Johnson-level-tool-mfg RAS-1 Manual de usuario descargar pdf (Pagina 38)

support rafter length. To begin with, we ﬁnd a 2' run having

a3'9"length.Thisthenleavesa5"lengthwhichresultsin

anapproximationofa2-11/16"run.Ifneeded,approximat-

ing can be done with the following equation, if desired:

Lm – Ll

( Rh x ( ) ) + Rl

Lh – Lm

Rm =

Lm – Ll

1.00 + ( )

Lh – Lm

Where R = run, L = length, l = low, m = middle, h = high.

 Inourexample:

5.00 – 4.63

( 3.00 x ( ) ) + 2.50

5.63 – 5.00

Rm =

5.00 – 4.63

1.00 + ( )

5.63 – 5.00

= 2.69

= 2-11/16"

Thuswehaveforthesupportrafterrun,2'plus211/16"

equalling2'2-11/16"(or26.69").Nowtondthesupport

rafter rise:

Inch Rise x Run (in.)

SUPPORT RAFTER RISE (in.) =

19 inch rise x 26.69"

= 42.25"

Converted to feet:

= 3' 6-1/4"

Nextweneedtondthehorizontaloverhanglength

(seeFigure21).Itisfoundbyndingtheroofrunbetween

pointsAandBandthen subtracting the support rafter run

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Johnson-level-tool-mfg RAS-1 Manual de usuario Pagina 38