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Recommendations: best glue/epoxy for carbon fibre?

Obviously, I wouldn't be so dumb as to try and glue a damaged frame or wheel back together!

Much smaller job in mind; one very skinny wing of a CF bidon-cage has cracked. It's one of the lifeline ones wiggle sell; as Keith Bontrager said, you can pick any two of strong, light, and cheap.

But anyway, it's obviously a small job with no implications for rider safety. And the forces it will have to withstand are not enormous, no matter how thirstily I yank out the bidon. But I'd rather not replace the cage. Anybody have recommendations?

If you're new please join in and if you have questions pop them below and the forum regulars will answer as best we can.

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20 comments

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Toro Toro | 8 years ago
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Not pretty, no, but very small and now largely hidden by the front mech!

About 45 minutes all told, I guess? By far the longest part of that was the painstaking winding and wicking.

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Iamnot Wiggins | 8 years ago
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Certainly not pretty but seems functional! How long did it all take to repair?

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Toro Toro | 8 years ago
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Tried the freezer-bag, but I had no dexterity at all with them! So I used a screwdriver tip to smooth it out, and let what got on my fingers get on my fingers.

Yeah, it's mostly off now. Hot water didn't do much, but chain degreaser did. Cheers again!

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jiberjaber | 8 years ago
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Looks alright - should keep you going for a while.  41 Did you not use the freezer bag trick I mentioned?  21

The CA will come off eventually - hot water may help.

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Toro Toro | 8 years ago
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Now, does anybody know how to get superglue off fingertips?  7

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Toro Toro | 8 years ago
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Okay, finally got this done!

First up, here's a view of the crack, flexed open:

//i.imgur.com/cmM97Fn.jpg)

Step one; crack filled with loctite and set:

//i.imgur.com/3yTW9x0.jpg)

Step two; splints glued on both sides and set. There's a tiny bit of paper fibre there, from dabbing away excess glue, which I removed before the next step:

//i.imgur.com/7wFD9h9.jpg)

Step three; splints lashed in kevlar thread, wicked in glue and allowed to set as I wound:

//i.imgur.com/3c3W4pT.jpg)

//i.imgur.com/udsApw4.jpg)

Far from pro-level elegance, but functioning perfectly, and only visible close up, at least if your eyesight is as poor as mine.

Cheers for the help, guys!

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Toro Toro | 8 years ago
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People with a genuine interest; I've been thrashing around North Wales for the last five days, which has delayed progress on the repair.

Kevlar thread having arrived, I'll be splinting, lashing, and wicking during the week, and will post pics of the job as it goes along.

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Toro Toro | 8 years ago
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Bloody hell.

I realise that you're far from alone in treating this whole board as an extended opportunity to demonstrate your spendthrift credentials, and show that anybody who has had the temerity to spend any more than you on a bike or bike component has wasted their money.

But firstly, I've never seen one of your ilk lapse into "ha ha, (minor) equipment failure!" before.

And secondly, most of your lot - when politely told to eff off - actually, y'know, eff off. It's clear that you've nothing to contribute to the actual purpose of the thread; so don't make me say it impolitely.

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Toro Toro | 8 years ago
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That's really helpful again, thanks!

I'll try and get a pic up when I get home. The crack is sort of diagonal, in a way that should perhaps splint itself as long as it's secured laterally.

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Toro Toro | 8 years ago
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That's really helpful again, thanks!

I'll try and get a pic up when I get home. The crack is sort of diagonal, in a way that should perhaps splint itself as long as it's secured laterally.

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jiberjaber | 8 years ago
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If you are going the superglue route, then you can use blue freezer bags as 'gloves' to smooth down the stuff you are gluing (eventually they might stick, but beats getting it all over your fingers.

Another thought we had when I was at the in-laws this weekend was using a small section of nylon fabric, you could then start like a cigarette paper, create a small section with some superglue ('CA') and get that to bond first, then wrap the break with the remainder, once happy, wet it while in place with superglue and it would probably act as the split and repair in one go.

