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Old 06-12-2013
dahicke
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Re: Heaving-To versus Bare Poles

I have been doing research into Heaving-to for the last two years as an Ocean Engineer for my Master's thesis. Two things to note about what has been said so far. The 1979 FASTNET report on the incident contained errors in the data analysis of the data they collected. After apply correct data analysis, heaving-to scored best tactic 8 times out of 12 categories. It also scored worse in 3 of which there where other data inconsistencies present that make those scores suspect. Lying a hull with bare poles was the worst base on that data. I would surmise is that heaving-to helped in dissipating the on coming wave and running off basically gave the skipper an opportunity to maneuver through it to the best of their ability. Lying a hull with bare poles, the boat just had to take it.

For my research, I am using Computational Fluid Dynamics to study what is happen to the waves, when a boat heaves-to. What I have found is that the boat is pull water with it in this slick and that water has wave momentum from a different part of the wave. When the water from the slick moves over the water adjacent to it, it reduces its motion. This means, that as the crest of the wave reaches the boat, the water it is pulling with it has downward momentum, which pushes down the crest of the wave. This flattens the crest and reduces the steepness of the wave and reduces its ability to break. For modern boats, applying a sea anchor the way it has been recommended should help the boat move the water in a similar way as a full keel, though a simulation or experiment will need to be done to verify this. It is not the Von Karman Vortex Sheet that dissipates the wave in heaving-to; it is Newton's Law of momentum that is doing the trick. I originally thought it was the vortex sheet also, until I did the simulation.

Last edited by dahicke; 06-12-2013 at 01:32 AM. Reason: grammer
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