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Old 07-02-2016, 09:31 AM   #61
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Backing own on anchor. Or not.

One man's view:
Backing down on an anchor is largely useless. Practical Sailor Magazine tests have shown that with a change in direction of wind or tide, all anchors pull out and reset. This is likely when we are sleeping or visiting on another boat. Consequently, we all need anchors that set themselves. If we are setting anchor in a breeze, the pull back is done for us. If setting in a calm, the direction of pull-back is wrong and the anchor will still have to pull out and reset itself.

I bought an ultra-light Danforth type a few years ago. It was very difficult to set. Think about it. I worked hard to set it. A breeze then came up from a different direction. The anchor then pulled out and off we went. A heavy anchor will set itself better than an light anchor.


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Originally Posted by dhays View Post
I come from sailboats with relatively small engines. My last sailboat had a 56hp engine on a 40' boat. When I set my anchor I would give it about 80% throttle in reverse. Worked fine.

Now I have a 43', 31,000lbs boat with a 380hp engine. I don't think giving it that much power to set the anchor is a great idea.

I recall hearing a rule of thumb (for what those are worth) to use about 1hp per foot of boat to set an anchor. That is about what I had been doing on my past sailboats.

Assuming that isn't a silly concept, my Cummins will idle at about 600rpm. At 800 rpm, according to Cummins, it produces 58 hp. So, how much power should I be applying to set the anchor? The last time I anchored this new boat I pulled the anchor out twice after bringing the rpm up to my normal cruise power. I didn't think about it until today that this is about 140hp, 3x what I could ever have generated with my sailboat.

Second question. What scope should the anchor be set at? I'm not talking about what scope should be out for the anchor to hold, so lets not get sidetracked. I'm asking what scope should I use to set the anchor with an all chain rode? I used to set at about 5-1 on my sailboat and then adjust from there but that was simply an uninformed practice that seemed to work most of the time.
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Old 07-02-2016, 09:41 AM   #62
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Quote:
Originally Posted by Marshall Muller View Post
One man's view:
Backing down on an anchor is largely useless. Practical Sailor Magazine tests have shown that with a change in direction of wind or tide, all anchors pull out and reset. This is likely when we are sleeping or visiting on another boat. Consequently, we all need anchors that set themselves. If we are setting anchor in a breeze, the pull back is done for us. If setting in a calm, the direction of pull-back is wrong and the anchor will still have to pull out and reset itself.

I bought an ultra-light Danforth type a few years ago. It was very difficult to set. Think about it. I worked hard to set it. A breeze then came up from a different direction. The anchor then pulled out and off we went. A heavy anchor will set itself better than an light anchor.
Not backing down to better set an anchor is sort of like not setting parking brake in a motor vehicle. Extra holding power security is worth the effort. Correct regarding change in direction due to currents, wind etc. Then a good anchor is needed for easy reset on its own volition.
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Old 07-04-2016, 02:32 PM   #63
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Quote:
Originally Posted by Marshall Muller View Post
One man's view:
Backing down on an anchor is largely useless. Practical Sailor Magazine tests have shown that with a change in direction of wind or tide, all anchors pull out and reset. This is likely when we are sleeping or visiting on another boat. Consequently, we all need anchors that set themselves. If we are setting anchor in a breeze, the pull back is done for us. If setting in a calm, the direction of pull-back is wrong and the anchor will still have to pull out and reset itself.

Can you post a link to the PS article? I have a subscription, but haven't been able to find that article...

I suspect a well-buried anchor really doesn't unset/reset every time a tide or wind shift changes the location of the boat relative to the anchor.

Might do sometimes, and if so that'd likely be at higher wind speeds or faster currents... but I know sometimes our boat only moves around the chain drop, i.e., without even ever bothering the anchor at all.

And when we used the Fortress as primary, it seemed it sometimes just flipped upside down and then buried itself some more...

FWIW... for the first time with our current anchor style... I think our anchor actually moved a bit on the tidal/wind shift Friday night. Not much, but the several different anchor alarms we had running at the time suggested we'd moved a bit. Seemed odd, until when we weighed anchor and we discovered it had been seriously fouled with something -- looked like a cross between a big roofing shingle and a tractor tire inner tube. The outer fluke tips were completely shielded... but the center fluke tip was still in play I think... and it still looked like we'd buried at least half of the shaft...

-Chris
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Old 07-04-2016, 02:41 PM   #64
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I believe there are videos that show anchors pivoting and staying set on swings.

So my guess, if buried well to begin with, the more likely a pivot than a pull and reset.
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