Lines in lieu of drogues?

[Kettlewell]

By the way, some talk of steering but there comes a point where you need some system that will let you go below and you have to assume the windvane and autopilot will be broken too. In our worst offshore gale we broke a steering cable, so no steering available and we were occasionally taking heavy breakers across the entire boat. It would have been dangerous to be outside even if we had been able to steer. We utilized a small parachute sea anchor off the stern rigged with a bridle which kept us going dead downwind at a knot or two in relative safety. We put out 400 feet of nylon rode, which dampened the ride considerably. There was never slack in the system, though the load went up and down. Interestingly, the small parachute acted like a small reef back there and I saw many breakers split around it, leaving us somewhat in protected water though of course we still got breakers onboard from time to time. In any case, my bottom line on drogues and chutes is the system must be capable of keeping the boat in a safe orientation without steering.

[Fi2010]

Originally Posted by CaptainMarkS

"Minimal?" Expected (designed) max loads with our Jordan drogue are 12,500 lbs. There is no "constant rode tension" in lurching seas. The drogue is designed to prevent the vessel's forward momentum including with breaking waves over the stern. That's a LOT of force. Folks have lost sterns cleats along with their drogues not considering such forces involved.

Jordan explained how his calculations were educated guesses. The open water test completed by Jordan led to his product breaking apart. In our opinion, there was too much slack in the system and shock loading created the issue.

Shock loading can increase force, usually, almost always, causing rode to part before anything else. Hence the importance of weight, which is one of the Constant Rode Tension solutions.

Jordan decided to recommend an average of 35 to 50 lbs. of weight be attached to the JSD to sink the cones to avoid breakage. This helped. We believe increasing the boat’s speed by deploying sail or using engine power is another option to counter the effects of “lurching seas”. It can take more than one Rode Tension solution to combat shock loading.

Dynamic load cell testing can reach the numbers you’re referring to Capt. Mark. This type of testing is when your boat is moving fast, while in rough seas, and you quickly deploy the equipment.

The US Navy conducted said test with the shark drogue. The ship was traveling between 13 –16 knots, the rode was low stretch, and there was no weight attached. Peak load reached was 2,500 lbs. Peak load for the 12’ para-anchor was 20,000 lbs.

Most of our real-life load cell testing in heavy gales to light storm is anywhere from 500 to 1,000 lbs. for the shark and 3 to 4,000 lbs. for the para-anchor. However, deployments were from sailboats and not a large naval ship. Boat size, how the equipment is rigged, how it’s deployed, or in the rare circumstance your boat falls down a wave, all change the numbers. In general, we believe loading isn’t as bad as sailors might think. There can be exceptions.

[MicHughV]

Some many years I got caught in some real gnarly weather such as described elsewhere on this thread.
I considered my options.
To continue to sail was not an option.
I did not have a drogue of any kind onboard.

So I started to concoct something from odds and ends on the boat, based on stuff I had read in various books.
My first attempt at anything was to stream a long line off the stern, about 200' of 5/8" nylon anchor rode, but this did little, if anything, to slow me down.
Next I added a line to form a bight, with each leg about 150' long. This too, did little to slow me down.
Next, tied an anchor and some fenders to the arse end of 200' rode. This too, did little to slow me down.
Finally, myself and my shipmate, took the storm jib, and rolled and wadded it up into a ball of sorts as best we could, and tossed it over the side tied at the end of the 200' rode.
This finally did the trick, in that it kept the stern of the boat, more or less, to the breaking waves, and reduced our forward speed to around 4-5 knots sliding down a wave, this under bare poles and even allowed us a modicum of steerageway. This was very useful in that it gave us the ability to steer the boat obliquely down the face of a breaking wave.

The strain on that line was humongous. Despite the ability to stretch a good amount, every once in a while the line would get bar tout like a guitar string.
In my particular case, my boat was a steel vessel with very strong welded on cleats.
Had I been on a fiberglass boat with standard bolted on cleats, I think it would have torn out.

