my best storm anchor technique

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Re; the concept of pulling in an anchor after the S hits the fan. That may not be that easy. I have read of boats slipping their anchor and heading out to sea. For those boats with all chain where the chain is fixed in place down below slipping anchor may be complicated.. Those with chain plus rope can tie a float to line and cut free to slip the anchor.
 
klee wyck said:
Markpierce,
Thanks for making that point.
First, I will stipulate that I know next to nothing about boats and exactly nothing about anchoring, but I have never been sure why anchor sizing recommendations go by boat length or weight. Just looking for some schooling here. When storm anchoring specifically, isn't this about windage? What forces do length or weight of the boat apply to the anchor system?
I have thought that the surface area presented to the wind by my boat to be what I need to consider for anchoring. When pointed into the wind, I think my boat represents a little under 20 square meters of wind surface and then I discount this to 0.7x that since my bow and upper house has a pretty fine entry into the wind and use this smaller coefficient of drag (arbitrary I know but bear with me).
If this is true, I come up with a force of about 350KG at 50 knots (25kg/sq meter).
If the Forfjord weighs 145# and 300' of 3/8 HT adds another 450# and the wind force is less than 1000# then I am not asking much for holding power from the flukes themselves. Even if I double this wind force to add some force for yaw and surge/waves (only if the chain and bridle have ALL the slack pulled out by wind alone) I don't think I get to 2000# total. The flukes then need only supply 400-1400 of holding force. The old Forfjord has pretty large flukes so even if it is not buried to the center of the earth, it should be capable of that, no?
I would really like to get comfortable with this. I do not relish the idea of multiple anchors and the horror of twisted rodes should I need/want to pull the anchor in a hurry when something else breaks loose and is bearing down on me. I do like the swivel shackle referred to in an earlier post if I get convinced I need to do this.
I think being in the PNW is part of why I am tempted to stick with my plan. Wind over 50 knots is pretty rare in my cruising area and depressions that might bring winds higher than this should give me fair enough warning to get to a protected harbor that would not experience winds this high. I never leave my boat anchored out while not on board for very long unless I am in the tender and then I would have bigger problems than my anchored boat if I got surprised by winds over 50 knots. When on the boat I am sure I would be on an anchor watch with anything more than a stiff breeze since I am a nervous Nellie. I read about the winds you East Coasters are forced to deal with and am pretty sure I would not have the cahones to even own a boat if I lived there.
I will probably be hanging on my single old fashioned hook until you guys enlighten me....plus, doesn't the old Forfjord look cool hanging off that hause?:dance:
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First of all a boat in a stiff breeze is a very lively animal , and they rarely point directly into the wind. You have to figure the drag of the hull, all the canvas, masts, antenne, dinghy, bbq , bla bla as they all contribute to the boats wind print.
Then try to figure the dynamic load on the anchor when the chain goes taunt and the bow is pitching up and down a couple feet.. ( or more). Lets not forget to add current to the mix.

My first suggestion is pitch your anchor and get just about anything else..even the badly bashed Bruce anchors are far better in any bottom other than bolders. The 40' boat we have now came with a 100# + Fortjford and the only value I can find in the thing is to use it as yard art. It failed to set all the time..and I had no faith that it would reset in a direction shift.

Anchoring is part science, experience, skill, luck, equipment and faith...no reason to use what is basically 100 year old tech to keep you, your boat and family safe
Hollywood
 
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klee wyck said:
I think being in the PNW is part of why I am tempted to stick with my plan. Wind over 50 knots is pretty rare in my cruising area and depressions that might bring winds higher than this should give me fair enough warning to get to a protected harbor that would not experience winds this high.
Click to expand...

Forecasting in the PNW is pretty good when it comes to what's going to happen, not so good when it comes to when it's going to happen. We almost lost our boat to a lee shore when forecast winds arrived some eight hours before they were supposed to. And we've observed or experienced weather arriving earlier or later than forecast many times.

It's not the forecasters' fault The terrain and wind patterns here can make it difficult to accurately predict a time of arrival.

