Over-specifying a Rocna anchor on a cat

[YPSILANTI]

Greetings,
My boat is a 50 ft Voyage Mayotte Catamaran. I will soon be purchasing a new Rocna anchor. Based on 50 kts of wind, surge and poor holding conditions, the sizing guide on their web site recommends a 40 kg anchor. However, it is probable that my boat will be moored on the other side of the globe for extended periods of up to a year at a time. I need to be certain that the anchor will hold in the most extreme of conditions. However, I am also nervous of over specifying. I'm not certain but think that my windlass is a Lewmar 1000. I'm particularly anxious on overstraining my windlass. Has anyone out there ever fitted a 55kg Rocna onto their 50ft catamaran? What is the advice, Stay with the recommended 40kg or go for the 55kg?

Regards
Mike

[donradcliffe]

The lewmar 1000 is recommended for boats up to 38 ft. What chain are you using? How much does your boat weigh?

[a64pilot]

I cut this from Rocna's website, but I feel better with an oversized anchor myself

Many Rocna customers, in improving their anchor type by switching to a Rocna from an older anchor which they have learned to be unreliable, make doubly sure about their upgrade by also increasing the weight of their anchor. We see this tendency a lot, and try to discourage it. As above, our official sizing is very conservative, and in many cases it's a case of "don't over-size – we already did that for you!"




You sure you have a Lewmar 1000? If that is the windlass I think it is, that's not going to work I don't think.
What size chain do you have?

[Jim Cate]

The only time I have ever wished that I had a smaller anchor was when lugging it down to the boat.

If you are using chain rode (as you should), the extra 15 kilos from the larger anchor will be a fairly small increment when anchored in deepish water. If your windlass won't handle that, get a bigger windlass... you will need it with either anchor!

Jim

[sailjumanji]

Hmm, that is an undersized windlass. I have a 33 ft cat, rocna 15 kg anchor, all 8 mm chain, and a Muir 1250 windlass. Have not dragged to date.

[leftbrainstuff]

You need to consider several related parameters and ensure all elements are sized appropriately.

1) chain and shackle size
2) anchor size
3) windlass
4) vessel weight, windage and worst case wind, sea, current load
5) weight, polar moment and load carrying points

Rocna's sizing seems reasonable based on empirical data.

If can clarify the above then you'll probably get more targeted responses.

Sent from my SM-N900T using Cruisers Sailing Forum mobile app

[Palarran]

Originally Posted by YPSILANTI

Greetings,
My boat is a 50 ft Voyage Mayotte Catamaran. I will soon be purchasing a new Rocna anchor. Based on 50 kts of wind, surge and poor holding conditions, the sizing guide on their web site recommends a 40 kg anchor. However, it is probable that my boat will be moored on the other side of the globe for extended periods of up to a year at a time. I need to be certain that the anchor will hold in the most extreme of conditions. However, I am also nervous of over specifying. I'm not certain but think that my windlass is a Lewmar 1000. I'm particularly anxious on overstraining my windlass. Has anyone out there ever fitted a 55kg Rocna onto their 50ft catamaran? What is the advice, Stay with the recommended 40kg or go for the 55kg?

Regards
Mike

Ypsilanti, I think the 40kg is the correct anchor for your cat and the 55 overkill. In the Med, the cost of a 55 over a 40 is nearly 100%! Save the money and get the better chain and possibly a stronger windlass.

I have a 55kg on a 56' cat with a fair amount of weight and windage. I'm using 120 meters of 10mm G7 chain and a Lofrens 1700 watt windlass.

[Sailingveterinarian]

I have a Knysna 480 with 40kg Rocna.....I don't regret that. I sleep well at anchor.
Have a Tigress windless. All chain rode.

[DMCantor]

My rule of thumb is that if the neighbors in the marina aren't giggling at how big your anchor is, you should go up a size. If the cost of the 55 vs. the 40 matters to you, then go with the 40. Otherwise, bigger is always better. 15 kg on the bow won't change anything about sailing performance or windlass sizing.

As an aside, we had a friend who proposed (I don't think ever executed) an April Fool's joke, cruising through the anchorage on a 45' boat with a dinghy-sized danforth on the bow, and a French flag. Sure to cause gasps among the cruisers. (I love French people, but I think their sailing education on anchoring leaves lots to be desired)

David
s/v Callisto

[SailFastTri]

I have a Rocna 20kg on a 12 meter trimaran. It happens to be the size they spec for the boat but it's also the largest I can fit on my bow roller because the hoop height would interfere with my sprit. I'd upsize if it was practical, and have occasionally considered the Manson Boss because it doesn't have the hoop.


