A sailor did an excellent job of computer modeling rode
reactions to wind
. The links are below. While computer models have MANY limitations, this one clearly pointed out one thing; when an abrupt gust hits a boat
on an elastic rode
, the boat
moves backwards and then the rode has to resist both the wind
and the energy of stopping the boat. The resulting force is nearly independent on the length of the rope
; the longer the rope
, the faster the boat moves, but the more rope there is to stop it. The conclusion: an elastic rope doesn't soften the blow. With either chain or rope the answer is the same; the gear
will feel about 2x the peak wind force. Odd but sensible. The one condition of the model is that the wind is still blowing when the boat comes up tight, which sees reasonable. A chain rode, with the catenary, reacts differently, but I suspect his model may over state the surges, since in reality we know there is enough damping that the boat does not bounce in the manner his models suggest.
Waves are a different matter because the time period is short; the boat won't begin to move backwards signifigantly before the wave is past. A long elastic rode or a very long chain will damp them almost completely; some effect from the friction of the line through the water
. However, if the boat is in relatively shallow water
, there is big chop, and the scope
is short, a boat on chain can hammer against the chop with no damping. The answer is a snubber long enough for the waves only. This will vary with the setting, but might be as much as 60 feet (4 foot waves) or as little as 15 feet (1 foot waves). Since the chain catenary will do something, perhaps 60% ofthis figure is a minimum chain snubber length. As stated, this is most important where the chop is material.
Not my theories, but the logic is sound and seems to reflect experience, at least in aproximation. It also explains why several schools can all think that they are right... because under specific circumstances, they are.