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Old 04-16-2014, 06:24 PM   #1
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Rocna sizing

Sitting here in Norfolk VA witing for the wind to lay down to finish my trip to Crisfield MD, and was pondering a new anchor. Thinking about a Rocna to replace my 30 kg (66 lbs) real Bruce. Have looked at the size charts and it appears that the 33 kg (73 lbs) anchor is the recommend with a 20% margin on displacement weight. Then there is the 40 kg (88 lbs) anchor which clearly is more than enough. For those who switched to a Rocna, did you follow the manufacturer's recommendation or go more than enough?

Eric, don't worry, the Bruce will likely go onto the second chain as a backup and the plow will be retired.

Ted
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Old 04-16-2014, 06:32 PM   #2
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We went a size up with 70 instead of the 55 which their chart recommends, just because we could. Were going be using it Friday for the first time so I'll get to see what she's all about and I'll update y'all.
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Old 04-16-2014, 07:15 PM   #3
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For our 35,000 pound, 42' Nordic tug we went with the 33 (73 pound) Rocna, which is right at the top of their sizing range for that weight and length of vessel. We also went with all chain.

It gives us a comfortable margin for cruising the BC coast I think.
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Old 04-17-2014, 12:03 AM   #4
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Oliver, do you have an underwater camera? It might be nice to get some photos of it setting in the nice clear water of the Bahamas.
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Old 04-17-2014, 12:07 AM   #5
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Oliver, do you have an underwater camera? It might be nice to get some photos of it setting in the nice clear water of the Bahamas.

Yes in fact we do have a GoPro, that's a great idea. Were going get to Great Sale early, so I'll throw in the dink and give it a try.
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Old 04-17-2014, 12:17 AM   #6
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The rule-of-thumb (it seems) is to go one size larger than the manufacturer's recommendation. I'm curious why you decided to "upgrade" from a Bruce. Did it fail you? ... The herring fishermen here are slowly upgrading from Northills to Bruces.


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Old 04-17-2014, 08:05 AM   #7
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Quote:
Originally Posted by O C Diver View Post
Sitting here in Norfolk VA witing for the wind to lay down to finish my trip to Crisfield MD, and was pondering a new anchor. Thinking about a Rocna to replace my 30 kg (66 lbs) real Bruce. Have looked at the size charts and it appears that the 33 kg (73 lbs) anchor is the recommend with a 20% margin on displacement weight. Then there is the 40 kg (88 lbs) anchor which clearly is more than enough. For those who switched to a Rocna, did you follow the manufacturer's recommendation or go more than enough?

Eric, don't worry, the Bruce will likely go onto the second chain as a backup and the plow will be retired.

Ted
It's R-O-C-N-A, Ted, sorry…might cause confusion, so took the liberty of editing. Hope that's ok.
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Old 04-17-2014, 08:29 AM   #8
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WE have a 40kg (88lb) Rocna as main anchor (350ft 3/8 chain) on our Selene 47 (65,000lb). Never failed to set or hold. Very satisfied. Would recommend you go larger if it can fit pulpit and windlass is up to the job. We moved our previous main 65lb CQR to the secondary position. That did not do so well in general.
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Old 04-17-2014, 10:30 AM   #9
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Five years ago we switched from a 66 lb (30 kg) Bruce to a 40 kg (88 lb) Rocna. Haven't dragged since. Don't know if the 30 kg Rocna would have had the same result but I am very happy.
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Old 04-17-2014, 10:47 AM   #10
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We went from a 30 kg Sea-Hook Claw to the 33 kg Rocna. The Rocna performs much better in speed of setting and holding in all bottom conditions. Our displacement is ~44k lbs.
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Old 04-17-2014, 11:11 AM   #11
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Everybody says to go one size larger than the manufacturer's recommendation. Why doesn't the manufacturer just recommend one size larger? How do you know they didn't?

And is a $500 anchor really better than a $100 anchor of the same general size and weight?
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Old 04-17-2014, 12:34 PM   #12
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Ron,
Very good point.

Look at several to many anchor manufacturers charts and I'll bet there will be considerable difference. Of course there's a considerable difference in the holding power of some to many anchors.

Good extreme example would be a Navy anchor and a Fortress. Huge difference in weight v/s holding power. But there are certain bottoms that the high performance anchor does not do well in but the big fat Navy anchor probably sets and otherwise works anywhere anytime on any bottom any anchor could possibly perform on.

