Anchor sizing confirmation

To my mind Size Counts, so I work from the other concept , how big can it be rather than how small.


The length of anchor line doesn't matter , you probably would not be pulling the anchor if the engine did not work.


That leaves the windlass and bow roller setup to contemplate.
In many large dock areas there will be a variety of anchors to view , when you see the BIG ONE , that you think will fit , work out something to borrow it .


Lowering it into a dink and hauling it to your bow rollers is simple , and fairly effortless



Most windlasses have a recommendation for their max hoisting ability .


There is an old saying ,,,,, Man plans ,,God laughs , so a marginal sized setup might work for a long time , BUT!

At this point, I'm thinking that as long as I can make the 33kg / 73lb Vulcan fit, I'll just go with that. They give good enough dimensions that between a tape measure and assembling the cardboard template version, I can confirm it'll fit. And I'm sure I can find 18 lbs of extra stuff that can be removed from the boat if I'm concerned about the weight.

Windlass-wise, the new Maxwell HRC10-8 that's going on has a rated max pull of 1540 lbs. So if we figure 1/4 of that for working load, that gives 385 lbs. The 73 lb anchor, 75 feet of chain, shackle and 350 feet of line is still under 200 lbs, so even coming up with a serious load of mud, the windlass shouldn't have any trouble bringing the stuff up.

I'm already taking the pulpit off to clean up and epoxy pot the holes through the deck and replace the structural wood on the pulpit (some of it is definitely wet). So I'll take that opportunity to figure out how much reinforcement I can build into it to make sure the pulpit is stiff and strong enough to handle the loads on the bow roller. Plan is to remove all of the wood below the fiberglass layer (not sure yet if I'll have to pull and reinstall the top teak). I'm then going to fill the fiberglass shell back in with teak or other hardwood boards laminated in with thickened epoxy. I might also epoxy a couple of pieces of heavy stainless angle to run from the forward part of the roller back and have the roller bolt through them for additional bending strength. The exact plan will come when I have the pulpit pulled and sitting in my garage.

Fortunately, the boat is on land and indoors right now, so having stuff opened up for work is no big deal. Just means I have to manage to carry a large anchor and the new rode through the boat maze in the storage shed.

rslifkin said:

I'm already taking the pulpit off to clean up and epoxy pot the holes through the deck and replace the structural wood on the pulpit (some of it is definitely wet). So I'll take that opportunity to figure out how much reinforcement I can build into it to make sure the pulpit is stiff and strong enough to handle the loads on the bow roller. Plan is to remove all of the wood below the fiberglass layer (not sure yet if I'll have to pull and reinstall the top teak). I'm then going to fill the fiberglass shell back in with teak or other hardwood boards laminated in with thickened epoxy. I might also epoxy a couple of pieces of heavy stainless angle to run from the forward part of the roller back and have the roller bolt through them for additional bending strength. The exact plan will come when I have the pulpit pulled and sitting in my garage.

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Thinking off the wall a bit...

If you can remove the original pulpit, might there be a way to replace it with a pulpit that gives you two fairleads, and room for two mounted anchors all the time?

And then a windlass with chainwheel/gypsy and a separate capstan for rope? (That was an available option on our Maxwell RC.)

-Chris

The windlass (already waiting in my garage) does have a rope capstan (I actually wanted the no capstan option, but it was cheaper with the capstan).

However, if I did feel the need to put a second anchor on this pulpit, it wouldn't be hard to set up a roller to deploy the second anchor over the top of the pulpit (and correspondingly over the front of the lower anchor). I'd just have to put the top roller all the way to the port side of the pulpit to produce appropriate capstan alignment.

Realistically, I'm not cruising full time anywhere in the near future, so travel away from home is pretty much 2 weeks or less at a time. Based on that and the areas within reasonable cruising range for me, I don't really see a need to carry a second anchor on the bow. I've got plenty of storage to carry another anchor and rode below (no lazarette on this boat, but there's a big storage space under the floor of the forward stateroom with another floor to separate the storage from the bilge). Hand hauling a Fortress (even a bigger one than I've got) isn't a big deal. The current Fortress and the chain that'll stay with it is only just over 30 lbs.

Plus, the current pulpit cosmetically and physically fits the boat well and the bow rail follows the shape of the pulpit perfectly. So it would be tough to replace it without giving something up in the process (or spending a bunch more money).

