Anchoring over bow rollers?

[Boatsie]

It might be a long shank shackle of much less strength than the chain. Long enough to go through eye and a link, short enough to maintain direction of lay pull.
I do remember breaking breaker at anchor because lay pull pulled upon breaker direct.. (Need to leave a bit of play)
The pull on anchor via lay of chain doesn't pull the crown up but does pull the crown into plough because the breaker force is basically directing the chain lay force. It is a marginal force compared to that from the lays line.
We probably used long shackle shanks and smaller diameter metal than that of the chain. If pulled at 90 degrees, eg straight up, the shackle is designed to be the weak link.
If pulled at lay; anchorage, the weak link takes some sidewards force as winds and tides shift the lay and some lifting force but not the direct pull..
Although pulled straight up, the weak link doesn't break unless it is attached to a well bedded anchor. Basically near the same strength but weaker. Something you can break if needed via the use of vertical pull strength but weaker than the chain.

I hope that helps.. I'm lost with the physics too bro.

Nathan

[Boatsie]

If wondering about strength. We'd probably set up bow to literally break chain using the boat as a lever hence the breaker is quite strong. Eg. With a 24 foot sailed we'd achieve a naturally buoyant lever of about 16 feet? Use the swell to torque the lever and keep taking slack until secured chain was snapped. There is no way I or any other can break the breaker without a leverage.
I do not understand powerboat leverage but a use if need be system is such.

Loving life to bro

Nathan

[Boatsie]

This might be useful.

I'd rather a breaker link shank too strong and lose or dive an anchor than a breaker link shank too weak and lose a lot.

Breaker link shank.
Long enough to link shank eye with a lay link.
Short enough to link lay chain along lay of shank.
Position such as to avoid direct pull of lay chain.

If bow volume of vessel not sufficient to snatch snap breaker link shank then bow will siink during uplift of swell upon leverage vessel.
Go diving. Use a separate bouy attached crown pull system instead of a breaker eye shank system.

I'd rather a breaker link eye of shank too strong than too weak!
I only tend to use sailing vessels which tend to behave nicely when used as a pitch leverage .
A separate bouy to crown release could be useful with a vessel absent of an easy pitch leverage.

All the best..

That's all I know.

Wanna race? WAZZA

Nathan

[Boatsie]

Thanx endlesspursuit..
I just realized why the old man was annoyed.

He'd just bought a new anchor. Shackled to shank eye. I clean snapped that!
He then researched anchor retrieval. The breaker here is of same size as previous shackle through shank eye.
The bow volume will snap that! His loss, our gain (including his).

WAZZA

I'm out of ideas. Peace

[Boatsie]

'Make sure the anchor sets! '

Oh yeah baby.. 'She's set, just 1 problem. Such a strong CLEAN AND JERK snapped the shackle'
Bow volume pitch leverage in 1 foot swell.

Set him well and rest away from ashore being ashored.

That shackle that was strong, it was of size to suit anchor, same as previous owners setup (different anchor).
That is the breaker and set to take partial load during lay loads.

Love u2
WAZZA

Many save voyages boaties.
Boatsie

[Capt Gill]

A few of the different types of bow rollers around the marina.Mine is the top left.

[Montanan]

Originally Posted by Capt Gill

A few of the different types of bow rollers around the marina.Mine is the top left.

A excellent representation of the various types, all of which are suitable for rolling and holding the anchor [or anchors] onto the deck which is their purpose.

It is evident that none of the thin axles on the rollers are suited to taking the shock loads of a boat at anchor which what the snubbers is intended to handle. [Note snubbers is plural there being two separate lines to the rode].

A roller may handle the stress of a lunch hook deployed in calm water and mild breeze but is not intended to deal with the loads of waves and swell and harsh winds.

[boatpoker]

Originally Posted by Montanan

[Note snubbers is plural there being two separate lines to the rode].

We lead our snubber from a hawse pipe 5' aft of the bow on one side only.
We find that this holds the bow slightly off the wind and greatly reduces our wandering.

[Montanan]

Originally Posted by boatpoker

We lead our snubber from a hawse pipe 5' aft of the bow on one side only.
We find that this holds the bow slightly off the wind and greatly reduces our wandering.

Tying off to provide a modest bias to the direction of the wind is a useful method to stabilize some boats from "sailing" at anchor or mooring, if the vessel is prone to such movement; but that method does not need to preclude the use of a two rode snubber so as to provide redundancy safety. One simply shortens one of the two independent snubber rodes to apply bias, just as one can due when trailing a speed reducing drogue and one desires to adjust the stern quarter alignment to the waves. A suggested approach is to use two snubber rodes with one snubber rode being of easier to stretch configuration, [diameter and material] for ordinary conditions and a thicker less stretch and strong breaking strength rode that could alone handle the more severe loads of storm conditions. The "storm" snubber rode being deployed a bit longer than the more stretchy non-storm snubber rode so as to become under load only when the conditions apply greater stress to the snubber acting as a system.

