﻿234 
  ANNUAL 
  EEPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1927 
  

  

  lems 
  are 
  not 
  at 
  all 
  strange 
  to 
  everyday 
  life. 
  There 
  is 
  a 
  rather 
  pecul- 
  

   iar 
  financial 
  analogy 
  to 
  soaring 
  flight, 
  viz, 
  making 
  money 
  from 
  

   dynamical 
  sources. 
  Soaring 
  in 
  gusts 
  is 
  ruled 
  by 
  much 
  the 
  same 
  con- 
  

   ditions 
  as 
  buying 
  and 
  selling 
  stock, 
  alv^ays 
  making 
  a 
  change 
  of 
  policy 
  

   coinciding 
  as 
  best 
  possible 
  with 
  every 
  climax. 
  Soaring 
  between 
  sta- 
  

   tionary 
  wind 
  layers 
  is 
  equivalent 
  to 
  trading 
  across 
  international 
  

   boundaries, 
  buying 
  merchandise 
  where 
  there 
  is 
  abundance 
  of 
  it 
  and 
  

   importing 
  it 
  to 
  where 
  it 
  is 
  lacking. 
  The 
  loss 
  due 
  to 
  centrifugal 
  

   force 
  represents 
  the 
  freight 
  and 
  import 
  duty. 
  Dynamic 
  climbing 
  

   in 
  a 
  vertical 
  wind 
  gradient 
  is 
  very 
  strikingly 
  paralleled 
  by 
  the 
  

   business 
  condition 
  in 
  a 
  country 
  where 
  currency 
  is 
  being 
  inflated, 
  the 
  

   inertia 
  of 
  the 
  money 
  devaluating 
  during 
  circulation 
  being 
  essential 
  

   for 
  the 
  profit 
  of 
  those 
  who 
  issue 
  it 
  and 
  the 
  loss 
  of 
  those 
  who 
  furnish 
  

   the 
  values. 
  Even 
  the 
  deeper 
  cause 
  for 
  the 
  maintenance 
  of 
  such 
  an 
  

   unstable 
  situation, 
  being 
  some 
  greater 
  disturbance 
  of 
  much 
  bigger 
  vol- 
  

   ume 
  than 
  the 
  individual's 
  concern, 
  finds 
  its 
  perfect 
  parallelism 
  in 
  

   soaring 
  flight. 
  

  

  Practical 
  soaring 
  flight 
  depends 
  not 
  only 
  on 
  the 
  wind 
  structure 
  

   and 
  the 
  pilot's 
  skill, 
  but 
  also 
  to 
  a 
  large 
  extent 
  on 
  the 
  design 
  of 
  the 
  

   glider. 
  Theoretically, 
  of 
  course, 
  any 
  airplane 
  can 
  be 
  flown 
  as 
  a 
  

   glider 
  provided 
  plenty 
  of 
  power 
  is 
  presented 
  in 
  the 
  aerological 
  

   situation 
  to 
  meet 
  the 
  modest 
  aerodynamic 
  efficiency 
  of 
  the 
  machine. 
  

   Extended 
  soaring 
  flights 
  have 
  indeed 
  been 
  made 
  with 
  regular 
  air- 
  

   planes, 
  the 
  motor 
  just 
  shut 
  off, 
  for 
  instance, 
  by 
  the 
  French 
  lieuten- 
  

   ant 
  Thoret 
  on 
  a 
  horseshoelike 
  bay 
  on 
  the 
  North 
  African 
  coast. 
  

  

  The 
  most 
  interesting 
  development^ 
  however, 
  was 
  that 
  of 
  the 
  modern 
  

   gliders, 
  machines 
  specially 
  designed 
  for 
  use 
  without 
  a 
  motor. 
  In 
  

   their 
  design 
  lightness 
  in 
  spite 
  of 
  strength 
  and 
  aerodynamic 
  refine- 
  

   ment 
  were 
  carried 
  to 
  unusual 
  extremes, 
  which 
  later 
  did 
  not 
  fail 
  to 
  

   have 
  some 
  marked 
  influence 
  upon 
  modern 
  design 
  of 
  motor-driven 
  

   aircraft, 
  too. 
  

  

  The 
  structures 
  of 
  most 
  gliders 
  are 
  made 
  of 
  wood. 
  Very 
  thin 
  ply- 
  

   wood 
  varying 
  in 
  gauge 
  from 
  three 
  thirty-seconds 
  down 
  to 
  one 
  thirty- 
  

   second 
  of 
  an 
  inch 
  for 
  the 
  total 
  of 
  the 
  three 
  plies, 
  is 
  the 
  preferred 
  

   material. 
  Wooden 
  beams 
  and 
  trusses 
  joined 
  by 
  plywood 
  gusset 
  plates 
  

   are 
  assembled 
  to 
  the 
  most 
  intricate 
  and 
  elaborate 
  internally 
  trussed 
  

   bridge 
  works. 
  Cantilever 
  wings 
  weighing 
  less 
  than 
  5 
  ounces 
  per 
  

   square 
  foot 
  are 
  built 
  with 
  ample 
  strength. 
  Waterproof 
  casein 
  glue 
  

   is 
  used 
  exclusively 
  and 
  nails 
  are 
  religiously 
  avoided 
  by 
  many 
  de- 
  

   signers, 
  since 
  with 
  a 
  well-glued 
  joint 
  they 
  contribute 
  nothing 
  to 
  

   strength 
  but 
  considerably 
  to 
  weight 
  and 
  deterioration. 
  The 
  weight 
  of 
  

   successful 
  gliders 
  varies 
  from 
  about 
  250 
  pounds 
  down 
  to 
  as 
  little 
  as 
  

   90 
  pounds. 
  Two 
  people 
  can 
  handle 
  them 
  on 
  the 
  ground. 
  

  

  