I have a new carbon roadbike frame with in the head tube a cable stop built in.

From the outside of the headtube the outercable ends in it, and then it guides the innercable through the frame.

This cablestop (alu hollow tube) can be seen at the inside of the headtube. It's partly uncovered and I think it’s a bad construction. Vulnerable for breakingout (see image)

 

I want to cover it on the inside with tiny pieces of carbon so the cable stop will be totally locked up on all sides.

 

Think I only need a few pieces of carbon of 2 x 4 cm and some resin and hardener.

What do you advise me?

Hope you can help me out

These a re generally bonded in after the frame is built. I would just leave it as it is as you won't add a lot of strength to to it by patching it, just make it look nicer and risk increasing corrosion on the aluminium insert. 

No its not ok.  The part of the stopper that is connected with the carbon wall is minimal. What you see is almost the whole stopper!!
The headtube wall is also uberthin. The stopper has too little "flesh" and therefore it too easily can breakout under pressure.
It's a simple construction mistake. Besides that, I have seen more bad designed cablestoppers breaking off (other situations however)
Fromout construction view its a stupid thing that I want to correct before something happens with it.

Your talk about corrosion I cant follow. Corrosion when locked into carbon would be less than in this situation.
That corrosion thing is a non-issue.

I hope Easy Composites can deliver me a small package with the right stuff to correct this myself.

Have to agree with Tom on this one. Simply wet laying carbon over the top will do very little. Unless you can vac bag it to consolidate everything the new carbon probably won't even be touching the insert. I would use either EC's Black Epoxy Repair Filler or ET 515 adhesive. Both can be applied with an artist's brush. Clean the area with acetone then build up the filler or adhesive around the cable stop. Put some wax or plasticine in the hole to prevent it becoming blocked. If you use the ET515 you will need the cartridge gun and mixing nozzles.

Carbon Copies Ltd

Agree with the above, an adhesive or filled resin would be a better idea. Working with carbon fibre is not like working with CSM, you would need to vacuum it. Even then you would ideally want a layer of glass in the first to minimise corrosion on the aluminium

I would also suggest sending it back to where you purchased it from if it is a brand new frame as you don't want to do anything to void the warranty.  

Yup ... Carbon fibre is electrically conductive and will cause galvanic corrosion, if left in direct contact with aluminium ...  Anyone making Alu inserts in CF, should wrap the alu part in glass or kevlar before bonding it into the CF. This is especially important if you bond into holes cut through CF sheet or tubing, as that WILL bring "raw" carbonfibre into contact with the Alu part.

Do not accept a brand new product with this sort of construction error, unless it was a real bargain ....

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Do I understand it wrong?
The stopper lays already partly in carbon so what's the hype with corrosion?

I thought about putting epoxy glue over it. But had the idea to use something like the carbon fibre repair kit, (but then a smaller kit)
Why should that not work?

This is my second frame first frame that came in had paint issues and needed to wait 3 months for replacement although it was new.
So I know that this is a design thing, the other frame had exactly the same stopper. To change it for another will not help.
I rather void warranty instead of waiting till this part crash. lol

So you guys say I use 2 best components glue / filler? do I  not need to reinforce that with fibres?

Yes I think you do ... If a bare metal aluminium part is directly in contact with Carbon fibres, there will be galvanic corrosion (caused by the electric potential difference between aluminium and carbon)

It will cause the aluminium part to "swell" up with aluminium oxides and crack the bonding to the CF.

I have seen this i a number of CF bike frames, but mostly some years ago when the CF frames were still very "new" ..

If there is no aluminium part there, that just means that you will not have that particular problem... If you want to reinforce an existing cable stop made from CF, thats probably best done by adding more fibre or a high strength fibre filled epoxy.

I would do this:

Drill the Alu stopper tube out, and replace it with a CF woven tube of suitable size, glue that in place with a small amount of CF fibres as reinforcement.

At the same time, key the area around the stopper, maybe even the whole inside of the head tube, and epoxy an extra layer of CF weave in there..

(Since you say it is "uberthin"  ... )

"Sapere Aude"... Dare to KNOW!

The written word is the only truly efficient vehicle for transmitting a complex concept from mind to mind...

103% of all people do not understand statistics...

Do not adjust our mind, theres a fault in reality :-)