The Blue View - Anchor Alarms

 

We routinely use an anchor alarm when we are on the hook. This is an alarm that goes off if we drift too far from our current position, warning us that we are either dragging our anchor or that the wind has shifted significantly. It is an especially good thing to have when we are anchored in an anchorage with less than optimal holding, in a small anchorage that has rocks or other hazards within swinging range of our anchor, or if there is bad weather in the forecast. It's also a good thing to have when the holding is good, the anchorage has plenty of swinging room and the forecast is benign – because you just never know.

When we first started cruising, GPS's were more expensive, less accurate and real power hogs, and didn't make the best anchor alarms. We learned from an old salt how to make a manual anchor alarm that usually worked pretty well. We would start with a small dinghy anchor and about 200 feet (60m) or so of small, non-floating line attached. Once we were anchored and settled in, we would drop the dinghy anchor over the stern and attach the bitter end to a cleat. Then we would wrap the line 2-3 times around a winch in the reverse direction, leaving about 6' (2m) of slack between the bitter end and the winch, and fake the remaining line on the aft deck. By wrapping it in the reverse direction, when the line is pulled in the direction of the anchor, the winch turns, making the clicking noise. If the main anchor dragged or if the wind shifted and the boat drifted more than the length of the line, the dinghy anchor would stay put until all the slack was played out, then the winch would turn until the extra line between the winch and the cleat was taut. The clicking noise of the winch wasn't enough to wake us from a sound sleep, especially if the wind was howling, but if we took something that would make a lot of noise if it got knocked over, like a can of bolts, and rigged the slack in the line so that it would knock the can over when it went taut, we were sure to wake up if we were dragging. We had a lot of false alarms, but it always let us know if we were dragging or if the wind shifted and we were in danger of running aground.

Now, of course, we have several GPS's aboard that have automatic anchor alarm features built in, and the accuracy has gone from a few hundred feet to something like 6 feet, so we no longer need to use the manual system. We have a couple of anchor alarm apps for our tablet as well. They are quite sophisticated, with lots of bells and whistles, and are quite fun to set up and play with. I'm not quite ready to trust them yet, however. Our iPad often loses its GPS fix below deck. Sometimes, it gets preoccupied and forgets to update its position. Sometimes it gets a bad fix and suddenly thinks we are somewhere else for a for a short period. Also, since it uses considerably more power when using the GPS feature and it must be left on continuously, it needs to be plugged in. I really like our tablet, but I still think of it as a backup system and am a bit wary of depending on it entirely.

Instead, we keep one of our handheld GPS's plugged in by our berth and set the alarm every night we are at anchor. If the anchorage is large with no hazards to worry about and the holding is good, we set the allowable distance quite large. If there is limited swinging room or there are any hazards downwind, we set the leash quite small. This makes for more false alarms, but false alarms are a reasonable trade-off for increased reaction time if there should be a problem. By having the GPS at the bedside, not only are we assured of hearing the alarm, but a quick glance at the display will quickly tell us if we have an actual problem or whether the alarm is due to a small benign wind shift.

We set the GPS to display our position graphically, then zoom in so that the page resolution is 200 feet (60m) or so and turn the tracking on. After a few hours, the display should show a nice arc as the boat swings at anchor. The graphic display will clearly show a large wind shift or if we are dragging. Each morning, if we are staying another day, we clear the tracking history, which clears the old track and starts a new one.

We have used the anchor alarm every night since leaving Adelaide. The combination of a new, unknown anchor, anchorages known for their bad holding, no shortage of hazards, and strong winds have made us especially diligent. We had several false alarms due to small wind changes, but during our first night in Kingscote harbor at Kangaroo Island, the alarm clearly showed we were dragging our anchor. We hustled on deck, but by the time we got there, the anchor had caught again and stopped dragging. We reset the alarm and kept an anchor watch for an hour or so. When we didn't drag again, we went back to bed knowing our anchor alarm was watching out for us.

The Blue View - How's the Boss Doing?

 

When we left the Adelaide area, we had just mounted our new Manson Boss anchor as our primary anchor and stowed our old reliable Bruce anchor. The thought was that our Bruce was good for most sea bottoms, but not especially great for the thick grass and hard sand bottoms that South Australia is known for. After looking at a lot of alternatives, I thought the Manson Boss had the potential to do well in this area, as well as perform well in other types of sea bottoms.

We have been on the hook every night for over three weeks now in 13 different anchorages, and I thought it might be time for a preliminary update on how it's doing. How well does it set? How well does it hold?

First some caveats. I have always been skeptical of anchor tests and reviews. Even the best designed tests have just too many uncontrolled variables when attempting to compare a number of anchors. An anchor that is dropped in two different spots 50 feet apart might exhibit totally different holding capabilities just because of differences in the sea bottom. Some anchors require different techniques to properly set them. If two anchors are dropped and tested in exactly the same place, the first one might disrupt the bottom enough to affect the performance of the second. I can think of a host of reasons why even the most unbiased anchor reviews often result in different conclusions about the anchors being tested.

My evaluation has even more shortcomings. We've never before dropped a hook in any of these anchorages, so we have no first hand experience. I didn't try the old big Bruce or any other anchor as a comparison. There were no gales blowing and the wind didn't shift 180 degrees during the night. There are a whole host of reasons why this is far from a scientific evaluation of the anchor.