[Montanan]

Images of anchor rollers that were damaged due to rode stresses.

The vertical and sideways loads of a rode can be immense. I have seen many a cleat break or get torn out and cleats are typically massively stronger devices than the rollers which rollers are intended to just provide for deployment and retrieval of the anchor when NOT under load and to just hold the anchor on deck. Do not lead the snubber lines over the rollers, nor a rode that is under an set anchor's load.

Just as you should not attempt to break your anchor free by applying vertical tension on the rode with the vertical forces applied directly to the roller and windlass, one should not use the roller as a load carrying device for your rode during anchoring.

I have watched boaters drive their boats forward when at anchor retrieving the rode as they approach over the anchor's location and then just let the boat's windlass or anchor stopper pin take up the vertical tension to pull the set anchor free from the bottom, instead of reapplying a snubber to take up the shock load. If they are lucky the clutch on the windlass will slip and only some friction wear will be derived but if the clutch is set hard or a chain stopper pin is set, that is when bad things happen, e.g., the bowsprit bends, the rollers bend, the windlass breaks, the stopper breaks, all because a snubber was not reapplied before incurring significant tension on the rode to break out the anchor. Certainly sometimes the anchor will break away cleanly and easily when very little scope and angle is derived after retrieving the deployed rode but at other times the anchor is set hard or even entangled on a hard object, log, corral, rocks, cable, etc. in which case it will not break free easily, instead things on the deck bend or break.

[Montanan]

Image of a recommended snubber system.

Note each of the two independent snubber lines have their own chaff protective eyelets AND each individually attaching to the chain hook. The two independent snubber rodes do not attach to a single rode which single rode is then attached to the chain hook. Alternatively each independent snubber line can be independently hitched to the anchor rode. The chain or anchor rode is allowed to have adequate slack to form a loop so as to never be under tension of that anchor rode at the deck, instead the snubbers take the anchor load.

There is redundancy of snubber rodes for safety and to allow for biasing one side or the other side of the hull to mitigate against sailing on the wind or to set against currents or waves. Also one of the two snubber rodes can be more robust in strength so as to be the "storm" snubber with the lighter / stretchier rode for typical conditions and the thicker, less stretchy snubber becoming under load only after the more stretchy rode has provides its give in the system.

[Montanan]

Images of improper deployment of rode, IMHO. Would welcome other's opinions in this regard:

Upper left picture: Totally inadequate length of snubber lines to avail much stretch and there is NO slack length of the chain; a generous loop should be provided in the chain rode so that the [need to be much longer] snubbers can be stretched to a considerable length before a shock load is slapped on to the chain and thence to whatever is restraining the further deployment of the chain rode. In this instance, the shock load that could be applied to the chain rode because of the short length of snubbers will be taken up by the cantilevered bowsprit, likely bending the bowsprit.

Upper right picture: The rode is supported only by the weak cantilevered anchor roller and the snubber [likely a short stretchy cord] has little length of stretching before the main rode pulls taught.

Lower left picture: Uses only a single snubber line which single snubber is of far too short of length to provide for much stretch capacity and which chain rode has been deployed with minimal slack [the loop in the chain is barely established] and yet again the load is being taken over the anchor roller and the bowsprit instead of directly to sturdy hardpoints by separate snubber rodes on either side of the bow.

Lower right: The chain is carrying the load and which load is over the roller and the bowsprit. Instead the snubbers should be under tension and the chain slackened to provide a generous loop. And these snubber rodes are too short to provide for much stretch capacity.

What you want is long snubbers [two independent snubbers] to provide for stretch capacity which snubbers do not apply a load to a roller or a bowsprit.
And one should deploy generous slack on the rode between the connection of the snubbers and the roller, which loose looped anchor rode is only deploying as load to the roller [and the bowsprit that may hold the rollers] the weight of the slack that forms the loop of the rode.

[Arthurwg]

Very interesting thread, and thanks for that diagram, Montana. What would be the material and diameter of the snubber lines? Any suggestions for the snubber hook? Manufacturer? I'm looking for a setup for a 20,000 lb boat with a 50 lb anchor.

[Montanan]

Originally Posted by Arthurwg

Very interesting thread, and thanks for that diagram, Montana. What would be the material and diameter of the snubber lines? Any suggestions for the snubber hook? Manufacturer? I'm looking for a setup for a 20,000 lb boat with a 50 lb anchor.

One evaluates the anchoring system as a whole and defines a weakest link because there is always one.

If a chain rode is used, then the snubber is to provide stretch to ease peak shock loads:

As per Practical Sailor snipets:

"What is Ideal Snubber Size? Longer is clearly better for reducing peak shock loads."

Snubber Length
• Double-braid or brait nylon snubber length = 1.3 x boat length. For dynamic climbing rope, snubber length = 1.1 x boat length. These are minimum snubber lengths; longer is better, up to about 60 feet.

