Kevlar isn't carbon. Now I know.

[Greenheart]

I butted into a thread last November to ask what would be the best way to prevent the very taut vang rubbing grooves in the deck at the front of my dinghy's cockpit.

Comments were made, regarding the fact that technically, perhaps the vang shouldn't be so taut when broad-reaching...

...but since I singlehand, there's every chance that I won't remember to slacken it in time every time, so I wanted something to toughen-up the rounded deck-edge. Products were suggested, including flexible stainless steel strips, and a narrow stainless strake...

...and I expect either would have been fine, but they were a bit blooming small for the application, so I'd have needed four or more likely six of each, with the cost running well north of £30...

...until I saw a KEVLAR equivalent...kevlar wear patches, at Force 4...I saw that the Kevlar patches could be cut to size, and calculated that one pack at under £20 would cover all the vulnerable area.

Unfortunately Force 4 also sells CARBON wear patches, and below is the picture of them in use, almost exactly as I had envisaged...I'm not quite sure if the carbon patches can be so easily cut as the Kevlar, but I definitely confused the products...

...and having fitted the kevlar strip, I thought I'd give the newly-armoured deck-curve a bit of vang-style abuse to test it. That lasted less than five seconds...photo below...the grey area in the middle is my GRP showing...the rubbing rope went straight through the kevlar, and the new paint, and began to bite into the deck.

So, I've learned a £20 lesson...carbon may be up to the job of resisting rope-wear, but kevlar definitely isn't.

Which leads me to wonder, what is the kind of wear which the product I bought, was meant for?

I'll get the stainless strakes. Or look for some wide-diameter scrap stainless tubing and segment it with the angle grinder.

 

[bbg]

That doesn't look like pure kevlar to me, and doesn't look like the kind of weave I would expect for an abrasion-resistant patch. But I'm no expert.

What kind of test did you do to get that kind of wear so quickly?

 

[prv]

On the plus side, at least the new strip will cover up the hole

Pete

 

[Greenheart]

I'm no expert.

What kind of test did you do to get that kind of wear so quickly?

I'm confident you're more expert than me, I know nothing. Except, I know a bit more than I did before.

I held the same diameter line as the vang (6mm), very tight like the vang usually is, and rubbed the patch up and down. 5 seconds.

It was as close as I could simulate to the action by the vang when sailing...the only way I can account for the damage I found, below...

The kevlar product certainly seemed to be marketed as top-quality, and was sold as such by Force 4...here's what the advert said:

A simple & great looking solution to avoid damage to your boat through rope burn, chafe or impact.

Made from Kevlar with a high specification adhesive, these protective pads can be fixed to flat or curved surfaces.

 

[grumpy_o_g]

I'd say neither. Carbon produces a lighter or stronger but more rigid and brittle structure than Kevlar. Kevlar is normally used more for impact resistance though in practice layups are often a combination.

The situation you have is about wear resistance though and what will happen is that the resin will wear through whereupon the rope can attack each individual strand of carbon or kevlar, which it would then fairly quickly wear through as well. Carbon fibre would probably last longer but still isn't the right thing really and the resin would be as important as the fibre. Strictly speaking I'd say something like stainless steel for this, not FRP.

 

[Greenheart]

Yup, thanks Grumpy, that's what I'd concluded. I should have been guided by the original suggestions last year.

 

[Mistroma]

I'm confident you're more expert than me, I know nothing. Except, I know a bit more than I did before.

I held the same diameter line as the vang (6mm), very tight like the vang usually is, and rubbed the patch up and down. 5 seconds.

It was as close as I could simulate to the action by the vang when sailing...the only way I can account for the damage I found, below...

The kevlar product certainly seemed to be marketed as top-quality, and was sold as such by Force 4...here's what the advert said:

A simple & great looking solution to avoid damage to your boat through rope burn, chafe or impact.

Made from Kevlar with a high specification adhesive, these protective pads can be fixed to flat or curved surfaces.

I'd be expecting a full refund if I'd ordered this and it didn't stand up to manually pulling a rope over it for 5 seconds. It cannot be fit for purpose if the advert says "solution to avoid damage to your boat through rope burn, chafe or impact". Worth pointing out to Force 4. Won't the Consumer Rights Act 2015 apply? All products must be of satisfactory quality, fit for purpose and as described (as per old Sale of Goods Act). I'd imagine that either quality and fitness (or both) aren't up to scratch.

 

[macd]

The yellow and black patch looks like carbon/kevlar hybrid, so you're stuffed either way.

I don't know why it should be so, but some materials which are very wear-resistant as solids seem to lose that quality when spun into tiny fibres and set in resin. Like your rubbing patch. But also like glass, perhaps...that very hard stuff you also sometimes encounter in resin?

We use proprietory stainless steel rubbing strakes where lines attack the edge of our coaming. Tough stuff. Wears hardly at all.

 

[Mud]

I'd be expecting a full refund if I'd ordered this and it didn't stand up to manually pulling a rope over it for 5 seconds. It cannot be fit for purpose if the advert says "solution to avoid damage to your boat through rope burn, chafe or impact". Worth pointing out to Force 4. Won't the Consumer Rights Act 2015 apply? All products must be of satisfactory quality, fit for purpose and as described (as per old Sale of Goods Act). I'd imagine that either quality and fitness (or both) aren't up to scratch.

