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National Advisory Committee for Aeronautics, Technical Notes - Tests of the NPL Airship Models in the Variable Density Wind Tunnel

Tests have been conducted in the variable density wind tun—
nel of the National Advisory Committee for Aeronautics, on two
airship models, known as the "N.P.L. Standardization Models,
Long and Short." The resistance or shape coefficients were de—
termined for each model through a range of Reynolds Numbers from
110,000 to 5,000,000. Comparison is made with previous tests
on these models and other airship models.

During the years of 1982 and 1923, comparative tests were
made on two N-P-L. airship models in-six American atmospheric
wind tunnels to determine their resistance with_particular ref—
erence to scale effect. These tests were made for the purpose
of determining some idea of the "standardization of wind tunnels."
The models used were developed and furnished by the British Aero—
nautical Research Committee.

It was desired that further tests on these models be made
and, as the models had been returned to England, replicas were
made at the Washington Navy Yard by the wind tunnel division of
the Bureau of Construction and Repair. It was of particular im-
portance that a greater ”scale" or Reynolds NUmber be reached;
simplicity in the method of support for the models was also rec—
ommended for the further tests.

The Navy replicas of the H.P.L. airship models were there—
fore forwarded to the Langley Memorial Aeronautical Laboratory
for testing in the variable density wind tunnel where a Reynolds;
Number fifteen times that of the original tests could be obtained.
The actual tests in the variable density tunnel were not per-
formed-until June, 1927.

These consisted of determining the resistanoe at the angle
of zero pitch for both models through a range of Reynolds Numbers
from 110,000 to 5,000,000.

The airship models used.in these tests were cast of alumi—
num and turned in a lathe to specified ordinates measured on
the original N-P-L- models.