Mooring Snubbers/Shock Absorbers!

[Zagato]

Before I go down the tyre route I was wondering if anyone has used one of these stainless steel shock absorbers whilst mooring - are they any good. Although made from s/s I have seen rusty ones, not sure they would be good rubbing against your hull.

http://www.force4.co.uk/1222/Force-4-Steel-Shock-Absorber-L370mm---Dia--7-0mm.html

The rubber snubbers form chandlers don't seem to be very good for moorings apparently as they break up quite quickly. I wonder if a bigger size would help or maybe these - link to follow.

http://www.unimer-marine.com/products/mooring-snubbers/?L=5

 

[sailorman]

are you refering to a swinging mooring here or marina berth

Before I go down the tyre route I was wondering if anyone has used one of these stainless steel shock absorbers whilst mooring - are they any good. Although made from s/s I have seen rusty ones, not sure they would be good rubbing against your hull.

http://www.force4.co.uk/1222/Force-4-Steel-Shock-Absorber-L370mm---Dia--7-0mm.html

The rubber snubbers form chandlers don't seem to be very good for moorings apparently as they break up quite quickly. I wonder if a bigger size would help or maybe these - link to follow.

http://www.unimer-marine.com/products/mooring-snubbers/?L=5

 

[Zagato]

Swinging mooring for when the Mobo's come piling past

 

[prv]

Do you jerk back on the mooring chain, then? I would have expected it to lift like an anchor chain...

Pete

 

[Zagato]

It can do even if the chain is quite tight as recommended by the the harbour guide. On slack tide when a mobo goes by it can snatch, it can also get quite wavy in a gale even where I am so anything to suppress the snatch is good.

Preventers/Snubbers mentioned in the harbour moorings guide

http://www.conservancy.co.uk/assets/assets/mooring leaflet_2011.pdf

It's rarely wavy but some mobos are a problem... err damn nuisance for many

 

[pvb]

Suppressing the snatch can be quite tricky.

Edit: sorry, thought this was The Lounge...

 

[billcowan]

All the rubber type ones, including old tyres, seam to decay very quickly.
Down in the med, in a lot of marinas where there can be a lot of surge, boats are nearly always moored end on to the quay or pontoon and just about everybody uses the stainless steel spring things.
That said, they do wear out after a few years, and can break, so you are advised to link the ends with a slack bit of safety chain.
But I see a new type in use, which have bolts right through but the spring itself is rubber in compression. at least they dont make a noise.

 

[Billjratt]

Interesting problem for a mooring as the chain would normally absorb the chugs. Problem with the solutions discussed so far is that they will peeyoing - Ie spring the boat back towards it's original position and maybe cause it to override the mooring in certain conditions. (these devices are usually used in lumpy marinas)
Perhaps consider a double junk where one is heavily weighted 3/4 way towards the buoy and the other is slightly shorter?
Don't have a weight half way or the boat will be drawn onto the mooring in calm conditions.

 

[rob2]

It's not really possible to absorb shock if the tide is high so the chain riser is nearly taut, you can only improve the situation by using a longer chain and then you'll swing too wide at low tide. I've always advocated a chain strop made fast on the foredeck, but with a nylon line attached and taken back to the sheet winches as the snubber. It answers the other criteria for anything on a boat - it can be used for more than one application.

Rob.

 

[johnalison]

Both steel snubbers and rubber ones have their uses but they work slightly differently. A steel snubber will add elasticity to the line but absorb very little energy whereas a rubber one will have some hysteresis in the rubber and absorb that energy. A rubber snubber will be more comfortable but a steel one may be a better option for marina fixed lines. A decent sized rubber will last many years but steel ones seem to be favoured in marinas. I doubt if there is much value in having one on a mooring since the catenary of the chain will probably do more.

 

[Zagato]

Thanks for the replies.

This would be the set up although the rope would tie to the mooring swivel not the bottom of the chain as instructed by the Harbour to prevent it getting tangled. They are only about £25, snubber or absorber or free scooter tyre so I'll test them out. The metal absorbers seem popular mainly I think because the others break up so easily but wondered if a larger one or different make might be better!