High Wire said:

Our 20 kg Vulcan never gave us any trouble on our Monk in Florida sand bottom until we added a full enclosure. In soft bottoms in NC, SC, and GA, during thunderstorms, we have dragged several times. Each time we were lucky and got ourselves out of trouble. Each time the anchor was set for several hours prior to the wind event. Each time we dragged was when the boat yawed to the side then a gust hit us.
Your boat has high side wind profile and I would personally go the next size up. We are moving up to the 25kg when our source gets them back in stock because we do anchor out in bad weather.
20 pounds of extra anchor weight on a 13 ton boat is nothing imho.

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What type and size of rode do you have?

sunchaser said:

What type and size of rode do you have?

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All chain 5/16" BBB. In the one TS, 100 ft of chain out in 7 ft of water did not hold. Bottom was soft muck. Oriental NC.

High Wire said:

All chain 5/16" BBB. In the one TS, 100 ft of chain out in 7 ft of water did not hold. Bottom was soft muck. Oriental NC.

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That is a lot of scope. The vessel could easily swing around 180 feet. There have been times when we had a lot of scope out that I thought the anchor was dragging but it was only re-orienting the vessel around the solidly dug in anchor. The anchor circle on the laptop helps give us piece of mind in high scope situations but boy do we wander.

sunchaser said:

That is a lot of scope. The vessel could easily swing around 180 feet. There have been times when we had a lot of scope out that I thought the anchor was dragging but it was only re-orienting the vessel around the solidly dug in anchor. The anchor circle on the laptop helps give us piece of mind in high scope situations but boy do we wander.

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That was after it pulled out with 6:1 scope. We reset after the first TS and laid out to the 100 ft marker because more storms were in the area. Around 11 pm we got hammered again. I was standing at the lower helm with the engine running just in case. Well it happened while we were yawed to port. The chartplotter showed the unmistakable movement to the East at 1.5 knots. The drag alarm went off. I laid on the thruster to try to get the bow West then put in FWD at idle hard to Stbd. The bow came into the wind for just a few seconds, enough to hook again. In those few moments we moved about 100 feet to the East and were now in 4.5 ft of water. The squall died. We pulled up anchor again and set up at our original mark with 105 ft (all of our chain). Fortunately no more squalls that night.

BruceK said:

Here`s how I think it works:
1. The Anchor mfr, afraid of getting sued, prepares a safe conservative length/weight/size table, errs on the heavy side, and sells a bit more anchor.
2. Buyer chooses next size up relying on common thinking,like on TF.
3. Retailer advises buyer to choose next size up from that "just in case". He sells some more anchor.
Why do people think the mfr/designer does not know what to recommend. Sure there can be special circumstances, boats much heavier than usual for length etc,but surely the mfr with his recommendation table has every reason to get it right.

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Totally disagree

Many are far to simplistic and don't take into account weight or windage
As an example, this CQR chart recommends a 60lb anchor for up to a 65 fter

https://www.anchoring.com/pages/plow-cqr-boat-anchor-sizing-chart

West marine sizing says pretty much the same
https://www.westmarine.com/buy/lewmar--cqr-anchors--P005_153_002_005

Any 60 to 65 fter I know who still uses a plough and actually uses their boat and sleeps soundly runs 180 lb to 300lb

Manson supreme chart suggests an 80lber would be good for us.
After actually contacting Manson in NZ and sending pictures and weight of vessel, 150lb was decided on as an armageddon anchor.
I tried to talk them up a size but they said not required.
Apparently they didn't want the extra money

North West Marine Distributors - Manson Supreme Anchor - NWM: supplier of Manson Supreme Anchors

Simi 60 said:

Totally disagree

Many are far to simplistic and don't take into account weight or windage
As an example, this CQR chart recommends a 60lb anchor for up to a 65 fter

https://www.anchoring.com/pages/plow-cqr-boat-anchor-sizing-chart

West marine sizing says pretty much the same
https://www.westmarine.com/buy/lewmar--cqr-anchors--P005_153_002_005

Any 60 to 65 fter I know who still uses a plough and actually uses their boat and sleeps soundly runs 180 lb to 300lb

Manson supreme chart suggests an 80lber would be good for us.
After actually contacting Manson in NZ and sending pictures and weight of vessel, 150lb was decided on as an armageddon anchor.
I tried to talk them up a size but they said not required.
Apparently they didn't want the extra money

North West Marine Distributors - Manson Supreme Anchor - NWM: supplier of Manson Supreme Anchors

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So you totally disagree with this part of my post too? As well as disagreeing with Manson NZ ?
"Why do people think the mfr/designer does not know what to recommend. Sure there can be special circumstances, boats much heavier than usual for length etc,but surely the mfr with his recommendation table has every reason to get it right."

