Parachute Anchor idea for rode length

[BigBeakie]

Something I've been wondering about as I set up system for the new cat is how do we adjust the rode length on a parachute anchor when it's in use?

If we deploy it on 300' of 24mm Polyester DB, and then the conditions continue to deteriorate, the swell length increases, and we want to put out another 300' length, how to do that safely?

My thoughts are to run a dyneema line from one bow cleat ( a massively big and strong one with appropriate deck re-enforcement & backing plates) that has a big low friction ring spliced in the end. The parachute anchor rode runs through the ring and is belayed on the other bow cleat, so there is effectively a bridle formed, similar to the Pardey's lying ahull bridle.

The rode would have a spliced eye in the end, as would the additional 300' rode, and they get soft shackled together. There are big (and very strong) low friction rings that are used in the tree lopping industry that would be big enough to have the eye splices & soft shackle joiner pass through it, unlike any type of block that I'm aware of.

Any thoughts on this idea? Anything I should be considering?

Any recommendations for really strong horn cleats? I have the strongest Vetus Taurus they have (#07 3,600 kgf), but stronger would be better. The Nomen cleats are strong but very pricey indeed.

Thanks in advance for any feedback

[UNCIVILIZED]

You're going to have to draw a picture of this, as I can't visualize what you're trying to say.

[BigBeakie]

Ok hope this helps.

In the drawing A is the line with the large low friction ring C, that runs from the port bow cleat, adjusted for length so that it forms one leg of a "bridle".

B is the parachute anchor rode that runs through the friction ring C to the para anchor.

If & when more rode is required, another 300' length of rode is attached to the end of B (the rode to the Para anchor) that has a spliced eye with stainless thimble. The 2 rodes are joined with a strong soft shackle through the thimbled eyes.

The motors take some strain off the starboard bow cleat rode, the rode is taken off the cleat and the extra rode is let out. The eyes joined together with the soft shackle will run through the large ring when they get there.

Being at the bows under those conditions would not be a happy experience I'm sure.

[Don C L]

Better practice out in some foul weather first. I have my doubts the soft shackle and eyes will not get hung up in the ring. Might be ok, but I find anything that CAN get stuck, will, at the worst time.

[a64pilot]

I have a mono but also have 600’ of rode for my parachute anchor.
My plan is if it’s bad enough to deploy the sea anchor, it’s getting all 600’ of rode. Why would you want to use less?

[BigBeakie]

A64,

One reason is that the para-anchor can be used in less extreme conditions, for instance just to park the boat for awhile. With only crew of 2, it may be necessary or desireable to take a break, due to illness or injury to one of us.

Another cruiser told us of a night with wind against current where they were bashing to windward and were exhausted, so put out the chute on shortish rode just to hold position. In the morning after a good sleep, they were several miles upwind as the current had kindly towed them towards their destination.


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[thinwater]

I've experimented with bridles like that on drogues and found that they can be unstable in yawing conditions. For one thing, the ring angle will bisect the bridle no mater what you draw on paper. The physics say it must. Thus, the bridle must be an equilateral triangle, and the ring can actually snap up the bridle arm, to the bow. In short it does NOT work as drawn.

Second, it is a chafe point.

The best answer is to deploy the full rode at the beginning. Easing the rode under high load, without the boat turning sideways to the weather, is very difficult.

[Paul L]

Originally Posted by BigBeakie

A64,

One reason is that the para-anchor can be used in less extreme conditions, for instance just to park the boat for awhile. With only crew of 2, it may be necessary or desireable to take a break, due to illness or injury to one of us.

Another cruiser told us of a night with wind against current where they were bashing to windward and were exhausted, so put out the chute on shortish rode just to hold position. In the morning after a good sleep, they were several miles upwind as the current had kindly towed them towards their destination.


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Heaving-to or fore-reaching would be more practical if you are looking for a break. Setting a parachute and retrieving it is not an easy restful thing to do.

[Larry Florida]

Originally Posted by BigBeakie

Something I've been wondering about as I set up system for the new cat is how do we adjust the rode length on a parachute anchor when it's in use?

If we deploy it on 300' of 24mm Polyester DB, and then the conditions continue to deteriorate, the swell length increases, and we want to put out another 300' length, how to do that safely?

:

Why would you need another 300 ft? Is 600 ft really necessary? Can't get the physics behind more than 300 ft

[maxingout]

I have had to use a parachute sea anchor one time on Exit Only about 300 miles north of New Zealand in a winter storm. It worked awesome, and it was on 500 feet of one inch double braid line with 15% stretch. I think it would have worked fine with more or less line, but 500 feet was excellent for us.

The point of attachment of the parachute bridle to the boat is the big challenge because I did not want the parachute to pull the cleats out of the deck.

