Anchoring Guide

     
1. Determine Your Holding Requirements.

Be sure that your anchor can give the performance you need. A “Lunch Hook” should be able to hold your boat in a 15 knot breeze. A main, or “Working Anchor” should hold up to 30 knots of wind. A “Storm Anchor” is for winds up to 42 knots. Remember that as the wind speed doubles, the holding requirement quadruples!

WIND

SPEED

BOAT LENGTH in FEET
20ft 25ft 30ft 35ft 40ft 50ft 60ft 70ft
15 kts 90 125 175 225 300 400 500 675
30 kts 360 490 700 900 1,200 1,600 2,000 2,700
42 kts 720 980 1,400 1,800 2,400 3,200 4,000 5,400
60 kts 1,440 1,960 2,800 3,600 4,800 6,400 8,000 10,800
 
WIND

SPEED

BOAT LENGTH in METERS
6m 8m 9m 11m 12m 15m 18m 21m
15 kts 41 57 79 102 136 181 227 306
30 kts 163 222 318 408 544 726 907 1,225
42 kts 327 445 635 816 1,089 1,452 1,814 2,449
60 kts 653 889 1,270 1,633 2,177 2,903 3,629 4,899
 

Use the handy “Horizontal Loads Table” above to determine in pounds your holding power requirements for different wind speeds. Note:This table assumes boats of average beam and windage. If your boat has above average beam or windage, refer to loads for the next larger size boat.  THe numbers in columns for feet = lbs., and the numbers in the columns for meters = kg.

2. Use Adequate Scope.

Scope is the length of anchor line relative to the distance from the boat’s deck to the sea bottom.  We recommend at least 5:1 scope.

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At 10:1 the holding power will double, and at less than 3:1 you will give up a significant amount of holding power and may experience problems setting the anchor.

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In crowded anchorages “Power Set” your anchor at 5:1 scope, then shorten scope as required.  Remember that your depth sounder may be giving you the water depth under your keel, rather than from the true waterline, in which case you need to add your draft plus the height of your deck when calculating scope.

3. “Power Set” Your Anchor.

Know that your anchor is properly set!  Back down very, very slowly.  Then as the anchor begins to set, very slowly increase the load with your engine.  Backing down at any speed at all may not give your anchor a chance to dig in and bury itself.

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You can simulate the force of the wind by using your engine’s thrust to set your anchor to a predetermined load. Match your boat’s total maximum horsepower and hull type in the table above to determine how hard your boat can“Power Set” your anchor.

4. Anchor Resetting.
In areas of changing tide or wind, set two anchors off the bow in opposite directions. Any anchor can occasionally fail to reset once it has been pulled out of the bottom.

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Don’t be fooled by some manufacturer’s claims about any anchor’s ability to dependably reset 100% of the time! Set two anchors if you expect a change in wind or current.

5. Anchor Retrieval.
Slowly move the boat to a position directly over the anchor, pulling in the line as you go. Then snub the line on a cleat and power backwards slowly to pull the anchor out of the bottom. Do not power forward because that will require more energy and put very heavy loads on the anchor and gear.

6. Support Hardware.
Remember that your anchor system includes the shackle, rope, chain, and deck cleats. Every item must be able to deliver the strength you need. Refer to the handy selection guide on the previous page.

7. Anchor Rode.
Use a short length of chain and three strand nylon line. The nylon is very elastic and greatly reduces shock loads on your boat and it’s anchoring system. The chain protects the line against chafe from the sea bed and also help provide horizontal pull on the anchor when it is initially beginning to set. If you regularly anchor in 25 ft (8 m) of water or less, use 6 ft (2 m) of chain. For greater depths, use 6 ft (2 m) for every 25 ft (8 m) of water depth. (ie: use 24 ft (7 m) of chain if you regularly anchor in 100 ft (30 m) of water).

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All chain anchor rodes lack the shock absorbing ability of nylon rope when the wind pipes up!

8. Soft Mud Bottoms.
All soft mud bottoms offer greatly reduced holding power, so be sure your anchor can provide the holding power you need. Some bottoms offer as little as just 15% of the holding available in firmer bottoms!

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Some soft mud bottoms have a sticky consistency which makes them difficult to set an anchor in. If soft mud setting problems occur, try setting the anchor initially at very short scope, e.g. 2:1. Then, increase the scope to at least 5:1 and “Power Set” the anchor. Special “Mud Palms” are included for both Fortress and Guardian anchors to aid setting in very soft problem mud. We recommend that you install the “Mud Palms” on your anchor, as they help the anchor set faster in any type of bottom.