The Rocna is a great anchor but it can drag in soft mud if I back down hard in a strong wind. (I think in certain situations the hoop can ball up the mud/vegetation and limit burying depth). There's no such thing as too much anchor at o-dark-hundred when a strong squall comes through.

[Bulawayo]

On our V45 we use a Mantus 85lb. The Mantus sizing chart suggests a 105lb for your boat. In my opinion there is little in the way of real difference between Mantus and Rocna. We upgraded our windlass to a Lofrans Tigress - which we have used on several boats and have had positive experience with. Following recent postings and lots of research we are also looking at purchasing 90 meters of new 10mm German made stainless anchor chain; this shall surely be criticised by many - but having done a heap of research this actually seems to be a very viable route to go. We are all taught not to buy stainless chain but the German chain is real quality and we have met several cruisers using it on heavy boats and with many years of success.
I dont think you'll regret going for the larger anchor as long as you ensure you have adequately sized/rated chain and a windlass powerful enough to retrieve the entire length.


YPSILANTI;2094895]Greetings,
My boat is a 50 ft Voyage Mayotte Catamaran. I will soon be purchasing a new Rocna anchor. Based on 50 kts of wind, surge and poor holding conditions, the sizing guide on their web site recommends a 40 kg anchor. However, it is probable that my boat will be moored on the other side of the globe for extended periods of up to a year at a time. I need to be certain that the anchor will hold in the most extreme of conditions. However, I am also nervous of over specifying. I'm not certain but think that my windlass is a Lewmar 1000. I'm particularly anxious on overstraining my windlass. Has anyone out there ever fitted a 55kg Rocna onto their 50ft catamaran? What is the advice, Stay with the recommended 40kg or go for the 55kg?

Regards
Mike[/QUOTE]

[contrail]

If you want a larger anchor, Spade make an aluminum version of their steel anchor, which is the same basic design and a precursor to the Rocna. For the last twelve years I have carried a Spade A200. It's the aluminum version (25 kilos) of their steel Spade (55kilos, which is huge). The two versions have the same surface area, thus the same holding power. The aluminum version, being lighter for the same size, can sometimes be a bit more difficult to set and get dug in, but it's not a big problem, and when it's set, it is set! We are a charter boat, so anchor a lot, and have never dragged, once set.

Not having the ring on top helps in some installations but the shank is also quite large, both vertically and horizontally, so the measurements need checking.

By the way, the Spade has most of it's weight concentrated in lead inside the tip, so it wants to be right side up. I have never seen it the anchor laying on its side and consider the roll bar on the Rocna to be superfluous on a Spade.

I use a Lofrans Tigress windlass, which is plenty, but the anchor is usually in so deep that, almost always, I have to use the weight of the boat and the engines to break it out.

[Bulawayo]

Seems the Tigress is popular.......

Originally Posted by contrail

If you want a larger anchor, Spade make an aluminum version of their steel anchor, which is the same basic design and a precursor to the Rocna. For the last twelve years I have carried a Spade A200. It's the aluminum version (25 kilos) of their steel Spade (55kilos, which is huge). The two versions have the same surface area, thus the same holding power. The aluminum version, being lighter for the same size, can sometimes be a bit more difficult to set and get dug in, but it's not a big problem, and when it's set, it is set! We are a charter boat, so anchor a lot, and have never dragged, once set.

Not having the ring on top helps in some installations but the shank is also quite large, both vertically and horizontally, so the measurements need checking.

By the way, the Spade has most of it's weight concentrated in lead inside the tip, so it wants to be right side up. I have never seen it the anchor laying on its side and consider the roll bar on the Rocna to be superfluous on a Spade.

I use a Lofrans Tigress windlass, which is plenty, but the anchor is usually in so deep that, almost always, I have to use the weight of the boat and the engines to break it out.

[YPSILANTI]

Gosh folks. The immensely informative replies and information is much appreciated. What has been confirmed is that my windlass is under specified which is what I've always suspected. I will mull over the information and will make a final decision. The feedback from the cats of similar size is helpful too.
Regards
Mike

[Bulawayo]

Was you boat built by Fred Scholtz or Voyage? Voyage are good quality byt Fred took quality to very new standard. I know some of 47's morphed into 50's.

Originally Posted by YPSILANTI

Gosh folks. The immensely informative replies and information is much appreciated. What has been confirmed is that my windlass is under specified which is what I've always suspected. I will mull over the information and will make a final decision. The feedback from the cats of similar size is helpful too.
Regards
Mike