On the other hand, the anchorages in this area are known for their poor holding and difficulty in getting an anchor to set. The thick deep grass is difficult for most anchors to penetrate, and the hard sand, sometimes covering limestone, and grass roots make for poor holding once the grass is penetrated. Our anchoring conditions ranged from calm to 35+ knots of wind. So, while this is in no way an exhaustive test, I feel we have enough experience with it to provide a preliminary evaluation.

So here are our impressions:

Ease of Use: The Boss requires only a small nudge to deploy and it comes back into the bow roller quite nicely. The Bruce was a bit of a pain to push out of the bow roller, invariably smacking into the jib furler drum on its way out, and retrieval required pulling it into place the last foot or so. Overall – a definite improvement.

Ability to set: Our technique for setting the anchor is to come to a stop, then slowly start backing up, letting the wind, if there is any, push us back, or using the engine, if not. Once we begin moving backward, we use the windlass to lower the anchor. We continue to back up at a knot or so until all the required chain is out – usually a minimum of 5:1 scope (the ratio of anchor rode to water depth). Once all the rode is out, we continue to drift backwards until the bow starts swinging towards the anchor. When the boat stops and the rode starts to tighten, I put the engine in reverse and slowly tension the rode. If it appears to be set, I increase RPMs to about 2/3 full throttle and hold it there for a minute or so while I check the GPS and try to line up objects ashore to see whether we are moving. Sometimes the boat will drag slowly or sometimes you can feel a definite jerk if the anchor breaks free from the bottom. If it still seems to be holding, I slow the engine to idle, put it in neutral and attach the snubber. The new Manson Boss set on the first attempt in all but two anchorages, and in those two anchorages, it required two tries to set. In our discussions with local yachties, even the most commonly recommended anchor for this area, a variation of the old admiralty anchor called a Marsh Stockless often requires more than one attempt to get it to set. We give the Boss a good rating for the hard grassy bottoms here.

Holding: The Boss held firmly in all but one anchorage. In the Kingscote anchorage on Kangaroo Island, the anchor broke free in 30+ knots of wind, dragged about 50 feet (15m) then reset and held firmly the rest of our stay there. We had the anchor alarm turned on, which alerted us to the fact we were dragging, but the anchor had reset before we could get on deck to investigate. Again, given the bottom type, we rate the Boss as good.

We will have the opportunity to try the anchor in a lot more grassy/hard sand bottoms as we move west, but we are beginning to gain confidence in it. Overall, our initial opinion is that it is a pretty darn good anchor.

The Blue View - Anchor Chock for the Bruce

 

When we bought the new Manson Boss anchor for Nine of Cups recently, the hardest part of making the switch was figuring out how to stow our big 50kg (110lb) Bruce anchor. I didn't know whether the new anchor would be a better all around anchor than our old trusty Bruce, and I was certainly not ready to part with it.

We now have an embarrassingly large inventory of anchors. Along with the 80lb Boss and 110lb Bruce, we have a 35lb Hi-Tensile Danforth which is a marvelous stern anchor and has definitely saved our bacon on a couple of occasions, an aluminum FX-37 Fortress anchor, and a 35 lb CQR. The CQR is too small by itself to hold Cups, but we have used it on many occasions along with the Bruce when using two anchors in series. This arrangement worked particularly well in the windy anchorages of Patagonia and Tierra del Fuego. The CQR and Fortress are stowed below deck under the aft bunk, but there was no way I'd want to try to wrangle the Bruce into the aft cabin, even if I could find room for it. I still want it available for use until I gain more confidence in the Boss, so ideally it should be stowed somewhere on deck and forward.

I made a few measurements and looked at all the possible locations where it could be stowed, and the best spot appeared to be next to the mast pulpit on the port side. I enlisted the help of Marcie, the designated winch wench, to hoist the Bruce up with the spare halyard while I guided it into place and made sure it would fit. This is where the Danforth currently resided, so I'd have to find another spot for it, but if I could build a chock that would support the Bruce in an upright position, it looked like it would fit nicely.

I drew up a sketch of what I thought would work and headed into town in search of materials. All I needed was a six foot length of 2 x 6 (180cm x 50mm x 150mm) seasoned or treated wood and a bunch of galvanized nuts and bolts to make the chock plus some hardware to attach it to the deck. After a train ride, two buses and a fair amount of walking, I found a salvage yard that had some great, well-seasoned hardwood timbers, and bought a length of jarrah wood. Jarrah is a red Australian hardwood that is quite heavy and dense, and it is well suited for marine applications. It was a heavy hunk of timber to carry back, but other than the odd look from bus drivers and fellow passengers, I managed to get it back to Cups without incident.

Cutting the dense, 2” (50mm) jarrah using only a jigsaw took some time, but eventually I got all the pieces cut to size, drilled and bolted together.

The groove at the bottom holds the Bruce upright and the two blocks under the flukes make sure it can't fall over. I through-bolted the chock to the deck to make sure it would stay put, then lashed the shank of the Bruce to the mast pulpit to keep it in place. Almost all the weight and strain is taken by the chock with very little stress on the pulpit.

I discovered that the Danforth anchor rests nicely on top of the chock as well, in its original location on the inside of the pulpit, so I didn't have to relocate it after all.

Hopefully, the new Boss will perform faultlessly and our old Bruce will spend its retirement happily ensconced in its new chock, but if not, we can have it attached and ready to deploy in half an hour or so. Then the only problem will be how to stow the Boss...