Breaking Strain

[Adelie]

Originally Posted by MasterMariner

I have indeed on 18' runabout worked great. Also on a 40' custom steel yacht worked great as well. The reason ships don't use it is as stated it is expensive/ too light for large applications but a small boat no problem. Been at anchor in 3' seas no different then nylon as long as the proper scope with chain is used. I'm simply offering a opinion I think it is great stuff for small boats. If you are at anchor in a small boat in over 5' waves with high winds you prob. should be heading for the harbor anyways.

But that's the point. What do you want on your anchor when the waves are over 5' or even 10' and heading for harbor is not an option?

[MasterMariner]

Originally Posted by Adelie

But that's the point. What do you want on your anchor when the waves are over 5' or even 10' and heading for harbor is not an option?

I would still use it because as stated the chain is the shock absorber. I would rather have something strong than shitty nylon. No different then boats using steel cable with a chain pendant at the end tied into an anchor! On a small boat you don't have the storage for cable so why not use spectra rope with the same characteristics.

[DumnMad]

For small waves and average winds the chain is the shock absorber but for storm conditions the nylon with 40% stretch and shackled to your chain is the shock absorber. Who uses steel cable anyhow?

[sabray]

I have substantial chain 220 feet 3/8. Cantinary effect is fine at 20 to 25 knots. I always use a snubber. Because I have seen my lines taught hard in 35 plus. With a line that will not give I would have long ago ripped my deck out. I use a plated rhode spliced to the chain. Very nice to handle and had similar stretch as 3 strand. Bad idea to use spectra.

[barnakiel]

Our rope is 16 mm. It gives better grip under load and wet. It also can take more chafing. The shortest chain we ever used was some 9 meters of 10 mm chain. Our anchors are all 10 kg and upwards.

Our boat is 26', 3000 kg light, we cruised extensively.

b.

[MasterMariner]

Originally Posted by DumnMad

For small waves and average winds the chain is the shock absorber but for storm conditions the nylon with 40% stretch and shackled to your chain is the shock absorber. Who uses steel cable anyhow?

About every commercial fishing boat on the west coast. Bering sea crabbers that anchor in 10-15' seas but what do they know....

[Adelie]

Originally Posted by MasterMariner

About every commercial fishing boat on the west coast. Bering sea crabbers that anchor in 10-15' seas but what do they know....

What works for an 100-150' steel hulled crabber weighing 500,000-1000,000lb would not necessarily work for a 35' fiberglass sailboat weighing 12-15,000lb full loaded. And vise versa. Scale effects will do that to ya. Try again.

[DumnMad]

Originally Posted by MasterMariner

About every commercial fishing boat on the west coast. Bering sea crabbers that anchor in 10-15' seas but what do they know....

Even with a steel boat you wouldn't go cruising with that sort of gear.

[rebel heart]

Originally Posted by MasterMariner

About every commercial fishing boat on the west coast. Bering sea crabbers that anchor in 10-15' seas but what do they know....

At least on sport fishers (that I work on), it's a pretty acceptable to do 2:1 scope and nonsense like that. We use crappy anchors made of scrap metal because we're always dropping the pick in some rocks because that's where the fish are (if we're not offshore).

But there's two masters on board and a couple of deckhands. Always people up and about moving and watching. The normal cruising boat can be left unattended for days and even while attended at night everyone is (hopefully) sleeping.

300' of chain and a 50' three strand snubber for me, hooked to a 65lb anchor. Mouse the hell out of the shackle. Two GPS anchor alarms and I sleep like a baby.

The first time I took a sportfisher out (~30 passengers) I was in 100' feet of water and we were setting anchor. I watch the deckhand pay out enough until it hit the bottom, he let out maybe another 20', then snubbed the line on the posts and walked to the back to smoke a cigarette and talk **** with his buddy.

[MasterMariner]

Originally Posted by Adelie

What works for an 100-150' steel hulled crabber weighing 500,000-1000,000lb would not necessarily work for a 35' fiberglass sailboat weighing 12-15,000lb full loaded. And vise versa. Scale effects will do that to ya. Try again.