You will need really 'thin' superglue for any of this to work as you need it to wick before it goes off ('kicks'). Most superglues in 'normal' shops aren't advertised with their 'thickness' but if you can get to a model shop nearby, you will see they do thick, medium and thin. You want the thinnest (runniest) they have, not all thins are equal  1

I've tried to do a little diagram just in cast the words don't make sense. you might want to experiment with different sizes of the 'cig paper' before committing else you might end up with a bunched up too thick repair from to many wraps of material..

It will run every where if you are not on top of it, so old cloths and in a well ventilated place and not over the front room carpet or sofa!  4 (don't do it in-situ else you will kicking yourself from that glue run on the frame you didn't spot, or a superglue fingerprint you didn't know you could make! - this is all from experience LOL)

Have you got a picture of what you are repairing ?

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Toro Toro | 8 years ago
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Kevlar thread option looks a good bit more cost-effective than carbon tow! WIll let you know how I get on.

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Toro Toro | 8 years ago
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If I wanted your recommendation for bottle cages, that is what I would have asked for.

The Tao is actually twice the weight of the Lifeline pro, but thanks for playing. I'll spend my time and money however I like.

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Batchy replied to Toro Toro | 8 years ago
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Toro Toro wrote:

If I wanted your recommendation for bottle cages, that is what I would have asked for.

The Tao is actually twice the weight of the Lifeline pro, but thanks for playing. I'll spend my time and money however I like.

Half the weight and half the strength don't you mean ! Oh and three times the price ! Though super glue may do the job !

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Batchy | 8 years ago
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Tacx Tao bottle cages ( about £9 ). Not carbon but just as light and probably stronger . Why spend time and money trying to fix /bodge an overpriced carbon cage ?

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gmac101 | 8 years ago
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Composite structures need both parts to work, the re-inforcement and the binder. Epoxy on its own is relatively brittle as the carbon fibre re-inforcement has failed at the break all you would have is the epoxy in the join which would probably fail quite quickly.

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Toro Toro | 8 years ago
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That's really helpful, cheers!

You'd recommend against just epoxying or gluing the edges together, then?

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jiberjaber replied to Toro Toro | 8 years ago
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Toro Toro wrote:

That's really helpful, cheers!

You'd recommend against just epoxying or gluing the edges together, then?

Correct, as Gmac said, the epoxy is just there to wet and bind the materials together, you could use superglue and some kevlar thread, wind the thread round the break tight binding and then wick superglue in.

You will still need some sort of splint and the finish will be that of a bound thread. Don't use cotton thread it will react with the superglue!

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jiberjaber | 8 years ago
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You want something like carbon tow and a thin - runny epoxy. Very popular in the model world but if you were just buying it for this repair, then it might almost be cheaper for a new cage  1

Laminating epoxy should get you by, you can get this from a RC model store. A 30 min epoxy also, generally, the longer the handling time, the thinner it usualy is (though not always!)
http://www.inwoodmodels.com/index.php?id_product=6355&controller=product

You probably dont need more than 5m or a lot less of the tow.
http://www.easycomposites.co.uk/carbon-fibre-reinforcement/carbon-fibre-...

You could give easycomposites a call and see if you can get some shorter length.

In terms of the repair, use gloves. Rough up the area, degrease the area.
Mix the epoxy, wet out the tow and then remove the excess epoxy with some paper towel.
Lay some short tow along perpendicular to the break
Bind the tow around the break and the layer you put down, tight and then give it a pat down again with some paper towel. The carbon doesnt need to be soaking wet with epoxy!

Depending on the finish, you can use old VHS tape and wrap the repair with that, or use electricians tape to tightly bind over the repair, this will compress the repair and squeeze out some more epoxy... so more paper towel.

Links above are just examples. I need to rush off to get a train, but I am sure I can dig out a youtube vid which should help visualize the above.

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jiberjaber replied to jiberjaber | 8 years ago
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4:55 in to this video gives you an idea of the video tape wrap (its making a tail boom for a glider, but similar idea to get a nice smooth finish  1 )

https://www.youtube.com/watch?v=lj4AaVYTHCI

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