This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
The following illustrations and text will explain the principles involved in developing the patterns for the ventilator, curb, hip bar, common bar, jack bar, and cross bar or clip, in a hipped skylight. These principles are also applicable to any other form of light, whether flat, double-pitch, single-pitch, etc.
In Fig. 178 is shown a half section, a quarter plan, and a diagonal elevation of a hip bar, including the patterns for the curb, hip, jack, and common bars. The method of making these drawings will be explained in detail, so that the student who pays close attention will have no difficulty in laying out any patterns no matter what the pitch of the skylight may be, no what angle its plan may have.
First draw any center line as A B, at right angles to which lay off C 4', equal to 12 inches. Assuming that the light is to have one-third pitch, then make the distance C D equal to 8 inches which is one-third of 2 inches, and draw the slant line D 4'. At right angles to D 4' place a section of the common bar as shown by E, through which draw lines parallel to D 4', intersecting the curb shown from a to f at the bottom and the inside section of the ventilator from F to G at the top. At pleasure draw the section of the outside vent shown from h to l and the hood shown from m to p. X represents the section of the brace resting on i j to uphold the hood resting on it in the corner o. The condensation gutters of the common bar E are cut out at the bottom at 5' 6" which allows the drip to go into the gutter d e f of the curb and pass out of the opening indicated by the arrow. Number the corners of each half of the common bar section E as shown, from 1 to 6 on each side, through which draw lines parallel to D 4' until they intersect the curb at the bottom as shown by similar numbers 1' to 6', and the inside ventilator at the top by similar figures 1" to 6". This completes the one half-section of the skylight. From this section the pattern for the common bar can be obtained without the plan, as follows: At right angles to D 4' draw the line I J upon which place the stretchout of the section E as shown by similar figures on I J. Through these small figures, and at right angles to I J, draw lines, and intersect them by lines drawn at right angles to D 4' from similarly numbered intersections 1' to 6' on the curb and 1" to 6" on the inside ventilator. Trace a line through points thus obtained; then A1 B1 C1 D1 will be the pattern for the common bar in a hipped skylight. The same method would be employed if a pattern were developed for a flat or a doublepitch light. From this same half section the pattern for the curb is developed by taking the stretchout of the various corners in the curb, a b 3' 3' c d e and f, and placing them on the center line A B as shown by similar letters and figures. Through these divisions and at right angles to A B draw lines which intersect with lines drawn at right angles to C 4' from similar points in the curb section a f. Trace a line through points thus obtained; then E1 F1 f a will be the half pattern for the curb shown in the half section. V represents the condensation hole to be punched into the pattern between each light of glass in the skylight As the portion c d turns up on c 4', use r as a center, and with the radius r s strike the semicircle shown. Above this semicircle punch the hole V.
Before the patterns can be obtained for the hip and jack bars, a quarter plan view must be constructed which will give the points of intersections between the hip bar and curb, between the hip bar and vent, or ridge bar, and between the hip and jack bar. Therefore, from any point on the center line A B as K, draw K L at right angles to A B.
As the skylight forms a right angle in plan, draw from K, at an angle of 45o, the hip or diagonal line K 1o. Take a tracing of the common bar section E with the various figures on same, and place it on the hip line K 1o in plan so that the points 1 4 come directly on the hip as shown by E1. Through the various figures draw lines parallel to K 1o one-half of which are intersected by vertical lines drawn parallel to A
B from similar points of intersection 1' to 6' on the curb, and 1" to 6" on the ventilator in the half section, as shown respectively in plan by intersections 1o to 6o. Below the hip line K 1o trace the opposite intersection as shown. It should be understood that the section E1 in plan does not indicate the true profile of the hip bar (which must be obtained later), but is only placed there to give the horizontal distances in plan. In laying out the work in practice to full size, the upper half intersection of the hip bar in plan is all that is required. It will be noticed that the points of intersections in plan and one half section have similar numbers, and if the student will carefully follow each point the method of these projections will become apparent.
Having obtained the true points of intersections in plan the step is to obtain a diagonal elevation of the hip bar, from which a true section of the hip bar and pattern are obtained. To do this draw any line as R M parallel to K 1°. This base line R M has the same elevation as the base line C 4' has in the half section. Prom the various points 1o to 6o and 1v to 6v in plan, erect lines at right angles to K 1° crossing the line R M indefinitely. Now measuring in each and every instance from the line C 41 in the half section take the various distances to points D" 2" 3" 4" 5" and 6" at the top, and to points 1' 2' 3' 4' 5' and 6' at the bottom, and place them in the diagonal elevation measuring in each and every instance from the line R M on the similarly numbered lines drawn from the plan, thus locating respectively the points N 1T 2T 3T 4T 5T and 6T at the top, and 1P 2P 3P 4P 5P and 6P at the bottom. Through the points thus obtained draw the miter lines 1T to 6T and lP to 6P and connect the various points by lines as shown, which completes the diagonal elevation of the hip bar intersecting the curb and vent, or ridge. To obtain the true section of the hip bar, take a tracing of the common bar E or E1 and place it in the position shown by E3 , being careful to place the points 1 4 at right angles to 1T 1P as shown. Prom the various points in the section E3 at right angles to 1P 1T draw lines intersecting similarly numbered lines in the diagonal elevation as shown from 1 to 6 on either side. Connect these points as shown; then E4 will be the true profile of the hip bar. Note the difference in the two profiles; the normal E3 and the modified E4.