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Old 09-08-2010, 19:01   #1
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Right Scope

Question on Scope
I usually try for between 3 to 5: scope .
A couple of weeks ago after a long day I approach anchorage to find most were taken as I was trying to find shallow enough water (30 to 40 feet) I found myself in 90 feet of water and I did not have 500 feet of chain so I kept searching and low and behold I found a patch about 50 feet in dia. at 32 to 42 feet I quickly dropped the Rockna anchor and settled for the night with 200 ft of chain. As I swung around the anchor I would see the dept at 90 + feet and we were good for the night but it got me thinking what the protocol in this situation is. I had enough Rode for the 30 to 40 feet but short at 90 feet but my anchor was in 30 to 40 feet any thoughts appreciated.
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Old 09-08-2010, 19:19   #2
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My first thought is... what if you dragged? It would be all downhill from there (literally).

If there is bottom conture we usually look to put the anchor in a deeper spot rather than a shallow point. That way your angle of pull (if you drag) is lower relative to the bottom, and if you drag the anchor uphill you stand a better chance of the anchor resetting on its own.
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Old 09-08-2010, 19:24   #3
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Sounds like it worked. That's about the best we can do.
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Old 09-08-2010, 19:48   #4
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Well, if you dragged off that seamount your anchor would fetch up on something before your boat did (most likely)....
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Old 09-08-2010, 19:58   #5
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Technically, geometrically, when that big storm comes anchor chain laying on the bottom does nothing to help the anchor. So a well dug in anchor, remember Rocna's have never dragged even 3 inches and set instantly in all conditions, on a seamount doesn't know the difference between chain lying on the bottom or suspended over a sea-valley.
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Old 09-08-2010, 21:52   #6
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G'day, mate. Other considerations should be what the weather forecast is, what the tides are in the area you are anchoring or how protected the anchorage is, to name a few. I think I could sleep good if it was a calm night, minimal tide and secure anchorage. Cheers
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Old 09-08-2010, 23:40   #7
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G'day, mate. Other considerations should be what the weather forecast is, what the tides are in the area you are anchoring or how protected the anchorage is, to name a few. I think I could sleep good if it was a calm night, minimal tide and secure anchorage. Cheers
Ditto! All things have to be considered. Sometimes it's a bitch trying to get settled, at other times it's a breeze. What I hate the most is a crowded anchorage with more coming in.

Then in the middle of the night the wind picks up. That's when I get up. A couple months ago I had a brand new 50' steel trawler banging against my mid-section just after midnight, who had been dragging anchor. It took me awhile to get the guy up (lots of mass in the hull) He asked if there was any damage, and I said no but I left some dark blue paint on your hull.

He wasn't happy but that's his problem. I'm repainting next year anyway.

So, as it goes give yourself plenty of room for swing in all directions and really watch out for others. If someone wants to anchor too close let'm know politely, tell them you have a lot of rode out. And do your part to set properly. Scope is a reference, not a law.
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Old 10-08-2010, 03:33   #8
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It is the depth of water where the anchor (not the boat) is lying that determines scope.
Be careful in these sort of situations. Often areas that are much shallower than the surrounding terrain are rock. They do not tend to retain much sand and mud on the top (a bit like many mountains on land) and often the holding is poor or intermittent.
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Old 10-08-2010, 19:21   #9
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Thanks everyone
It was a semi protected anchorage and if the wind began to blow hard I was prepared to pull up and leave but this was not the case. PS just for information I have anchored out maybe 50 times since the new Rockna 25 KG and have never moved and was able to sleep every night.
One other comment has anyone tried dropping anchor as you are moving forward is there a potential risk.
I have on a couple of occasions dropped the anchor as I was drifting forward the anchor would set the boat would swing around and then I would let out the appropriate rode. If there was 30 feet of water I would drop 40 feet of anchor and chain then when set let out more. Can this method get into keel or prop??
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Old 10-08-2010, 21:46   #10
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No harm done as long as one doesn't over stress the bow roller, winch or score the hull.
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Old 10-08-2010, 22:26   #11
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...has anyone tried dropping anchor as you are moving forward is there a potential risk.
It's called 'French Anchoring'. If you have a plumb bow you might mar the finish. Otherwise, go slow or you'll have a sort of broach maneuver when the rode straightens out. Why not stop first, one wonders?
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Old 10-08-2010, 22:30   #12
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In the Med, I often anchored in a patch of sand that was small in size compared to all the weed in the surrounding area.

In the Red Sea, I once had to anchor on a steeply sloping bottom with full knowldege that holding was marginal.

In all these situations, I have an exit strategy figured out in advance so that if I should drag in the dark, I already know what I am going to do to get to safety.
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Old 11-08-2010, 15:24   #13
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Yes I usually plot a course out on my chart plotter + set the anchor drag alarm
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Old 11-08-2010, 15:55   #14
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I'm sittin here doing all the metric conversions... lol

I try for 5 to 1 ratio nowadays.

If the water is very deep I get the feeling that less ratio is OK because of the catanery weight of the chain.

But the thing I am worried about for you (and for me int aht situation) is that if your BOW is in 90 feet of water you have 90 feet of chain hanging straight down. Can you windlass wind that up?

Mine begins to grumble about 23-24 meters (75 feet) so I don't anchor in more than 22 meters (72 feet)

If the windlass can';t pull it up how much does that amoount of chain weigh and how the hell can I winch it up?



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Old 11-08-2010, 17:10   #15
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If you had 200' of chain in 40' then I think you'd be OK as long as the wind didn't pipe up. That much chain would probably be sitting on the bottom and possibly down the slope some. I wouldn't try that with a short piece of chain and nylon rode though.

I've anchored on the up-slope a couple times and used all chain rode. I didn't sleep all that well but when I dove the anchor the next morning it was well set and the chain doing a good job of keeping me safe.
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