Bruce Anchor Would Not Set

[nigel1]

Bash beat me to it, for any anchor, I let it soak for a while before attempting to test it by going astern, (provided of course you are not immediately dragging onto something nasty)

[psneeld]

Originally Posted by Cormorant

Just curious about all this. . . . Has anyone ever quantified the setting/holding characteristics of combo chain/nylon rodes? Any comparative tests out there?

Is 75 or 30 feet of chain really better for setting than 15? I think the answer is Yes, but how much better? How much closer to horizontal do you get the anchor? Even with all-chain rode when you're setting the anchor you're pulling the whole rode near-straight. So we're talking a difference of maybe a degree or two?

How does the chain diameter/weight change setting characteristics? (I.e. what's better: 30 feet of 3/8" or 40 feet of 1/4"?)

I imagine there's a sweet spot in the calculation if you can take into account length of chain, weight of chain, size of boat, and overall scope of rode. This is assuming you want to maximize setting/holding but minimize weight of your ground tackle, for instance if you don't have a windlass and need to haul it all by hand.

Just curious if anyone ever did the numbers on all this.

I think one of the problems is how people and tests refer to the extremes...

Most power cruisers will NEVER sit out hurricane conditions...why would they when they can outrun it? Sure...you might...but you might sink with a much greater probability than riding out a hurricane yet few if any carry a trash pump capable of keeping them afloat.

back to anchors...some say NEVER use a lunch hook..only your GIANT primary...well that's a great idea...but not the only one...again..weather in many locations is never "sudden" on most days... if ever... so planning ahead isn't that hard unless you are specifically "weather challenged". So the same theory can apply to anchors and rodes in general. What works 99 percent of the time may not under storm conditions. Plus what may work in a protected anchorage amy not in an exposed one..same with bottoms. So less than storm anchors/rodes may be used with the proper precautions.

So predicting what anchor may hold or what rode and length is best is a roll of the dice. But there seems to be a common thought...the heavier the better in anchors and some will add that the more chain you got lying down there the better (with the exception is swing room or storm situations where it's better to have the weight in the anchor cause it's the only thing touching)

[capn_billl]

I use 30' of 3/8" BBB chain on my Bruce. The best catenary is to have the chain be 1/3 - 1/2 the total rode. So in 8' - 10' of water with 60' - 80' of rode, (1:7), my 30' is perfect.

I mostly anchor in mud over clay, I've never had a problem setting the Bruce, but I have a lot more chain, and I play the rode out slowely, and back down after it has had time to sink.

I usually tug the rode with my hand near the end and feel the anchor drag, then bite. when I can no longer pull it by hand then I let the boat's weight hit the rode, and put it in reverse. If I can keep pulling it by hand it will never hold the boat. It's tim eto pullit back up, check for fouling, and re-place it.

I've found it takes longer to set, (longer drag times), if I back down too quickly.

[terrygandh]

We have a 42ft trawler and have cruised for 5 years. We use a 30 kilo Bruce with 200 ft of chain. We have drug 3 times. Two times a front came in and the wind shifted 180 degrees. The anchor reset both times without any assistance from me. The third time i was on a rock shelf in Maine. We have 200 ft of chain. I don't think you can have too much chain.

[Cormorant]

Originally Posted by capn_billl

The best catenary is to have the chain be 1/3 - 1/2 the total rode.

Bill -- where does that rule of thumb come from? Is it conventional wisdom, or the result of tests, or someone's physics calculations? I'm just trying to sort out fact and fancy here. . .

I did come across this bit after Googling around:

Earl Hinz, a former aeronautical engineer and inveterate Pacific Ocean sailor, in his work The Complete Book of Anchoring and Mooring, says the chain lead should weigh at least as much as the anchor whose weight it is supplementing.
From his experience, he has determined that the length of the chain lead has nothing to do with the depth of the water or the length of the boat. He suggests using the following formula to help you determine the minimum
length of chain lead you will need:

Minimum Anchor weight in lbs.
length of = x Anchor materials factor
chain lead Unit weight of chain,
. lbs./ft.

Minimum length of chain = Anchor weight in lbs. X anchor material factor / unit weight of chain in lbs per foot

(edited to make that formula a bit clearer.)


Anchor materials factor = 1 for steel and 1.6 for aluminum

[psneeld]

Originally Posted by Cormorant

Bill -- where does that rule of thumb come from? Is it conventional wisdom, or the result of tests, or someone's physics calculations? I'm just trying to sort out fact and fancy here. . .

I did come across this bit after Googling around:

Earl Hinz, a former aeronautical engineer and inveterate Pacific Ocean sailor, in his work The Complete Book of Anchoring and Mooring, says the chain lead should weigh at least as much as the anchor whose weight it is supplementing.
From his experience, he has determined that the length of the chain lead has nothing to do with the depth of the water or the length of the boat. He suggests using the following formula to help you determine the minimum
length of chain lead you will need:

Minimum Anchor weight in lbs.
length of = x Anchor materials factor
chain lead Unit weight of chain,
. lbs./ft.

Minimum length of chain = Anchor weight in lbs. X anchor material factor / unit weight of chain in lbs per foot

(edited to make that formula a bit clearer.)


Anchor materials factor = 1 for steel and 1.6 for aluminum

I would have to say the same about this formula..where did he come up with it??? What's his testing method? Where's his science?

I still go back to every test or formula I have seen or read doen't include all the vaiables for all situations EXCEPT max pull/holding power for a given rode and bottom. Wow...how often will I encounter exactly the same?

Rule of thumb...use your system...whatever you have...learn to trust it or keep changing / trying till you can. After that it's all just a guess or advertising.

[Cormorant]

I agree -- I'd like to see all the work that led Earl Hinz to that formula. Just cause it looks scientific doesn't mean it's true. . . .

