11. Set your dividers equal to one of the numbered

of a five-piece 90-degree elbow. Take a pair of dividers

divisions in the half-plan.

and a straightedge and develop a five-piece 90-degree

elbow using this method.

12. Step off twice the number of equal spaces in

the stretchout that you have in the half-plan.

1. Using figure 12-42 as a guide, scribe horizontal

line AB. From point A, scribe line AC to form angle

13. Erect perpendiculars from the base line of the

CAB, which should be equal to the degree of angle that

stretchout and number them as shown in figure 12-42.

the elbow is to be. In this cast, we will use 90° for our

The number with which you begin and end in your

elbow.

stretchout will determine the location of the seam in the

2. Set the dividers for the throat radius and scribe

finished elbow. The best location for a seam on an elbow

the arc, using A as the vertex.

is on the side, so you would number from 4 up to 7, then

down to 1 and back up to 4. Numbering from 1 to 7 and

3. Set your dividers for the heel radius, and using

back to 1, as was shown in the previous development,

A as the vertex, scribe the heel arc. (The heel radius is

would place the seam on the heel. A layout done in this

determined by adding the diameter of the elbow to the

manner is undesirable because it would require more

throat radius.)

time and material to complete the seam. Numbering

4. Divide the heel arc BC into equal spaces. To

from 7 to 1 and back to 7 is also undesirable. This

determine the number of spaces to use and the degree

method would put the seam in the throat of the elbow;

of angle per space, follow this rule: Multiply the number

normally it would be too small to make a strong seam.

of pieces in the elbow by 2 and subtract 2. This will give

The location of the scam is a matter of preference and

you the number of equal spaces. Then, divide the degree

is determined by the job you are laying out.

of the elbow by the number of equal spaces. You now

14. To transfer the pattern from the elevation to the

have the degree of angle for each space on the heel arc.

stretchout using dividers, follow these steps:

SAMPLE:

a. Using line 4, measure its distance between

5 × 2 = 10 - 2=8

lines AB and HJ with your dividers.

90° ÷ 8 = 11.25° of angle per space.

b. Using this distance, mark off three spaces on

each of the three lines that are numbered as

5. Now, draw lines from the vertex A to the points

4 in the stretchout. Start from the base line

stepped off on the heel arc, making pieces I and V equal

to one space each on the heel arc. Pieces II, III, and IV

of the stretchouts.

are made equal to two spaces each on the heel arc. They

c. The point on each line 4 that would divide

are twice the size of I and V.

the second and third space in half forms the

6. Using AB for the base line, construct the

center of the stretchout. To make the center

half-plan.

line AB for the stretchout, draw a line to

connect these three points.

7. Step off the circumference of the half-plan into

equal spaces, and number the dividing lines from 1 to

d. Now, using the point where the center line

7. For a larger diameter, use a greater number of equal

and the numbered lines (elements) in the

spaces. The more spaces you use, the more accurate

stretchout intersect, scribe arcs cutting each

your plan will be.

of the lines the same length as the

corresponding lines in the elevation between

8. Use AG for the miter line. You have now

the base line AB and line HJ.

completed your elevation for making the stretchout of

piece II, which will be the same for III and IV, and for

e. Connect these points with smooth lines that

making the stretchout of piece I, which will be the same

will be curved. Your stretchout is now

as V.

completed. Piece I in the stretchout (the

lower piece) is the pattern for pieces I and V

9. To join the elbow together, you must make

in the elbow, and piece II in the stretchout is

allowance for your elbow seam. Add the allowance

the pattern for pieces II, III, and IV.

from line AG up and draw line HJ.

Figure 12-43 is a pictorial view of the five-piece

10. Extend line AB to the right of the elevation to

elbow you have just laid out.

make the stretchout.

12-16

Integrated Publishing, Inc. |