Need help choosing the correct anchor weight & rode? Reference the charts below for the correct anchor weight & rode:
Anchor Weight Guide
|BOAT SIZE||ANCHOR WEIGHT|
|Length (ft)||Weight (lbs)||Bruce (lbs)||Danforth* (lbs)||Fortress(lbs)||Plow (lbs)||Yachtsman (lbs)|
|20 - 25||2,500||4.4||8-S, 5-H**||4||10||15|
|26 - 30||5,000||11||13-S, 12-H||7||15||25|
|31 - 35||10,000||11/16.5||22-S, 12-H||7/10||20||35 - 40|
|36 - 40||15,000||16.5||22-S, 20-H||10||25||50|
|41- 45||20,000||22||40-S, 20-H||15||35||65|
|46 - 50||30,000||22/44||65-S, 35-H||21||45||75|
|51 - 60||50,000||44||85-S, 60-H||32||60||100|
Anchor Rode Guide
|BOAT SIZE||ANCHOR RODE|
|Length (ft)||Weight (lbs)||Chain (dia.-inch)||Nylon (dia. -inch)||Length (ft.)|
|20 - 25||2,500||3/16||7/16||90|
|26 - 30||5,000||1/4||7/16||135|
|31 - 35||10,000||5/16||1/2||190|
|36 - 40||15,000||3/8||9/16||225|
|46 - 50||30,000||1/2||11/16||315|
|51 - 60||50,000||9/16||3/4||360|
* Danforth is a registered trademark. Similar-style anchors may differ significantly in performance
** S indicates standard anchor; B indicates high-tensile anchor.
To obtain maximum holding power of your anchor, the total anchor rode should be 4 to 7 times
the depth of the water you will be anchoring in.
A good compromise between all-nylon or all-chain rode is a short length of chain (6'-30')
connected to the anchor, with a long length of three-strand nylon line connected to the chain.
This combination satisfies nearly all requirements of a good anchor rode, except that it is not
abrasion resistant over its entire length. Long scope must be used to keep the pull on the
anchor shank horizontal. Nylon is preferred for its elasticity. Its stretch reduces peak loads on
the anchor and on your boat. The primary function of chain is to handle the chafe from rough
bottoms that would otherwise abrade the soft nylon line.
Scope is defined as the ratio of water depth (plus freeboard) to anchor line paid out. Most
anchoring texts and anchor manufacturers agree that a scope of 7:1 achieves the anchor's
designed holding power, and more scope is better than less. In theory, 7:1 scope is great, but at
a crowded anchorage most cruisers scoff at the idea of paying out more than 3:1 or 4:1-there
just isn't much space for boats to swing. Any reduction in scope, of course, must be made up for
by using larger anchors and/or larger chain.
How much chain you should have in a chain-and-rope anchor rode is not fixed because of the
variety of factors involved (boat displacement, draft, surface conditions, etc.). There isn't a set
formula for equating the amount of line to chain in an anchor rode.
John Rousmaniere, the noted author of "The Annapolis Book of Seamanship," recommends at
least six to 10 feet of chain accompany every anchor rode (except of course those for dinghies
and those that are all-chain), but that's a bare minimum for anything over 25 feet LOA. You
could say that twice as much line as chain would keep you safe in almost any situation.
Calculations for the optimum length of chain on a combined nylon chain rode are complex.
However William van Dorn in "Oceanography and Seamanship"; Dodd, Mead (1974), presents a
graph based on calculations for anchoring oceanographic vessels in storm conditions. It
suggests that the optimum chain/nylon combination for anchoring vessels < 50ft. in 30 ft. of
water under storm conditions is a 20% chain, 80% nylon rode with an overall scope of 6:1.
Assuming that the boat's bow chock is 6 feet above the water and that the waves are 4 feet (8
feet peak to trough) this works out to a 240 foot total rode comprised of 48 feet of chain and
192 feet of nylon. Clearly these are extreme conditions. In shallower water the rode could be
reduced proportionately. However, the length of chain required approximates one boat length
and a good working rule for a combined rode is a boat length of chain plus whatever nylon is
required to give a 6:1 scope. In shallower water, the scope should be increased, within swing
limitations, to 7:1 to permit the bow to lift more easily to the choppy waves near the shore.
In summary, at a fixed anchoring depth, the longer the rode, the less chain required. The
shortest rodes are achieved with all chain, the heavier the better, but the penalty is increased
weight and handling difficulty, and the slightly increased possibility of catastrophic failure if
the chain stretches taut.
More questions? Please feel free to contact our Product Support Team.