But somewhere there is a truth that can be discovered, or at least an optimum setup for 98% of your cruising conditions. A lot of what people aver as fact or strongly held opinion rests on a foundation of "that's how it's always been done." Or "that's what we all agree on." I just wanted to drill down a bit.

[SailFastTri]

I'm sure someone has posted this before in many of the endless anchor threads, but this concept of catenary affecting holding is a proven fallacy, except in very deep anchoring situations. It is proven by engineering calculations at this linked site Tuning an Anchor Rode

The benefits of chain for 99% of typical anchoring situations for pleasure boaters and cruisers are:
1) chafe and cut-resistance
2) stops "wandering" and drifting around aimlessly when the wind dies
3) works and stows better with windlesses

The negatives are obvious -- more weight in the bow, more difficult to handle by-hand without windlass, expense in most cases.

A lower angle of pull helps setting and holding. This is achieved by scope. Yes, chain can lower the angle of pull through catenary thereby simulating scope, but under high loads (when you really do need to be concerned about holding) the catenary of your chain may become almost non-existent, and scope is all that matters.

In a dynamic situation when you also need to worry about snatch loads, the calculations on the linked page prove that rope (or chain combined with long elastic snubber) actually holds better than all-chain.

[psneeld]

Originally Posted by SailFastTri

I'm sure someone has posted this before in many of the endless anchor threads, but this concept of catenary affecting holding is a proven fallacy, except in very deep anchoring situations. It is proven by engineering calculations at this linked site Tuning an Anchor Rode

The benefits of chain for 99% of typical anchoring situations for pleasure boaters and cruisers are:
1) chafe and cut-resistance
2) stops "wandering" and drifting around aimlessly when the wind dies
3) works and stows better with windlesses

The negatives are obvious -- more weight in the bow, more difficult to handle by-hand without windlass, expense in most cases.

A lower angle of pull helps setting and holding. This is achieved by scope. Yes, chain can lower the angle of pull through catenary thereby simulating scope, but under high loads (when you really do need to be concerned about holding) the catenary of your chain may become almost non-existent, and scope is all that matters.

In a dynamic situation when you also need to worry about snatch loads, the calculations on the linked page prove that rope (or chain combined with long elastic snubber) actually holds better than all-chain.

2 things...the first that rope holds better is only assuming a substantial surge which smart cruisers try to avoid when picking hurricane holes or the inability for all chain users to provide adequate stretching during shock loading
the second is that many have "shown" "proved" through geometry that scope in excess of 7:1 is just insignificant in decreasing angle of pull.

[rtbates]

You sure there isn't and old highway under the water? haha You should have AT LEAST as much chain as length, ie, 33 feet..Should help the set...

[Cheechako]

"...any attempt to back it down and set it will simply result in you towing the anchor around the anchorage."
This has been my experience with Bruce anchors in sand for sure. Great anchor in a rocky bottom though, but as mentioned, a big propensity to wrap the rode around a fluke tip. For Florida I would be using a different anchor.
"It is proven by engineering calculations at this linked site ..." Engineering calc's are great, but they aren't necessarily correct until proven with testing, and trust me ( i am an engineer) there are so many varibles in the real world that the calcs are often not correct until revised many times. The engineer's motto: "revise, revise... let no numbers evade thine eyes" :>)

[bobconnie]

Well I believe there is no reason to use any amount of chain less then, the amount that the bow of your boat will carry !! and if I can I use all chain !!! why not ??? if you boat has a manuel windless, then maybe as much chain as the boats overall lenght will be all you you can handle! For me if I have a Drum style windless I use 100 ft of chain and back it up with cable LOL but I like to stay in one place when I anchor up LOL but when my No1 Delta wont set, then danforth go's out ! but im old fashion I guess. just my 2 cents Bob and Connie

[gonesail]

ok it was a typo .. i have 35 feet of chain on the bruce 33 with 12000 lb. boat .. and could not let it soak cause the wind was up. i did not back down on it but saw it was skipping along the sand .. had about 60 feet of rode out in 8 feet of water. already passed thru daytona and in melbourne

[AnchorageGuy]

Originally Posted by gonesail

ok it was a typo .. i have 35 feet of chain on the bruce 33 with 12000 lb. boat .. and could not let it soak cause the wind was up. i did not back down on it but saw it was skipping along the sand .. had about 60 feet of rode out in 8 feet of water. already passed thru daytona and in melbourne

8 feet of water and assuming that the anchor roller is at least 4 feet off the water and minimum scope should have been at least 80 feet, and if the wind was up probably should have been at least 90 to 100 feet or more. So maybe.......

[downunder]

Originally Posted by Cormorant

Just curious about all this. . . . Has anyone ever quantified the setting/holding characteristics of combo chain/nylon rodes? Any comparative tests out there?

Is 75 or 30 feet of chain really better for setting than 15? I think the answer is Yes, but how much better? How much closer to horizontal do you get the anchor? Even with all-chain rode when you're setting the anchor you're pulling the whole rode near-straight. So we're talking a difference of maybe a degree or two?

How does the chain diameter/weight change setting characteristics? (I.e. what's better: 30 feet of 3/8" or 40 feet of 1/4"?)

I imagine there's a sweet spot in the calculation if you can take into account length of chain, weight of chain, size of boat, and overall scope of rode. This is assuming you want to maximize setting/holding but minimize weight of your ground tackle, for instance if you don't have a windlass and need to haul it all by hand.

Just curious if anyone ever did the numbers on all this.

Most long distance cruisers and those who are in areas with coral consider nothing else but all chain.

If anly anchoring in mud or sand can get away with rope/chain.

If winch matched to chain don't have issue of chain/rope to deal with.