 |
|
|
| Anchor Sizing and Relative Holding Power Ratings
|
|
Febuary 22, 2002
|
|
|
Marin Faue sent this note about anchor choice and sizing, and relative holding power statistics:
|
|
|
|
I know you were the Bruce rep for many years in this area, so I have a question for you. When we bought our 1973 GB36 three years ago, we immediately replaced the extremely heavy, no-name, Danforth-type anchor on the bow with a new 33-pound Bruce and 200 feet of all-chain rode. I understand the Bruce's ability to set under a much wider variety of bottoms than the Danforth-type of anchor. However, the Bruce is always rated at or near the bottom of the list when it comes to holding power.
Obviously, Bruce anchors work well in this area as so many boats, including Grand Yachts' charter fleet of Grand Banks, use them. But my wife and I haven't done much anchoring yet, so I have little experience to draw on.
Question- In your opinion, is the Bruce's lower holding rating adequate for most of the weather and current conditions one is likely to encounter in year-round cruising in the San Juan and Gulf Islands, the islands north of Campbell River, and the Inside Passage to Southeast Alaska?
I do not include the west coast of Vancouver Island, the Queen Charlotte Islands, or the outside waters along the Inside Passage, as I know from my floatplane flying experience that conditions out there are considerably different than what is normally encountered on the inside.
In addition to the Bruce, we also carry a 15-pound Fortress on the swim step for use as a stern anchor using a chain and line rode. The 15-pound Fortress is the size "recommended" for 39-45 foot boats in 20 knot winds, so in addition to being a handy weight and size to use as a stern anchor, I believe it should also be able to double as a spare main anchor under normal conditions. Does this arrangement seem sensible to you?
|
|
|
Response
|
|
|
|
You bring up some very good points, because they go straight to the heart of anchor sizing and design choice.
Several publications have gone to great effort to develop relative holding power ratings for various anchor designs. At first glance, this seems like a reasonable thing to do, but in reality their findings are of only limited usefulness. In the case of Practical Sailor's tests the findings are just plain wrong, because their test parameters were deeply flawed. They had garbage going in, and they certainly got garbage coming out. Anyway . . .
As far as holding power is concerned, all you're looking for with any design is an anchor big enough to hold your boat. Once you've found that anchor, the holding power problem is solved. In the case of your 1973 GB 36, a 33-pound Bruce is big enough. If you had a CQR anchor, it would be the 35-pound CQR.
The real questions are:
1. Does the anchor set in the kinds of bottoms I'll be anchoring in
2. Is the anchor strong enough to resist bending or breaking under extreme loads
3. Does the anchor break out of the bottom easily, to make recovery less difficult
4. How much scope does the anchor require to work satisfactorily
5. Does the anchor remain buried or reset reliably when the boat veers, such as in changing wind or current directions
6. Does the anchor fit on my boat
Once you've answered questions 1-5, find the size that will hold the boat and see if it fits. If it does, you've got your anchor. Price differences, by the way, should be of little or no concern. You're not buying an anchor; you're buying safety and peace of mind when storm force winds are imminent and your best bet is to put the hook down in some little bay. Does the skipper want to say to the crew, "I got a low price on my anchoring system. I hope it works," or does he want to say, "I've got the best anchoring system I could find. We should be just fine."
The reason I like Bruce -- genuine Bruce, not the knock-offs -- is because they work in the bottoms we find throughout the Northwest, they're enormously strong, they break out easily, they require less scope than other anchor designs, and they remain buried when the boat veers. Although the sizing chart says the 33-pound Bruce would be right for our Tollycraft 37, I put on a 44. It's oversized, but I wanted a no-excuses system. The Tolly is a bigger boat than your GB 36, so the 33 should be okay for your boat.
As to the Fortress stern anchor, I would think the 15-pounder would be a good, manageable stern anchor (although my stern anchor is a 22-pound Bruce). I don't know my Fortress sizing, so I can't comment on the 15 as a primary anchor. Look at other Danforth-equipped boats on the docks. Find the ones that look like they have the right size anchors. If your Fortress has about the same physical dimensions, then you're probably fine. Remember, it's not the anchor weight that holds the boat, it's the physical size of the flukes.
--Bob Hale
|
|
|
Back to Readers Write In |
|
|
|
