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Old 24-09-2007, 00:38   #1
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Para-anchor on a Mono?

After reading the ‘Series Drogue’ thread (on Multi’s) I’ve been doing a lot of thinking about attachment points on my Mono. It seems if one were to attach to the bow with a para-anchor that it would drag the bow right into a large on coming wave.

So I’m considering putting the attachments a few inches below the hull/deck joint just forward of the structural bulkhead, forward of the mast as in the picture below. And heavily reinforced, of course!

This way when the bow heads into the wave it’ll want to head up and over more so (pivoting on the attachments) then drug thru the wave. These pictures maybe a little over exaggerated, but it’s the best I can do by hand and with limited space in the window.

As well, use of the bridle method to keep the boat from yawing and maybe add a small riding sail on the backstay.

All theses were positives in much that I have read. So I’d like to get some opinions!

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Old 24-09-2007, 00:55   #2
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Hi Del
you may want to have a look at the Pardeys method of attaching a sea anchor. They have one line from the bow wih some heavy duty anti chafe, protection and the other from the rear quarter with a block on the bow line. This keeps the head of the boat just off the seas in a "hove to" position. By ajusting the angle on the rear penant the heading can be varied. The next part of the trick is to adjust the boat so that it is not for reaching, and at the same time staying in the slick created by the para anchor. This hopefully lessens the chance of getting wacked by a breaking wave.
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Old 24-09-2007, 01:07   #3
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I've seen a web site where they had the attachments connected to the upper transom corners and ran a bridle over the decks thru a bow loop. They said it pulled the vessel from the rear and kept it from nose diving. But I'm not buying it. It still pulls down on the bow.

As for a heave-to, I'm thinking shoten up one of the legs of the bridle would do the same..................._/)
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Old 24-09-2007, 02:31   #4
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Circular waves...

What worries me about a sea anchor is that it is going to be difficult to set properly.

That is, if one considers the view forward from a boat being blown back from a sea anchor the top of the wave is going to be moving towards the boat so that the sea anchor is going to a) move toward the boat if it is close to the surface or b) rotate and collapse if it is in the centre of the wave motion or c) move away from the boat if it on the bottom of the circular motion or d) be stationary if it is below the circular motion.

Given that storm waves can easily exceed 5m in height this suggests that the circular motion could have a diameter of 10m and the sea anchor must set below this to be effective. That is the centre of a 5m diameter anchor would need to be 15m or more below the surface.

Using standard 5:1 scope some 75m+ of rode would need to be laid out to keep a properly weighted sea anchor in position.
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Old 24-09-2007, 11:05   #5
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Quote:
Originally Posted by delmarrey View Post
...
As for a heave-to, I'm thinking shoten up one of the legs of the bridle would do the same._/)
I don't see how you could avoid chafe on the leeward side of the bride if you did this.

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Old 24-09-2007, 12:20   #6
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What worries me about a sea anchor is that it is going to be difficult to set properly..........Etc.

Using standard 5:1 scope some 75m+ of rode would need to be laid out to keep a properly weighted sea anchor in position.
As mentioned in another thread I could use a throw bag, getting the chute well away from the boat while moving with the wave until the chute opens. I'm sure this would take a few practice runs in less severe weather.

Where do you get the 5:1 scope from? In the picture it shows a broken line to represet a longer line. From what I have read the chute should be at least 3 swells away.

Quote:
Originally Posted by Paul L
I don't see how you could avoid chafe on the leeward side of the bride if you did this.
That's something to consider!! Necessity is the mother of invention.
If I'm going to a heave-to position there might be a need for a bow attachment for one of the legs of the bridle. I don't like the idea of putting all the load on one single attachment. The shock load would be greatly reduced by a pair. Having a foam cored hull, my worry is the side shear to the attachment bolts. I'm actully considering carbon fiber attachments like on the new aircraft 757's, mounted on the inside and coming thru the hull, then glassed in becoming a part of the hull.

I'm not really sure how an IOR would handle in a heave-to. That's one of those things I'll have to put to a test. My outside T-tracks run right up to where the attachments would be. So temporary cleats can be used as test points.

Thanks for the input!! It keeps the mind/gears rolling........................._/)
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Old 24-09-2007, 12:34   #7
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Originally Posted by delmarrey View Post
..
I'm not really sure how an IOR would handle in a heave-to. That's one of those things I'll have to put to a test...._/)
In general, it probably won't heave-to well. It will probably fore-reach much better. To get a picture of how your boat might sit to para-anchor, you can judge from how it sits to a single anchor in a rough anchorage. If it tends to sail around in the anchor, it is probably going to do the same thing, but worse, on a para-anchor. Unless you try the Pardy type bridle.
Are you stuck on using a para-anchor from the bow? It seems like with a typical IOR tucked in stern and fin keel, you might be better off to rely on a standard drogue or even a Jordon drogue off the stern.

