A catenary is defined as the shape of a perfectly flexible chain suspended by its ends and acted on by gravity. Many boaters assume that if you do not use a snubber, the catenary of the chain serves the same purpose. Pulling all that chain up off the bottom absorbs a lot of energy. But the idea that an anchor chain forms a perfect catenary is another one of those maritime legends. Typically, in still water with no wind, the chain hangs down from the bow until it rests on the bottom, then proceeds horizontally to the anchor. As the wind picks up, enough chain is lifted off the bottom to balance the wind pressure. This forms a short catenary from the bow to the bottom. It is only when the wind is quite strong that the chain is entirely lifted off the bottom forming a true catenary from the bow to the anchor. Any increase in wind strength flattens the shape of the catenary and provides a small amount of snubbing action, much less than would be provided by an appropriately sized nylon line. If the wind increases further, the chain becomes bar tight and there is no snubbing. The main advantage of chain, considered only from the perspective of anchor dragging, is that the weight tends to keep the anchor shank parallel to the ground. There is no pull on the anchor until the entire chain is lifted off the bottom. A similar effect could be accomplished with a lighter chain or a nylon rode by using a kellet or weight close to the anchor. If you want to estimate exactly how much a boat will move backward when the anchor rode is all chain, consider the following case. You are anchored on a calm day in 10' of water. The bow is 5' above the water. Being a traditionalist you use a 7:1 anchor rode, not forgetting to add in the height of the bow. So you have a total of 105' of chain. Fifteen feet of chain drops down directly from the bow and the remaining 90' lies on the bottom directly to the anchor. The wind builds up to near gale force. The chain is stretched bar tight. Because of the angle made by the chain to the bottom, the boat moves back about 24 feet. For shorter lengths of chain, the boat moves less. There is some snubbing and shock attenuation action until the chain stretches tight. After that there is none at all. If you want to increase the snubbing action of a chain either increase the weight of the chain or fasten a substantial kellet weight to the chain. The maximum snubbing effect is when the kellet is placed close to the boat, preferably at the point where the chain first hits the bottom, i.e. one anchoring depth. That way the weight will have to be lifted off the bottom as the catenary begins to form. I put my money where my mouth is. My permanent mooring for a Willard motorsailer was a 350 lb. mushroom with two waters depth of 3/4" chain. This was shackled to a length of 1/2" chain, whose weight was supported by a mooring buoy. From the mooring buoy a 3/4" polyester (Dacron) pennant led to the boat. Polyester was chosen because for a short mooring pennant I considered abrasion resistance more important than elasticity. At the point where the 1/2" and 3/4" chains were shackled together, I fastened a 50 lb lead weight. Any weight will do, even a weight lifter's dumbell. Before the boat could pull on the mushroom, the weight and the 3/4" chain had to be lifted off the bottom. The mooring held my boat firm through two hurricanes while boats around mine were being dashed on the rocks. Larry Z