So explain it to me than since you seem to think you know what you are talking about.

[MasterMariner]

Originally Posted by DumnMad

Even with a steel boat you wouldn't go cruising with that sort of gear.

I take it you know from what
Expirence?

[Adelie]

Originally Posted by MasterMariner

So explain it to me than since you seem to think you know what you are talking about.

As a starting approximation assume that a nylon rode should have a breaking strength about the same as the displacement of the vessel.

I found data on 160mm (6-1/4" dia) 8-strand nylon braid indicating a minimum breaking strength of 414,000kg (910,000) and 128mm (5") having 266,700kg (587,00lb) . Nylon rope - Langman Ropes

So for the size and weight of vessel we are talking about nylon would be have a serious storage problem.

Steel cable with 604,000 to 850,000lb breaking strength would be 2-1/2" to 3" in diameter. Having half the diameter means the wire take less than 1/4 of the volume to store. http://www.wcwr.com/catalog/webcat.pdf.

So that's part of the attraction of wire. Also the wire has vastly better abrasion resistance so that is another big attraction.

The down side to the wire is the lack of give in the wire. Lets assume that snatch loads instead of being 10% of breaking strength as with nylon, they are more like 40% with a non-stretching material like steel wire.

To live with this at least 2 things have to happen:
1. The belaying point has to be massively built. In a steel boat this is much more economically accomplished, at least relatively.
2. When the vessel is anchored, there is always an anchor watch on duty. When the weather deteriorates sufficiently, the engine is run in forward to take a significant amount of the strain off the rode thus reducing the snatch loads. The boats are only un-manned in very protected waters or when at dock.

Being comparatively non-stretching also means that the steel does not generate as much heat when it stretches and it is less susceptible to heat damage.

[MasterMariner]

Originally Posted by Adelie

As a starting approximation assume that a nylon rode should have a breaking strength about the same as the displacement of the vessel.

I found data on 160mm (6-1/4" dia) 8-strand nylon braid indicating a minimum breaking strength of 414,000kg (910,000) and 128mm (5") having 266,700kg (587,00lb) . Nylon rope - Langman Ropes

So for the size and weight of vessel we are talking about nylon would be have a serious storage problem.

Steel cable with 604,000 to 850,000lb breaking strength would be 2-1/2" to 3" in diameter. Having half the diameter means the wire take less than 1/4 of the volume to store. http://www.wcwr.com/catalog/webcat.pdf.

So that's part of the attraction of wire. Also the wire has vastly better abrasion resistance so that is another big attraction.

The down side to the wire is the lack of give in the wire. Lets assume that snatch loads instead of being 10% of breaking strength as with nylon, they are more like 40% with a non-stretching material like steel wire.

To live with this at least 2 things have to happen:
1. The belaying point has to be massively built. In a steel boat this is much more economically accomplished, at least relatively.
2. When the vessel is anchored, there is always an anchor watch on duty. When the weather deteriorates sufficiently, the engine is run in forward to take a significant amount of the strain off the rode thus reducing the snatch loads. The boats are only un-manned in very protected waters or when at dock.

Being comparatively non-stretching also means that the steel does not generate as much heat when it stretches and it is less susceptible to heat damage.

As I said before that is what the CHAIN is for.

[Adelie]

Originally Posted by MasterMariner

As I said before that is what the CHAIN is for.

Are you saying chain stretches significantly?

[sabray]

Ooovay. Your being given experienced advice and denying it. I have been there done shock loads. It can be bad enough even with stretchy line. So bad that 3 strand heats up and gives way. Yes. Saw 3/4 inch line burn through. It cooked because the shock is energy. The energy needs to transfer. With all cable or chain the energy is transferred to the fittings and the deck. With 3 strand the energy is transfered by abrasion to the line. You want to find a balance between chafe and shock. Yes I will power into a gail while anchored to relieve shock loads. Yes I oversize my plaited line. Yes I add chafe gear that is able to disipate heat. All if this is meant to transfer energy created by the waves or wind to something other then a single point. Hope that helps explain why the majority of us transfer wave energy to a line with a good ability to transfer energy to friction.