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  #21  
Old 02-26-2012
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JohnEisberg,

I LOVE your idea of practicing the bridle method at anchor. I will definitely try that next time I get a chance. I've been known to row out a stern or kedge anchor in order to avoid ferry wakes or other rollers. Your idea looks much better for making a rolly anchorage more comfortable and had the advantage of practicing a storm tactic to boot. Great suggestion!

I have always wondered the same thing about the Pardey Bridle. Seems to me like it would slide down against the hull. The solution I have in my head, is to depoly the sea anchor on a long rope rode (I have a 400footer I would use) that is attacked to my main anchor chain. An amount of anchor chain would be payed out from the boat. This would eliminate (mostly) the major issue of chafe on a rope rode. Also, having chain at the boat end of the sea anchor rode would allow you a fixed point to shackle (or otherwise secure) your bridle line.

Actually, since many sea anchor proponents recommend a length of chain at the boat end, I don't see why the main anchor chain isn't used more often. It seems like you could let out a few hundred feet of chain, rather than just a few feet, and it would aid in keeping the anchor sunk and allow you to adjust your wave/rode length as needed for your wave period.

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  #22  
Old 02-26-2012
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I would think in a heavy blow that the snatch block would be fairly stable and only ride forward or aft with a significant change in the pressure applied to the parachute. I did not that he found a huge difference in the volume of water with only a relatively small change in parachute size. For example, in the book he talked about the volume doubling when increasing diameter from 8 to 12-feet. Also he talked of the effectiveness with different lengths of the anchor rode and said it was imperative to get the parachute out to at least the second trough. I read another book where the author added a 10-foot length of chain, which placed the parachute about 20 feet below the surface, which decreased the amount of turbulence on the chute. As Pardey point out, this is NOT an exact science, the you'll have to experiment a bit to get the right combination and best results. He also pointed out that during a 70-MPH blow that lasted 3 days he was accompanied by a couple large, container ships that also hove to during the storm and incurred no significant damage. One of the larger sailboats, a 76-footer, tried to outrun the storm and attempted to take refuge behind a reef. The boat suffered a 90-degree knockdown, several crew members were injured and the boat was nearly destroyed. Like I said previously, I'm going to do my best to avoid these conditions.

Good Luck,

Gary 8)
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  #23  
Old 02-27-2012
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Perhaps some additional reading might be:

1. Tartan association site- which has posts by Russ Comb of Hygelig and his
experiences with being hove-to in a storm, using para tech anchors and drogues (including the loss of one).

T27Owners : Tartan 27 Owners Yahoo Group

2. James Baldwin discusses parachutes on his Atom site.

3. The loss of the boat Puffin off of New Caledonia and the owner's
first hand experience as expressed in an archived letter to Latitude 38.

Changes in Latitudes
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  #24  
Old 02-27-2012
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That's a great picture! Looks like everyone is on a "Bahamian moor" to keep bows into the swell. I think the snatch block part of the rig is one of those things that can really only be tested in a great amount of steady wind so that the forces are continual. It seems to make sense that if a block intersects the anchor rode anywhere in front of the bow that it will slide to a point of equilibrium when tightened; form a triangle with intersect, bow attachment, and cockpit attachment as the corners. By changing the length of the cockpit line, the angle of the boat relative to the wind would change. Geometrically, it works in theory.

Boat design, of course has a lot to do with whether any of the idea works. It's likely that boats that heave-to easily will probably work better with this "enhanced heaving-to."

Would be nice to actually deploy the sea anchor on a snotty day but the prospect of trying to get it back in and the clean-up and repacking have always squelched the idea. If actually used, I'd try to sit it out until the seas calmed back down to retrieve it.
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  #25  
Old 02-27-2012
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Quote:
Originally Posted by MedSailor View Post
Biliruf,

What gear did you choose for your bridle? What is your boat's displacement?

MedSailor
I have a 16 ft para by Fiorentino Fiorentino ParaAnchor - manufacturers of sea anchors and parachute anchors and storm droguesto be deployed on a 450 ft 7/8” braided nylon rode. The bridle was supplied by Fiorentino and I can’t remember the size -- probably something on the order of 3/4” braid.

BR displaces 24 tons loaded for sea.

Re. the Coles book and the 28 ft para anchor -- that seems pretty big for a boat that size. I went with Forentino’s recommendation and ended up with a 16 ft anchor for a boat of roughly the same size and 1/2 the displacement. I think that a 28 ft anchor would probably fully stop the boat and in a big blow that means that the rode would take all the strain, much as it would if it were anchored to the sea bed. I think the idea is to have the boat slowly moving backward while maintaining a safe angle of attack to wind/seas. In Coles’ time I think many people used surplus military parachutes for sea anchors and that may be why the boat in question had one of 28ft diameter.

A smaller diameter para anchor should place less strain on the rode and bridle. Also, you can use the anchor with sail up and hove-to. This might also take some strain off the rode/bridle.
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  #26  
Old 02-27-2012
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Quote:
Originally Posted by MedSailor View Post
Personally I've always thought that, for my boat/crew/situation a parachute sea anchor will be the first line of defense for a survival storm if heaving-to is no longer a viable option.