But based on over three decades of boating and floatplane flying in the PNW, BC, and SE Alaska, we have learned to regard the forecasts in terms of their predicted times the same way drivers in China regard traffic signals-- they are simply suggestions.:)

Particularly problematical can be the forecast times for wind shifts. What started out as the upwind side of a bay may become the downwind side before it was supposed to, and this can cause problems for boats at anchor.
 
A friend of mine was in a hurricane in La Paz, Mexico and he saw many boats drag using the 20 degree multiple anchor system. It looks good on paper but it's still an angle which the anchor wasn't made to perform at it's best.

He used two danforths in a row, one 100' out the other closer in. He didn't move.
 
I have 20' of 3/8" three strand on the bitter end of our chain to cut and tie a fender onto if we have to drop the rode. Hope I never need to use it!!
 
For those really interested in multiple anchor anchoring there's an extensive thread in the archives.

Deflin,
If you tie a rope to a tree and pull on it w 100 lbs the tree will feel 100lbs. If you tie the rope to two trees say 75' apart w very little slack and then pull at right angles to the rope (in the center) w another rope and 100 lbs of tension the tension on the trees should be much more than 100lbs. So if those trees were anchors they would experience more tension than is applied to the rope center at 90 degrees.
But of course the line between the two anchors would not be straight so the situation would be less bad than expressed above. And when the angle between the two rodes became about 90 degrees perhaps the two anchors would hold more tension than one but it wouldn't take much of a wind direction change to be anchored mostly on only one of the two anchors.

It would seem best to me to forget about the second rode and double the weight of all components of one rode and have much more holding power.

But it would be far better yet to increase the weight of the anchor instead of the chain and then even better than that to put nylon on the upper half of the rode and double the weight of the chain on the lower half. But once you have the anchorage established adding weight to the anchor is way way more advantageous than anything else. Look at Klee's setup. With 450# in the rode and 145# in the anchor taking 100# from the rode and applying it to the anchor .. that then would be a 245# anchor and a 350# rode. Plus it would have the stretch of the nylon. Far more holding power IMO. Now what if that anchor was a Fortress?

I think the only good thing about the Forfjord is possibly their ability to veer gracefully. But the possibility of having one fluke down and one up like a Kedge is fairly high IMO. My experience w the Forfjord's setting was a big failure also. I'm not a Forfjord fan. Fishermen love them though in SE Alaska. The Claw is on the bows of about 25% of fish boats in SE now and seems to be gaining favor. Probably just more available.

Here is a picture of a Fjord w increased fluke area accomplished by welding on more fluke. Quite a few Forfjords can be seen w this modification and that indicates to me there must be a lot of dragging going on. Perhaps having only one fluke in the bottom is more common than most think. The chains in the top of the pic are of a forked forestay.
 

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Capthead said:
A friend of mine was in a hurricane in La Paz, Mexico and he saw many boats drag using the 20 degree multiple anchor system. It looks good on paper but it's still an angle which the anchor wasn't made to perform at it's best.

He used two danforths in a row, one 100' out the other closer in. He didn't move.
Click to expand...

I agree. As the boat swings all or most of the load on the anchors will suddenly be on one. It drags a bit and then the other ...........

As to the two in a row I think that has merit. I'd use an anchor that had a better rep for short scope closer to the boat.
 
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So what happens to your two in a row anchoring when the wind switches 90 or 180 degrees. The idea doesn't appeal to me at all if a wind direction switch is in the cards, and who knows it's not.
 
manyboats said:
For those really interested in multiple anchor anchoring there's an extensive thread in the archives.

Deflin,
If you tie a rope to a tree and pull on it w 100 lbs the tree will feel 100lbs. If you tie the rope to two trees say 75' apart w very little slack and then pull at right angles to the rope (in the center) w another rope and 100 lbs of tension the tension on the trees should be much more than 100lbs.
Click to expand...
I'm sorry Eric, but if there were true, then you would have discovered a solution to the world's energy problem. 100# in and 110# out is the basis for perpetual motion.
 
freshalaska said:
So what happens to your two in a row anchoring when the wind switches 90 or 180 degrees. The idea doesn't appeal to me at all if a wind direction switch is in the cards, and who knows it's not.
Click to expand...

