Yachting and Boating World forums: More on flopper stoppers

You can obtain the same result by just putting a spring line on your anchor line:
"ANCHOR SPRING LINES:

Often, you anchor where the Wind and the Water work at cross-purposes. Some anchorages may have a strong current running through them, or sometimes experience a strong surge or groundswell. Even a smaller current or surge can set your boat to rocking - and you know how uncomfortable a rolling boat can be. A really fast current or big swell can make the harbor untenable.

Fortunately, there's an easy way to alleviate all that by the use of a forward quarter spring line to the anchor rode, a technique called "springing the rode".

To understand how Anchor Spring Lines work, it will be helpful to visualize the conditions that call for it. Suppose you're anchored in a harbor where the wind is blowing from the east. Lying to her anchor, your boat will point east into the wind. Now, suppose there's a surge rolling into the harbor from the north (or a current running South). It could be a ground swell generated by some distant storm, or just a remnant of seas outside the harbor bending around the headland. Whatever the source, waves from the north will strike your boat on the port beam and she'll rock-n-roll.

But if the vessel were turned 90 Degrees to port, pointed into the waves rather than into the wind, the effect would be a much reduced, fore-and-aft motion, i.e., pitching instead of rolling. By comparison, pitching in these circumstances is hardly noticeable unless it becomes really extreme. So, how best to point the boat into the surge is the key to comfort in this harbor.

Most sailors will immediately think of setting a second anchor from the stern. In this scenario of an east wind and northerly wave action, the stern anchor would be set well out to the southeast. Then, by hauling in on the rode aft the boat can be made to face north. There's nothing really wrong with this solution, except that
(a) It is more work than necessary, carrying out and later retrieving the second hook, and
(b) The boat can no longer swing with other boats nearby that are laying to only one anchor. This may create spacing problems if the wind shifts.
(c) You are constrained by two anchors, which would delay your departure in the event circumstances necessitate a rapid escape.

A much easier, more efficient solution can be accomplished using the bow anchor that is already set and a spring line. Simply tie a long dock line to the bow anchor's rode or chain at the bow of your boat. A roving hitch works well for this. Lead the line aft alongside the hull to (in this case) the starboard cockpit sheet winch. On a center cockpit boat it would be best to pass the line through a stern quarter turning block before leading it to the winch. Check that the line is running outboard of the bow pulpit, stanchions, and shrouds.

Next, pay out the anchor rode, about 1/3 to 1/2 of a boat length. Finally, take up on the spring line until there's roughly equal pull on the rode and the spring. The boat will swing broadside to the wind and will face the swell. It's as simple as one-two-three!

Our example illustrates a perpendicular wave (or current) to wind angle. But you can adjust the vessel's heading to suit other conditions: If the waves are forward of the beam, feed out less of the rode and/or take in less on the spring line. To head her further off, slack the anchor rode more and/or haul in some more on the spring. A little experimentation and you'll easily master this useful technique.

Here are a few other pointers:

If the waves are abaft the beam it may be equally comfortable to lay your boat's stern to face them rather than the bow. This will require less line adjustment than swinging the bow all the way around.

Remember: To turn the bow to port, use a starboard forward quarter spring line; to turn to starboard, use a port spring.

If the wind gets to blowing harder and you feel uneasy about the strain your boat's beam-on position is putting on the anchor, you can instantly return to the normal anchor mode - bow to the wind - just by releasing the spring line. The boat will quickly swing to the breeze. The spring line can be recovered later when you weigh anchor.

This technique does rely on a fairly consistent breeze. If the wind shifts, you'll have to readjust the boat's angle. If the breeze dies altogether, deploying a stern anchor may be the only way to hold your boat end-on to the waves."
(http://www.cruisersforum.com/forums/f74/anchor-spring-lines-653.html)

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