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Old 01-06-2016, 23:29   #1
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Para sea anchor advice

Hi I am getting a sea anchor fabricated for a 10ton 41ft ketch

Now I need a bit of advice on rope from para anchor to boat please

Bearing in mind Pacific Ocean storm conditions.

Best type of rope?
Breaking strength?

And length of rope frome chute to boat?

Anything else that I may need to take into consideration.

Cheers
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Old 02-06-2016, 01:19   #2
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Re: Para sea anchor advice

Quote:
Originally Posted by Exit door View Post
Hi I am getting a sea anchor fabricated for a 10ton 41ft ketch

Now I need a bit of advice on rope from para anchor to boat please

Bearing in mind Pacific Ocean storm conditions.

Best type of rope?
Breaking strength?

And length of rope frome chute to boat?

Anything else that I may need to take into consideration.

Cheers
This site should help:
Victor Shane's Drag Device Data Base | Using Parachutes, Sea Anchors and Drogues to Cope with Heavy Weather – Over 130 Documented Case Histories
good luck! Send photos!
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Old 02-06-2016, 01:47   #3
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Re: Para sea anchor advice

The best type of rope is generally considered to be braided nylon due to it's strength and elasticity. 3 strand nylon is good also, but will generate twist when it stretches. (The sea anchor should have a swivel where it attaches to the rode.)


I have 110 metres of rode plus 25m bridles. Mine is around 35mm thick. Breaking strain is huge, something like 30,000 kg. (This is for a 6 tonne boat)
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Old 02-06-2016, 02:54   #4
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Re: Para sea anchor advice

Ok so Nylon braid seems to be the call

35mm breaking strength 30000kg +. Is this a bit of an over kill? No offence but it is very Expensive stuff.

I'm all for paying for safety but can anybody out there tell me what type of rode strength is the minimum! Severe weather.


Cheers
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Old 02-06-2016, 08:55   #5
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Re: Para sea anchor advice

And your life (not to mention your boat) is what, chopped liver!!! Don't forget a small section (5' or so) of anchor chain just before the chute to keep it below the surface.
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Old 02-06-2016, 08:59   #6
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Re: Para sea anchor advice

The jordan series in the equation?
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Old 02-06-2016, 09:28   #7
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Re: Para sea anchor advice

Kaptain Ken dude please don't be angry! If this is what is truly required I will pay the pennies! What I am trying to ascertain is what is the appropriate strength! If 40mm rode is appropriate then so be it.
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Old 02-06-2016, 09:35   #8
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Re: Para sea anchor advice

Just trying to interject a little levity. We spent quite a bit on our para anchor for our Lagoon 440.
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Old 02-06-2016, 09:39   #9
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Re: Para sea anchor advice

We chose to deploy our sea anchor (18' ParaTech) when we were hit by a gale while sailing our 48', 20-ton ketch from Hawaii to Alaska. It was not a true 'storm' as the winds never got over 45 knots but I still feel that the sea anchor was the best decision at the time - with my wife and three young children aboard, we felt safe lying on the sea anchor for about 18 hours but not particularly comfortable.

For a rode, we used 600' of 5/8" twisted nylon, shackled to our 30kg Bruce anchor and we also had 100' of 3/8" chain out. We had our usual anchor bridle restraining the chain.

I no longer carry the twisted nylon rope but have since acquired 300' of 1" nylon single braid but I have yet to deploy the sea anchor with it.

Fair winds and calm seas.
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Old 02-06-2016, 09:45   #10
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Re: Para sea anchor advice

very roughly - the rode needs to have strength equal to 60-75% of your displacement. That is to deal with loads imposed by breaking wave situations. In a 'regular' storm (eg not big breaking waves) the loads are actually pretty low - on the order of 15% of displacement.

There is a significant debate about rode material - nylon has the elasticity, BUT it generates heat while it is stretching and that weakens it - testing indicates it weakens significantly in severe cycling. And it is more vulnerable to chafe when cycling. The most knowledgeable people I know now recommend dacron for this application.
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Old 02-06-2016, 09:47   #11
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Re: Para sea anchor advice

I've never deployed a sea anchor, but believe chafe may be more of an issue than breaking strength?
40mm three strand? I feel sure there is nothing on my boat that I could attach that to that wouldn't fail long before the rode did?
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Old 02-06-2016, 12:32   #12
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Re: Para sea anchor advice

Does anyone know of a serious evaluation of using a series drogue deployed from the bow to act as a sea anchor?
I'm presuming that it would need to both have larger cones and greater length than one deployed from the stern to provide the anchoring effect.

I've read some of the stuff readily available and can't find anything on it.
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Old 02-06-2016, 12:44   #13
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Re: Para sea anchor advice

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Originally Posted by Bluebeard View Post
Does anyone know of a serious evaluation of using a series drogue deployed from the bow to act as a sea anchor?
I'm presuming that it would need to both have larger cones and greater length than one deployed from the stern to provide the anchoring effect.

I've read some of the stuff readily available and can't find anything on it.
The design and function of a series drogue isn't what it needed off the bow of a boat. A series drogue is design to let the boat move with the wind and waves but to keep the boat stable and limit the speed of the drift. If you are bow to the wind and waves you want to minimize the movement astern; too much, too fast can damage the rudder. A drogue should be deployed off the stern.
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Old 02-06-2016, 13:03   #14
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Re: Para sea anchor advice

I would assume shroud line size would also be a limiting factor in determining size of rode?
Any point in connecting a 60,000 lb rode to a parachute who's shroud lines will burst at 10,000 lbs?

Those numbers are made up to illustrate a point.
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Old 02-06-2016, 13:35   #15
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Re: Para sea anchor advice

Skipmac,

series drogues as currently peddled as designed to function as you describe, but if you put enough surface into the water, ie more and bigger cones, then it will have the same effect as a para-anchor. I don't know how big that would have to be but there is no practical reason why not.
One immediate questions is, would there be enough drift to keep the cones open? but it may be self regulating.
The potential benefit is that the drogue could be long enough to always have a significant portion in the next crest and hence keep the rode taught.
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