The anchors would rotate 45 degrees and you'd be held by two hooks unlikely to entangle?
 
No, sorry it doesn't. Perhaps Eric meant something else when he said "So if those trees were anchors they would experience more tension than is applied to the rope center at 90 degrees", but how I read it is that the anchors would each experience more than 100#. As your diagram shows, that wouldn't be the case, and the amount of energy to be absorbed is never more than the pull exerted. It just gets distributed differently as the angles decrease.

But I probably misunderstood what Eric meant.

p.s., Sorry, this was a response to a post by MurrayM, which he apparently deleted. That post was:

MurrayM: Eric's right...check out diagram at bottom of page (rock climbing 101);

Bay Area Rock Climbers | Castle Rock State Park | Sanborn Skyline | Mt. Diablo Climbing Areas (http://bayareaclimbers.com/htssrene.html)
 
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Delfin said:
p.s., Sorry, this was a response to a post by MurrayM, which he apparently deleted
Click to expand...

You're too fast today :D

Yup...tried to sneak a post in quickly between getting home from work and walking the dog before he jumped out of his skin with excitement...then realized the post didn't make sense.

What the diagram doesn't address is how much force would be applied to the common point at which all three lines meet. If there is 1000lbs to each anchor, and 1000lbs force being applied to the main rope, how much additional force is being applied because of the tension between the two anchor points? Wouldn't this put more than 1000lbs force to the common point? That's what I was getting at...
 
Delfin said:
I'm sorry Eric, but if there were true, then you would have discovered a solution to the world's energy problem. 100# in and 110# out is the basis for perpetual motion.
Click to expand...

Delfin this is not about energy but just tension. And tension can break out an anchor. I really do think I'm right and it's a function of mechanical advantage. The line pulling sideways on the straight line connected to almost immovable objects can move much more than the ends of the lines connected to the heavy thing or immovable object. Quite likely one could move the sideways line several inches and only pull in the straight lines in a fraction of an inch. Does that compute?

Re multiple anchors ... any time the boat moves laterally the tension on the two rodes will change. One will go up and the other down. And of course the one that goes up stands a chance to drag an anchor that will probably stop dragging when the other rode takes up a significant share of the tension. So constant trading places re position and tension will occur.

One big anchor will probably out perform.
 
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MurrayM said:
You're too fast today :D

Yup...tried to sneak a post in quickly between getting home from work and walking the dog before he jumped out of his skin with excitement...then realized the post didn't make sense.

What the diagram doesn't address is how much force would be applied to the common point at which all three lines meet. If there is 1000lbs to each anchor, and 1000lbs force being applied to the main rope, how much additional force is being applied because of the tension between the two anchor points? Wouldn't this put more than 1000lbs force to the common point? That's what I was getting at...
Click to expand...
Wouldn't be the first time I am wrong, but I am pretty sure that it could never exceed 1000#. I think there is a law of thermodynamics that covers this. That said, I find this pretty confusing as well.
 
manyboats said:
Delfin this is not about energy but just tension. And tension can break out an anchor. I really do think I'm right and it's a function of mechanical advantage. The line pulling sideways on the straight line connected to almost immovable objects can move much more than the ends of the lines connected to the heavy thing or immovable object. Quite likely one could move the sideways line several inches and only pull in the straight lines in a fraction of an inch. Does that compute?

Re multiple anchors ... any time the boat moves laterally the tension on the two rodes will change. One will go up and the other down. And of course the one that goes up stands a chance to drag an anchor that will probably stop dragging when the other rode takes up a significant share of the tension. So constant trading places re position and tension will occur.

One big anchor will probably out perform.
Click to expand...
Well, like you I happen to be of the one big, properly deployed, properly snubbed, properly set single anchor, which is why I carry a big one. As a practical matter, if you were anchored to a Bahamian moor in very high winds, the initial angle between rodes would probably be 45 degrees or so. If the rodes were evenly loaded, the pull on each would be less than if there was a single rode, or at least I think so, and I think Murray's link above says the same thing. However, the rodes wouldn't be evenly loaded - the load would probably bounce back and forth between them, so the advantage would be to have two rather than one hook. If one drags, the other takes up the slack. That's the theory, but like you, I like just worrying about one really good hook rather than dealing with multiple hooks.
 
