PSB#120399 Tandem Riser 3-ring
Locking Loop Modification
Instructions
The following instructions illustrate how a Relative Workshop tandem riser with a short loop – as described in PSB#120399 – should be modified to increase its working load capacity. As noted in PSB#120399, this work can only be performed by a Certified Master Rigger. Please read these instructions several times before beginning any work. If you have any questions, please contact Relative Workshop by phone at (904) 736-7589 or by e-mail at tk@relativeworkshop.com.

As a reference, review the Three-Ring Riser Construction Manual, August 1998 Specifications for Type-8 Standard 3-ring risers. Because this is a modification to risers built before these specifications were published, the dimensions shown in the manual will not be the same as the affected risers. However, the construction techniques are the same. This manual is available from the Relative Workshop for $10 plus shipping.

Materials Needed:
1. Type 2A Sheathing – 7”
2. Type-4, 1”
3. Tape – 5-1/2”
4. E-thread 5-cord or 6-cord

Tools Needed:
1. Seam Ripper or Sharp Scissors
2. Razor Blade (Optional)
3. Hot Knife with Basting Tip (Optional)
4. Hot Glue Gun
5. Zigzag Sewing Machine (304, single-throw; or 308, double-throw)
6. 7-class “Harness” Sewing Machine

Step 1: Using a seam ripper or scissors, carefully remove and discard the 1”, Type-4 tape which forms the confluence wrap.
Step 2: Using a razor blade (pictured above), seam ripper, or scissors; carefully remove and discard the Type 2A sheathing that forms the 3-ring locking loop. Regardless of the tool used, use extreme caution to avoid damage to the 1”, Type-4 tape underneath the sheathing or the riser webbing itself.
Step 3: Fold the 7” length of Type 2A sheathing in half. Temporarily secure the new 3-ring locking loop in place as shown using hot glue or a basting tip. The folded edge of the Type 2A sheathing should be even with the folded edge of the 1”, Type-4 tape inside the small ring.
Step 4: Set your zigzag machine to the following settings: 1/8" wide; 42 stitches per inch. Using E-thread, place two, 5/8" long passes of zigzag stitching - one on top of the other - through the Type 2A sheathing in the area once covered by the confluence wrap. If available, a bar-tack machine can be used with the following settings: 1/8" wide; 5/8" long; 42 stitches.
Step 5: Place the 5-1/2” length of 1”, Type-4 tape around the riser; forming a confluence wrap as shown in the sequence figures above. The lower edge of the confluence wrap should be between 3/16” to 1/4” from the upper edge of the #2 grommet.
Step 6: Using a 7-class sewing machine with 5-cord or 6-cord, place a box stitch through the confluence wrap as shown. Keep the stitches 1/8” to 3/16” from the edge. Start the box stitch so that two passes can be made along both side edges and the upper edge.
Step 7: The picture on the right side shows the completed modification. Repeat steps 1 – 6 for the other riser. Inspect each modified riser with the specification shown below.

WARNING

- Check the condition of your machine’s sewing needles before beginning the work. Poor needle condition will weaken the riser.
- Only two (2) attempts should be made to effect this modification. If you are not successful on the second attempt, the riser may be irreparably damaged and should be discarded.