+1

I've found Force4 good with refunding me for a product which I didn't think was up to the task.

Worth a phone call?

 

[prv]

I'd be expecting a full refund if I'd ordered this and it didn't stand up to manually pulling a rope over it for 5 seconds. It cannot be fit for purpose if the advert says "solution to avoid damage to your boat through rope burn, chafe or impact". Worth pointing out to Force 4.

+1, it does seem spectacularly useless at precisely the thing for which it was sold. I'm sure either of my local Force 4 shops would refund it with a sincere apology.

Pete

 

[Kelpie]

I've got an old Venetian blind made of strips of thin aluminium. These have proved quite handy as wear strips, epoxied in place. I could probably send you a few strips, rolled up, if you like?

 

[Bobc]

The only use these patches have is to "bling-up" a dinghy and make it look more hi-tech.

Neither material has any abraision resistance.

A thin piece of stainless is what you need.

 

[colind3782]

Kevlar is rubbish against abrasion and always has been, it was never designed for it.

Back in the 80s, it came into use as parachute rigging line for a while but was soon discarded as it didn't stretch like Dacron and the lines wore through in double quick time causing some "interesting" situations. One of the main design uses for it when it arrived in the 70s was for reinforcing concrete as it didn't corrode like steel, had similar properties and was a fifth of the weight.

 

[snowleopard]

That doesn't look like pure kevlar to me, and doesn't look like the kind of weave I would expect for an abrasion-resistant patch.

That mix of Carbon and kevlar is known as 'squashed wasp' for obvious reasons. It is used to give both light strength (carbon) and puncture resistance (kevlar).

I'm surprised by the claim that a kevlar patch is 'easy to cut to size'. Kevlar is a s*d to cut. Ordinary scissors won't touch it. When I skinned my dinghy with it I found the only way to cut it was using a snap-blade knife on a hard surface and snapping a new edge every couple of feet.

 

[ip485]

I appreciate it is more costly but the perfect application for thin stainless sheet. There are plenty of suppliers that will cut the sheet to size for you and it can be formed to that radius easily.

 

[Topcat47]

Kevlar and carbon fibre are predominantly strengthening fibres to make light and strong constructions. Neither are particularly good at abrasion resistsance and neither is the resin upon which the panels rely for rigidity. Most appliqué panels like this are "bling", you'll find them prevalent in the motorcycle industry. Neither fibres like being woven. Woven Kevlar is difficult to wet out and in both cases, the strength and rigidity of panels relies upon using uni-directional sheets. We laid them in pairs at 90 degree angles, interleaving them with a second pair at 45 degrees to the first. We also used the unidirectional sheets to strengthen structures along load lines such as shroud plate hull reinforcement etc.

 

[lw395]

This looks like fake carbon-kevlar tape, usually found on vauxhall corsas in dodgy housing estates. Along with a loud exhaust and a sticker promoting energy drinks.
The edge of the weave does not look right for a proper tape.
Actually I had some on one of my motorbikes, it was to protect the vulnerable belly fairing's edge from stone chips. It lasted a few thousand miles I suppose.

A lot of dinghy racers used to simply use a layer of duct tape, it was only intended to protect from incidental damage on edges though.
Actual Kevlar tape and epoxy ought to work fairly well, but it's still a throw-away. I think you'd get loads of it for £20 from a decent composites supplier?
http://www.cfsnet.co.uk/acatalog/Kevlar-Tape-200gm-50mm-wide--1-49m-rate-FKT200_050.html
My last wooden dinghy had a lot of SRPB (Paxolin) inserts on wear areas.
But the systems were sorted to avoid obvious gross wear areas.
I reckon decent kevlar might damage the rope dragged across it? I'd avoid it, it is a sod to sand off, unlike carbon or glass.
Force 4 seems to be into 'giftware' and tat these days.

 

[Greenheart]

Neither material has any abrasion resistance.

Kevlar is rubbish against abrasion and always has been

...it does seem spectacularly useless at precisely the thing for which it was sold.

Yes, outstandingly incompetent as far as I can judge. But it's difficult to believe that Barton wouldn't have tested and rejected them, or at least, specified what sort of gentle abrasion they're able to resist...hence my original question, what are they actually meant for?

If it's just 'bling', £20 seems unduly costly...and anyway, what would there be to show off about, in a product which is so inadequate.

Thanks for encouragement regarding refunds - I know Force 4 are honest chaps (as far as chandlers can be) and won't deny a refund.

Anyway, I'll be glad if no-one else here buys the same thing and regrets it.

Kelpie, thanks for the blind-panel idea. Actually there's one of those in my sister's garage...wonder why I didn't think of it before. :encouragement:

 

[prv]

But it's difficult to believe thence my original question, what are they actually meant for?

Wait, so they weren't specifically sold as wear patches? I assumed from your original post that that's what it said on the packet. Are you saying that was actually an assumption on your part?

Pete

 

[Greenheart]

No, they were sold as resistant to wear, and specifically ropes rubbing, at which they are abjectly rotten. Here's the F4 site description:

...to avoid damage to your boat through rope burn, chafe or impact...

...but I wondered whether the marketing spiel on the Force 4 website was an assumption by Force 4, rather than the particular purpose the manufacturer Barton had produced the patches for...which made me wonder what they might really be intended for.