untrustworthy Rocna?

Ross · Aug 8, 2012

You can't fix low alloy steel. If it is a good alloy but sold in an annealled condition then it can be heat treated. It should be worth about 20 cents per pound for scrap.

tkanzler · Aug 8, 2012

What's the failure mode of these anchors?

jibes138 · Aug 8, 2012

Since the situation is infinitely variable all you can really do is calculate some loads and see if you have sufficient safety factor. I looked up AISI 1018 steel and got a yield strength of 53,000 PSI. This is typical low carbon steel, not an alloy you'd expect in an anchor but used a lot for general purpose applications. You didn't mention the size of the Rocna but make a few assumptions. For fatigue or cyclic loading use 50% of the yield strength as the maximum load. A worst case scenario might be the fluke is jammed in the rocks and a bending load applied to the shank. So lets model this as a cantelever beam in bending with maximum load at the joint where the shank is welded to the flukes. Here is a stress calculator you can play with based on the dimensions of your anchor. If the max stress is below about 25,000 psi you should be pretty good. Keep in mind yield strenght is when it starts to plastically deform, actual breakage would be a higher strength number. http://www.efunda.com/formulae/solid_mechanics/beams/casestudy_display.cfm?case=cantilever_endload

Timo42 · Aug 8, 2012

There is a simpler formula.

A= how much your boat is worth, B= how much you save by relying on a suspect anchor. If A>B then this isn't the anchor for you.

Stu Jackson · Aug 8, 2012

capta said:
jibes138

1. But again, I ask, Because it is in the "bad" group will it definitely fail?

2. Or am I going to have to foul it in some rocks and power a 75000# boat over it at 6 knots to make it fail?

3. I guess that's really the question isn't it?

1. Definitely? No. Possibly? Yes.

2. Most likely.

3. Seems from the reports that it will bend, not actually break.

Worst case you end up with a really expensive bent anchor. From what I understand, the bent anchors held the boats, just came back up on deck being really wonky.

As long as the size fits your boat and exceeds your anticipated conditions, it seems like a reasonable deal.

The risk, of curse, is yours to accept or not.

PS Your post #5 on cruisersforum essentially answered your own question.

Good luck.

kloudie1 · Aug 9, 2012

I remember same as Stu's comment.. The shank bends if pulled sideways after it had been buried very hard.. and the result was the boat held, but the anchor was toast when it was retrieved. I'd think that if you're anchoring on sandy/muddy/clay.. not rocks.. that it would be fine.. as long as the price justifies.... Even if bent, a good metals shop could salvage it by straightening and inspecting afteer a re-heat and quench..

jibes138 · Aug 9, 2012

There really isn't any way to answer your question. You need to take the strength of the material, the cross section area (that I have no way to determine from a 88# response) and then look at how the loads are applied in the application. If bending the shank is the issue then you are likely having a complex loading scenario of a moment around where the shank is welded to the fluke. The only way to answer your question is to model the expected conditions and then the loading and do some calculations. If you have access to a finite element analysis program you could get an answer easily and do some what-if games for different conditions. If I had a boat as large as yours I would not trust my life and boat to a suspect anchor, what I would consider is using this anchor as a secondary anchor to be connected in series with a primary anchor (two anchors on the same rode) to give enormous holding power and the twisting and bending would be applied to the primary anchor. This would be great in hurricane conditions along with a few more anchors scattered about.

Maine Sail · Aug 9, 2012

Of the 2000+ anchors that were supposedly built with the lower grade steel I only know of one or two that actually bent. None have broken only bent. I'd say take the deal and use the anchor. If you love it and want more piece of mind, because you just can't sleep knowing about the steel, then invest in a new one... Rocna made several statements to the fact that even the anchors with the suspect steel exceed RINA standards.

The problem with the whole mess was that the previous manufacturer and the designer publicly bashed other products (every anchor made really) "supposedly" built to lower standards then they themselves built the Rocna to a "lower standard" than what the designer had vociferously impugned was necessary...

During this debacle I had communicated with West Marine, who did a voluntary "sort of" recall. At this point they have not taken back a bent Rocna that I know of and they were the largest distributor in the US..

shemandr · Aug 9, 2012

This thread gives me a chance to post this pic of my danforth which came up from the bottem as shown after riding out a gale in Coecle's Harbor several years ago. Bent but now bowed. We didn't drag.

Gunni · Aug 9, 2012

This type of anchor sets really well AND really deep. As such it doesn't budge and when your boat swings or veers the shaft takes a tremendous side load. On the day you retrieve a bent anchor, you should be shopping for a new one.

Be prepared to enhance your retrieval drill. None of that push-button windlass stuff. These anchors don't pop out like a CQR (a good thing).

Stu Jackson · Aug 9, 2012

Gunni said:
These anchors don't pop out like a CQR (a good thing).

Well, that's a good thing.

I agree.

However, once the rode is vertical, my five + years of experience with our Rocna (pre China NZ model) anchor is that it does come out fairly readily. One has to be patient if there has been a load on it.

Gunni · Aug 9, 2012

Stu Jackson said:
Well, that's a good thing. I agree.

However, once the rode is vertical, my five + years of experience with our Rocna (pre China NZ model) anchor is that it does come out fairly readily. One has to be patient if there has been a load on it.

I've got a 66# Manson Supreme - the blade on that dog is as big as a tractor seat.

I get over top of it, re-connect the snubber, and drive over it, being careful not to drag my chain rode down the hull.

Can not believe how nicely the Manson sets - way better than my lunch hook CQR. Sleep like a baby now...

untrustworthy Rocna?

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