4mo said:

I'm pretty sure that nobody plans of staying overnight in unprotected anchorages with heavy winds... but if you end up in that situation the 25kg Rocna is plenty.

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I agree. Your boat at 26,000lb =~ 11 tonne, which is the weight of my CHB34 when I had her, and the 22kg (45lb) S-Sarca I had on her was plenty. The Rocnas tend to use similar weights/length. You might also want to consider the Sarca Excel, now available over there, and designed for exactly your type of pulpit, but a bit more orthodox in shape than the spade types like the R-Vulcan, Manson Boss and Spade itself.

BruceK said:

So you totally disagree with this part of my post too? As well as disagreeing with Manson NZ ?
"Why do people think the mfr/designer does not know what to recommend. Sure there can be special circumstances, boats much heavier than usual for length etc,but surely the mfr with his recommendation table has every reason to get it right."

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Works if people actually contact the manufacturer which I'm guessing most don't.
Doesn't necessarily work if they rely on the published recommendation table.

Simi 60 said:

I wonder how all those people on bigger boats and much bigger anchors manage?

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Our boat is only 42 feet, but we have an 85 pound Mantus for our main anchor.

I'm 62, and I don't have any trouble with handling it as long as the windless works. It comes up and stows pretty easy.

I admit, the one time I had to pull it up by hand (when our windless breaker switch gave up the ghost) was not the funnest day of boating I ever had. It's not just the weight of the anchor, it's the chain, too. We were only anchored in about fifteen feet of water. If we had been in thirty or forty feet, I'm not sure I could have got it up.

When that happens on a sailboat, it's easy. You just use one of the sail winches to get it in (which has made me think many times about finding a good used sailboat winch and mounting it on my fore deck as a capstan.

Anchor manufacturers recommendations for anchor size vary a lot.

That’s because there’s a lot of variables.
Windage. Low freeboard to oxygen tent and high rigging.
Wind.
Steady
Variable w gusts
Veering winds.
Anchor design.
Weight of chain.
Length of chain.
Snubbers or/and line stretch.

With all the variables anchor weight estimates (or guesses) would span a wide range of weights/sizes.

But of course the biggest variable of all is the seafloor.

And then there’s the person buying the anchor. ASD would go one size up. I would lean more on my own experience. Re that though I know I have changed my opinions about several anchors capabilities considerably over time.

But in the end we all pick our way of choosing and most are probably a combination of numerous sources of input and .... go for it.

Nomad Willy said:

Anchor manufacturers recommendations for anchor size vary a lot.

That’s because there’s a lot of variables.
Windage. Low freeboard to oxygen tent and high rigging.
Wind.
Steady
Variable w gusts
Veering winds.
Anchor design.
Weight of chain.
Length of chain.
Snubbers or/and line stretch.

With all the variables anchor weight estimates (or guesses) would span a wide range of weights/sizes.

But of course the biggest variable of all is the seafloor.

And then there’s the person buying the anchor. ASD would go one size up. I would lean more on my own experience. Re that though I know I have changed my opinions about several anchors capabilities considerably over time.

But in the end we all pick our way of choosing and most are probably a combination of numerous sources of input and .... go for it.

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All good points Eric, and I totally agree with you as long as you use the same anchor that I do!

firehoser75,
“totally agree with you”
This must be my day!
And since I’m using the same anchor as you ......

I’ve been using a 25kg/55lb Vulcan on my 40’ 2,200lb Pilgrim trawler with great success but have recently downsized to the 20kg/44lb. The 25kg put a lot of strain on the windless, seemed overkill for my inland river conditions, and it’s what Rocna specifies in their sizing chart as the direct middle-match for my size and displacement. You’ve probably seen Peter Smith’s directive on sizing his anchors... “Unlike other manufacturers, our anchor sizing recommendations are intended to provide an anchor adequate for use in most all conditions. We base our calculations on 50 knots of wind, associated surge, and poor holding bottoms. ”
Now that I have 2 Rocna’s, the 20kg on my boat and the 25kg in my garage, I have myself in a pickle since I’m convinced that if I sell the 25kg I’ll find myself in a severe condition where I’ll be regretting having downsized to the 20kg, yet I don’t want to carry the 25kg along for the ride. The 20kg has performed amazingly well (it held fast while anchored directly below the McAlpine locks and dam in a horrendous current with 38’ trawler hanging on my hip because he couldn’t get his anchor to set). I try to convince myself that my secondaries (a 44lb Bruce, 30 CQR, and 20lb Danforth) will give me a lot of back-up options... but I still struggle with letting go of the 25kg Rocna. What to do?