Most all the time pleasure boats anchor in benign conditions and the only thing tested is setting ability. Often I've said "just give me an anchor that sets all the time". That should take care of 97% of anchoring situations. Some people have the Fortress and I have my modified XYZ for the storms. When we went to Alaska in 03 we used a Bruce and It performed very well. Didn't want to set right away a couple of times but did'nt require re dropping or positioning. Held fast in all weather ....... But I don't remember any wind over 10 knots in the evening on that whole trip. They said it was the best summer weather SE AK had experienced in 50 years.

But back on topic what anchor you have should be determined by what sets well, veers well, limitations like scope tolerance and resistance to being damaged down there being dragged over rocks and over logs. And a few other things like how well it fits on the bow. Then the size should be considered and as Ron said or implied that's not as cut and dry as looking at the manufacturers recommendation. And anchor weight, one anchor to another isn't what you're after but a level of performance. We can look at anchor tests but they vary more than anchor manufacturers weight recommendations. I think the Rocna is an excellent anchor but I have an anchor test that presents a poor performance by the Rocna.

A lot of experience is great as you get a good sense of what works and what doesn't but you may anchor for years in a way that another may rarely encounter. TF is great in that we hear of anchoring experiences by others that don't exactly add to your experience but one's scope and range of possibilities is expanded.

There's a boat in our yard that uses a Navy anchor and he regularly goes north to Akaska. His Navy isn't that large either. Almost all anchors work reasonably well. The CQR has seen some bad press here lately but many many skippers depend on them the world around. If you're the kind of boater that is driven to sport only the very latest state of the art highest performing things available the world over then an Ultra, Rocna, Supreme or Fortress will be your anchor irregardless of it's short comings just to be seen w the best. But any anchor is just another anchor plus it's edge over other anchors. But you usually get what sells well over time and what costs more. Usually.

HaHa ... Basically I just used a LOT of words to say the same thing Ron said in very few words.
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Old 04-17-2014, 01:15 PM   #13
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Quote:
Originally Posted by markpierce View Post
The rule-of-thumb (it seems) is to go one size larger than the manufacturer's recommendation. I'm curious why you decided to "upgrade" from a Bruce. Did it fail you? ... The herring fishermen here are slowly upgrading from Northills to Bruces.
Anchored out maybe 10 times in the last 2 weeks bringing the boat from FL to MD. Always pick sheltered anchorages. Never had the hook pull out, but have pulled it out a couple of times when setting it. Always wait for the hook to catch, wait a few minutes, then put the boat in reverse at idle speed. Wait for the chain to go tight and see if we hold position. It's dragged a couple of times in mud. Was thinking about going up one size, but real Bruces aren't being made anymore.

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Old 04-17-2014, 01:28 PM   #14
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Ron,
Very good point.

Look at several to many anchor manufacturers charts and I'll bet there will be considerable difference. Of course there's a considerable difference in the holding power of some to many anchors.

Good extreme example would be a Navy anchor and a Fortress. Huge difference in weight v/s holding power. But there are certain bottoms that the high performance anchor does not do well in but the big fat Navy anchor probably sets and otherwise works anywhere anytime on any bottom any anchor could possibly perform on.

Most all the time pleasure boats anchor in benign conditions and the only thing tested is setting ability. Often I've said "just give me an anchor that sets all the time". That should take care of 97% of anchoring situations. Some people have the Fortress and I have my modified XYZ for the storms. When we went to Alaska in 03 we used a Bruce and It performed very well. Didn't want to set right away a couple of times but did'nt require re dropping or positioning. Held fast in all weather ....... But I don't remember any wind over 10 knots in the evening on that whole trip. They said it was the best summer weather SE AK had experienced in 50 years.

But back on topic what anchor you have should be determined by what sets well, veers well, limitations like scope tolerance and resistance to being damaged down there being dragged over rocks and over logs. And a few other things like how well it fits on the bow. Then the size should be considered and as Ron said or implied that's not as cut and dry as looking at the manufacturers recommendation. And anchor weight, one anchor to another isn't what you're after but a level of performance. We can look at anchor tests but they vary more than anchor manufacturers weight recommendations. I think the Rocna is an excellent anchor but I have an anchor test that presents a poor performance by the Rocna.

