The great anchor debate - whats are take

[roly_voya]

Re: Two anchors

Yes I think you are quite right, very often in sailing products are brought out without anything that most industries would recognise as through assessment and testing in the conditions they will be used in. Some stuff is, to an extent tested by giving it to racers in something like the round the world races and to the extent thet that is relevent to cruising may be a good thing. Cant see them having much chance to test anchors though, even if they where prepared to take a range of different sizes and patterns on board. So yes if you buy new desinged stuff you probably are part of the product development process! But then half the suff we use is not a 'normal' comercial product its something made almost by hand by an enthusiast (probably a sailor) in a small workshop because they thing they can make something better than others have done it. To make a comparison to flying its like being a pilot in the barnstorming days. It does have a positive side, would we really want boating to be controlled and regulated to the extent the airline or car industry is - "sorry sir but you cant go to see with that arrangment of sheets it's not type approved for you class of boat"

 

[roly_voya]

Re: Snubbers

Hadn't thought of using these in the anchor warp but can definatly see the sense. I suspect that what is happening is that the rubber streaches more easily than the nylon so in effect make a 'rising rate' spring but that only a guess. I am using one on the dingy tow line and It definately make a huge difference, probably halves the amount the dingy dances around and that is on an all rope line.

Incidently where do you put it? The reason for asking is that with the dingy line I have it set so that the rubber is in the cleat. The origional reason for fitting it was chafe protection, the improved ride being an unexpected bonus! Wonder if the same could be done one the anchor rode?

 

[Robin]

Re: Snubbers

We use an all chain rode (up to 200ft) so the snubber is in a line attached to the chain with a chain hook, this line goes over our 2nd bow roller to one of the foredeck cleats mounted behind the anchor well, there is an anti-chafe tube where the line runs over the roller. The rubber snubber is wound into the line about 3ft/4ft above the chain hook and when in use the chain is allowed to hang in a big slack loop from it's bow roller to where the snubber line hook is attached, with the rubber snubber out of the water.

I think it is more effective than rope alone as it stretches easily in the first instance and with far less load than needed to stretch the nylon line.

 

[wagenaar]

Re: Snubbers

I would guess that both rubber and nylon elongate in proportion to the force applied, in formula
elongation = force/constant.
If this formula is transformed to "basic units" it becomes
delta L/L = stress/E, where E is the modulus of elasticity.
The modulus of elasticity of rubber is much lower than that of nylon and with the same stress rubber elongates much more. The snubber has therefore an effect of better accomodating a sudden surge in load, making the movements more gradual.

 

[jimbaerselman]

Re: Snubbers

Yes. You'll get the same 'soft' effect of springing with rope alone if you use a greater length of rope snubber.

More rope length = smaller force for same stretch

 

[Roberto]

Re: Snubbers

Same boat as Robin (hello), same setup for the nylon snubber with the rubber thingy (I think it s called Forsheda)

I put the rubber compensator a bit farther away from the chain hook, say 5/6m: when it begins being stretched a lot it means that loads are already around a few hundred kilos, so it indicates it is time to pay out a lot more length of the 25m snubber rope, the rubber compensator only finishes underwater when loads are quite high and it is almost permanently stretched

 

[Robin]

Re: Snubbers

[ QUOTE ]
Same boat as Robin (hello), same setup for the nylon snubber with the rubber thingy (I think it s called Forsheda)

I put the rubber compensator a bit farther away from the chain hook, say 5/6m: when it begins being stretched a lot it means that loads are already around a few hundred kilos, so it indicates it is time to pay out a lot more length of the 25m snubber rope, the rubber compensator only finishes underwater when loads are quite high and it is almost permanently stretched

[/ QUOTE ]

Hi Roberto

We change to a thicker and stiffer rubber if really strong winds are expected but that is rarely needed in practice as if that were known in advance we would seek better shelter!

With a bit of thought however as we have 2 snubber lines made up, one standard one and one heavy duty one, we could probably rig both at the same time with the second one through a bow fairlead left slack enough only to come in play when the first is just becoming fully stretched. It might mean swapping the existing chain hook for a shackle type (Wichard do one) to stop it falling off the chain (as it wouldn't be under load most of the time) but that might just give the best of both worlds.

Robin

 

[Roberto]

Re: Snubbers

[ QUOTE ]

Hi Roberto

We change to a thicker and stiffer rubber if really strong winds are expected but that is rarely needed in practice as if that were known in advance we would seek better shelter!

With a bit of thought however as we have 2 snubber lines made up, one standard one and one heavy duty one, we could probably rig both at the same time with the second one through a bow fairlead left slack enough only to come in play when the first is just becoming fully stretched. It might mean swapping the existing chain hook for a shackle type (Wichard do one) to stop it falling off the chain (as it wouldn't be under load most of the time) but that might just give the best of both worlds.

Robin

[/ QUOTE ]

nice idea! Now next thing I have to do is to prepare a second snubber /forums/images/graemlins/smile.gif

 

[roly_voya]

Re: Snubbers

Cant see any reason for not putting more than one snubber on the same line, if matched as one ran out the other would take over. They are designed so that when they reach there limit of streach the load is transferred to the warp so they are not going to break.

 

[Robin]

Re: Snubbers

[ QUOTE ]
Cant see any reason for not putting more than one snubber on the same line, if matched as one ran out the other would take over. They are designed so that when they reach there limit of streach the load is transferred to the warp so they are not going to break.

[/ QUOTE ]

Yes that is right! I wonder what the effect would be also of two same size ones on the one line, maybe the same easy take up but more movement allowed before the stops are reached?