Storm Anchor Snubber

[CarlF]

While getting ready for the hurricanes, I realized that my snubber is the weak spot in my 3/8" G4 chain anchoring system. For normal situations, I use a relatively small diameter nylon snubber designed to give a lot of stretch in normal winds. It would break or melt from internal friction quickly in a real storm.

I don't have a chain stopper but the ones I see are lower breaking strength and - worse - provide no shock relief to the chain.

I guess I could just get a MUCH bigger piece of nylon. I've also seen some talk of using dyneema as a snubber. Less stretch than nylon but better than a stopper. More chafe resistant and not as prone to internal melting.

But how would you secure it to the chain? Grade 70 chain hooks exist for trucking but they have a pin that looks like it would chafe. Maybe a soft shackle?

Ideas?

[captstu]

I used a wichard chain stopper on hurricane Wilma. Put out $100 feet of 5/16 chain in 8 feet of water on a 43’ x 25’ beam cat. Wichard chain grabbers are unbreakable.

The chain grabber was attached to the chain, but both strands of 5/8’ nylon and the backup bridle attached with a rolling hitch broke. The windless pulled out of its backing plate, actually the windless shelf pulled out of the Boat.

Some sale with more years of experience than my 50 had suggested I put a stop knot in the chain just before the hard point where it attached to the Boat. The factory hard point pulled out.

The overhand knot jammed in the hawse pipe and saved the boat from destruction.

These chain stretched but did not snap. The Boat took no other damage except I had attached a Fortress F-39 to the trip point on my standard 25kg Danforth. When the eye passed and the wind veer hit, it looks like the Boat ran down the chain and tripped the Danforth. The Fortress, set 6’ further forward in front of the Danforth bent itself into a pretzel but held until the Danforth reset. It took quite a while to winch them both up.

Moral, Wichard chain grabbers don’t fail. Buy one and you can be sure something else is the weak point,

I’ve also used a Kong - seems just as strong, but easier to use.

[Dockhand]

You should pick up a copy of August & September issue of SAIL, they cover anchoring in all weather conditions. It goes into how length, diameter of rode, type of rode and how all chain doesn't absorb energy when the wind get to hurricane strength.

[conachair]

Originally Posted by Dockhand

You should pick up a copy of August & September issue of SAIL, they cover anchoring in all weather conditions. It goes into how length, diameter of rode, type of rode and how all chain doesn't absorb energy when the wind get to hurricane strength.

Which is actually wrong IMHO. Cateneries can and do absorb masses of energy - if the anchor stays set it has to go somewhere.

The energy transfer just happens in increasingly shorter distances so the force goes through the roof.

[noelex 77]

Originally Posted by CarlF

I don't have a chain stopper but the ones I see are lower breaking strength and - worse - provide no shock relief to the chain.

Chain stoppers are typically manufactured to have a SWL greater than the SWL of the chain they are designed for. The weak point is the deck attachment. On many boats the deck attachment point, or the deck itself is nowhere near as strong as this, but this can sometimes be beefed up by adding extra fibreglass and large backing plates etc.

An alternative to the chain stopper is a short length of strong line like Dyneema. Once again, the attachment point (in this case the bow cleats) is the weaklink and generally these will be less strong than the chain or Dyneema, unless modified.

A dyneema strop is not the same or quite as good as a chain stopper. A chain stopper works like a one way clutch. The Dyneema strop is just an attachment point.

As you point out, both of these systems have no stretch so are only the last line of defence. Ideally you want a stretchy snubber attached all the time while anchored in bad conditions. Dyneema is not suitable for this as it has minimal stretch, but some boats are combining Dyneema with nylon to achieve a snubber that has stretch (the nylon component) combined with chafe resistance (the Dyneema component) in areas where the snubber will be subject to most chafe. This produces perhaps the ultimate snubber.

For strong conditions you need a reasonably long snubber. Something in the order of 10-15m of nylon seems the best solution for most boats. If going to thicker nylon, it will need to be on the longer side. There is some danger if the snubber becomes too long, especially if relatively thin, that excessive elasticity can increase the sheering, so some some experimentation is needed. Most snubbers do not have enough elasticity rather than the other way around.

For severe conditions the risk of a snubber breaking is very high so multiple snubbers are needed. There is a delicate balance between a snubber that is strong enough and one that is thin enough to have enough stretch.

For connection between the chain and the snubber I think Dyneema soft shackles are the best answer.

