Claw Lines for RafterTools for iPhone

Claw Lines for RafterTools+ app for iPhone Help file.

RafterTools+ app for iPhone Claw Lines Usage.

The hip roof claw lines are based on the Main and Adjacent side roof slope angles. These claw line dimensions will only work on hip rafters that are backed out and offset to have equal shoulder heights at the eave line. The claw lines allow you to check your geometric roof surface layout or use these claw line dimensions to layout the claw lines on the roof surface independently of the the other parts of the roof to cut the upper and lower claw angles on jack rafters, purlin rafters and skewed purlin rafters. Gratsparren bei unterschiedlicher, verschiedener Dachneigung.

The claw lines are based on the

  1. Profile Rafter Depth
  2. Hip Rafter Depth
  3. Hip Rafter Width
You can select these parameters in the first 4 rows of the Claw Lines display. Click on the parameter you want to change and enter the new value. The profile rafter depth depth should be the same size as the hip rafter depth if your rafter has an lower claw. Use the claw line dimensions for the correct side of the roof if your roof has two different roof slopes. 

Claw Line Dimensions
  • Claw Line #1 represents the center line of the hip rafter. It is always equal to 0.
  • Claw Line #2 represents the edge of the backed out hip rafter.
  • Claw Line #3 represents the internal edge of the hip rafter backing triangle. It is the intersection of the edge of the hip rafter and the bottom of the rafter. Use lines 2 & 3 for the development of the miter angle on the side of the rafter.
  • Claw Line #4 represents the intersection of the bottom side of the rafter with the hip rafter.
  • Claw Line #5 represents the intersection of the top side of the rafter with the hip rafter.
  • Use lines 4 and 5 to develop the lower claw line on the side of the rafter.

If you use the claw lines  independently of the roof, use the Sheathing Angle to draw out the correct roof surface. To draw out the roof surface you can enter the eave length, like 24" in a calculator and use the roof Sheathing Angles as the roof slope angle to calculate the length of the common rafter length on the roof surface.
Roof Sheathing Angle Example:
  1. Rafter Length on Roof Surface = tan(Roof Sheathing Angle) × Eave Length
  2. Eave Length = 24"
  3. Roof Sheathing Angle = 58.84094°
  4. Rafter Length on Roof Surface = tan(58.84094°) × 24 = 39.69269" or 3 11/16"

Once you have the claw lines laid out you can place a jack rafter, purlin rafter or skewed purlin rafter on the claw lines to draw out the miter angle and claw angle on the sides of the rafter. The Roof Sheathing angle is also transferred to the top and bottom edges of the rafter for the correct back bevel on the rafter.
























    Example email print out with an 7:12 & 10:12 with an 90° eave angle.
    Rafter Tools
    Claw Lines

    Main Slope Angle
    30.25644
    Adjacent Slope Angle
    39.80557
    Main Plan Angle
    55.00798
    Adjacent Plan Angle
    34.99202
    Hip Rafter Slope Angle
    25.54245

    Geometric Roof Surface Layout

    Profile Rafter Depth
    3.50000 in
    Hip Rafter Depth
    3.50000 in
    Hip Rafter Width
    3.50000 in
    Main Side Roof Sheathing Angle
    58.84094
    Claw Line 1
    0.00000 in
    Claw Line #2
    2.45366 in
    Claw Line 3
    3.51005 in
    Claw Line 4
    0.51668 in
    Claw Line 5
    12.11278 in
    Seat Line for Rafters in Plan View
    6.94622 in
    Seat Line for Rafters on Roof Surface
    6.00000 in
    Adjacent Side Roof Sheathing Angle
    42.33965
    Claw Line 1
    0.00000 in
    Claw Line #2
    1.35184 in
    Claw Line 3
    3.50774 in
    Claw Line 4
    0.99145 in
    Claw Line 5
    6.67354 in
    Seat Line for Rafters in Plan View
    5.46717 in
    Seat Line for Rafters on Roof Surface
    4.20000 in

    Example email print out with an 7:12 & 10:12 with an 120° eave angle.
    Rafter Tools
    Claw Lines

    Main Slope Angle
    30.25644
    Adjacent Slope Angle
    39.80557
    Main Plan Angle
    76.99609
    Adjacent Plan Angle
    43.00391
    Hip Rafter Slope Angle
    29.61276

    Geometric Roof Surface Layout

    Profile Rafter Depth
    3.50000 in
    Hip Rafter Depth
    3.50000 in
    Hip Rafter Width
    3.50000 in
    Main Side Roof Sheathing Angle
    78.71865
    Claw Line 1
    0.00000 in
    Claw Line #2
    2.89844 in
    Claw Line 3
    3.29784 in
    Claw Line 4
    0.19906 in
    Claw Line 5
    30.86969 in
    Seat Line for Rafters in Plan View
    6.94622 in
    Seat Line for Rafters on Roof Surface
    6.00000 in
    Adjacent Side Roof Sheathing Angle
    50.52159
    Claw Line 1
    0.00000 in
    Claw Line #2
    0.70193 in
    Claw Line 3
    2.55631 in
    Claw Line 4
    0.86991 in
    Claw Line 5
    7.47589 in
    Seat Line for Rafters in Plan View
    5.46717 in
    Seat Line for Rafters on Roof Surface
    4.20000 in

    Example email print out with an 7:12 & 10:12 with an 70° eave angle.
    Rafter Tools
    Claw Lines

    Main Slope Angle
    30.25644
    Adjacent Slope Angle
    39.80557
    Main Plan Angle
    42.04411
    Adjacent Plan Angle
    27.95589
    Hip Rafter Slope Angle
    21.33859

    Geometric Roof Surface Layout

    Profile Rafter Depth
    3.50000 in
    Hip Rafter Depth
    3.50000 in
    Hip Rafter Width
    3.50000 in
    Main Side Roof Sheathing Angle
    46.23362
    Claw Line 1
    0.00000 in
    Claw Line #2
    2.37592 in
    Claw Line 3
    3.78818 in
    Claw Line 4
    0.67951 in
    Claw Line 5
    9.35355 in
    Seat Line for Rafters in Plan View
    6.94622 in
    Seat Line for Rafters on Roof Surface
    6.00000 in
    Adjacent Side Roof Sheathing Angle
    34.63849
    Claw Line 1
    0.00000 in
    Claw Line #2
    1.57219 in
    Claw Line 3
    3.97189 in
    Claw Line 4
    1.08462 in
    Claw Line 5
    6.18943 in
    Seat Line for Rafters in Plan View
    5.46717 in
    Seat Line for Rafters on Roof Surface
    4.20000 in

    Here's an example of using the claw line dimensions on an equal pitched 8:12 roof.

    1. Draw the roof surface triangle using the roof sheathing angle.
    2. Draw parallel lines from the hip rafter line on the roof surface using the claw line dimensions.
    3. Draw the seat line on the roof surface using the seat line dimension from RafterTools.
    4. Lay the timber on the roof surface and transfer the lines as shown in this drawing for the miter angle on the side of the rafter and the claw lines for the claw on the rafter.
    5. Lines 2 & 3 develop the mite angle on the side of the rafter.
    6. Lines 4 & 5 develop the lower claw angle on the side of the rafter.
















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