Using anchor as drogue

[m0ggy]

I have about 80m or yards of 8mm galvanised chain and 15kg cqr anchor, would it be possible to use as a drogue in a seaway? Or am I much better using a long line?
This is on a gibsea 32 of approx 4 tonnes
Thanks
Tony

[Shrew]

I would think a drogue would be better as a drogue. A traditional drogue has a conical chute at the end. A Jordan Series drogue has a 'series' of small conical cones. A Line in the water will create some drag, but I have doubts as to how effective it would be. Even a bucket tied to the end would be better, however you're putting a lot of trust in the forces that bucket handle can take. I doubt an anchor tied to the line will give enough resistance to be effective.

I suppose anything is better than nothing. However that really applies to when you are in a situation and have nothing. At that point any workaround is worth trying. Here you are in the planning phase. I would caution against implementing 'work-arounds' as a functional plan. That is not sound foul weather planning.

[xxxxx]

No bueno situation.


First, I an anchor with chain would sink significantly more more than a drogue. This means the angle to the boat would be significant, and the resulting load would be more "downward" on the stern than "rearward" if that makes sense.


A drogue does have a weight on it to keep it in the water, but the way it streams causes a drag load pulling backwards on the boat, slowing it. This is the force you want.

The other issue is that a chain and anchor would apply its load suddenly. Imagine the boat is going down a big wave, possibly faster than the anchor can sink. The chain has slack, and the anchor has inertia. Then, a big wave forces accelerates the boat upward. Once the slack is pulled out of the chain, it will be a sudden downwards "BANG" when the anchor reverses direction. Impact loads like this are no bueno.

Conversely, a series drogue will more slowly apply load, and in the correct direction. Even if the rope has some slack, each cone will engage the water individually, one at a time, (in "series"). This will apply the load to the boat over time, in smaller increments, thereby nearly eliminating the impact load mentioned above.

A series drogue is what you want. Even warps would be better than the anchor and chain.

[xxxxx]

https://www.jordanseriesdrogue.com/p...uardreport.pdf


Read this.

[psk125]

There is also the question of when to use a drogue, if at all. Slowing the boat down too much, stern to the waves, can cause problems with them catching the rudder and tearing it off. Faster boats sometimes fare better by maintaining some speed and dealing with the weather by running more with it. Each boat and situation is different: YMMV.

[Saleen411]

I like the idea of 2 roped up tires bound together with a dinghy anchor attached to a 400 foot rope on a swivel.

Not only do you have an effective drogue, but 2 nice fenders.

[Searles]

Have used anchor and chain over the bow rollers as a drouge in the Tasman sea ,works verry well ,not a lot of load but holds the bow up well even in breaking seas ,so yes it is do able. ⚓️⛵️

[thinwater]

A. Try it. You read a lot, and you will get advice, but most of the people have never used a drogue.

B. The anchor in the center of the long loop of line would have some value, but not enough to stop surfing in big waves, just a little directional control. BTW, lines (warps) are always towed as loops with the center weighted, and more weight helps. towing just a line is completely useless, and if the warp is not weighted, it will start skipping out just when you need it. Additionally, the weight increases the drag by pulling the warp through the water at more of an angle.

No, it will NOT pull the back of the boat down. It will exert only 35 pounds of downward pull, which is better than the 35 pounds on the bow! The total drag in unlikely to ever exceed 250-500 pounds, and nearly all of the is horizontal (yes have tested these things with a load cell).

[xxxxx]

Originally Posted by thinwater

It will exert only 35 pounds of downward pull ... (yes have tested these things with a load cell).

Wow! Weird eh? I wonder how come.


The anchor and chain weigh about 280lbs. I would expect the force of impact loads to be much higher. How is the testing done?



I'd expect that to be true of a static load, where the anchor is just hanging. And I'd agree that the drag would be as you stated when the anchor and chain are steadily trailing behind the boat since that is just friction against the water.


For a boat in irons surfing down a wave, and then being thrust upward again, a situation where the chain has developed some slack, I would expect several kN of force to be seen at the attachment point to the boat. Similar to using snubbers to reduce shock loads when mooring.

I'm curious to hear your thoughts on this. You almost certainly have way more sailing experience than I do, and I've never done these real world tests. Yet, the physics seem to support my hypothesis. I'm not trying to argue, I'm just trying to fully understand. I might be missing something.

[m0ggy]

Originally Posted by Searles

Have used anchor and chain over the bow rollers as a drouge in the Tasman sea ,works verry well ,not a lot of load but holds the bow up well even in breaking seas ,so yes it is do able. ⚓️⛵️

Ahh ok thanks. I was planning to use this over the bow. Just trying to cut down on the enormous amount of stuff one needs.

Mind you the 2 tyres bound up with rope also sounds like a good alternative

[m0ggy]

Originally Posted by xxxxx

https://www.jordanseriesdrogue.com/p...uardreport.pdf


Read this.

So is a series drogue a long rope with lots of little droguelets on it?

[sailortype]

"Ahh ok thanks. I was planning to use this over the bow."
we seem to be talking alternately here about drogues and sea anchors as if they are the same thing. I think the OP is really talking about a sea anchor situation

[Gaia]

Make your own series drogue. It is easy. Having said that will you ever need it? We made our own in Bermuda before a 20 (now 25 saling) year long circumnavigation and never came even close to using it. (We were told this when we also bought a parachute drogue in New Zealand but did not listen. They were right.)

We did almost all our sailing in tropical waters outside of three forays: one from Canada at the start, one up to Northern Europe, another to New Zealand and a fourth (oops) to South Africa from the tropics and back up into the tropics. We never encountered a multi day storm.

Jim sv Gaia

[RiverRat37]

It's an interesting idea, but it occurs to me that dragging an anchor could have unintended consequences (that should clearly have been considered first). That being: What happens if you get into water a good bit shallower than the 80M chain with a hook dangling on its end? What if the hook suddenly performs it's intended design task? That could be exciting and elicit the comment "Well, It seemed like a good idea at the time."

Also just a thought, but might the configuration of the anchor be a consideration. Would the drag of a Herreshoff be the same as a Danforth or a Plow? Testing needed.

[Paul Howard]

Using an anchor as a drogue is bad idea. Not enough resistance to hold boat and the anchor would spiral and twist line into knots.
Better to remove anchor from chain and attach a rope and have equal rope at both ends of chain to trail out from either quarter.