Chain Versus Rope Scope ?

[Rakuflames]

Originally Posted by DutchTreat

Dockhead,

Was I wrong in my previous post? I still have to think at least 50% of the weight of the chain will be putting downward pressure on the anchor in the case that the chain is pulled tight. This has to add to the positional strength of the anchor as opposed to, let's say, a nylon rope which would not have much weight in water?

I just have to think in that case an all chain rode still has that advantage.

It is the cantenary in the chain that will help hold your anchor. It flexes horizontally, absorbing some of the stress from the boat bobbing and weaving. The reason to have more scope is to allow that cantenary to flex. I have to agree. There are pros and cons to all chain vs. chain/rope rodes, but it doesn't change the need for adequate scope.

[stevensuf]

Id go with all chain and some rope for emergency situations, 50m min chain.

[JoeFish]

Originally Posted by jeremiason

I swam from the bow and followed the rode, after about 75 feet, the chain took a 90 degree turn in the sand and ran to the anchor. In other words, my 37,000 lbs. boat was riding along in 25 knots of wind, using the weight of the chain only. So regardless of what the experts say, at least in this instance the weight of the chain did help.

Look the fact is, chain lasts longer, won't caffe, provides more weight for cantanary and with a proper windless is easier to handle...

In my humble opinion, if your boat can handle the weight... Chain is the way to go.

After a few years of this I'd have a close look at your hull deck joint up in the bow.

A brait line will absorb much more of the loads that are otherwise transferred into the hull by all chain. The catenary disappears in any real load (sorry 40 knots is not a blow in my book, try 80), and all that load is going directly into your hull and deck hardware.

In any real blow you will have a lot of gusty conditions. This is borne out by stripcharts I maintained in two big tropical storms in the Bahamas one year. I rode those out in a 19,000 lb wood 40' yawl with tons of windage using 60 feet of chain and brait rode with a 60# danforth high tensile anchor at 8:1. I didn't drag an inch with sustained winds between 50-70 with gusts to 87 knots.

When the hard gusts hit you could feel the boat surge back on the rode. When it was at it's worst I was on deck to check everything. The rode was BAR TAUGHT in the gusts and the brait was hot to the touch, but more than 100 feet of brait acted like a giant shock absorber when the gusts hit dramatically reducing loads on the deck hardware.

These anchoring strategies were taught to me by Olin Stephens years ago and I have nothing but strong experience with these techniques to back up his advise.

Other considerations; All chain rode also adds a HUGE amount of weight to the boat and most are not going to shift this weight to the bilge amidships when they aren't at anchor. This weight forward increases the yachts pitching moment and this radically impacts performance and comfort aboard. This weight is your enemy in steep following seas and is a huge detriment in a rollover scenario. Especially if it breaks free.

There are a lot of people who say that weight doesn't matter but the fact of the matter is, weight does matter, and it matters a lot. It matters even more where it's located.

I've never had use for more than 60 feet of chain and I have two chain rodes, one 25' length and another 60' length. The latter lives amidships in the bilge secured to the deadwood unless it's in use, and I can count the times it's been used on 10 fingers.

It's been linked before but the conclusions drawn in Peter Smith's article cannot be ignored: Catenary & Scope In Anchor Rode: Anchor Systems For Small Boats

Weight is better put into the anchor, not chain. Chain has only one legitimate use and that's chafe resistance and most still employ far more chain than necessary.

[wolfenzee]

As I know people who have lost thier boat because thier rode was cut by the propeller of another boat, for that reason alone I will stick with all chain (I wouln't bother to argue holding power or the fact my boat sails better with the extra ballast in the chain locker..a pecularity of it's design). I will make a long double/bridle snubber which ill absorb shock and distribute stress evenly.

[webejammin]

Originally Posted by wolfenzee

As I know people who have lost thier boat because thier rode was cut by the propeller of another boat, for that reason alone I will stick with all chain (I wouln't bother to argue holding power or the fact my boat sails better with the extra ballast in the chain locker..a pecularity of it's design). I will make a long double/bridle snubber which ill absorb shock and distribute stress evenly.

Just wondering what the average depth is in your anchorages you frequent ?

[JoeFish]

Originally Posted by wolfenzee

As I know people who have lost thier boat because thier rode was cut by the propeller of another boat, for that reason alone I will stick with all chain (I wouln't bother to argue holding power or the fact my boat sails better with the extra ballast in the chain locker..a pecularity of it's design). I will make a long double/bridle snubber which ill absorb shock and distribute stress evenly.

A small 5# ball on a pennant clipped to the rode with a carabiner will hold the top of the rode well under water. That will keep it well out of the reach of other propellers while eliminating all the problems you hope to solve with countless lbs of chain in the forepeak.

If the boat sails better bow down (as mine does) you can easily re-balast with lead pigs forward of the mast with all that weight low and secured to the keel where it's not going to easily break free or shift in a seaway.

Just a thought.