Preventers here also, scroll down... http://www.conservancy.co.uk/assets/assets/mooring leaflet_2011.pdf

 

[William_H]

Our club for their marina specify Foresheda rubber snubbers. However they do not last all that long especially in harsh sun.
For a swing mooring I think nylon or polypropelene rope is best having lots of elasticity. I have never had chain onto my deck on swing mooring. (just several back up ropes) good luck olewill

 

[alahol2]

Although nylon rope has a lot of stretch we are talking about a relatively short length of rope. Would it be possible to arrange a longer length of nylon, perhaps to a midships cleat or even a cockpit winch? Because of its length it would stay onboard the boat and a shorter length from the buoy would need to attach to it when you moored. Because it would not be subject to chafe over the bow roller it could actually be a fairly light gauge 10 - 12mm rope.

 

[Ric]

When I need to go onto a swinging mooring I use my dual-purpose snubber. Attached is a picture of the Mk1 version. The small hook attaches to anchor chain while at anchor. The larger hook clips to a mooring bouy. I added small inline rubber dampers to the Mk11 version for added damping.

 

[wotayottie]

Interesting problem for a mooring as the chain would normally absorb the chugs. Problem with the solutions discussed so far is that they will peeyoing - Ie spring the boat back towards it's original position and maybe cause it to override the mooring in certain conditions. (these devices are usually used in lumpy marinas)
Perhaps consider a double junk where one is heavily weighted 3/4 way towards the buoy and the other is slightly shorter?
Don't have a weight half way or the boat will be drawn onto the mooring in calm conditions.

Basic physics - anything designed to absorb the energy of a sudden boat movement will give it back in some form or another. So everything will peeyoing ( nice word!) - chain, angel, car tyre, snubber.

I use both a metal spring and rubber snubbers on my pontoon berth. On the swinger I found it useful to rig a 10mm nylon line from the point where the mooring chain came over the bow through several blocks on the toe rail and back to a sheet winch. The mooring chain was still attached to the cleat but with 2 foot of slack. This system worked like a dream and the stretch of the nylon easily and gently absorbed the wash of passing boats.

 

[charles_reed]

I'm in the Med and use spring mooring connections as the rubber ones only last 3 years.

In the case of the OP with a swinging mooring, I'd suggest a length of octoplait or dockline, with a chain connector at one end, of about the same length as his boat to a point below the water (best done @ LW) which will be taut at HW, leave the chain, with as much bight as possible, still attached to the boat. That will employ the elasticity of the textile rode and the catenary of the chain.
Chain over the anchor roller and the textile though one of the bow fairleads, to reduce chafe. Pickup buoy is probably on a line to the chain at present and the chain would be first to be lifted.

 

[jimbaerselman]

Good to see the comments about the value of nylon.

Simple sums. Typical springs and rubber snubbers give you around 25cm. 2m of nylon gives you up to 40cm of spring. Seems like a no brainer if you can deploy enough length of nylon. Difficult when on a mooring because of chafe issues; easy when alongside or stern/bows to.

Of course, if you want to use the full stretch of nylon, the line would have to be light weight - and backed up by a full strength line 20% longer!

 

[FWB]

This is a better arrangement for a swinging mooring, not the same as in your diagram I know but there is no snatching with this set up...
Please excuse sketch !

 

[Zagato]

At a guess we can get around 3' wake coming from some inconsiderate mobo's so springing back does not even factor, the bow will be coming back down with a force to beat any 'peeyoing'! It's all about trying to reduce the hard slamming/snatching which can be quite regular from the traffic coming out of Chichester Marina.

10mm Nylon does seem to be a well used method of absorbing the impact and having it coming over the bow roller to the winches seems to be a common method, think they recommend 2 strand for the job, can't remember! I'll have a look at the boat when next down to see about routing it to avoid the coachroof but may try a spring, rubber snubber or tyre first as it is easier to set up and undo each time i.e. just loop it off the sampson post!

 

[northwind]

At a guess we can get around 3' wake coming from some inconsiderate mobo's so springing back does not even factor, the bow will be coming back down with a force to beat any 'peeyoing'! It's all about trying to reduce the hard slamming/snatching which can be quite regular from the traffic coming out of Chichester Marina.

10mm Nylon does seem to be a well used method of absorbing the impact and having it coming over the bow roller to the winches seems to be a common method, think they recommend 2 strand for the job, can't remember! I'll have a look at the boat when next down to see about routing it to avoid the coachroof but may try a spring, rubber snubber or tyre first as it is easier to set up and undo each time i.e. just loop it off the sampson post!

Alternatively, have you thought about getting a mooring in a quieter area of the harbour?