Perchem

A swinging mooring is sized before it goes in the water, not watched after it is in. Perchem is the bench for that job. Describe the berth — depth at low water, the level 🧗 range, what the bed is made of, how far the wind gets at you — then describe the boat, and build 🔨 the mooring from the bed upward: sinker, ground chain, swivel, riser, snubber, strop, buoy. Swap any piece for another and every figure moves with it. The arithmetic is the whole point. Perchem works out the load the wind and the current put on the boat, adds the snatch that comes with fetch, and sets it against what that particular bed gives back, because a cast dome in firm clay and a concrete 🧱 block in soft mud do not hold alike. It sizes the riser for the top of the level 🧗 range, counts the metres of ground chain the load lifts off the bottom, checks the buoy still floats the chain it carries at high water, and draws the swing circle to see 👀 what the boat clears. The verdict is one of three — holds, marginal, drags — and it names the term that decided it, so you know 💡 which piece to change and which to leave alone. Twenty-two pieces of ground tackle stand behind the bench with their masses and working loads, six holding grounds with the factors that go with them, and the Perchem fault key reads what you find when you lift the lot a year 🗓️ later, nine of them: chafe, a wasted link, a seized swivel, a waterlogged buoy. Photograph the berth and the computed elevation, the low-mean-high water band and the boat at full swing are drawn over your own picture at true scale. Perchem keeps every berth you lay out, so next spring you open the one you want and grade it again. No map 🗺️, no chart 📊, no alarm. Metric or imperial, fresh water or salt, and it all works on the device 📱 with nothing going anywhere else. This is the end of the job that happens on the quay with a tape and a pencil, before anything is dropped over the side.