Tandem Anchors - a Thought

[Jim Cate]

Kudos to all, especially Evans and Dragon. This has been the all-time (for me) best thread on CF, especially in the BS:info ratio. Well done and thanks... but my old bones specifically have vetoed such high latitudes no matter how lovely they may be!

Cheers,

Jim and Ann s/v Insatiable II lying Great Keppel Is, Qld, Oz

[gettinthere]

the argument against 2 anchors on 2 rodes is that rarely are you getting an even pull on both. So one is doing all the work...no?

[ggray]

Originally Posted by gettinthere

the argument against 2 anchors on 2 rodes is that rarely are you getting an even pull on both. So one is doing all the work...no?

When I use 2 anchors/rodes, it is usually to limit swing toward an undesireable direction, so it doesn't bother me if one or the other is not under load at times.

[Dragon701]

There are many ways to approach “extreme” anchoring and they all have their good and bad points. It seems that the two negatives mentioned most often about tandem anchoring are:
1) It is a complicated rig to deploy. Given my comments in post #12 about the contortions we went through to anchor safely in Patagonia, we would be more than willing to figure out a way to make tandem anchoring work for us, if we felt that we needed a better solution. It seems like the article on the Rocna website cited earlier would be a good place to start to learn this system.
2) Some people question the efficacy. They say that the second anchor might pull down the furrow of the first and that will make it less effective. Or … they correctly point out that as the wind shifts, the pull isn’t as true … and they say that it loses its effect. There are very few people (me included) who have the first hand knowledge to really know. This is the crux of why I might NOT use this system until I was convinced that it works better than whatever else I might do.
So … for me, I would probably try it out, but first in warm, clear water a number of times, so I could perfect the technique and also so I could dive on it to see what happened in a number of cases. Alternatively, I could just wait for someone to do a thorough test that convinces me of its strength and weaknesses.
We have been quite satisfied with two rodes for “normal” bad weather. For example, we used this system recently in Utila in Honduras when a front was passing. We expected around 30 knot winds in an anchorage that was a little dicey.
It is true that two rodes can lead to unequal loads as the boat swings to a changing wind. On the other hand, we like the ease of deployment; what Evans called “practicality” in an earlier post. There were two factors that have helped to make this system work for us in our situations. First, many weather events give you only a relatively modest wind shift during the worst of the winds (not talking about a hurricane here). During the front in Utila, the strong winds shifted about 30 degrees over several hours (there was more shift over time, but the wind speeds were reduced).
Second, we lay out our anchors on about a 30 degree angle with the mid-point being the worst expected wind direction. We then adjust the lines to compensate for wind shifts. We allow for plenty of extra rode to do this, because we find it difficult or impossible to pull in rode as opposed to letting it out during a blow. We use sheepskin chafing gear on the rodes and hold it as we let out the line so it stays in place. This profile gives us quite a bit of flexibility on wind shifts.
Not to be overly repetitive, but three concepts have helped us anchor safely, not just in much more extreme conditions, but generally as well.
1) Go big on your anchor: ‘nough said (and said before).
2) Be willing to put in the extra effort to get it right: Perhaps we are overly chicken, but we have always been willing to “put in the time” to anchor in a way that made us feel secure. In warm waters, this often meant taking the extra precaution of diving on our anchor. I feel that I have learned a lot by seeing how it set “in person” versus how it felt from the deck. I would often take a look at other people’s anchors too (and keep my thoughts to myself). In colder waters, it meant going through the extra steps necessary to tie ashore or lay out two anchors or deploy a 150# Fisherman. When we were cruising in the islands around Cape Horn, we stopped in an anchorage that was somewhat open and didn’t have the usual trees to which to tie ashore. Just a few years before us, a famous world cruiser had dragged and gone aground there using a 35# plow on a 35 foot boat (I might have a few details wrong, it was a long time ago). We used our two Luke Fishermen, had a nasty blow and didn’t move at all. One success doesn’t prove a thing. I can be certain, however, that our crazy deployment (see post #12) took much longer than their drop off the bow using a windlass.
3) Have a Plan B: We have always tried to consider what we would do if our original solution fouled up. Every night, before we would hit the rack, we would have a good look around to see if the boat was ready for a 2am fire drill and what we would do if it happened.
And … then I would worry all night anyway .

[lancelot9898]

Originally Posted by Sharkman

One advantage with the Rocna is that it has a dedicated attachment point for a tandem anchor in the first place, a point I'm sure you haven't missed.

I've considered using a tandem setup for severe conditions like a hurricane even though my 35 lb CQR held up well by itself on a Cat 1 back in 1985. Don't plan on being aboard again on the next one and have since upgraded to a 45 lb Manson Supreme. My thoughts on a tandem anchor is placing a second anchor on the rode directly rather than attaching it to the primary anchor. It would seem that such an attachment might not limit the pentration of the primary anchor which might be the case when the secondary is attached directly to the primary.