Generally when choosing the properly sized boat anchor, it is best to do so based on the ratings for its holding power in a 30 mph wind, or more. (see chart below)
Many factory anchors are low quality, and under-sized and will result in the anchor not holding the boat properly in anything above 15 mph winds. The wind speed and boat size are the two most important things to consider when figuring out how much holding power your anchor needs to meet your requirements.
Do you remember playing tug of war? Your legs did most of the work, but you used every muscle in your body to pull on the rope as hard as you could. The average adult male can generate about 150 lbs of force when doing so.
This 150 lbs of pull would be the approximate amount of force on your anchor in a 15-20 mph wind on a 25’ boat. So in order to keep the boat in place, the anchor must be able to generate this much resistance without sliding.
This chart created by the American Boat & Yacht Council shows the estimated amount of resistance needed to keep a boat in place in various winds:
Note: The pounds of holding power shown in the chart should not be confused with the weight of the boat. Holding power required is the amount of pull force the anchor must withstand to hold the boat in the referenced wind speed as described above in the tug of war analogy.
For example a 30 foot fiberglass cruiser weighing 10,000 lbs will need an anchor that can withstand 700 lbs of pull force to hold the boat in a 30 mph wind.
If the wind speed doubles, the amount of resistance needed now quadruples.
Anchors that rely strictly on their weight - such as mushroom anchors, navy anchors, and river anchors, are incapable of generating anything more than approximately twice their weight in holding power. This is why a 20’ boat using a 20 lb low quality anchor will always end up dragging anchor - if the anchor design is one that only relies on its weight.
New generation style anchors like our Hurricane Boat Anchor rely on their design, and not their weight. In fact, if the anchor was made out of lightweight materials rather than steel, the anchor would have the same amount of holding power as the galvanized steel version.
So how much holding power does your boat anchor need? Well, that would depend on the conditions you anticipate being in:
-Will you be anchoring in a sand or a mud bottom? Typically mud bottoms offer slightly less holding power.
-Will you be out on the water only for day trips? Or also anchor overnight?
-If the weather takes a turn for the worse, are you close enough to cruise back into shore? Or will you have to anchor and ride out the storm?
-If your boat has engine trouble, how far away is help and how long will it take for them to reach you?
Many times when anchoring on the beach or sandbar, the holding power is reduced due to inconsistent firm ground. With water swirling around, and people, dogs, etc walking around, the bottom is constantly stirred up and not packed tightly. This can lead to less than ideal holding ground, but many times this can be overcome by setting the anchor manually by hand to see it is set properly, and increasing the scope.
Also, deploying a second anchor off the side or stern can also help limit the swing of the boat, and the chances of the primary anchor coming loose.
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