometric configuration of the met- 
ric half of model 10. Further, because the supporting 
nonmetric half-span 11 is symmetrical relative to metric 
half-span 12, there is no alteration of the aerodynamic 
flow of air around the metric half of model 10 during 
testing. 
With tests at subsonic speeds, the distortion effects of 
the sting mounting mechanism 13 are greatly reduced 
due to the remoteness of the mount. At supersonic 
speeds where the metric half-span 12 is forward of the 
Mach cone emitting from sting support 13, Schlieren 
4,3273 8 1 
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the metric break and thus functions as an O-ring seal to and oil-flow photographs show no evidence of flow 
prevent air flow through the model during a test. Canti- field interference from the sting support. 
levered faired beam sting support 13 is attached to the Although no specific material has been discussed for 
wing tip 17 of nonmetric half-span 11. Sting support 13 model 10, the model in the preferred embodiment of the 
is also attached to support in  the wind tunnel test 5 present invention is constructed of steel. Any suitable 
section (not shown). M~~~~~~~~~~~ of moments and rigid material such as, for example, aluminum, titanium, 
manner by of strain gauges (not shown) posi- for the model construction without departing from the 
tioned on beams 19 of balance 15. A four component spirit and scope Of the invention’ 
Thus, the illustrations described herein are consid- 
or scissor effect at the metric break. This balance design ment of the invention. The invention is not so limited 
does not include side force or yawing moment but this and many modifications and variations thereof will be 
component measurement be added if readily apparent to those skilled in the art in the light of 
needed and the simpler four component bahnce design 15 the foregoing description without departing from the 
was chosen for verification of the inventive concept. spirit and scope of the invention. 
The balance loads in this system are: Normal for- What is claimed as new and desired to be secured by 
ce= 890 N (200 Ib); Axial force= 178 N (40 Ib); Pitching Letters Patent of the United States is: 
moment=226 Nm (2000 inch-lb); and Rolling mo- 1. A wind tunnel model and support system for use in 
ment= 102 Nm (900 inch-lb). 
Referring now to FIG. 2, the attachment of sting a symmetrical model of an aircraft having wings; 
support 13 to the wing tip 17 of nonmetric half-span 11 said symmetrical model comprising a metric half-span 
can be clearly seen. Bolts 21 secure sting support 13 to and a nonmetric half-span; 
the model 10 and maintain nonmetric half-span 11 fixed. said metric half-span being adjacent to said nonmetric 
half-sPan at the Plane of symmetry of said model; 
sting support means attached to the wing tip of said 
forces are taken on metric half-span 12 in a conventional metal alloys, composites and the like may be 
10 
is to provide a Of deflection ered mere]y representations of the preferred embodi- 
20 a wind tunnel test section comprising in combination: 
FIG. 3 provides a clear indication of the position of 25 
nonmetric half-span and adapted for attachment to 
a wind tunnel test section; 
a strain gauge balance positioned within the fuselage 
of said symmetrical model and connected to said 
metric half-span and to said nonmetric half-span; 
said sting support means being disposed parallel to 
the model plane of symmetry and aft of the strain 
gauge balance position to thereby minimize airflow 
interference around the model and avoid affecting 
said strain gauge balance measurements; 
a sealing gasket positioned between said metric half- 
span and said nonmetric half-span; and 
said gasket creating an airtight interface between said 
metric half-span and said nonmetric half-span. 
2. A wind tunnel model support system as in claim 1 
wherein said sting support means comprises a cantilev- 
ered faired beam extending from the rear of said wing 
tip of said nonmetric half-span. 
3. A method for supporting a model in a wind tunnel 
test section which comprises: 
providing a symmetrical model of an aircraft having 
wings and comprising a metric half-span and a 
nonmetric half-span; 
providing a strain gauge balance for measuring mo- 
ments and forces on the model; 
positioning the balance between the metric half-span 
and the nonmetric half-span; 
positioning a sealing gasket within grooves extending 
along the perimeters of the insides of the half-spans; 
connecting the metric half-span to the balance so as to 
maintain the metric half-span adjacent to the non- 
metrc half-span thereby creating an airtight seal; 
connecting the nonmetric half-span to the balance; 
attaching the nonmetric half-span to a fixed sting 
support in the wind tunnel test section such that the 
sting support does not interfere with aerodynamic 
air flow around the model during testing; and 
measuring the moments and forces acting on the met- 
ric half-span during a wind tunnel test. 
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Metric half-span model support system

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