So for extreme conditions have lots of scope, multiple preferably new 10-15m snubbers with chafe protection and finally have the chain secured to a strong point as a last resort. If you will be on board and not tied to mangroves etc consider how you would release this system in an emergency such as another boat dragging down on your vessel. This will not be possible at the height of a very severe storm, but may be your best option in the lead up or aftermath or if conditions are not as severe as predicted.

[capngeo]

Snubbers are great and fine, but my choice for shallow water heavy weather anchoring is to use a kellet in the rode to absorb shock loads; additionally a good strong attachment point incorporated into the stem (which traditionally is the strongest area of a hull).

[Dockhead]

Originally Posted by CarlF

While getting ready for the hurricanes, I realized that my snubber is the weak spot in my 3/8" G4 chain anchoring system. For normal situations, I use a relatively small diameter nylon snubber designed to give a lot of stretch in normal winds. It would break or melt from internal friction quickly in a real storm.

I don't have a chain stopper but the ones I see are lower breaking strength and - worse - provide no shock relief to the chain.

I guess I could just get a MUCH bigger piece of nylon. I've also seen some talk of using dyneema as a snubber. Less stretch than nylon but better than a stopper. More chafe resistant and not as prone to internal melting.

But how would you secure it to the chain? Grade 70 chain hooks exist for trucking but they have a pin that looks like it would chafe. Maybe a soft shackle?

Ideas?

Chain stopper and snubber perform two totally different functions. You need the chain stopper (or Dyneema strop as Noelex suggested, or a wire strop, or a chain strop) to belay the chain. The chain has to be attached to the boat somehow, and this attachment should be as strong as the chain, or there is no point to the chain's strength.

But that won't absorb energy and dampen snatch loads. You are right to be questioning your thin short snubber. Use a thick long one. Thicker rope won't stretch as much for a given force as thinner rope. Make up for that by making it longer. My storm snubbers are 100 feet long; normal one is 10 meters. The storm ones are 25mm nylon.

Also in storm conditions, it's very good to use TWO of them, and protect them fanatically against chafe.

As to securing it to the chain -- take your pick. Soft shackles through a spliced eye at the end work great. Some people swear by chain hooks, but I don't personally see the point to them, and they can fall out (you'll have to make up your own mind about that). I personally just use a rolling hitch -- KISS. Rolling hitch was MADE for this kind of situation -- the snubber kind of melds with the chain, and I've never seen one come loose in decades of cruising. Takes all of three seconds to tie.

[Dockhead]

Originally Posted by captstu

I used a wichard chain stopper on hurricane Wilma. Put out $100 feet of 5/16 chain in 8 feet of water on a 43’ x 25’ beam cat. Wichard chain grabbers are unbreakable.

The chain grabber was attached to the chain, but both strands of 5/8’ nylon and the backup bridle attached with a rolling hitch broke. The windless pulled out of its backing plate, actually the windless shelf pulled out of the Boat.

Some sale with more years of experience than my 50 had suggested I put a stop knot in the chain just before the hard point where it attached to the Boat. The factory hard point pulled out.

The overhand knot jammed in the hawse pipe and saved the boat from destruction.

These chain stretched but did not snap. The Boat took no other damage except I had attached a Fortress F-39 to the trip point on my standard 25kg Danforth. When the eye passed and the wind veer hit, it looks like the Boat ran down the chain and tripped the Danforth. The Fortress, set 6’ further forward in front of the Danforth bent itself into a pretzel but held until the Danforth reset. It took quite a while to winch them both up.

Moral, Wichard chain grabbers don’t fail. Buy one and you can be sure something else is the weak point,

I’ve also used a Kong - seems just as strong, but easier to use.

What a story!!

Very glad to hear your boat survived!

You should send the Fortress to the Fortress guys. Knowing them, I guess they'll make a video out of it, and send you a new anchor!


Your story is a perfect example of why you should NEVER rely on a nylon snubber as the only attachment of the chain to your boat!

[captstu]

The folks at Fortress promptly replaced the damaged parts under their lifetime unrestricted warranty (they and Zippo just fix it if I break it). They were even thoughtful enough to express pleasure at saving my boat from a storm that destroyed so many neighbor boats that were double or triple anchored in the usual.

Finally, they saw a similar posting a few years ago and sent me a Fortress hat.

Tandem anchoring has rescued a non dragging Boat a few times, including once when I threw a line to a lager dragging Boat in a squall and the Danforth- Fortress random held us both.

Easy to recover, the windless lifts and stores the Danforth (or any ploughing like an hot of your choice) and I reach the 5’ length on the ploughing trip point and just pull the aluminum Fortress on deck.

Sleep well