Quote:
Originally Posted by SailorGreg
For what it is worth, I think stretchability of a snubber is overrated and very hard to calculate. For a given boat, trying to determine just the right diameter of snubber that will stretch but not degrade or break under various wind and wave loads is next to impossible.
The goal is to avoid shock loads at the limits of swing or bucking at anchor. And those shock loads are only an issue under storm conditions. In normal conditions, the lifting of the chain absorbs any shock loads, not the snubber, so there is no need to select a snubber diameter that provides stretch. And one that stretches under normal conditions will degrade rapidly with any conditions above “ normal”.
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It's not as hard as a lot of people make it. Size the snubber to be strong and durable enough, then just make it longer until you're getting enough stretch.
And ideally, when you let out extra chain to allow the snubber to stretch, don't over-do it. If you only let the snubber stretch 20 - 25% before the chain goes tight, you're much less likely to have a snubber failure. And if you see the chain going tight, you have an indicator that you're using up all of your available stretch and either need to make the snubber longer or larger.