<DOC>
<DOCNO>
289
</DOCNO>
<TITLE>
a theoretical study of the aerodynamics of slender
cruciform-wing arrangements and their wakes .
</TITLE>
<AUTHOR>
spreiter,j.r. and sacks,a.h.
</AUTHOR>
<BIBLIO>
naca r1296, 1957.
</BIBLIO>
<TEXT>
  a theoretical study is made of some cruciform-wing arrangements
and their wakes by means of slender-body theory .  the
basic ideas of this theory are reviewed and equations are developed
for the pressures, loadings, and forces on slender cruciform
wings and wing-body combinations .  the rolling-up of
the vortex sheet behind a slender cruciform wing is considered
at length and a numerical analysis is carried out using 40
vortices to calculate the wake shape at various distances behind
an equal-span cruciform wing at 45 bank .  analytical expressions
are developed for the corresponding positions of
the rolled-up vortex sheets using a 4-vortex approximation to
the wake, and these positions are compared with the positions
of the centroids of vorticity resulting from the numerical analysis .
the agreement is found to be remarkably good at all distances
behind the wing .
  photographs of the wake as observed in a water tank are
presented for various distances behind a cruciform wing at 0
and 45 bank .  for 45 bank, the distance behind the wing
at which the upper two vortices pass between the lower two is
measured experimentally and is found to agree well with the
  the calculation of loads on cruciform tails is considered in
some detail by the method of reverse flow, and equations are
developed for the tail loads in terms of the vortex positions
calculated in the earlier analyses .
</TEXT>
</DOC>