A lot of experience is great as you get a good sense of what works and what doesn't but you may anchor for years in a way that another may rarely encounter. TF is great in that we hear of anchoring experiences by others that don't exactly add to your experience but one's scope and range of possibilities is expanded.

There's a boat in our yard that uses a Navy anchor and he regularly goes north to Akaska. His Navy isn't that large either. Almost all anchors work reasonably well. The CQR has seen some bad press here lately but many many skippers depend on them the world around. If you're the kind of boater that is driven to sport only the very latest state of the art highest performing things available the world over then an Ultra, Rocna, Supreme or Fortress will be your anchor irregardless of it's short comings just to be seen w the best. But any anchor is just another anchor plus it's edge over other anchors. But you usually get what sells well over time and what costs more. Usually.

HaHa ... Basically I just used a LOT of words to say the same thing Ron said in very few words.
Excellent post Eric. I think from this moment on this should be the standard answer to any queries about anchors.
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Old 04-17-2014, 04:00 PM   #15
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E...And is a $500 anchor really better than a $100 anchor of the same general size and weight?
Between the Sea-Hook and the Rocna, absolutely!!! Setting is so fast we now back down with a snubber where we use to back down and then add the snubber. I firmly believe the difference is in the design not the 3 kg difference in weight.
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Old 04-17-2014, 05:12 PM   #16
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Weight is a big part of the Rocna formula. Most mfrs recommend a range of boat size for each weight, with overlapping lengths. So "one up" is picking the weight with the range of the higher of the two (your boat length being more toward the lower end of the range). This resulted in an 88 lb Delta for my boat vs a 110lb Rocna 25% heavier. Plus, the Rocna wouldn't fit in my pulpit/roller set up, not that the Delta was a very much better fit.

So decided to go with a Delta, I had used them or CQRs a lot on the boats we chartered so had a good feel as to how to set them. After a few anchorage-intense trips up and down the whole east, never got around to trying a Rocna, or actually if I was going to try something else, a SuperMax which is great for places like the Chessie. But after hundreds of nights on the hook in all kinds of reversing currents, bottoms, winds... that Delta is still on there.

I would never dissuade someone from a Rocna, Manson Supreme or SuperMax, having seen them all in action. Just keep in mind, your windlass will fail someday. Now what is your plan for getting that extra heavy bad boy up when it does?
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Old 04-17-2014, 05:46 PM   #17
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Most cruisers here could probably go with one size smaller...I don't plan on anchoring during hurricanes or even any decent storm...thunderstorms you can always power to the rode like the big boys do....

Take every bit of advice you see on anchoring and put it in the blender....power up then and have some fun... what you need is in there some place..just probably not what any one person says....

Most newbies don't need anchor advice...they need anchoring advice...if they want anchor advice before learning the way to do it...buy anchors 2X larger than...no make that 3x larger...no...just go with anchors 5X bigger than the manufacturer recommends and then technique probably won't matter...
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Old 04-17-2014, 07:03 PM   #18
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I've talked to boat owners who don't own an anchor. When I ask their response is "We don't need an anchor because we never anchor out."

I ask what they plan on doing if the engine quits. They have no response.

If you are leaving the dock you need suitable ground tackle and the knowledge to use it. Chapman Piloting is a great place to start.
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Old 04-17-2014, 07:23 PM   #19
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Ron wrote,
"I ask what they plan on doing if the engine quits. They have no response"

That's why I have 430' of anchor rode.

And now that Marin's gone I can say ditto the Chapman's.

And Thank you Conrad re post #14.
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Old 04-17-2014, 08:02 PM   #20
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Quote:
Originally Posted by rwidman View Post
Everybody says to go one size larger than the manufacturer's recommendation. Why doesn't the manufacturer just recommend one size larger? How do you know they didn't?

And is a $500 anchor really better than a $100 anchor of the same general size and weight?
Good point, and I think a lot of the people who go with approach of "what the manufacturer says, then go one size larger", have probably wasted their money, because the manufacturer is not going to risk bad press by recommending something too light in the first place. It does however constitute a belt and braces approach, which maybe contributes to better sleep at night, and if one can afford it - and one's winch arrangement can cope with it without shortening its life, then I guess it's ok, even if a bit unnecessary.
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