The worst of our situation carried on for around 24 hrs or so, and another 12 hours to allow the seas to quieten down a bit, at the end of which, we pulled our contraption back on board.
We could not untie the rode from our makeshift drogue, as the knot looked like it had fused together, and we had to cut it loose.

Afterwards, we tried to analyze how much strain was taken by the line, and came up with the number of 4,000 lbs plus. How did we do this. I am a marine engineer by profession and we used a catenary line equation to figure out the strain based on observed sightings. Not very scientific, but all we had to go by. It could have been more, or it could have been less, but around 4K seemed to be about right.

That said, in 35 years of living and sailing on a boat, that was the only time, I ever experienced such inclement weather.

Some other points to ponder. Breaking waves washed everything from the deck.
My buddy and I, were ourselves lashed into the cockpit by criss-crossing sheet lines across the cockpit and we were constantly under water. Though we both had foul weather gear on, we were soaked to the skin.

Going below was out of the question. Besides the waves, it was raining like stink. During the day, we could see what was going on, but the night was pitch dark, and we had to listen to the crest rolling down a wave.

Interestingly, we figured wave height to be around 15-18' high comparing them to the spreader height on the mizzen. They weren't breaking per se, but their crests were getting blown off.

After the first 24 hours, we were exhausted beyond description. 15-30 minutes behind the wheel was about all we could manage.

When were finally able to plot a position, we saw we had been blown about 100 miles off course. We were fortunate in that we had plenty of searoom.

Just adding my 2c to this thread.

I could have...and should have....made better preparations, like having some food and water available, etc, but at the time, having never experienced such weather, we simply did the best we could under the circumstances.
I would, at the very least, use a similar kind of drogue as I've seen this work for me.

[Fi2010]

Interesting story.

5/8” nylon anchor rode on average has approximately 16,000 lbs. break strength. The moment it becomes wet it can lose up to 40% of its strength, dependent on what expert you rely on. Shock loading can add another 50% loss. This only leaves an average of 10%, lets call it 20% strength, to handle the storm.

It’s one of the reasons we realized years ago how certain drag device deployments, makeshift or not, have less loading on equipment than originally thought. Load cell readouts also confirm the information. However, manufacturers should assume a worst case scenario and beef up their equipment anyway.

[MicHughV]

There are some threads on here which delve into the amount of strain an anchor rode takes.
Seem to recall some or other instrument was used to determine line pull. A strain gauge.

I know that chain employs a 5:1 safety factor, but not sure what SF is applied to nylon rode.
Some Google searching seems to indicate the SF of nylon rope is even higher than 5:1.


But for example, using the 5:1 ratio, would suggest the 5/8" nylon 3 strand rode has a "safe" capacity of 3,200 lbs, so figuring about a 4,000 lb load should be within the " 4:1 safe" margin a 5/8" rode could handle. I could live with that.

I have some old text books somewhere that go into greater depth on this issue pertaining to ship mooring lines which may provide some guidance, but I'm confident a 5/8" 3 strand nylon rode could safely handle 4,000 lbs.

[Eder]

Originally Posted by nofacey

Ahh -

Hopefully I never need it - but then I carry a certified life raft too.

Most of us do but few of us will ever be able to get into it when SHTF

[Andrew Lippman]

I would consider figuring out a midships turning point for drogues rather than the stern. That makes it easier to steer the boat with them.

[MicHughV]

Yes, from a technical point of view, I would agree with that.
Speaking from experience, trailing a drogue from the stern made steering very slow and sluggish.
However, you'd have to arrange for some kind of bridal attachment, so the boat could be turned either way, and there is bound to be a number of things in your way.
Too many variables her to think thru'.

[Andrew Lippman]

Agree: a bridle is needed. Maybe even a turning block to lead the bridle from midship back to the primary winch.