Videos of Anchors Setting

[Seaworthy Lass]

Originally Posted by fugue137

......further questions:

* Why not a locking brummel?

Unfortunately, you can’t do a locking brummel on a loop.

[fugue137]

Originally Posted by Seaworthy Lass

Unfortunately, you can’t do a locking brummel on a loop.

Thanks! I see that what people tend to call a locking brummel loop (e.g.

https://www.youtube.com/watch?v=DUSYUsWprc8

) doesn't actually lock, but I've heard a few people claim that they're still more secure especially under variable load. Aside from the misnomer, you think they have any merit?

[Panope]

Originally Posted by Seaworthy Lass

Hi Steve

That was innovative work.

One small tip (courtesy of StuM): With no splicing tools on hand, just bend a thin piece of stainless steel wire in double and use that to bury the tapered end. You can wind the loose ends of the wire tightly around something to give you a makeshift handle. It makes the task very easy and prevents snagging of strands. This simulates a splicing wand, takes seconds to make and costs peanuts.

A long bury splice needs somewhere between 50-70 x line diameter for maximum strength (there is debate regarding this). The relationship is not linear.

The potential strength of the cow hitched loop is probably much greater than you require so you do not need a perfect splice to end up with something more than adequate for your needs. Regardless, I would not go smaller then 30 x line diameter for your bury. It does not matter if some of the bury ends up being in the cow hitch, the length of your bury is not limited by the distance between the roll bar and shank.

Samson Ropes have an excellent pdf on long buries (and lock stitching). They take the conservative approach and recommend 63 x line diameter for the bury. The end is gradually tapered for 1/3 of the bury (21 x line diameter) with single strands pulled out and snipped to accomplish this:

https://www.samsonrope.com/docs/defa...rsn=25bec1f7_2

NOTE: 1 tubular fid = 21 x line diameter

You are correct that the join does not need to be stitched for your final purpose. The ends are only likely to come out when not under load, which applies here only during construction, but this is all to easy to do unless you at least firmly tape the join while you are working.

One comment regarding the length. The loop needs to have some load applied to stretch out the splice, primarily because the outer cover is relatively loose in the buried portion. Although yours appears drum tight, I think it will loosen up under load.

A small amount of bending may be acceptable, but if it is not then I would stitch your join to stop it moving while you are handling the loose loop, throw the loop over a fixed object, attach a line to the loop with a bowline and apply some load using one of your sheet winches. Then cow hitch it on.

Thank you very much, Seaworthy.

I'll give the current set-up a couple 'in-water' tests and see if it remains nicely tensioned. If not, I'll do as you say, and pre-load the splice prior to reassembly.

Just one problem: What are these "sheet winches" that you speak of?

Steve (wannabe sailing luddite )

[wsmurdoch]

Originally Posted by Don C L

I may have missed it, but any idea why Rocnas have that upturn at the end? I would think that upturn, besides catching mud, could only serve to discourage the anchor diving, rather than encourage it.

See https://www.petersmith.net.nz/boat-a...-explained.php The skids assist with setting. There is a nearby photo of a setting Rocna anchor.

They are further described in US patent 8,950,352 which says the skids rotate the dragging anchor to an upright position.
United States Patent: 8950352 (Search [ctrl F] for 'upright attitude' to find the paragraph.)

Bill

[Panope]

Originally Posted by fugue137

Interesting. My read is that Mantus recommends the 17- or 25-lb anchor for winds > 50 knots for boats 20' and expects forces on the order of 500--1000 lbs based on the ABYC tables (https://www.mantusmarine.com/mantus-...anchor-sizing/). If so, then it's bending under loads for which they recommend it. Oops. OTOH, Drew Frye has documented that a sufficiently long shock-absorption component in the rode can reduce loads by a factor of >4 vs. all-chain... but that doesn't mean Mantus is off the hook

If going by ABYC loads, perhaps your mod is more important for the rest of us than you think. I was about to chime in with a much less well-informed attempt at what Seaworthy Lass just said, but further questions:

• Why not a locking brummel?
• Thoughts on rounding those sharp edges of the trip loop, or adding a shackle or quick link?
• I'm interested in seeing how the dyneema survives regular use. If it does, I'll start wondering about how much of my rode I could replace with it. Might cut into some seabeds and allow deeper burying than chain or nylon, and not much worse than the former in terms of requiring a shock-absorbing component somewhere (if only I could get faster at tying my bridle on with an icicle hitch...).

Fortunately, the hole in the Mantus shank (tripping hole) is chamfered nicely from the factory. However, even if it were a sharp corner, I would be reluctant to disturb the galvanizing. Dyneema is grossly over size, so things like chafe and UV degradation will not be as much a factor.

One could probably go years and years with Dyneema rode, and not have a problem. However, with our deep water (not able to see bottom), I would get no sleep, on account of constant worry for rode chafe.

Steve

[Don C L]

Originally Posted by wsmurdoch

See https://www.petersmith.net.nz/boat-a...-explained.php The skids assist with setting. There is a nearby photo of a setting Rocna anchor.

They are further described in US patent 8,950,352 which says the skids rotate the dragging anchor to an upright position.
United States Patent: 8950352 (Search [ctrl F] for 'upright attitude' to find the paragraph.)

