Is Dyneema chafe-resistant enough for this unusual application?

[jerrytug]

I would be grateful to any rope experts for guidance about the best type of line to use. This situation is a bit unusual.

My anchor, a 25kg Delta (not the lighter Bruce in the pics, but the same set-up) is normally parked dangling from a cheek block, halfway along the bowsprit.
This arrangement keeps the anchor away from the bows, she sits better like that, and I can avoid tricing up the bobstay, it's excellent. I also chain on to mooring buoys from the same location, never get any twists.

The anchor when stowed is held up towards the S/B bow fairlead, by a line round a SS shackle in the tripping line eye, which means it can't ever hit anything in theory, and is ready to drop.

I have been using new English Braids 10mil braid on braid, but now I'm concerned, as after a 7 hr trip a couple of days ago with the boat being smashed about in evil cross swells*, the line is about to part around the shackle, another couple of hours it would have snapped I reckon, and the anchor would have been flailing about close to the stem.

My question is: Would Dyneema resist the stress concentration and chafe much better than polyester? How tough actually is it?

I was also considering 7mil chain or similar, but a line would be better.

The whole set up works great apart from the risk of the line parting.

Thanks for advice as to what material to choose, Jerry

(*rounding Penmarc'h at springs, don't try this at home etc)

 

[bedouin]

I think any line will struggle in that situation - a single turn round a metal fitting will always chafe. I think most dyneema has a polyester outer braid any way so will have the same characteristics, and dyneema doesn't like tight bends.

If I were you I would consider an alternative way of attaching it - just taking one extra turn round the shackle would vastly reduce chafe or better use a single length tied off or with a thimble spliced in.

 

[jerrytug]

Thanks I agree, I didn't know that D didn't like tight bends, that's good to know. I'm inclined to go for chain spliced into a line, cheers Jerry

 

[noelex]

Dyneema is very abrasion resistant for a rope. A use unsheathed Dyneema in the form of a soft shackle to attach my snubber to the chain.

There has been a little bit of abrasion and am betting a life of about 1 year between replacements (I anchor almost 365 days a year), but it is a very tough application.

I don't quite understand your system, but hopefully this helps.

 

[LadyInBed]

I would use a long shafted hook with a eye bent in the back end to secure a rope to.
Either an 18 inch or so length of S/S or, easier to work and cheaper, a length of heavy duty braising rod.

 

[jerrytug]

I would use a long shafted hook with a eye bent in the back end to secure a rope to.
Either an 18 inch or so length of S/S or, easier to work and cheaper, a length of heavy duty braising rod.

Excellent idea, I actually have a Swedish Hook but never thought of using it..

 

[jerrytug]

Dyneema is very abrasion resistant for a rope. A use unsheathed Dyneema in the form of a soft shackle to attach my snubber to the chain.

There has been a little bit of abrasion and am betting a life of about 1 year between replacements (I anchor almost 365 days a year), but it is a very tough application.

I don't quite understand your system, but hopefully this helps.

Thanks for the info noelex, the 'system', as you kindly call it, is still evolving..

 

[bbg]

I may be wrong but I thought Kevlar was very resistant to chafe. A kevlar line might work for you.

 

[Woodlouse]

Do you pass the line though the shackle and back to the boat? First thing to do is check the shackle over for edges that could cause chafe, stainless jobs are usually pretty smooth but a small nick will chew though a line in no time.

Dyneema has pretty good chafe resistance but it is still rope and isn't impervious. For what you seem to want to achieve I'd probably splice one end of the line to the shackle with a thimble and leave it as a short permanent trip line on the anchor that you can then use to secure it when stowed.

 

[prv]

I may be wrong but I thought Kevlar was very resistant to chafe. A kevlar line might work for you.

Certainly it's a bugger to cut with an ordinary knife, as I found when I tried to make something with a bit of cast-off old line I found lying around the house I used to share. Turned out to be a kevlar trapeze "wire" discarded by the dinghy guys downstairs .

Pete

 

[bedouin]

Certainly it's a bugger to cut with an ordinary knife,

Perhaps that is why they use it to make knife proof vests, and even protection from chain saws

 

[snooks]

Rather than double up the rope I'd be tempted to do a halyard knot on to the shackle and just use a length of single line and leave it attached all the time, hook it up with a boat hook, job done.

 

[jerrytug]

Rather than double up the rope I'd be tempted to do a halyard knot on to the shackle and just use a length of single line and leave it attached all the time, hook it up with a boat hook, job done.

