Carbon frame repair- Mtbr.com
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  1. #1
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    Carbon frame repair

    Hey team. As some of you know i cracked my beloved Rocky Mountain Slayer by massive over clearing of a step up.

    I got an insurance payout and bought a replacement Slayer and so have ended up with the old cracked bike. I decided to repair the frame stronger and heavier than before and build it up into a park/dh slayer.

    Here's the repair journey.

    Initial crack discovery.... Bummer!
    Carbon frame repair-0-02-07-250e8a30869f62247096c6bddfc17a7028a15ec6e24250a24d5682fb0fd1927c_39e7aecc.jpg

    Frame pull down and crack propogation identifying
    Carbon frame repair-img_20190413_072109.jpg

    Carbon trimming and layup development. 600 gram uni directional used.
    2 layers spiral wrapped sleaving the crack. One layer full length top tube. This will give me torsional strength, plus extension and compression strength. Extending the repair fill length of the top tube will add more strength than the original design.

    Carbon frame repair-img_20190413_082211.jpg

    Dry wrap, mask area.
    Carbon frame repair-img_20190413_084943.jpg

    A couple of hours of fasdidious sanding back to raw carbon.
    Carbon frame repair-img_20190413_125801.jpg

    Crack propogation checking. 70% delamination around the circumferance of the top tube. The repair will essentially have to take all the load. Existing structures are broken.
    Carbon frame repair-img_20190413_125925.jpg

    Hand layup.
    Carbon frame repair-img_20190413_142713.jpg

    Removing breather cloth and peel ply after curing. Heavy 600grm uni will need some fairing and filling to make smooth.
    Carbon frame repair-img_20190414_052242.jpg

    Fairing and filling complete.
    Carbon frame repair-img_20190419_075205.jpg

    Painted ready for assembly

    Carbon frame repair-img_20190419_165255.jpg


    Carbon frame repair-img_20190419_165246.jpg

    Assembled and ready to ride!
    Carbon frame repair-img_20190419_195807.jpg

  2. #2
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    Cool project, well done! You trust it?

    Its funny I was just thinking about this. Some one posted this frame for sale on craigslist, my first thought was you'd have to be crazy to buy it but you just proved me wrong.

    They're asking $200, still seems a bit steep though.



    Carbon frame repair-trek.jpg

  3. #3
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    Nice work!!
    skidding is the signature of the novice; learn how to use your brakes.

  4. #4
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    Quote Originally Posted by Train Wreck View Post
    Cool project, well done! You trust it?

    Its funny I was just thinking about this. Some one posted this frame for sale on craigslist, my first thought was you'd have to be crazy to buy it but you just proved me wrong.

    They're asking $200, still seems a bit steep though.



    Click image for larger version. 

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    Both reputable carbon frame repairers state unequivocally that repaired carbon is stronger than original. As far as that frame goes: thats way steep. I bought a much lesser damaged Niner RKT RDO for 1/10th the price.

  5. #5
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    Is trust carbon repaired properly for sure.
    I have a frame on the way back from bring repaired actually. I would not disagree that repaired carbon is stronger - they are not concerned with weight. If they add 5 layers of carbon, they effectively doubled the amount of material there. That is of course going to make it stronger. The trade off is the frame weighs more than when initially manufactured. (Who cares, in my mind!!)

    How many layers of carbon were on your repair?
    How did you remove voids? Any internal carbon?

    Most repairs will involve internal supports being used to allow compression of the carbon layers (internally and externally). Usually they use an inflatable bladder so they can remove the air voids. This is absolutely important for long term strength and durability.

  6. #6
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    Do i trust it? Yes. i've over trippled the cabon in the top tube. It is definately stronger than before.

    But, what i don't know if there is any designed flex it the top tube. If there is designed flex, i have just removed the flex and created a very rigid member (pun intended). It could created a stress point elsewhere to that could cause failure. My gut say no. There is no designed flex, they are simply optimising the weight of teh frame. So it should simply be stronger.


    How many layers? see picture 3. 3 layers of 600gm uni. Note that a typical layer weight for a frame build will be 100 or 200gm. I've got the equivalent to 9x 200gm layers!. I could run the top tube over with a truck an it wouldnt break.

