Splicing 4mm Dyneema to a 20mm Double Tii-On
A Brummel splice is a strong and reliable way to create a loop in Dyneema rope, commonly used in high-performance sailing applications. In this guide, we’ll show you how to make a Brummel splice using 4mm Dyneema (TY4112) and attach it to a 2mm Tii-Shackle (A20120), which will then be used to secure a Dynamic 20 Tii-On Double Block (A2022Tii).
The A2022Tii— a dynamic 20mm tii-on block—is designed for soft attachment with thinner lines, up to 3mm is best. While a 4mm line can pass around the block, it can be difficult to rig due to the size of the opening. Instead, using a 2mm soft shackle simplifies the installation and provides a secure attachment point for the Brummel-spliced loop.
Another advantage of using a Tii-Shackle is that it helps maintain the block’s structural integrity under load. Thicker lines can exert outward pressure on the block’s body, increasing the risk of the top opening up under shock loads. A crossed Tii-Shackle ensures the load pulls inward, reducing this risk and allowing the block to operate at its designed working loads.
At Allen, we sell all the tools and components you need to complete this splice, including the rope, block, and splicing tools. Follow along with our step-by-step video and use this written guide below for reference.