Bill

Thanks for that, and I read through it, but I still didn't see how the upward angle of the flange or skids would assist with the anchor rotating up to the right position for setting. Interesting it mentions the roll bar would be tapered into a foil cross-section. Do they have that? My friend's Rocna doesn't, as far as I can tell, but I'll look more closely next time I see it.

[Seaworthy Lass]

Originally Posted by fugue137

Thanks! I see that what people tend to call a locking brummel loop doesn't actually lock, but I've heard a few people claim that they're still more secure especially under variable load. Aside from the misnomer, you think they have any merit?

Sorry, I forgot about Grog slings. I don't think of these as a locked Brummel splice, but they actually are a form of this. I was introduced to these by Dockhead a few years ago, but I haven’t used one in earnest. A Brummel lock is used non conventionally in a Grog sling (the tails are turned 180° to bury them).

I was a bit put off them when EStarzinger commented they weaken the sling, but for many applications where the load is low relative to the breaking strength of the line and there is no risk of the tails flogging loose when not under load, I guess they would serve well. I would still make the bury length a minimum of 30 x line diameter, as recommended.

Originally Posted by Panope

Thank you very much, Seaworthy.

I'll give the current set-up a couple 'in-water' tests and see if it remains nicely tensioned. If not, I'll do as you say, and pre-load the splice prior to reassembly.

Just one problem: What are these "sheet winches" that you speak of?

Steve (wannabe sailing luddite )

Sheet winch = a mechanical device not needed by real men

[fxykty]

Originally Posted by Seaworthy Lass

Sorry, I forgot about Grog slings. I don't think of these as a locked Brummel splice, but they actually are a form of this. I was introduced to these by Dockhead a few years ago, but I haven’t used one in earnest. A Brummel lock is used non conventionally in a Grog sling (the tails are turned 180° to bury them).



I was a bit put off them when EStarzinger commented they weaken the sling, but for many applications where the load is low relative to the breaking strength of the line and there is no risk of the tails flogging loose when not under load, I guess they would serve well. I would still make the bury length a minimum of 30 x line diameter, as recommended...

I made four loops and had them failure tested on a hydraulic bench a few years ago: one pair was grog slings (basically made with two locked Brummels with tails buried 180 degrees as SWL described) and the other pair done with a simple bury and lock stitched. We tested as a single loop stretched out and in a basket configuration around a 2x diameter shackle pin.

I don’t remember the results exactly but for the loop configuration the grog sling broke at 30% less load. The grog’s break was at one of the splices, not surprisingly as there is a considerable bend and lump there. The simple splice broke just inside one of the buries. The simple loop was slightly below the breaking strength of the cord.

Once put into a basket configuration, both configurations broke at nearly the same load, just above 1.5x breaking strength, again at the Brummel splice for the grog and at the end of the bury for the simple splice.

[noelex 77]

The loop of Dyneema could be twisted to adjust its length.

So if the Dyneema strop is a little loose, adding an extra turn will shorten the loop, if the strop is a little tight removing a turn will lengthen it slightly. Much like a Spanish windlass, this shortening that occurs when a loop is twisted can induce a high load.

In this way the strop does not need to be exactly the right length when made. There is some adjustment possible for the elongation that will occur if the Dyneema is not pretensioned with a high load before use.

Twisting the Dyneema loop will reduce its ultimate strength, but I expect that in this application the material has plenty of reserve.

[Izikalvo]

About two years ago we addressed this "what if" problem developing a special flange to be added to the anchor kit that would solve the problem, at the end, we didn't use it, and instead, we made few adjustments to the rollbar, we have thickened the rollbar bases and made them wider, and shortened the distance between the locking screw location to the bar.

[Panope]

Originally Posted by noelex 77

The loop of Dyneema could be twisted to adjust its length.

So if the Dyneema strop is a little loose, adding an extra turn will shorten the loop, if the strop is a little tight removing a turn will lengthen it slightly. Much like a Spanish windlass, this shortening that occurs when a loop is twisted can induce a high load.

In this way the stop does not need to be exactly the right length when made. There is some adjustment possible for the elongation that will occur if the Dyneema is not pretensioned with a high load before use.

Twisting the Dyneema loop will reduce its ultimate strength, but I expect that in this application the material has plenty of reserve.

Brilliant.

[double u]

poultice corrosion under the Dyneema?

[Panope]

Originally Posted by double u

poultice corrosion under the Dyneema?

I thought about that, but reckon the roll bar will rust from the inside at perhaps an even faster rate due to mud being trapped inside.

I have seen at least one picture (on-line) of a (hollow) rollbar that was rusted completely through.

Steve

[Panope]

https://www.youtube.com/watch?v=qYXdy2LNOvA

[Souzag818]

Originally Posted by jtsailjt

Regarding adding an anode to the SPADE, drilling a hole in the anchor may void the lifetime warranty because it’s a modification. Adding an anode sounds plausible to me that it would help but you might first want to check with the manufacturer regarding any effect it would have on their warranty.

I did contact Spade a couple years ago about drilling a hole in the shank to add a second bolt near the one that is there now. They told me any modifications to the anchor would void the warranty. Just FYI