    Did i have internal layers on the frame. No that is impractical for a frame repair that is is not fully broken. I used the existing top tube to provide the internal structure and externally compressed the layup by applying peel ply, breather cloth (the old towel you can see in picture 8, then i wrapped the repair tight with cling wrap. The breather cloth absorbs any excess resin and the cling wrap compresses the layers to remove voids.

    Essentially i created a new top tube over the old one.

  7. #7
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    Did you make a homeowners insurance claim on the broken one? Just curious.
    My name is George. Iím unemployed and I live with my parents.
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  8. #8
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    Yes, Contents insurance. I was suprised that it was covered. But it was.

  9. #9
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    Quote Originally Posted by Train Wreck View Post
    Cool project, well done! You trust it?

    Its funny I was just thinking about this. Some one posted this frame for sale on craigslist, my first thought was you'd have to be crazy to buy it but you just proved me wrong.

    They're asking $200, still seems a bit steep though.



    Click image for larger version. 

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    That adds another level of complexity. You have to jig that precisely or it will not be aligned correctly.

  10. #10
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    First ride yesterday back to back with the new Slayer. Its good, rides solid, no flex or noise of any kind. I hit some hard and rough features, some drops to bottom out and all good.
    There is no creasing, cracking or shown paint work.


    To be honest, if my filling and paintwork job was a tad better and you didn't know Rocky paint schemes you would have no idea the bike has been repaired. I'm pretty stoked really.

    Carbon frame repair-img_20190420_151909.jpg

  11. #11
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    What did you use for resin, cured at room temp?
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

    You're turning black metallic.

  12. #12
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    Quote Originally Posted by Jayem View Post
    What did you use for resin, cured at room temp?
    I use West system with 105 slow curing resin. Been using it for years. It cures at room temperature.

  13. #13
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    Quote Originally Posted by plummet View Post
    I use West system with 105 slow curing resin. Been using it for years. It cures at room temperature.
    Cool, ill probably be doing something similar, banged up a chainstay the other day doing some service.
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

    You're turning black metallic.

  14. #14
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    Awesome repair! I take it you work with carbon fiber or at least fiberglass for a living? Or is this just a serious DIY endeavor? Sounds like you did your homework and overbuilt out of safety / caution. If you're still alive to read this, great job!

  15. #15
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    Got my CF, my resin and hardener. Gotta take a vacation, but when I come back gotta get a respirator and some more sandpaper and my friend that works with CF recommended a ribbed roller to get the air out. Stoked to try it all out.
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

    You're turning black metallic.

  16. #16
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    Quote Originally Posted by Jayem View Post
    Got my CF, my resin and hardener. Gotta take a vacation, but when I come back gotta get a respirator and some more sandpaper and my friend that works with CF recommended a ribbed roller to get the air out. Stoked to try it all out.
    Talk to your buddy about peel ply and absorber cloth. Then wrap to remove excess resin.
    Be very carfull when you sand back the paint, you dont want to remove carbon if possible. Also talk to him about the ideal layup. You want the fibres running in the direction that want the strength.

    Buy yourself some paper overalls and disposable gloves, Carbon dust is itchy as all hell and carsenagenic. You dont want to breath it in or get it on your skin, in your clothes.

    If you have never worked with glass/carbon before do a trail run first to get the techniques down. Even ask/pay your CF experienced buddy to help you out the first time. Once you mix that resin up you have 15-20 minutes to layup/wrap before the resin turns "green" You need to know what to do and how to react when/if something doesnt go to plan before the resin turns green.

  17. #17
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    Quote Originally Posted by GuitsBoy View Post
    Awesome repair! I take it you work with carbon fiber or at least fiberglass for a living? Or is this just a serious DIY endeavor? Sounds like you did your homework and overbuilt out of safety / caution. If you're still alive to read this, great job!
    Haha, Yep im still alive. I don't work with glass/carbon as a day job. But I did manage a glasss/carbon devision in a previous job many years ago. So guess you could call me a serious DIYer with some professional knowledge.