[wolfenzee]

The man who put all chain on this boat has sail all sorts of boats all over te ocean, including skippering a couple of 100'+ schooners...he is the sort you look to for blue water cruising advice. Mu chain locker is set up o I could use either or both. I sleep better with chain.

[roverhi]

You have fun with your rope anchor rode in a blow. I'll stick with the peace of mind chain gives me. I've ridden out three tropical depression/former hurricanes and 2 weeks of winds gusting beyond 50 mph. If I hadn't been aboard and constantly changed the position of the chafe from the bowchocks, the boats would have been up on the rocks within a couple of hours. Rope just can't handle chafe under load and you can forget chafing gear. The stretch of the rope pulled it through the chocks as fast as I could stuff it in. Luckily I had enough rope in the tail to outlast the storms.

The one I rode out with chain was no problem. Had a rope pennant attached to the bobstay fitting and the boat did just fine.

[wolfenzee]

Originally Posted by webejammin

Just wondering what the average depth is in your anchorages you frequent ?

At present I carry 300' of chain (also 250' of rode w/25' of chain) ...scope I use depends on the bottom, weather and anchor, useually I use a 22 lb. Bruce primary anchor, but also have a 20 lb CQR and 45 lb Forfjord (and 15 lb northill I run off the stern when anchored in a river as a seconond anchor).

I am not stubbornly one way or the other and as rode is all ready to go, just have to swap connections, or better yet hook up my secoundary (CQR).
The best feature about rode...is being able to check your scope without a depth sounder....just look.
First time I anchored I had no idea (because I didn't trust the newly installed depth sounder)...the next morning I dug out the lead line and discovered I had spent the night anchored with a 10:1 scope useing 45lb forfjord storm anchor in a flat calm/lee of a 60' cliff.

[webejammin]

Originally Posted by wolfenzee

At present I carry 300' of chain (also 250' of rode w/25' of chain) ...scope I use depends on the bottom, weather and anchor, useually I use a 22 lb. Bruce primary anchor, but also fave a 20 lb CQR and 45 lb Forfjord.

We are hopeing to sail to the San Juan islands and Seattle this summer and wondered how deep your gunkholes are normally ?

[JoeFish]

Originally Posted by webejammin

We are hopeing to sail to the San Juan islands and Seattle this summer and wondered how deep your gunkholes are normally ?

You can be in anything from 15-60 feet depending on the location.

[webejammin]

Originally Posted by JoeFish

You can be in anything from 15-60 feet depending on the location.

I'm guessing 15' at low tide and 60' deep at high tide. At 60 ft deep that's 420' of chain at 7to1 or do you use chain and rode ?

[JoeFish]

Originally Posted by roverhi

You have fun with your rope anchor rode in a blow. I'll stick with the peace of mind chain gives me. I've ridden out three tropical depression/former hurricanes and 2 weeks of winds gusting beyond 50 mph. If I hadn't been aboard and constantly changed the position of the chafe from the bowchocks, the boats would have been up on the rocks within a couple of hours. Rope just can't handle chafe under load and you can forget chafing gear. The stretch of the rope pulled it through the chocks as fast as I could stuff it in. Luckily I had enough rope in the tail to outlast the storms.

The one I rode out with chain was no problem. Had a rope pennant attached to the bobstay fitting and the boat did just fine.

I don't just play a physicist on TV, I actually am one.

I've been using samson ice cover over the rode passed through fire hose for chafing gear for years and have yet to experience a problem. I have seen 80+ knots in an anchorage on a 20,000# boat and would never want all chain.

Think of it this way; Anchor and rode are a complete system and that system works best when the weight in that system is concentrated on the bottom.

In high load situations the catenary is gone, full stop. Any advantage the chain's weight provided in terms of holding power is gone and the majority of the weight in that anchoring system is now taught between the anchor and the boat.

In gusty conditions over 50 knots the boat is spending most of it's time at 70-80% of the elongation of a rode like Yale Brait, and that remaining elongation not only saves load on the deck fittings you tie off to, it reduces peak loading on the anchor.

At the same wind strength an all chain rode has virtually no remaining elongation so the task you are asking of the anchor is far more difficult as even in 50 knots there is no remaining catenary to speak of to absorb loading in the gusts.

Put the weight where it will actually do you some good.. in the anchor.

You're more than welcome to use all that chain is you want, just anchor downwind from me in a blow.

[s/v Jedi]

Originally Posted by webejammin

I'm guessing 15' at low tide and 60' deep at high tide. At 60 ft deep that's 420' of chain at 7to1 or do you use chain and rode ?

7:1 ??!! with chain at 60' depth ??!!

at 60' of depth I set 250' of chain and keep the last 50-100' in the locker. I can take 60 kts wind with that without a thought as it's actually a bit more scope than the 3:1 that I know will hold me

cheers,
Nick.

[Bash]

I'm no physicist, just a sailor.

When naval ships give up their chain in favor of heavier anchors backed up with nylon, I'll do the same.

Until then, I'll sleep better with all chain.