(...)
Thoughts?
After doing quite a bit of research on the same topic, I've decided that parachute sea anchors suck, because if you don't have the right amount of rode paid out to exactly match the period of the waves, it's going to jerk your boat to pieces. And even if you do get it matched up right so you're rising when your anchor rises and falling when your anchor falls, what happens if the wind shifts or the period changes? The much better option is a "series drogue," because you get the same anchor force but it's distributed along the line. I believe most series drogues are intended to be attached at the stern.

These guys have some videos:

Jordan Series Drogue

I have no personal experience with either, and I hear that trying to reel a series drogue in can be a real bastard once it's deployed, but I'll be trying the latter before the former.
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  #27  
Old 02-27-2012
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Where to attach the seaAnchor rode? That depends on how well you get along with your "in-laws" and your ner-do well cousins.
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  #28  
Old 02-27-2012
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[QUOTE=beej67;837367]After doing quite a bit of research on the same topic, I've decided that parachute sea anchors suck, because if you don't have the right amount of rode paid out to exactly match the period of the waves, it's going to jerk your boat to pieces.
RESEARCH?? What kind of "reasearch" did you do?? Consult with other people on the internet that did the same kind of "reasearch" as you?? Advertisements from vendors?
When you're anchored firmly in a blow, does your boat get jerked to pieces?
When you're on a mooring in a blow does your boat get jerked to pieces?
What "reasearch" have you done? NONE.
Marc

Last edited by gershel; 02-27-2012 at 02:52 PM.
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  #29  
Old 02-27-2012
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You mad bro?
Quote:
What kind of "reasearch" did you do??
Read a bunch of personal accounts of people who had problems with sea anchors, then learned about wave motion to figure out why.
Quote:
When you're anchored firmly in a blow, does your boat get jerked to pieces?
"anchored firmly" is a very loose term when we're talking about a parachute that's moving in circles in one ocean swell, and my boat is bobbing up and down on another ocean swell two swells down. Please clarify it, thanks.

If you mean "anchored firmly to the ocean floor while my boat bobs in 20 foot seas," I can happily say I've never been forced to endure such a thing, and if I had, I can imagine it might jerk my boat about quite a bit.
Quote:
When you're on a mooring in a blow does your boat get jerked to pieces?
I wasn't aware moorings existed out in the middle of the ocean where you might experience 20+ foot swells during a hurricane, and if such things did exist, I would be wary of tying up to them, for fear I get my boat jerked to pieces. Maybe you've had a different experience you'd like to share?

Now, in my boat, if I'm in less than 12 foot seas, there's no point in deploying a sea anchor anyway. I'm sailing it. The point of a sea anchor, as I understand it, is to deploy something, batten down, and go below if you get hit by a small to medium sized hurricane and you're too far to run for shore. Right? For that, you need to plan on 20 foot swells or more. When tied up to a parachute sea anchor in 20 foot swells, you need to understand something about how wave motion works. When a wave moves, the molecules that make up the wave don't actually move themselves except in a big circle. Read this:

Motion in the Sea -- Waves

So if you have your rode panned out to the wrong length, you can end up in a situation where your boat goes one way and your parachute goes the other way, once per wave, jerking your rode tight. Then in the trough it goes slack again as you and the parachute come together. Once per wave. I've read several personal accounts of people who didn't get this right when deploying in a hurricane, and they had to cut the damn thing loose. You don't have that problem with a series drogue, because the resistance to motion is distributed all along the length instead of at one spot at the other end.

I've also read some other accounts of people who are experienced at using parachute sea anchors, most notably commercial fishermen from New England where the practice is common, and they pay a lot of attention to how far out to pay their rode so they match the wave period. They will also reel it in or let it out if the conditions change. Seems like a certainly smart and prudent thing to do, that I just don't want to have to fool with if I'm just choosing among emergency gear.

What storms have you deployed a parachute sea anchor in, and what were the conditions? Did you pay attention to the wave period when you deployed it?
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  #30  
Old 02-27-2012
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I must say that this is an interesting and thought-provoking discussion. I have all the gear but have never deployed it anger (I suspect getting the parchute back might be a pretty big task since even when conditions moderate it may still be blowing 30 knots.

Couple of notes:
- I think the size of the parachute matters. You don't want to be stopped, you do want to slide sideways. We have an 18' chute for a 36,000 lb boat. This was bought by the first owner and is the recommended size for the boat. Too big and it might act as too much of a brake and increase the loads on everything.
- Jon, my sense is that being anchored and using a midship bridle is not the same, dynamically, as doing it with a parachute since the entire system - boat and sea anchor rig is free too move sideways rather than being tied to a point in space. Also, according to the pictures and diagrams in the Pardey's boat there is a considerable amount of force on the bridle so the angle in the main line is significant, reducing the ability of the snatch block to slide forward and back too much. I get the impression that the purpose of the snatch block is mainly to reduce the potential for chafe.
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