    Here's my latest build. A hydrofoil kiteboard. A somewhat harder endevour than a mountianbike frame repair!


    Carbon frame repair-img_20171223_142854.jpg

  18. #18
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    Well, I don't have pictures of each step of the process, but I sanded down to carbon, laid some opposing helix strips, then put a few layers on top of that, then let it cure. Then went to town sanding it down. Some clear-coat on top and hopefully this holds up. Originally, I had damaged it from a sharp impact and I noticed some delamination on the chainstay. It wasn't visibly cracked, but sanding it down it appeared similar to the sanded down top-tube above, where there appeared to be some underlying delamination. I was in my full-on ebola suit for this and yes, those carbon fibers can get everywhere.

    Carbon frame repair-01f25db76defb7433a79c5c3413ab74de31540681b.jpgCarbon frame repair-010e8698692037c29440270fd5d749df727c025c9e.jpgCarbon frame repair-0134c5fe3c5de34e0d99254092ad48b08df57fd9b4.jpg
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

    You're turning black metallic.

  19. #19
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    Quote Originally Posted by Jayem View Post
    Well, I don't have pictures of each step of the process, but I sanded down to carbon, laid some opposing helix strips, then put a few layers on top of that, then let it cure. Then went to town sanding it down. Some clear-coat on top and hopefully this holds up. Originally, I had damaged it from a sharp impact and I noticed some delamination on the chainstay. It wasn't visibly cracked, but sanding it down it appeared similar to the sanded down top-tube above, where there appeared to be some underlying delamination. I was in my full-on ebola suit for this and yes, those carbon fibers can get everywhere.

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    A worthy looking repair.

    2 months in and my repair is still going strong. No creeks or growns or any sign of an otherwise awesome repair. I'm using this bike for my super chunk fest mountain runs. Its getting a good work out.

  20. #20
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    Well we are a full 12 months on from my carbon repair.

    How is the long term test going?

    Excellent. The bike has performed as expected and is still going strong.

    In fact unless you are a perveyor of slayer frames you can tell it has been repaired unless i point it out to them. Even then you have to have 2 slayer frames next to each other to tell the difference.

    It is safe to say the the repair is a total success. Plus i get to enjoy the decadence of a 2 slayer quiver.

  21. #21
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    So my first carbon repair, above, is around 2 years at least, it's seen thousands of miles of races and rides since. Attempting another repair right now due to a rake that caught caught in my seat-stay and cracked it.
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

    You're turning black metallic.

  22. #22
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    Quote Originally Posted by plummet View Post

    Carbon trimming and layup development. 600 gram uni directional used.
    2 layers spiral wrapped sleaving the crack. One layer full length top tube. This will give me torsional strength, plus extension and compression strength. Extending the repair fill length of the top tube will add more strength than the original design.
    Quick question Plummet, you said UD, but it looks like 2x2 weave? 2x2 would seem like the easiest to work with for any repair, vs. UD being used for some original structures where it provides the best strength to weight.

    I had another "incident" recently. During a trail-building session, caught a rake in my seat-stay and made loud cracking noise, which wasn't the rake.

    Wasn't going to aesthetics, but I probably shouldn't have wrapped it in tape after the repair, but just left the painted surface. I'll probably take the tape out sometime soon. I wasn't using 600g, so I used more layers, opposing helix strips, etc. Final structure is now oval, vs. original rectangular, which adds beef to the structure. Got out and rode hard yesterday, lots of air time, seems ok so far. Hopefully good for the long run again.


    Carbon frame repair-013b2bf2dc8d2aa4934b511e12d9326e9121ffc771.jpg

    Carbon frame repair-01c431c606a9b033ba37e9180d17235002f49fbfa9.jpg

    Carbon frame repair-01f5ccf343f6f9ccddd544fcc559d4c5939548cd55.jpg

    Carbon frame repair-0174c19e9a929c2d0bc8ee496f9b663621f37ab1b3.jpg

    Carbon frame repair-01bae68d13e298a790ba30c80941254aed7c1845c0.jpg

    Carbon frame repair-010d613a9136f511df62e66eab5b2f98787c39e82e.jpg
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

    You're turning black metallic.

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