So with two hooks inline basically on one rode with the pull of the anchors inline with the pull of the boat and then the wind changes 45. 90 or even 180 degrees then your two hook inline to the pull of the boat doesn't look to promising to me. Kind of kills the idea of the second anchor hooked to the back of the first anchor. Least that's how it appears to me. Nothing wrong with one very good anchor and a strong rode. Still I kind of don't like all my eggs in one basket. Thus my style of two or three independent anchors set at the same time. I've had the rodes cross but never a rode tangle with a anchor or two anchors coming together. The way I look at it is as long as the boat doesn't drag then we have successfully weathered the storm.
 
Chain,chain,chaaain...

The harder it blows the more important the chain is ! most of these anchors will dig and hold fine, if there the right size. But they have to be pulled across the bottom almost horizontally "Not on an upward angle!" ,thats where the weight of the chain is so important. Protected anchorages can get crowded when the wind kicks up.You need an anchor to set were you put it ! So Forget about the fortress! "Light weight" will never be a good anchor thing!
And forget about the six foot coated anchor chain they sell at the boat store!
A heavy primary anchor (CQR,Bruce,Rocna)with lots of heavy chain 75-100' and a back up danforth, again lots of chain 25-30' set in a "V" is what I've found works best.I also use a short rope snubber with a chain hook on it to eliminate the chain noise at night.
I Had a Bruce for 20 year( I was suprised it didn't work better than it did) In the northeast we have some anchorages that can be a challenge (hard clay and rubble bottom).I got one one of these weird Rocna's last spring and it seams amazing. Sticks right where you put it,and diggs deep
even in these hard bottoms! its a little tougher to get out of the bottom, But thats a "Good thing"!
 
In a heavy enough blow your all nylon or all chain rode will be almost at the same exact angle to to anchor. Only letting more rode out will be lessen that angle, (in a very strong blow if that is what we are talking about).
 
There are advantages and drawbacks in tying the stern to shore as a method of managing strong wind. Unless you can be certain that the wind is going to come continually from close to the stern, or you can tie shore lines in the direction of all possible wind directions, I would urge some caution.

The practice is called Med-mooring here and is very popular in Europe. It is a great way to anchor in a very deep bay, to pack a lot boats into a anchorage, or just for a change. It is a nice alternative, although generally I prefer conventional anchoring.

The big drawback is that with any cross wind component the sides of the boat present significantly more drag than meeting the airflow head on. The side area is larger and the shape is considerably less aerodynamic than the bow facing into the wind. This increases the load on the anchor significantly. The other drawback is that rocks and obstructions are close to the stern so there is little chance to do anything before damage occurs if the anchor drags. Even a slow drag of the anchor creeping backwards can be a problem.

The side wind component is significant because wind/gusts tend to get funnelled parallel to the shore line. So there is often a much higher local cross wind component than would be predicted from the forecast.

The advantages include that the anchor is typically being pulled uphill. This increases the effective scope far more than people realise. The anchor has a nice constant direction of pull irrespective of the wind direction. A very long scope is usually practical. If you set multiple anchors, each anchor shares the load more evenly than "free swinging" (here, when the boat yaws, almost the full load is alternatively taken by one of the anchors). The final advantage is that the wind is often also lighter close to the shoreline.
 
In a heavy blow the chain will be stretched bar tight , have no catanary and pass high shock loads to the anchor. UGH!

The nylon will seldom be stretched so sight that there is not a bit more give for a puff or a large wave.

Chain that would work well in a blow , 5/8 or 3/4 requires deck hardware too heavy and expensive for most cruisers.

If all you have is chain in a blow a 100lb weight attached so it touches the bottom would be best assistance.
 
The following article, explaining how waves are formed from a surfers perspective, is good for our consideration as it hints at how an anchorages shape and bottom topography could come into play;

How Waves Break

(Even though they're talking about ocean swell, the same physics would apply to wind waves).

