A Second Wind for Rocna

[estarzinger]

Originally Posted by JonJo

Load developed by an engine

I'd welcome some informed further comment.

Its prop and hp dependent.

If you have 20 hp driving 15" 3 blade fixed props then your 'bollard pull' (steady state forward pull) should be 375kg (per engine or 750kg for the two engines).

I have good formula for that. But then it gets to a bit of guess work as I don't have as good formula for a folding prop in reverse.

But let's say that the 2 bladed folding prop has only 66% the surface area and the blade shape is only 50% as efficient in reverse. That would then give you very roughly 250kg on steady state pull in reverse - which is surprisingly close to what you indicate (I actually did that estimate without looking back to see your what your number was).

Side note: the particular 'maxprop' type design makes much better than 50% effeciency in reverse, more like 90%.

[estarzinger]

This link is appropriate if any of you want to read the removed e-mail discussed above.

http://www.bethandevans.com/pdf/rocnatext.pdf


My intent here is purely public service. At issue is a device we all depend on for our safety and this e-mail publicly reveals several important things for I believe the first time. Primarily: #1 that both the Smiths have been completely aware of and involved with the below spec anchors since 2009. even while touting their (not followed) specs publically and trashing other anchors specs, #2 That they have been providing special 'tuned' anchors to anchor testers possibly making many of the previous rocna anchor test results suspect. And #3 that they suggest that the out of spec Chinese anchors can have inferior holding performance.

This is clearly allowed under 'fair use' law as:
1. The Purpose and Character of The Use is clearly "for the purpose of criticism, news reporting, or commentary and in the public interest" and is not for personal profit.
2. The Nature of the Work is clearly "a factual e-mail" and not a creative work
3. The value of the specific work is zero as "simple e-mails are unlikely to have a market value" (clearly established in Diebold case) and that is clearly the case with this specific e-mail
4. The source of the work was that I received the e-mail fairly (it is not stolen or hacked) because I was mentioned in it and asked for my comment on the contents, and it does not contain any notice of confidentiality

[sdowney717]

following the mentioned Sarca Excel links
(the part which says Sarca eats their lunch)
I came across what looks like a test between Manson and Super Sarca?

Super SARCA to The Test - YouTube

some videos from them.
http://www.anchorright.com.au/sarca/video

[smackdaddy]

Originally Posted by estarzinger

The mods say that This link is appropriate if any of you want to read the removed e-mail discussed above.

My intent here is purely public service. At issue is a device we all depend on for our safety and this e-mail publicly reveals several important things for I believe the first time. Primarily: #1 that both the Smiths have been completely aware of and involved with the below spec anchors since 2009. even while touting their (not followed) specs publically and trashing other anchors specs, #2 That they have been providing special 'tuned' anchors to anchor testers possibly making many of the previous rocna anchor test results suspect. And #3 that they suggest that the out of spec Chinese anchors can have inferior holding performance.

This is clearly allowed under 'fair use' law as:
1. The Purpose and Character of The Use is clearly "for the purpose of criticism, news reporting, or commentary and in the public interest" and is not for personal profit.
2. The Nature of the Work is clearly "a factual e-mail" and not a creative work
3. The value of the specific work is zero as "simple e-mails are unlikely to have a market value" (clearly established in Diebold case) and that is clearly the case with this specific e-mail
4. The source of the work was that I received the e-mail fairly (it is not stolen or hacked) because I was mentioned in it and asked for my comment on the contents, and it does not contain any notice of confidentiality

Well done estar. This is a great compromise.

[JonJo]

Estarzinger,

Thanks for the info on the props etc. Fortunately I never worry about how much load I generate in reverse, but good to know my props are pretty useless! I'll try to do it in forward gear.

However the load developed of 260kg is the load that would be imposed on the shank of an anchor, which leaves no room for safety with anything that is not either robustly built or built from robust steel. What is amazning is that more anchors do not bend.

Again, thanks

[estarzinger]

Originally Posted by JonJo

However the load developed of 260kg is the load that would be imposed on the shank of an anchor,

Well, that's the minimum load, very gently applied. I agree with MainSail, that if you build up any speed at all in reverse, you could impose peak loading much higher than this as you stop the momentum of the boat. How much higher would depend on too many things to estimate, but it would not be hard to double it.

which leaves no room for safety with anything that is not either robustly built or built from robust steel. What is amazning is that more anchors do not bend.

Completely agreed. . . . but it sounds like you have perhaps watched some anchors in action. If you have done 90 dgeree shear tests you will note that its not that easy to put a direct side load on the anchor shank. Most designs in nice sand and mud will pivot pretty quickly in line with the load and while pivotting will roll over a bit so the load is more vertical on the shank than side ways. In rocky/coral head bottoms they can get somewhat trapped, but in fact often in those conditions the chain is trapped and transmits all the load to rocks and none gets to the anchor shank.

.......

[David_Old_Jersey]

Does the new Rocna maker have a new (or re-written) website to see what they are claiming? - or did it get everything from Rocna, and is sticking with the tried and tested approach of using the half truths that have worked so well?...........on the basis that the punters will mostly be dumb as donuts

[JonJo]

In terms of testing

If you set an anchor and then load it at 90 degrees virtually every anchor (except a CQR) will slide round, or pull on its side and then re-set. This scenario is one where you make a controlled and not too aggressive side pull. If you take a modern anchor, Supreme, Fortress, Excel and drive it in hard (full reverse maybe a bit of a snatch load to ensure it is well set) and then run at it from 90 degrees the impact can be too quick and the anchor too well set for the anchor to slide round. Yes it does give, but not difficult to impose 300kg of side load, horizontal to the seabed, as a snatch load. How often in real life, often enough I would think.