Thanks, and to Woodlouse, for that suggestion, it would be easy, but what about potential risks having 3m of strong line permanently attached to the anchor's tripping line eye, it might get wrapped round the anchor?

 

[Neeves]

It is very fashionable to have a line attached to the tripping eye, permanently, with a small float. This keeps the tripping line short and out of the way of props and provided it has a loop gives something on to which to tie a longer tripping line. You obviously need to dive - so this solution might not be attractive in colder water. But tripping lines are common and do not appear to hinder anchor effectiveness. Personally we have never seen the need - I'd attach a carabiner so that you can simply clip the line onto a shackle in the anchor tripping eye

Dyneema is very chafe resistant and there is another thread, active, where dyneema chafe sleeve is a recommanded solution. It is also possible to buy dyneema braided hollow tape, to sleeve another piece of cordage (so, for example, you can sleeve 'elastic' nylon enjoying the abrasion resistance of dyneema and the elasticity of nylon - though you have to make sure the sleeve can allow the nylon to stretch). Basically the options are limited to your imagination. Kevlar is another option - but there have been comments on its UV resistance (and it certainly does not like tight turns). Dyneema traditionally came with a braided cover but uncovered dyneema is now readily available. Unbraided dyneema and hollow tape is very slippery - splicing is a good idea, if you knot, I'd sew the loose ends (with braided dyneema fishing line,)its neat and stops the knot unravelling.

I'm not entirely sure of how you intended to attach all this - but if you want abrasion resistance then dyneema is the best bet. If you need any stretch (and abrasion) 'id sleeve nylon with a braided dyneema cover (sew one end of the cover to the internal cordage leave the other end slack. I'm not convinced that in your application tight turns are an issue - I'd check - Liros make dyneema in many combinations (as might Marlow et al) and we have used it with a very tight spliced eye on halyards, only big enough for a clevis pin - and have had no issues over the last 18 years.

If another line rubs on dyneema then the dyneema can quickly melt - which is why it is no longer allowed for lifelines by ISAF (headsail and spinnaker sheets can rub on lifelines - there were some major failures). it is also, effectively, inelastic.

Jonathan

 

[jerrytug]

Thanks Jonathan for the very helpful ( and educational ) reply!

 

[Woodlouse]

Thanks, and to Woodlouse, for that suggestion, it would be easy, but what about potential risks having 3m of strong line permanently attached to the anchor's tripping line eye, it might get wrapped round the anchor?

I've seen plenty of boats with short trip lines on their anchors and not heard of a single problem. If the line can be persuaded to float then so much the better.

There's a lot of talk about dyneema and Kevlar not liking tight turns. Whilst it will have a detrimental effect on the strength of the line any thickness that you use for the task will be so over specced in terms of strength that it really will be a non issue.

 

[noelex]

Like many, I have used an underwater float on my anchor for several years. It is mainly to help find the anchor in soft mud or dense weed. The roll bar of the Mantus is quite tall and by the time is disappears the fluke is a long, long way down, but the anchor has buried below the roll bar in strong wind and a soft substrate, so the float has been put to use.

The line and even float have occasionally caught under the fluke, as can be seen here. Probably not ideal, but it's hard to imagine this would make much practical difference. As you can see from this excellent set, it has not affected the anchor in any apparent way in this instance. However, I would have some concern about a very thick and bulky line (in relation to the size of the anchor), particularly with a bulky knot that was tied in a spot that usually buries. The concern is the bulk will (slightly) inhibit the anchor from diving under the surface. With modern lines there is no problem going to quite a small diameter.

The underwater float was caught under the fluke on this drop, but has had little apparant practical effect:

 

[snooks]

Thanks, and to Woodlouse, for that suggestion, it would be easy, but what about potential risks having 3m of strong line permanently attached to the anchor's tripping line eye, it might get wrapped round the anchor?

Does it need to be 3m? The delta has no moving parts for it to jam, and the anchor will be led around by its shank. If you're worried it might catch on something underwater it's probably not the best place to be dropping the hook anyway.

You could always just hitch it to the chain, leaving a bit of slack of course, then you wouldn't even have to catch it with a boat hook each time.

 

[jerrytug]

Does it need to be 3m? The delta has no moving parts for it to jam, and the anchor will be led around by its shank. If you're worried it might catch on something underwater it's probably not the best place to be dropping the hook anyway.

You could always just hitch it to the chain, leaving a bit of slack of course, then you wouldn't even have to catch it with a boat hook each time.

Thanks for your suggestions and the others above, I'm not back on board til the wknd, and will take some up to date photos to explain my problem, cheers Jerry