The gears continue to turn as I further contemplate ground tackle…
While I’m still working through the options on an anchor selection (I’d like to get it done by October 15th in order to take advantage of the Boat Show Specials at Defender), I believe (read: hope) selecting the rode should be a bit less troublesome.
West Marine suggests that 1/8” of line diameter for every nine feet of boat length is appropriate. For a 29 foot boat this suggests a little more than a 3/8” line, or round up to 1/2”. Anchor chain would typically be half the size of the line, or 1/4”.
Rocna recommends 1/4” high test for their Rocna 10 (the recommended size), and 5/16” high test for their Rocna 15. Presumably the other anchors would benefit from similar sizing.
With agreement from two sources, if I go with a recommended size anchor, I’ll probably also go with 1/4” high test, upsizing slightly to 5/16” if I oversize the anchor. Although the larger chain isn’t that much heavier or more expensive and might be worth considering if I even think I might upsize sometime in the future.
How much chain and how much rope on the rode?
The general rule of thumb regards scope is 7:1 for the typical short length of chain followed by rope, and 5:1 for all chain rode. In heavy conditions as much as 10:1 might be called for, and in tight anchorages many people lie to as little as 3:1 ( hopefully all chain). It is important to remember to include the height above the waterline of the anchor roller and the expected tide in the scope computation (10 feet of water + 4 feet of freeboard + 2 feet of expected tide increase would equal 16 feet for the purpose of figuring scope).
I figure that 100′ of chain would allow me to lie to all chain at a 5:1 scope in fifteen feet of water (plus four feet of freeboard). Add 200′ of anchor line and I can anchor at 7:1 in thirty-five feet of water or 5:1 in fifty-five feet, which should cover me in most anchorages I’m likely to find myself in. Any more than that and I’ll have to add another length of line to the rode.
|Water Depth||Total Depth||Scope|
|Anchor Chain||Size||WLL||Weight/ft (pounds)||Feet||Total Weight (pounds)||Price/Ft (Defender 10/8/12)||Total Price|
|Anchor Line||Size||Average Tensile Strength||Weight/ 100 ft (pounds)||Feet||Total Weight (pounds)||Price/Ft (Defender 10/8/12)||Total Price|
|Sampson Pro-set 3 strand||1/2”||6300||6.5||200||13||$0.57||$114.00|
|Sampson Pro-set 3 strand||5/8”||10000||10.5||200||21||$0.94||$188.00|
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