High Wire said:

All chain 5/16" BBB. In the one TS, 100 ft of chain out in 7 ft of water did not hold. Bottom was soft muck. Oriental NC.

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Being a firm believer in the new style anchor (Ultra as primary, Vulcan as backup ex Bruce primary) In soft muck, i find that only a Fortress set at 45 degrees will hold.
My $.02

sailorjoe said:

Now that I have 2 Rocna’s, the 20kg on my boat and the 25kg in my garage, I have myself in a pickle since I’m convinced that if I sell the 25kg I’ll find myself in a severe condition where I’ll be regretting having downsized to the 20kg, yet I don’t want to carry the 25kg along for the ride. The 20kg has performed amazingly well (it held fast while anchored directly below the McAlpine locks and dam in a horrendous current with 38’ trawler hanging on my hip because he couldn’t get his anchor to set). I try to convince myself that my secondaries (a 44lb Bruce, 30 CQR, and 20lb Danforth) will give me a lot of back-up options... but I still struggle with letting go of the 25kg Rocna. What to do?

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First TF instance of "Anchor Buyers Remorse". Why not make it your 4th secondary anchor, that should cover it.

"yet I don’t want to carry the 25kg along for the ride"


Anyone that has been cruising for a while has run aground . Styff happens.


A second anchor on board to replace a lost anchor and line is great insurance .


If located where its easy to access , it can be used to pull off a grounding , or to stop dancing L & R in shifty winds.Stern anchor or Bahama style anchoring come to mind.



Instead of leaving it ashore , contemplate setting it up with line so it can be easily/instantly deployed.

sailorjoe said:

I’ve been using a 25kg/55lb Vulcan on my 40’ 2,200lb Pilgrim trawler with great success but have recently downsized to the 20kg/44lb. The 25kg put a lot of strain on the windless, seemed overkill for my inland river conditions, and it’s what Rocna specifies in their sizing chart as the direct middle-match for my size and displacement.

Now that I have 2 Rocna’s, the 20kg on my boat and the 25kg in my garage, I have myself in a pickle since I’m convinced that if I sell the 25kg I’ll find myself in a severe condition where I’ll be regretting having downsized to the 20kg, yet I don’t want to carry the 25kg along for the ride. The 20kg has performed amazingly well (it held fast while anchored directly below the McAlpine locks and dam in a horrendous current with 38’ trawler hanging on my hip because he couldn’t get his anchor to set).

What to do?

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I'd have thought being right in the middle of the maker's recommendations would be a good thing...

What is your windlass, and what was the nature the "lot of strain" with the 25kg model?

Think I'd be inclined to keep the 25kg and jettison the 20kg if at all viable (and I'm just guessing, without knowing full details of boat, the whole ground tackle system, expected bottom types, etc.).

-Chris

rslifkin said:

At this point, I'm thinking that as long as I can make the 33kg / 73lb Vulcan fit, I'll just go with that. They give good enough dimensions that between a tape measure and assembling the cardboard template version, I can confirm it'll fit. And I'm sure I can find 18 lbs of extra stuff that can be removed from the boat if I'm concerned about the weight.

Windlass-wise, the new Maxwell HRC10-8 that's going on has a rated max pull of 1540 lbs. So if we figure 1/4 of that for working load, that gives 385 lbs. The 73 lb anchor, 75 feet of chain, shackle and 350 feet of line is still under 200 lbs, so even coming up with a serious load of mud, the windlass shouldn't have any trouble bringing the stuff up.

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We have a 33kg/73lb Rocna on Blue Sky and it works beautifully. I once had to pull it up manually (using the manual ratchet system on the windlass), and although it was a slow laborious chore, it was not heart attack inducing whatsoever for these old muscles. I had to pull up the anchor (73#) and 240' of chain (~240#) in 40' of water.

