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  #21  
Old 02-24-2008
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There's a lot to read on the subject and I've read a good bit of it. I've also had a parachute deployed on a 46' ketch in a mess of weather and sea outbound to Antigua from Morehead City in the Gulf Stream in 1971 - my observations were constant chafe issues and bending of the sampson post. The stresses are scary. The ketch also tended to skate around at anchor in a wind so she had a good bit of forward windage which added to difficulty of keeping her angled off (ala Lin/Larry Pardy.) After that experience and several less threatening experiences, we are fitting chainplates to our quarters to accomodate a JSD for our 33,000# 50' cutter. Spent a good bit of time talking to Para T and others prior to the decision.
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Last edited by jimmalkin; 02-24-2008 at 09:12 PM. Reason: I was so tired I wrote ketch instead of cutter...duh.
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  #22  
Old 02-24-2008
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sailaway21 is just really nice sailaway21 is just really nice sailaway21 is just really nice sailaway21 is just really nice
It's also my understanding that one can have too large a sea-anchor, providing too much anchoring capability at the expense of strain and desirable leeway. I'd anticipate the need for beefing up a bollard or cleat as well. 15 tons of stress either by single part or bridle is a load no matter what.

Please let us know of your on-going experiences, Jim.
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  #23  
Old 02-24-2008
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I am in the market for one or the other and having read till my eyes bled, I still dont know which way to go.
ITS ONLY SOME PAGES BUT QUITE ABIT ABOUT SEA ANCHORS towards the end.
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Last edited by SimonV; 02-24-2008 at 06:52 PM.
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  #24  
Old 02-24-2008
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No, you don't have to steer when using a properly sized Jordan Series Drogue. In fact, Don Jordan, when I spoke with him said, that would defeat the whole point of the device. It is designed to keep the boat from needing to be steered, and to allow the crew to get in out of the weather and get some rest.

There is a difference, despite what Sailaway says, between a sea anchor, which is supposed to effectively stop the boat, and a drogue, which is designed to slow, but not stop the boat. A lot of the confusion comes from the fact that some people do use the terms interchangably, and some people use a small diameter parachute as a drogue, but call it a sea anchor.

One major difference, sea anchors are generally deployed from the bow of a boat, and drogues are deployed from the stern. Another major difference is that the drogue is designed to let the boat run with the storm at a controlled, manageable speed, the sea anchor is designed to stop the boat head to wind, much as it would be if the boat were actually at anchor.

The problem with shock loading and sea anchors comes from the fact that the wave motion can cause the parachute sea anchor to partially collapse or for slack to build up in the rode. When the boat is then moved by a wave, when the parachute re-fills or the rode tightens up, there is a relatively large shock load on the mounting hardware. The JSD avoids this since the JSD is made up of many small cones...and as the load comes onto the JSD, the cones react gradually, starting with the ones closest to the boat and moving along the JSD until all of the small cones are fully expanded and under load.

As for how you use a JSD in a storm... generally the JSD is in a bag or locker. The JSD is essentially a long piece of rope with a lot of small cones sewn to it. At the terminal end of the JSD is a weight, about 15 lbs. in the case of my JSD, a bit more for a larger boat. At the boat end, the JSD is attached to a bridle that is attached to the outboard sides of the transom, and the bridle is about 2.5 times the distance between the attachment points.

To deploy it.. you dump the weight into the water, and let it and the drag on the cones pull the JSD overboard. You really have to take care to set this up properly, since once the cones are in the water, the JSD will tend to deploy itself very quickly and under a fairly significant load, with little opportunity to untangle it if it isn't feeding fairly.

When you've done that and checked the bridle to see that it is led fair and not chafing...you go down below and batten the hatches. Ride out the storm and then when it calms down, you have the PITA task of retreiving the drogue, which is not easy.

Quote:
Originally Posted by danielgoldberg View Post
Dawg, I'm not sure I see how you can deploy a drogue and then go below and get some rest, or even just chill out in the cockpit. Don't you still need to sail the boat? And ini the kind of conditions that require a drogue, I would think you would need to sail the boat quite actively.

Also, I think (but don't consider myself the expert) that a properly sized sea anchor shouldn't really stress boat fittings all that much (chafe is a much different story). The boat still moves with a sea anchor, you are using very long lengths of three-strand rode with a lot of stretch, and generally it seems to me that there will be give in every way conceivable. Surely the loads on the boat are less than if you were at actual anchor considering the additional rode and the designed sliding motion of the boat. In my experience, a sea anchor is best essentially when you are having trouble heaving to, for whatever reason (in our case we have a self-tending jib and with the mast stepped so far forward heaving to is not the easiest thing to do). Retrieving them is a pain in the stern to be sure, but that would be a small price if it allows you to ride out a storm more comfortably and safely. At least that's my view.

I don't have any experience with a drogue at all, but I would be very curious to hear how you use it in practice and not still have to sail the boat. I'm not criticizing the technique, just in case that's not clear.
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  #25  
Old 02-24-2008
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A sea anchor is big and essentially stops the boat. For a 46+ catamaran it seems like it would put a lot more stress on the boat than anchoring because the anchor chain's weight acts like a shock absorber in the waves. If a wave jerks the boat really hard, the anchor chain will straighten out and absorb a lot of the shock before it is fully tight.

This isn't true with a sea anchor on a rope. The sudden jerk of a breaking wave will be transmitted to the boat almost immediately because the rope or chain to the sea anchor is already tight. The wind and waves in a storm will put a lot more pressure on the boat than normally encountered at anchor.

Where is the strongest place to attach a sea anchor? cleats? windlass? winch? No matter where you put it, you should be able to let out a few inches of rope every so often so it will chafe in a new place. With either a drogue or a sea anchor, you can probably tie off the helm and go inside, or use the autopilot if it's available and can handle the conditions.

A drogue, because it is smaller, will have much less pressure, maybe by a factor of 10. That's why the boat moves. The purpose of the drogue is not to stop the boat. It's to prevent surfing so one of the hulls won't dig in at the trough of a wave. Also, with some forward motion a catamaran will ride on top of the waves better because the speed of the waves relative to the boat is less.
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  #26  
Old 03-08-2008
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You may like to check out an Australian site called Para-Anchors Australia Pty. Ltd as we have found them very helpful. We have a 40' cat and know other multihull owners who have used the above product. Good luck!
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  #27  
Old 03-10-2008
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Should this thread be merged with the one in Seamanship?
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  #28  
Old 03-10-2008
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I don't see why not...they're basically on the same subject. And I wouldn't have to repeat myself...
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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
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  #29  
Old 03-10-2008
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For what its worth I just bought a Para anchor, as for the sudden shock, 400
foot of 9/16" three strand nylon I would take up any shock loading, also the para vents at shock loads of 7000lbs.
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  #30  
Old 03-10-2008
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Quote:
Originally Posted by SimonV View Post
For what its worth I just bought a Para anchor, as for the sudden shock, 400
foot of 9/16" three strand nylon I would take up any shock loading, also the para vents at shock loads of 7000lbs.
Doesn't nylon have something like a 50% stretch value? If it is like a climbing rope the nylon will work like a big bungee, perfect!
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