Snubber Diameter
• Snubber diameter = Displacement^0.4 x 0.00832, where diameter is in inches and displacement is in pounds. Multiply this by 1.6 for catamarans to compensate for added windage. For two-leg bridles, multiply the final diameter by 70 percent. (One leg will occasionally carry the load, but this is offset by reduced yawing.) Two which I would recommend oversizing one for storm use redundancy instead of the anticipating the cyclic dual loading scenarios.

I have read that the snubbers should be sized to be equal in strength to the chain [so e.g., I have read for those who are less scientifically or mathematically oriented as a rule of thumb, say around 50 to 125 percent larger than the chain diameter, obviously depends on type of chain and type of rope rode]. Alternatively, one could opt to use two distinct snubber rode types one for "ordinary" modest load conditions and one of higher strength for storms realizing the exponential nature of the loads under storm conditions. The snubbers should be matched with the appropriate sizing of the hard points on the vessel to which they are attached.

As to length one does not want the snubbers to be stretched anywhere near their breaking limit [which limit decreases with wear use and cyclic loads, replace frequently / cheap insurance]. Again I have read that a desired stretch limit is not beyond 10% of length maximum [some say 15%], and perhaps more conservatively say 5%. So then one has to determine a desired stretch capacity in your design which depends on the size of load the boat will derive and the conditions that one is facing. How tall of waves and swell are you going to be subject to? Note: I perceive that wind loads may be less severely peaking in their cyclic manner than the wave / swell derived peaking loads where the water height rising loads invoke cyclic displacement loads, whereas the wind loads will alter between peaking gusts. So if gusts become extreme in variation of velocity, then the wind loads cycle exponentially; I believe by the square of the velocity.

I am going to throw out a reference of say minimum of 20 to 30 feet for small boats and upwards of 50 to 60 feet for larger yachts. [40 foot boats] and longer still for larger vessels.

As to what "hooks" to use. I strongly prefer one the designs that are disinclined to become unattached to a chain if the hook rests and drag on the bottom; so I suggest a hook with a retaining mechanism, not just a hook that will hold in a slot under continuous gravity or tension. It can be one you make or have made or it could be one you purchase. Some types that come to mind are the type where the chain is linked in with 90 degree shift into a slot such as Suncor, Mantis https://www.mantusmarine.com/mantus-chain-hook/. There are others and I am not "marketing" one over another and have no affiliation with any. Or one can use the type with a retainer, such as Witchard, or shackle type but they are cumbersome to install and uninstall as one has to thread the retaining pin.

Be sure to let out more than enough sag in the chain so as to allow the snubbers to perform fully. One wants to avoid at all cost the chain becoming bar tight with a WHAM onto the chain stopper on deck.

If a rope rode is deployed then one is not utilizing the snubbers for shock absorbing purposes as the rope rode will perform that function. The snubbers are instead used to avoid loads on the roller or bowsprit and / or the windlass by providing loads to the sides of the bow attached to hard points. And also to avoid chaff on the long length of rope rode where it would be otherwise be placed under rubbing tension where it comes aboard the deck or attaches to the cleats. One can use much shorter rope snubbers hitched to a rope rode as the purpose of the rope snubber is to be just disposable rodes upon which chaff guards can be readily configured and which use of two snubbers can be biased in load so as to adjust the boat to avoid sailing in the wind or to adjust for waves, swell and current angle.

A low stretch, durable line can be used for snubbers when rope rode is deployed. Stretching invokes heat in a line so a non-stretch snubber may perform well. I would recommend that the snubbers attached to a rope rode be stronger than the rope rode so as to avail added safety for the point stresses that the snubbers will incur as they pass over the deck rail and chocks and cleats. That is to say, size up your snubbers compared to the rope rode. They are short and cheap and again should be replaced frequently if they are showing wear as they are intended to be disposables.

[Jim Cate]

I'm still of the opinion that an anchor roller can be made strong enough to easily absorb the loads imposed by running the snubber over it. The damaged ones shown are all of the flimsy aftermarket type, made up of thin sheet metal and bent into shape and incorporating small diameter axles. Not very strong at all!

The rollers on many cruising boats, including ours, are massive weldments made up of 6 to 8 mm stainless plate, and either not cantilevered out far or with vertical bracing from below. The axle is 16 mm s/s, well supported on both sides of the roller, and the roller has an OD of 100 mm. The whole thing is part of the stemhead fitting and incorporates the chainplate for the forestay. That this is adequately strong is supported by the fact that we've had our snubber and chain lead over the roller for literally thousands of days at anchor, and it has not distorted nor bent the axle. And during those days, there has been no significant chafe on the snubber (double braid nylon, 16 mm).

IMO your blanket condemnation of the practice of leading a single snubber over the roller should be modified to accept that some rollers are stronger than others and for them, it is an acceptable practice... or else show me where I'm wrong.

Oh... in storm conditions I do rig a backup snubber, and it is lead via a chock. However, it is not loaded unless the primary breaks and thus is not subject to routine chafing.

Jim