TM 1-1500-204-23-3 (h)    While    still    tacky,    apply    patch    to cemented    area    on    the    cell,    centering    patch    over damaged area.  With the one-inch roller (item 20, table 2-11) or similar tool, roll the patch to the cemented area and roll it down a 1/2 inch to 1 inch across at a time, so as not to trap air between the patch and cell. (i)    Place   a   10   to   25   pound   force   by damping (C-damp (item 21, table 2-11) and two pieces of wood (item 22, table 2-11)), shot bag (item 23, table 2-11),  etc.,  if  practical  on  repair.    Polyethylene,  waxed paper  (item  24,  table  2-11)  should  be  placed  between the patch and force applying device to prevent sticking of the force applying device to the repair. (j)    Allow  repair  to  remain  undisturbed for at least 8 hours.  The fuel cell should not be returned to   service   for   24   hours   after   a   cold   patch   has   been applied,  which  is  the  time  required  for  the  adhesive  to become  fully  cured,  at  a  temperature  between  60 °F  to 80°F. (k)    Visually inspect repair for workmanship,  no  loose  edges,  no  voids  and  adhesive fully cured.  If there is a defect in repair, recement per above procedure. (6) External and Internal Surface Hole Repair, Including Through Hole. WARNING Acetone  and  repair  adhesives  are flammable  and  toxic.    Keep  away from heat, sparks and open flame. Wear  safety  glasses,  gloves  and protective     clothing     to     prevent contact.  Wear a NIOSH approved air-purifying respirator for organic vapors and work in a well ventilated area.  If contact occurs, flush   areas   with   water   and   get medical    attention.        If    ingestion occurs get medical attention at once. (a)    Clean  innerliner  of  fuel  cell  at  least 3 1/4 inches larger in all directions around hole.  Use a piece    of    dean    cheesecloth    (item    16,    table    2-11) dampened with acetone (item 3, table 2-11). (b)    Lightly,  hand  buff  innerliner  of  fuel cell  around  hole  using  emery  cloth  (120  grit)  (item  17, table 2-11), 3 1/4 inches in all directions. (c)    Clean  buffed  area.    Use  a  piece  of dean  cheesecloth  (item  16,  table  2-11)  dampened  with acetone (item 3, table 2-11).  The surface must be clean and dry in order to apply patch. (d)    Cut    a    patch    from    internal    patch material fabric (item 19, table 2-11).  The patch should be 3 inches larger in all directions around hole.  Lightly, hand  buff  gum  side  (side  with  dull  finish)  of  patch  with emery cloth (item 17, table 2-11).  Remove buffing dust by  wiping  patch  with  cheesecloth  (item  16,  table  2-11) dampened   with   acetone   (item   3,   table   2-11).      Wear gloves (item 4, table 2-11). WARNING Repair adhesive is flammable    and    should    be    kept away from any ignition source. NOTE Adhesive materials should be kept tightly sealed in individual containers in a cool, dry place. (e)    Refer     to     paragraph     c(1)(e)     for mixing instructions. NOTE The     adhesive     should     be used    sparingly.        Two    (2)    thin, even    coats    will    provide    better adhesion  than  two  thick,  puddled coats.        Acetone    is    used    as    a solvent    for    the    adhesive    and, when the cemented surface appears  dry  to  touch,  it  may  be freshened or made tacky again by application of this solvent. NOTE Do not apply adhesive beyond buffed areas. (f)    Apply   one   coat   of   adhesive   (item 18,  table  2-11)  to  buffed  side  of  patch  and  buffed  area of cell innerliner, allow to dry 20-60 minutes. NOTE To determine if adhesive is tacky, test    it    by    pressing    a    knuckle gently against the cemented surface    and    withdrawing    it    (if practical).      Proper   tackiness   is achieved  when  a  few  threads  of adhesive    stick    to    the    knuckle. This  procedure  is  referred  to  as the knuckle test. Change 2  2-63