Can chaffed Dyneema be "repaired" without splicing?

[Robert Wilson]

Can it be glued or melted (or whatever) to repair it enough for non-safety/non-critical use?
An unidentified problem inside the mast and just below the top sheave is chaffing my topping-lift (8mm dyneema - rather expensive). The 20mm-long chafe is about 1/3 into the 35metre length. The damage is mainly to the outer core, but a very small bit of the inner is "clicked".

It would be a great shame, and financial disappointment, to have to cut the rope into two lengths if it could be repaired, albeit to less than original integrity/performance.

Obviously the rope would need to retain flexibility, so Arraldite etc is not suitable.

Any bright ideas?

 

[sailorman]

end for end it

 

[srp]

Adhesive heat shrink possibly. Not sure it will add any strength, but it might slow or stop further damage.

 

[Robert Wilson]

end for end it

Fair point, but I shall not be using it for the topping-lift, rather for "general use". I'd like to salvage the dyneema in its full 35m length, if practically possible.
I have already replaced the topping-lift with a new wire+rope-tail arrangement on the assumption that the problem is something sharp enough to damage rope but not wire.
The original wire+rope lift did not have damage at the chafe-point when I replaced it last year; it was damaged down near the boom fitting and had been bodged by a previous owner.
I had thought a dyneema lift would be a sensible and attractive replacement, but perhaps there is a constriction near/below the sheave which is too tight for the 8mm rope, but not the 4mm wire.

 

[sailorman]

I have never heard of a wire topping lift do you mean main halliard

 

[cryan]

No, you can not glue or melt Dyneema back together again. Far better to fix the problem that causing the wear.

 

[Robert Wilson]

I have never heard of a wire topping lift do you mean main halliard

Well, now you've got me thinking. When I bought the boat in 2010 "off the cradle", the boatyard rigged her for me. Topping lift was rigged with the wire+rope and main halyard was just rope. I stuck with that for two seasons, more through not thinking than ignorance - or both! Perhaps the previous owner had the same chafe problem and swapped the halyard/lift?????
Hmmm.
Anyway, wire it is until I can think of a way to get inside the mast to fix the problem. Which as far as I can see is totally impossible short of cutting-off the top of the mast

No, you can not glue or melt Dyneema back together again. Far better to fix the problem that causing the wear.

See above for "fixing the problem":sorrow:

Thanks for your warning, but I'm not trying to join together two ends of damaged dyneema, just want to "tidy" the chafe damage. I wouldn't be using it for immense loading, perhaps just as an outhaul/mooring warp for the dinghy etc.

 

[Woodlouse]

If the core is mostly intact then tidy up any frayed ends on the outer sheath and then put a serving over it. Alternatively you could milk a section of slightly larger sheath over the top of the damaged section and whip into place.

 

[knuterikt]

Can it be glued or melted (or whatever) to repair it enough for non-safety/non-critical use?
An unidentified problem inside the mast and just below the top sheave is chaffing my topping-lift (8mm dyneema - rather expensive). The 20mm-long chafe is about 1/3 into the 35metre length. The damage is mainly to the outer core, but a very small bit of the inner is "clicked".

It would be a great shame, and financial disappointment, to have to cut the rope into two lengths if it could be repaired, albeit to less than original integrity/performance.

Obviously the rope would need to retain flexibility, so Arraldite etc is not suitable.

Any bright ideas?

You cannot glue it back - the rope is made up of fibers spun into a yarn.

But if you have a Dyneema rope with polyester cover you should know that the cover does not add strength to the rope, so the cover can be removed without reducing the strength

Or as I did when the middle of my Code 0 sheet got caught in the prop and the cover damaged.
I tidied up the two ends of the cover, secured on cover with a sewn whipping then pushed the other part of the cover towards the whipped end and secured the other part with a sewn whipping. The rope run through sheaves without any problem.

One possible cause of the chafe can be that halyard and topping lift is crossing inside the mast.
If the chafe i close to the mast head you should be able to take the sheaves out and look inside the mast..

 

[estarzinger]

^^ yea, just sew it neatly. ALL the strength is in the dyneema core, so some repaired damage to the cover does not make any difference to strength at all. You can potentially restore some strength to the core by putting a thin dyneema insert inside the hollow core, but given your intended use and what sounds like minimal core damage, it is probably not worth doing. But if you are sewing it, it might be worth sewing it with dyneema fishing line.

 

[Birdseye]

you undoubtedly have the halyard and topping life wrong way round - the halkyard will have a far higher load whilst the topping lift only has to hold the wight of the boom and sail. So the halyard will have been the wire/ rope one.

as for the abrasion carefully work out where the abraded part sits within the mast and then have a look at the outside of the mast. The most likely culprit is something like a self tapper or rivet through the wall of the mast. The mast extrusion itself will be smooth inside - you simply cannot extrude something with sharp bits sticking out. I suppose its possible that in the final manufacturing stage, they cut away part of the inside of the mast and thats whats doing the cy=utting but I doubt it.

there is a second issue. If you have had a wire halyard going over a metal sheeve for some years ( likely to be 20 0r more since wire was last used for halyards) it could well have worn sharp edges on the sheeve itself. Put dynema on that and it will quickly wear the outer.

as for repair, dont bother. from your description it seems unlikely that you have affected its strength by an serious amount and 8mm dynema will hold almost 4 tonnes or maybe 100 booms. tidy it up with a cover and then ignore the damage

 

[Robert Wilson]

You cannot glue it back - the rope is made up of fibers spun into a yarn.

But if you have a Dyneema rope with polyester cover you should know that the cover does not add strength to the rope, so the cover can be removed without reducing the strength

One possible cause of the chafe can be that halyard and topping lift is crossing inside the mast.
If the chafe i close to the mast head you should be able to take the sheaves out and look inside the mast..

That's good news - I may have a useable length of nearly brand-new rope!

as for the abrasion carefully work out where the abraded part sits within the mast and then have a look at the outside of the mast.

there is a second issue. If you have had a wire halyard going over a metal sheeve for some years ( likely to be 20 0r more since wire was last used for halyards) it could well have worn sharp edges on the sheeve itself.

I've made a thorough inspection of the outside of the mast and there's nothing at all to indicate any "through mast" interference. I've also stripped out both sheeves and found them both to be without damage. Likewise, the flanges(?) which support the sheeves are clean of spikes, nicks or roughness.

However, there IS something on the topping-lift side which is catching and damaging the rope. I have measured the location of the damage and it seems to be about 50mm - 80mm down from the sheeve. I tried a borescope but it wasn't quite flexible enough to get a good view.

Very perplexing, and annoying.

 

[yachtorion]

Is it catching on the back of a screw or rivet?

 

[Robert Wilson]

From where the chafe is I can't see anything on the outside of the mast that would be catching it.
All I can think of is that because I had the mast rewired and a new aerial put on it may be that a screw/rivet has fallen inside and become lodged on something - but from the position of the damage I can't imagine what might be holding such an obstruction.

I also installed a new roller jib-foil and forestay along with a halyard guide. However the halyard guide is at the front of the mast, well away from the sheeve and lower than the damage point.

Mystery!:mad-new:

The boat is staying in the water this winter so it will be next winter before I take the mast out, then I can have a better look hopefully with a borescope threaded up from an entry point such as steaming/deck light point.
If I find anything of a structural nature, rather than a "lodged" loose screw, then I'll have a real problem sorting it as the mast-top is welded-on!