help?

[millyman01]

my boyfriend is in the FL Keys and sustained 20 mph winds @ his anchorage his boat keeps whiplashing. At the end of each yank it is pulling hard on the anchor and he is worried about anchor drag! He shortend up his scope and put the smaller anchor at the rear but the wind is still pushing the boat sideways straining both anchors. He is wondering if his 3/8 ths polly rope is too springy which is causing this, also boater supplies in key west are out of business other than sears or home depot not sure where to buy better rope?

[ardoin]

Two things to try. First, put up wind resistance in the aft of the boat. They make a small sail that you can put on the backstay that will make it more stable. Second would be to put a small anchor on the bow (in addition to the existing anchor) but set it for a 2 to 1 scope, this will drag to and fro and slow down the movement. Keep the main anchor at the proper scope 7 to 1 or a little more for all nylon.

[millyman01]

Thank You He Never Thought About Putting The Second Anchor In The Bow. The Weather There Is Getting The North Winds From Up Here In Wisconsin For The Next Few Days Will Not Let Up Until Sun Night. Thanks Again. Happy Sailing

[sailingdog]

First, shortening scope is the WRONG THING TO DO. It makes it far more likely that you'll pull the anchor out.

Second, adding a second anchor to the stern means that if the wind shifts significantly, it will be blowing against the PROFILE of the boat, and very likely will RIP BOTH ANCHORS FREE. From a post by Rich_H on jacklines, the reasoning for this is:

For you with math ability ... when you apply load perpendicularly to a 'taut' line, the reaction load in the terminal ends is the perpendicularly applied load divided by the sine of the deflection angle. Dividing by small deflection angles (taught line) result in forces approaching 'infinity'; the more slack the 'line' the larger the deflection angle (dividing by larger sin value); hence, lesser reaction loads in the 'terminals'.

How big is this boat? 3/8" line is worthless as an anchor line for anything larger than a daysailer IMHO. It would help if you said what kind of boat he has as well as what kind of anchors he is using.

BTW, if the boat is bigger than a daysailer, it is likely that you're straining the anchor line past what is safe to do so. Also, the best anchor lines are NYLON, as that has much better characteristics for an anchor line than does polyester or polypropylene lines.

Without knowing more specifics, it is hard to give you decent advice. Generally, the more relevant and specific information you give related to a problem, the better the quality of the answers you'll get.

As for using a second anchor off the bow, I generally don't recommend this, unless you know what you're doing. The two rodes can chafe against each other and cause you to lose both anchors.

A better idea might be to use a bridle to help keep the boat from hunting side-to-side. A riding sail, which is what Ardoin describes, might also help.

Originally Posted by millyman01

my boyfriend is in the FL Keys and sustained 20 mph winds @ his anchorage his boat keeps whiplashing. At the end of each yank it is pulling hard on the anchor and he is worried about anchor drag! He shortend up his scope and put the smaller anchor at the rear but the wind is still pushing the boat sideways straining both anchors. He is wondering if his 3/8 ths polly rope is too springy which is causing this, also boater supplies in key west are out of business other than sears or home depot not sure where to buy better rope?

[travlineasy]

One of the latest anchoring sails I've seen seems to be a big step forward, and while the cost is not cheap, it works very well. He can check them out at Banner Bay Marine

Good Luck,

Gary

[millyman01]

The Boat Is A Mac 22

[millyman01]

Maybe I Should Have Been Along To Tell Him What To Do

[sailingdog]

Originally Posted by millyman01

The Boat Is A Mac 22

That would be a Macgregor Venture 22? What kind of anchor is he using?

[sailingdog]

BTW, 3/8" line of various types and their breaking loads:

StaSet polyester double braid........ 4400 lbs.
NE Ropes 3 strand laid anchor........ 4400 lbs.
NE Ropes Polypropylene tow line.... 3000 lbs.

Your boat weighs 1800 lbs... that means you're using an anchor line with less than 3:1 safety margin. That's not a very good idea. Generally, you need to have at least 5:1 or better safety margins.

You should be using 1/2" nylon at a minimum, since 3/8" rope really leaves you no safety margin against chafe, abrasion damage or uv-degradation.

[travlineasy]

Gotta' agree-- 1/2-inch nylon would have been my choice.

Good Luck,

Gary