I constructed parachute sea anchor chainplates with a bail on the leading of the chainplate so the parachute bridle could be attached with shackles in a chafe free manner. It worked great, and the chainplates will never pull out even in the worst conditions.

You can see the construction of the sea anchor chainplates in a schematic at the following link:

MAXING OUT - JOIN TEAM MAXING OUT AS THEY SAIL AROUND THE WORLD ON THEIR PRIVILEGE 39 CATAMARAN - EXIT ONLY

[UNCIVILIZED]

Originally Posted by Larry Florida

Why would you need another 300 ft? Is 600 ft really necessary? Can't get the physics behind more than 300 ft

Wavelengths in the open ocean can be incredibly long, especially in large, well developed storms. As in several hundred meters long. And in order for the chute (or drogue) to work well, it may need to be a full wavelength or more away. Even a couple of wavelengths (ideally, in theory) at times. So a long rode is desireable for this reason. There's more on this topic in many of the drogue threads (JSDs), including the one below, from my post till the thread's end. Including some comments & testing by Evans Starzinger, along with Beth Leonard & the Dashew's. Also, if you're buying or making a drogue or chute system, do some reading of the Drogue Device Database (DDB). There's volumes of useful info on real world deployments of various chute & drogue types in there. By a multiplicity of boat types. http://www.cruisersforum.com/forums/...ml#post2483372

[BigBeakie]

Thanks All, this is what I love about CF:

I wish there was an embarrassed emoji as well, I would've used it too.

Thinwater - Thankyou, you are of course, absolutely correct. The geometry of the "bridle" just does not work with a friction ring. I tried it in my garage simulating this idea. I should have done that in the first place...lesson learned
If the arm is long, the ring just slides up to the other bow and the pull is directly on the Chute rode cleat. If the arm is short enough to give a bridle effect, the pull vector is pulling the cleat at a horrible angle to the center line of the boat. Hat tip to you, Sir!

Paul L - Thanks, but I think both heaving to and fore reaching can have their issues. I'm not sure how this cat will heave to, or if it will at all. I have had a bad experience trying to heave to in a cat. It got pushed sideways in confused seas and was hit broadside by a breaking wave. It was a cedar strip epoxy glassed boat 20 mm thick cedar strips with 1200gsm quad glass both sides and it still delaminated the West System epoxy and popped the furniture off the walls. Not good.
And fore reaching is not a passive storm mitigation technique either. We had to hand steer for 2 full days and nights on a trip back from Lord Howe Is. in very nasty big (10-12 meter) breaking seas, trying to steer between the breakers as they barreled down on us. Not relaxing at all, bloody exhausting. If one of us in incapacitated for any reason, both these options seem wrong.

Maxingout _ LOVE your attachment plates, I've looked at them several times before in the past. Now that I see the wisdom of laying out the full 600' rode and be done with it, I'll revisit your fine idea of using chafe free shackles. How did you work out the engineering loads on those rings? Did you find any data on what the forces are on a cat that is hit by a fully developed breaking storm wave? I would love to know.
Also liked your ingenious use of oars down the ring to ward off nasties that would hit & dent the cutwater. Nice!

Thanks again for all your thoughts.

[KP44]

Originally Posted by a64pilot

I have a mono but also have 600’ of rode for my parachute anchor.
My plan is if it’s bad enough to deploy the sea anchor, it’s getting all 600’ of rode. Why would you want to use less?

I also carry a 600' line for the 18' para-anchor. If it is bad enough to use the parachute, I will deploy the full length. I have a large enough chain locker to securely carry the line and anchor, stored out of the way.

[daletournier]

I've never used a parachute anchor or a drogue.

We had a 14-16hr gale this year while crossing the Indian ocean. We ran with it during the night under bare poles averaging approx 7 knots, but surfed at 16.3k once, wind was high 30's-low 40's for most of it and gusted to high 40's.
Down below it was actually quite comfortable in the large following seas. But when I ventured out into the cockpit it was a different world.

While out there I was considering if conditions worsened and speed became an issue I'd have to look at setting the drogue (conditions never got close to that). Being in the cockpit at night, tired, soaking wet in the middle of a strong gale made me realise how hard it would be to get the drogue setup let alone adjust if I felt the need.

My point is, I believe once it's out there it would be difficult to adjust, but I haven't done it so can't do it say for sure.

On big passages I now have the drogue setup ready to go, just unzip the bag and throw it over board.

[a64pilot]

I think deploying a large parachute anchor with some chain and a whole lot of nylon rode is a lot like reefing, better do it prior to needing it, if you wait, it may be too late.
I have never deployed mine, but have been on the bow in severe weather trying to put an anchor back into position, and it is a dangerous, difficult place to be. That weather wasn’t nearly severe enough to warrant deployment, if I waited until weather is that bad, I’m not so sure I could do it safely.