We also had a Maxwell HRC10-8 on our last boat, albeit with a smaller 33 kg Rocna, and it also worked very well; we had 150' chain and 250' brait. On the rare occasion where we had let out some brait, the windlass seamlessly pulled up the brait and chain (plus anchor), dispelling any misgivings I might of had about the effectiveness of the brait/chain gypsy.

Conrad said:

We also had a Maxwell HRC10-8 on our last boat, albeit with a smaller 33 kg Rocna, and it also worked very well; we had 150' chain and 250' brait. On the rare occasion where we had let out some brait, the windlass seamlessly pulled up the brait and chain (plus anchor), dispelling any misgivings I might of had about the effectiveness of the brait/chain gypsy.

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Hearing another confirmation of that is good. I'm currently assessing whether I can step the line size up to 3/4" instead of the 5/8" that's spec-ed for the windlass to make it a little less stretchy and a little more durable. I've got a test piece of 3/4" 8 plait here to bring down to the boat over the weekend. Maxwell told me there's no way it'll work, only 5/8" will, but I want to see how it sits in the gypsy before deciding. I did find a mention of someone using 3/4" 3 strand in an RC8-8 (also spec-ed for 5/8" line), so considering how squishy 8 plait is, there's a decent chance it'll sit fine in the gypsy.

" I'm currently assessing whether I can step the line size up to 3/4" instead of the 5/8" that's spec-ed for the windlass to make it a little less stretchy and a little more durable."


It is the stretch built into modern nylon line that allows the use of light weight anchors.


Most of the line wear I see is chafing from a poor line setup going overboard, not from stretching.


It takes about 10% of the breaking strength of nylon to begin to stretch the line , usually thinner line reduces the shock loads on the anchor and gives a smoother heavy weather ride aboard.

I've now got 2 weekends of use on the new anchor and related gear. The 73lb Vulcan fits the pulpit nicely after I modified the slot a bit, and it both self-launches and docks nicely with the windlass, no manual fiddling required. The HRC10-8 windlass did a great job with the rope/chain combo. Seamless going out, and coming back in you just stop right before the splice hits the windlass, bump it gently, then continue (if it tries to transition while pulling at full speed and lifting 50+ lbs of chain it slips and won't grab the chain).

I put it through its first mild wind test this weekend, anchored in 48 feet of water with 275 feet out (5:1 scope after accounting for freeboard, first 90 feet are chain). Bottom was dark, sticky mud, but not overly soft. Anchor was set with a gentle tug, then brought up tension again, sat with both engines at reverse idle for about a minute, then 1000 rpm for about 30 seconds.

Sat through a couple hours of 20 - 25 kts with gusts to 30 - 33 and somewhat shifty wind direction on the gusts. So we were getting blown off sideways down wind at a pretty good pace (saw 1.5 kts on the plotter a couple of times) before fetching up on the rode. Between chain catenary and almost 200 feet of stretchy nylon, the take-up was very smooth and gentle, so no comfort or holding concerns. Wind became more steady (both direction and much smaller gusts) around sunset, so with the back covers up we sat nice and steady with about 18 kts of wind, just a mild yaw over maybe a 10 degree range. Slept great, then sat through a few more hours of 18 gusting to 25 the next day.

When we pulled the anchor up to head home last night, the mud caked into the slot and shackle led me to believe that we had the anchor fully buried including the shank despite having pulled on it in various directions over about a 90* range. Based on our swing circle, the anchor never moved. Retrieval on the Vulcan doesn't seem too bad even when it's deeply buried. A couple minutes with the rode vertical (with an occasional bump on the windlass to keep tension) loosened it up enough to lift it right out. Much easier than the Fortress break-out dance...

One of the photos shows the anchor about to be docked into the pulpit (with plenty of hull clearance, the point of least clearance is when fully docked). I'd say that overall, it worked out nicely.


The first time using the new rig even provided some good entertainment. Sitting in 49 feet of water when some people in a small boat come into the cove we were in (deep until very close to shore) and tossed out an anchor. After a few minutes, I notice they're drifting around. Shortly before they got close enough to concern me, I see them realize they're moving, pull their anchor up (looked like they only pulled in 40 or 50 feet of line) and move elsewhere. I don't think they realized how deep it was and I don't think their anchor even touched the bottom. Most of the boats that anchor in this bay tuck into the shallow spots, so they probably figured that if we were anchored there, they could too, not thinking that anyone would ever anchor in nearly 50 feet of water.

Dup post!