[estarzinger]

Originally Posted by JonJo

If you take a modern anchor, Supreme, Fortress, Excel and drive it in hard . . . .

We need some video! I should have taken some. I have included some stills that are not perfect but . . .

Our experience, when doing exactly that, was that the anchors (Rocna and Supreme included) after being set (first photo below) and then side loaded would 'roll over' on their side very quickly (2nd photo) with relatively little force (the blade edge slices quite easily sideways thru sand/mud), and only then start to pivot (3rd photo) (which I agree completely required more force with the deeply set anchors). And the roll back upright at the end of the pivot (4th photo)

So, yes, the 'pivoting' load was horizontal to the sea bed 90 degrees to the anchor, but with the anchor 'rolled over' it was pulling more on the wide section of the shank (top to bottom) rather than the narrow section (side to side). I think this must be at least part of the explanation for why relatively few (I may be wrong but I believe 'both sides' publically agree that about half a dozen rocnas have bent, while no manson supremes have) of the 400 grade rocna shanks have in fact bent (along with the fact that many anchors just sit on bows and don't get used much).

Again, I agree completely with you that we depend on these anchors to hold our boats safely and that they must be strongly built.

[JonJo]

Video would have been good, hindsight is so useful. I have similar still sequencies.

We set our anchors deeper, in water. We did it in soft sand and in a hard seabed (we did some work in mud (but you can see absolutely nothing!). We had the same result as you in a soft sand, Spades, Ultra, Kobra slid round most others rolled and reset. But if well set in a firm seabed and shock loaded, they jerk - but that's it. But if you shock load a Delta or Bruce they do move, even in a hard seabed, because they never set quite so well under the equivalent load as the well set Spade etc.

So the modern anchor if well set has a greater resistance to movement, from a 90 degree load, than something designed earleir than our current crop of 'modern' anchors.

This certainly 'helps' explain why Deltas might not fail. But there is also the fact that 90 degree shock loads on set anchors are not common - but it would be comforting to know ones anchor would not bend should the situation arise.

[estarzinger]

Originally Posted by JonJo

But if well set in a firm seabed

Just fyi, The set in those pictures was a tested 1000lb (450kg) set.

So the modern anchor if well set has a greater resistance to movement, from a 90 degree load

Agreed, the Ray/Bruce we tested actually did not roll over during the veer but just pivoted directly in place.

it would be comforting to know ones anchor would not bend should the situation arise.

Completely agree

......

[Pete7]

I am really disappointed with Canadian Metals.

They had the ideal opportunity to take a failing product and turn it around to produce something that would sell well world wide and have a very long product run. However, so far they have made a complete hash of it. Becoming embroiled in internet forums across their main markets has been a disaster too.

They should have done the following:

Kept any previous Rocna business at spinnaker poles length away.

Moved production to Canada. Easier to ensure QA and the two largest markets of Europe and North America would be far more inclined to trust a product from Canada over China. Can they not make anchors in Canada

Re-branded the product so there is a clear distinction between the old and the new make by calling it something different.

So to help them I have come up with the Rocna2 brand. I suppose I should copyright it but would be happy to strike a deal with them for a new 10kg anchor delivered to my door for the IP rights to use the Rocna2 idea.

Pete

[Dhillen]

As someone who lives in Asia (Hong Kong) and deals with China on a daily basis, I have been following the Rocna debacle with some interest. They got screwed and didn't face up to the problem, in my opinion, but tried to hide it. West Marine comes out of this looking great with their unconditional recall and by comparison, Rocna's response was woeful. From toys to medicine, manufacturing in China requires everything be inspected up and down the supply chain everyday. As soon as you look away BAM! somebody will have replaced a key component with something cheaper and crappier, usually from his brother's factory...
It won't be easy for the new owner to turn this around and as Rocna's website is down as I write this....I don't see any information of what the game plan will be.
I was in the market for a Rocna 55. No more.

Another China Product Recall?


Cheers.
Dhillen

[marinextreme]

Originally Posted by Dhillen

As someone who lives in Asia (Hong Kong) and deals with China on a daily basis, I have been following the Rocna debacle with some interest. They got screwed and didn't face up to the problem, in my opinion, but tried to hide it. West Marine comes out of this looking great with their unconditional recall and by comparison, Rocna's response was woeful. From toys to medicine, manufacturing in China requires everything be inspected up and down the supply chain everyday. As soon as you look away BAM! somebody will have replaced a key component with something cheaper and crappier, usually from his brother's factory...
It won't be easy for the new owner to turn this around and as Rocna's website is down as I write this....I don't see any information of what the game plan will be.
I was in the market for a Rocna 55. No more.

Another China Product Recall?


Cheers.
Dhillen

There is a vast difference between being screwed and being the screwee.

When you deliberately order what you get you become the .....ee not the .....ed.

[Dhillen]

Are you THE Grant King, formerly at Rocna? Wow. I tried to send you an email privately but am not allowed as I am a new user.

I would be very interested to know what you think went wrong there and if Rocna's are too risky to buy now.

Many thanks.

Dhillen