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Old 24-09-2007, 13:07   #8
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Watch Pardy's DVD video is the best advise I can give on this issue. A para-anchor with only an 8 foot diameter holds something like 12,000 pounds of water, so the para-anchor is pretty rooted in place; you will have drift with the current however. Other than heaving too, you can also use the para-anchor to slow the drift of your boat down if heading towards nasty shoals or land when your motor dies and you need critical time to repair it.

Here is a link to the cover of it:

http://www.landlpardey.com/Products/Images/STDVD.jpg
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Old 25-09-2007, 11:03   #9
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Quote:
Originally Posted by Paul L View Post
To get a picture of how your boat might sit to para-anchor, you can judge from how it sits to a single anchor in a rough anchorage.
Isn't this why one puts a bridle on an anchor line?

I think I'll build a model of my boat and do some experiments.

Quote:
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Are you stuck on using a para-anchor from the bow? It seems like with a typical IOR tucked in stern and fin keel, you might be better off to rely on a standard drogue or even a Jordon drogue off the stern.
Excuse my ignorance, but why would one want to subject their cockpit to some monster wave (5 M+)?
I've been in some pretty nasty weather (typhoons) aboard ships (100 M) and I've seen what a 7 -8 M swell can do. And I'm not sure I'd want to put my back to one of them.

And why would a heave-to be any better then staright on? Cresting the wave quarterly would cause a rolling motion that would whip the rigging, stressing the shrouds/mast.

I'm still in the research mode and maybe I'll change my ideas after more input.

rsn48, thanks for the info. I think I'll invest into the video.


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Old 25-09-2007, 11:32   #10
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Quote:
Originally Posted by delmarrey View Post
Isn't this why one puts a bridle on an anchor line?

{Paul} It is certainly one of the reasons, reducing the jerk on the anchor caused by chain is another. What I was trying to point out was that different boats behave differently. Some boats (say with windage up front) tend to sail and shear all over an anchor, others sit much more quietly.
I think I'll build a model of my boat and do some experiments.
{Paul} Having an exact model of the boat and a test wave tank would interesting.


Excuse my ignorance, but why would one want to subject their cockpit to some monster wave (5 M+)?
I've been in some pretty nasty weather (typhoons) aboard ships (100 M) and I've seen what a 7 -8 M swell can do. And I'm not sure I'd want to put my back to one of them.
{Paul}You aren't sailing a classic full keel boat where much of the lessons of para-anchors were learned. It does not follow that your style of boat will necessarily sit calmly and peacefully on a para-anchor in extreme conditions, allowing the crew to dine elegantly and sleep well. If it does, then great. Many experienced small boat skippers sailing more modern underbodys feel that drogues off the stern are superior. Some to check out include: Dashews (Storm Tactics book), Evans Starzingers/Beth Leonard (Vogaer's Hnadbook), John Neal(Mahina).
And why would a heave-to be any better then staright on?
{Paul}There is no way to keep the bow of the boat pointing directly into the on coming seas while in real storm conditions. We are talking chaotic conditions here. By setting the bow off at an angle you can put pressure on one side and have the boat tend to stay more in that consistent position.
Cresting the wave quarterly would cause a rolling motion that would whip the rigging, stressing the shrouds/mast.

I'm still in the research mode and maybe I'll change my ideas after more input.
{Paul}And I'll probably change mine a 1/2 a dozen times in the future too
See bold above.
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Old 25-09-2007, 13:05   #11
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I am providing a link to a pod-cast (only voice, no video) of a chap who did the around the world circumnavigation over an eleven year period. Some of you will be familiar with him, I am not. Also he sailed in a Catamaran and the advise he has to offer works equally well with a mono hull.

There are five pod-casts in the series, you only need to listen to one - "The Perfect Storm." He discusses the use of a para-anchor and basically reflects what the Pardey's have to say about it (still get the Pardey's video - best on how to deploy one). In this pod-cast, he covers para-anchors, seeking cover, and warps. You will hear a little musical interlude of about 5 seconds at the end of the para-anchor discussion, this is his way to change topics.

Also there is an irritating song I almost didn't last through at the very beginning, grin and bear it, you will be happy you did:

Maxing Out Podcasts
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