Makes one consider there could be another reason why many Alaskan and BC commercial boats have 700' rodes...anchoring further out would put you in deeper water where the waves would be smaller and not as steep, especially where there are steep bottom slopes or shelves.
 
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sunchaser said:
Mark

Those are not protected waters
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I think Mark has experienced them during the cruise ship season approximately between April and August. I'm guessing a wind rose would prove that to be the calmest part of the year.
 
No, May through September.
 
Marin said:
Forecasting in the PNW is pretty good when it comes to what's going to happen, not so good when it comes to when it's going to happen. We almost lost our boat to a lee shore when forecast winds arrived some eight hours before they were supposed to. And we've observed or experienced weather arriving earlier or later than forecast many times.

It's not the forecasters' fault The terrain and wind patterns here can make it difficult to accurately predict a time of arrival.

But based on over three decades of boating and floatplane flying in the PNW, BC, and SE Alaska, we have learned to regard the forecasts in terms of their predicted times the same way drivers in China regard traffic signals-- they are simply suggestions.:)

Particularly problematical can be the forecast times for wind shifts. What started out as the upwind side of a bay may become the downwind side before it was supposed to, and this can cause problems for boats at anchor.
Click to expand...

this surprises me. "We almost lost our boat to a lee shore when forecast winds arrived some eight hours before they were supposed to."

Marin, as an flyer, why you would depend on a wx forecast for the safety of your boat or are you saying you have amended your ways and now know better??
 
I know sombody that said he spent years anchoring in SE AK and it was always calm. I have as well and say it's usually calm. Chris and I went to SE in 03 and it was calm. We later heard it was the best weather in SE in 50 years. That was a magic summer. I've met people that say they went to SE and it rained all the time. They were from down south and of course it was cloudy. Californians equate any weather that's not bright and sunny as rainy.

The anchorages are small and rarely have any fetch. And the weather is cloudy (except in 03) so there's little wind. I tell stories on TF of anchoring in 50 knot winds but that is rare. Not so rare that one need'nt be prepared for it. I anchored in Windfall Harbor on a forecast calling for calm. I should have taken a clue from the name of the place but as it turned out I used my smallest anchor (a 13lb Danforth) based on the forecast but Windfall Harbor was a blow hole. There is a topographical canyon between Clarence Stright and Kassan Bay near the village of Kassan and it did blow 35 knots most of the night. The bottom must have been good and we all know the Danforth is good so we remained attached to Mother Earth. Windfall Harbor is very small though and very narrow so we were too close to the so beach for comfort but we didn't touch.

So I support Marin's notion that weather forecasts are a prediction and nothing to depend on. In our Windfall Harbor experience the calm "weather" did come to pass but localized conditions were not calm where we were due to the topigraphical conditions. In Alaska there's a saying that anyone that predicts the weather is either a fool or a green horn. But on the other hand we'd be fools not to take the weather forecast seriously (and they are very good these days) but be aware that different things can and will happen. And not only for people you see in the news. Younger people tend to think technology will save us from all evil and inconvenience but everything on this earth is relative to notions and facts alike.
 
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Some small anchorages in BC (mostly) and SE Alaska.
More often the beach - shore - rock is just as close as what you see in the picture or closer.
 

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More,
Notice all the calm water and near beaches (rock) ... also the small size of the anchorages.
The only pic that shows an anchorage open to some waves is the first in post #87. That's in Very Inlet behind Foggy Bay. It's open to Dixon Entrance that is open to the Pacific .. but only at high tide .. then the waves come over that saddle in the pic. Remember the 20'+ tides. I the 70s came over that saddle in an OB boat running from 10' seas outside surfing in to Very Inlet. We were stuck there for 5 days.
 

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Looks like at 120 degrees the force or tension is the same on all three places. At 45 degrees the tension is split about evenly to the two anchors. Great for theory but as soon as the boat swings even a small amount one anchor loads up so the supposed advantage of taking the load w two anchors so the tension will be less on one is doubtful. And Delfin .. if you had energy multiplication you'd get 10-1 at 170 degrees. Imagine what it would be at 175 degrees.
 
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