For heavy-duty release applications, a Seacatch is THE thing to use. I’ve never found a better way of releasing a heavy line under tension. It’s a better solution than a pelican hook (not strong enough, tough to get a smooth release), or a sacrificial line (inelegant, and can foul up launch). Personally I use a Seacatch model TR7LM for homemade trebuchets and ballista releases. Ballista — as in a giant crossbow, suitable for launching bowling balls, pumpkins, etc. (It’s one of the more bizarre hobbies that has arisen in the last 25 years.) But I’ve also seen Seacatches used by tractor-pull people, construction, you name it. Comes in a wide variety of sizes as well. Beautifully engineered, bombproof, cool.
The action of a Seacatch is smooth, the construction is top-quality. I’ve never heard of one failing. Their electrically/pneumatically/hydraulically actuated models are commonly used in the Hollywood special effects industry for dropping things at precise moments. They were originally designed for shipboard use (tugboats, fishing boats, etc.) but they’ve found niches elsewhere.
This is an expensive specialty item for sure, but if you need what it does, it is absolutely worth its price. Before I learned they existed, I spent at least that much on materials and machining yet without being able to create a better release mechanism.