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Old 07-26-2013, 03:50 PM   #1
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Bent Shank on Anchor

Hello all. I have a 70lb plow type anchor for my 70,000 lb steel Diesel Duck Seahorse (50') Marine sedan trawler. The Anchor has no manufacturer's marking on it. I assume it is a Chinese knock-off that came with the boat. The anchor was secured to my 3/8" Ht chain with a swivel. I have anchored in the Puget Sound area numerous times and have never had a problem with dragging. After reading about the dangers of just using a swivel, I attached a Crosby shackle in front of the swivel. In doing that I noticed that the shank of the anchor is bent a few degrees away from the center starting about 2/3 down from the shank attachment hole. It is bent enough to be clearly visible. I have no idea how this happened. I am not sure if this was an original defect with the anchor, or it some how got bent during one of my anchoring. My question to the forum is: Do I need to worry about this? The local marina in Seattle has a hydraulic press that they say can be used to straighten the shank. However, they say that this may compromise the integrity of the anchor. I can replace the anchor with a Rocna or similar type, but the Rocna site suggests that for my weight I need a Rocna 35kg or bigger anchor. These are upwards of a $1k. So, I would rather not do this unless it is necessary. By the way, I do have a claw type 70lb anchor on my dual bow spirit. I have never used this anchor.
Your advice would be much appreciated.
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Old 07-26-2013, 06:35 PM   #2
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I straightened the shank on a Danforth anchor that I used on my 33' boat many years ago that got bent while I was riding out some high winds.

I locked the shank into a big vise just above the point where the bend was, then hooked a chain around the "meaty part" of the anchor. I used a come-a-long to pull the meaty parts in the direction needed to straighten it and it worked. When I was done you could never tell it had been bent or straightened.

I used that anchor for many years after that without any issues. If you used the marina's press to straighten it the worst that could happen is it bent again in the same spot and you'd know you had to replace it.
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Old 07-26-2013, 07:01 PM   #3
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Has anyone here experienced, heard of or witnessed an anchor shaft that separated under the strains of anchoring? I can see where they'd bend under great pressure from attempts to retrieve them under boat power...maybe even snap under that pressure. But for the shaft to fail/separate under anchoring stress seems highly unlikely. I bet if it has happened, some here would have evidence of it.
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Old 07-26-2013, 08:07 PM   #4
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Practical Sailor's review of Anchor Shaft Strength

GFC & Fly Wright: Thank you. I will go ahead and get the shank straightened. You might find the following articles from Practical Sailor interesting.
Attached Files
File Type: pdf Practical Sailor-Anchor Shaft Strength-01.pdf (198.6 KB, 155 views)
File Type: pdf Practical Sailor-Anchor Shaft Strength-02.pdf (85.4 KB, 96 views)
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Old 07-26-2013, 08:18 PM   #5
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Quote:
Originally Posted by FlyWright View Post
Has anyone here experienced, heard of or witnessed an anchor shaft that separated under the strains of anchoring? I can see where they'd bend under great pressure from attempts to retrieve them under boat power...maybe even snap under that pressure. But for the shaft to fail/separate under anchoring stress seems highly unlikely. I bet if it has happened, some here would have evidence of it.
I haven't.
But it's obvious that the metal wouldn't be as strong as it was if the anchor haden't ben bent. It would be weakened by being bent and weakened more than that by being bent back because it would be bent in the opposite direction. Bent anchors are always weaker than original and it weakens them more to be bent back.

But you may find 100 boat ownwers that never have put a maximum load on their anchor. Perhaps even a 50% load. I've seen numerous bent anchors on fishing boats .. on the bow and presumably being used. Fishermen have very big anchors though. And that of course makes their bent anchor even more unlikely to fail because it's bent. And there probably were more anchors on the fish boats in Craig that were bent AND straightened as I problbly wouldn't have noticed them.

But for azubair the odds are real good that his anchor won't fail because it's articulated. A bending load is unlikely on the CQR unless it's a vertical load. But the shank is shaped like an I beam so is very strong in a vertical plane. Because of the hing a heavy side load is very unlikely.

So azubair should replace his anchor but it is very unlikely his anchor will fail if he dosn't straighten it and fairly unlikely it will fail even if he dosn't straighten it. The reason to straighten it is so it will work as designed on the sea bottom but I believe it will dynamically work 999% as good as new because of the hinge. Most anchors are VERY questionable when bent.

A big Claw anchor on a big boat is (I believe) a good combination and they are very inexpensive so a 100lb Claw may be a good move as azubiar DID mention cost. A bigger Claw would outperform a bent CQR and for not much more money. A Manson Supreme and a number of others would be even better. One of the reasons I mention the MS is that it's relatively inexpensive compared to other high performance anchors. Available at WM. That's where I got mine when we lived in Alaska.
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Old 07-26-2013, 08:35 PM   #6
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My concern is of they use heat to set the shank at the correct alignment or they bend it past straight allowing for it to align back when the press is turned off.

Another option is to buy your Rocna and use your fixed anchor for a back up or stern, not a cheap option but still an option.
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Old 07-27-2013, 11:12 AM   #7
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When I was a firefighter we would straighten anchor shanks by putting them under the outriggers on the ladder truck. Worked great.
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Old 07-27-2013, 11:44 AM   #8
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If the bend is only a few degrees bend it back...getting it totally straight may be nearly impossible unless you or the marina guy are wizards at presses.

I'll bet low single digits of structural loss if any ....if it's only bent a few degrees and I wouldn't use heat unless I absolutely had to and then I think I'd just replace the anchor.

I'd be more worried about performance than strength. A degree here or there I can't imagine changes much as anchors probably flex in use anyway. But at some point I think a bend does affect performance of some anchors in some conditions, have experienced it myself and have read quite a few comments from people with similar experiences.
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Old 07-27-2013, 10:32 PM   #9
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Good Practical Sailor articles, very interesting reading.

I guess the key-words are that the the shank dimensions AND the steel specifications are important things to compare when selecting anchors.

Some ship yards delivers a home made plate steel anchor with new boats.....uhhhh - it gives me the chills to think about the big investment protected with a cheap knock-off anchor...

Give me 7-800MPa steel please - at least for the storm anchor.
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Old 08-03-2013, 03:58 PM   #10
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There was a lot of hype and complaints about the steel quality of the Rocnas some time ago and as far as I remember the old Rocna company made a statement that their anchors complied with the design holding criteria even though the steel was not the high strength type they had claimed.

I assume this means that the Rocnas would not break (or break-out) in a straight pull, where the steel quality is of lesser importance compared to a sideway pull. If it was a sideway pull, then a lesser steel quality would probably result in a bent shank.

I checked the new Rocna company pages and I could not find any references to the steel they are using now - is there any info available about this?

According to the Practical Sailor articles - assuming the same dimensions of the shank, then high strength steel is the best. Stainless steel or lower steel grades will not be as strong in a sideway pull.
Anyway - Anchorright webpages says that they use Bisplate 80 shanks - which is high strength. That would be something to consider when choosing an anchor.

On the other hand, can high strength steel be straightened in case of a bent shank?
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