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SKETCHING
Sketching angles by visual comparison

Engineering Aid 3 - Beginning Structural engineering guide book
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redrawn   more   quickly   than   mistakes   can   be erased. For  making  dimensioned  sketches  in  the  field, you  will  need  some  sort  of  measuring  tape—either a pocket rule or a surveyor’s tape, depending on the extent of the measurements taken. If you are required to collect extensive field data, it would be to your benefit to maintain a sketch notebook. A  surveyor’s  field  notebook  works  well  for  this purpose. TECHNIQUES OF SKETCHING The sketch should conform to one of the stan- dard  types  of  projection  discussed  in  this  chapter. You   must   apply   correct   proportion   whenever possible.  When  you  use  cross-section  paper,  its grid will provide a ready scale that will aid you in sketching proportionally. You do this by counting the squares within the object to be drawn. The size of  your  sketch  depends  upon  the  complexity  of the  object  and  the  size  of  paper  you  are  using. Sketching  Straight  Lines In sketching lines, place a dot where you want a line to begin and one where you want it to end. In  sketching  long  lines,  place  one  or  more  dots between the end dots. Then swing your hand in the direction your line should go, and back again a  couple  of  times  before  you  touch  your  pencil to the paper. In this way you get the feel of the line. Then use these dots to guide your eye and your hand as you draw the line. Draw each line with a series of short strokes instead of with one stroke.  Using  short  strokes,  you  can  better control  the  direction  of  your  line  and  the  pressure Figure 5-58.-Use of paper, pad, or table as a guide when drawing straight lines. of  your  pencil  on  the  paper.  Hold  the  pencil  about three quarters of an inch to an inch from the point so that you can see what you are doing. Strive for a free and easy movement rather than a cramped finger  and  wrist  movement. Another useful technique in drawing straight lines is to use the side of the paper, pad, or table as a guide for your hand. Hold the pencil at the desired starting point of the line and place the heel of  your  hand  and  one  finger  on  the  guide,  as shown in figure 5-58. Move the pencil, in this case, with one uniform stroke to complete the line. Try drawing several light horizontal lines and, after each  one  is  drawn,  examine  it  for  straightness, weight, and neatness. If it is too light, use either a  softer  pencil  or  a  little  more  pressure. Vertical lines are usually sketched downward on  the  paper.  The  same  suggestions  for  using locator  dots,  free  movement  of  the  entire  arm, and  guides  apply  to  vertical  lines  as  they  do  to horizontal  lines. Slanting lines may be drawn from either end toward  the  other.  For  better  control,  you  might find  it  helpful  to  rotate  the  paper,  thus  placing the desired slanting line in either the horizontal or  vertical  position. To  keep  your  sketch  neat,  first  sketch  your lines lightly. Lines not essential to the drawing can be  sketched  so  lightly  that  you  need  not  erase them.  Darken  essential  lines  by  running  your pencil over them with more pressure. Figure 5-59 shows line conventions drawn with various types of  pencil  points. Figure  5-59.-Line  conventions  drawn  with  various  types  of pencil points. 5-30







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