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Big hole in top tube of new bike (Pics attached) aluminum repair with carbon fiber

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Big hole in top tube of new bike (Pics attached) aluminum repair with carbon fiber

Old 11-19-20, 12:25 PM
  #1  
Yellowlab
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**Update post 78** Big hole in top tube (aluminum repair with carbon fiber

So long story short I punched a huge hole in the top tube of my 2019 Specialized Allez that I've only had for about 6 months. Of course I can't replace it because there are zero bikes/frames at this price point available in this pandemic. The steps I took to fix it are as follows, with pics.


Sad day, backing tractor into shed and bucket swung out just enough to do this.



Step one, completely strip paint to bare metal. I just used a mouse sander and a dremmel to get into the tight spots in the damaged area.


Close up pic of the damage



Closer up pic of the hole. Ouch, what a hole!


Step two: You need to fill the hole with something to bring the area to be repaired back to shape. This will add strength to the damaged area and keep the carbon fiber in a uniform shape which will make it stronger when you lay it down later. I chose JB Water Weld because it specifically a.) is formulated to adhere to aluminum b.) hardens to a strenght rating of 1300 psi c.) is sandable after curing.


Step three: After curing, sand down material to match original shape as best as possible.


Step four: It is recommended etching the metal surface with some kind of acid. I used Krud Kutter Metal Clean & Etch. (About $10)
Step five: You can't put carbon fiber directly on aluminum because it would cause a caustic, or corrosive effect over time and the repair would probably not last.The fix is to put a coating of fiberglass over the etched aluminum to act as a buffer before proceeding. You can find the fiberglass at any big box home store for about $12 or so.



Step five: Prepare the carbon fiber. I found a carbon fiber repair kit on Amazon for $26. It came with a 3 ft by 6 inch rolled up sheet of fiber and 2 part epoxy to mix together with instructions. The company also has an instructional video on YouTube that is very helpful. I wanted the finished product to have a natural tapered look so I cut the fiber in a manner that would have it thin out as I wrapped it around the top tube. This particular piece of carbon fiber wrapped around far enough to provide 4 layers of carbon over the damaged area. The second wrap, later, will provide an additional 3 layers of carbon for a total of seven layers of carbon and one layer of fiberglass.


Step seven: This is several steps at once. Mix a small amount of the two part epoxy mix as directed and apply to area getting the wrap. Wait about 45 minutes until tacky so that it grips and holds the carbon fiber. You will need to mix another batch of epoxy when you start the wrap so that you can paint a layer of epoxy over the carbon fiber as you lay it down so that when the wrap come around again it is laying on epoxy treated fiber.
As soon as the carbon fiber is laid down you will need to wrap it with shrink tape (about $8 online) that has holes punched in it. The shrink tape is to both hold the carbon fiber down but also to compress it and push out excess epoxy so the fibers get a nice tight bond. I could not find the pre-holed shrink tape so I punched holes in mine with an razor. Once the shrink tape is on, use a hair dryer or heat gun to shrink it. The tape will tighten and compress the carbon fiber and the excess epoxy will come out of the holes. It's messy so I recommend having an old towel or rags down to catch the dripping epoxy.

There is a helpful instructional video on YouTube you can find by searching "carbon fiber bike repair" It will be the one with the nerdy looking guy in the lab coat.


Step eight: Wait 24 hours for the epoxy to cure and remove tape. It will be a sticky, somewhat uneven mess.

Last edited by Yellowlab; 11-26-20 at 12:57 PM.
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Old 11-19-20, 12:26 PM
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Part 2 continued

Part 2

Step nine: Sand first carbon treatment to desired look. I tried to keep as much of the original shape as possible without sanding off enough to compromise the structural integrity of the carbon fiber.


Step ten: Wash, rinse, repeat steps seven through nine for second carbon fiber wrap. The first wrap was about 6 inches wide, this second one was about 11 inches wide, again with thinner edges and getting thicker towards the middle to maintain a tapered look. The first 6 inch wrap was 4 layers of carbon. The second wrap was three layers as I ran out of fiber but there are a total of seven layers directly over the damaged section which should be plenty.


Step eleven: Again, wait a full day and remove tape to sand to desired shape. At this point once I had the basic shape, there was still a couple of "pits" here and there and I wanted a nicer finish so I took the time to apply two more coats of just epoxy during the next two days, over the final sanded layer of carbon fiber.


Once the final two layers of epoxy cured I sanded the final product down 400 grit sandpaper. If I was going for an actual carbon fiber look I'd probably get down to wet sanding with 800 grit but I'm just going to paint it clear so I can continue to have a visual on the repair and see if there are any potential issues popping up with it in the future.


Nothing can be done to prevent the fact that seven layers of carbon fiber and a layer of fiberglass will inevitably add a visible bulge to the fixed area that can be noticed upon closer inspection.


So that's it. The total cost of materials for the fix was about $70. It's mostly just a lot of time and elbow grease but I think it was worth it to not scrap the frame.

***Update*** I've taken the bike to a shop that has experience with frame repair for a hands on inspection before riding it. They said they thought the repair was a little overkill if anything and was done so that they don't see it failing any time soon.I told them I was going to clear coat it so that I could keep an eye on it moving forward and they said not to bother, just go ahead and paint it black. I'm still going to clear coat it, I actually like being able to see the repair. They have a great rep and have been around for 30 years so I feel pretty good about trusting them. I since have ~100 miles on it and it feels solid as a rock, tip to tail, hoping to report back after 1000 miles. Thanks for looking and thank you to everyone for participating with constructive conversation, I've been learning a lot!

Let me know what you think or if anyone here has any experience with this type of fix and did it hold up.

Thank you!
Cliff

Last edited by Yellowlab; 11-30-20 at 05:31 PM.
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Old 11-19-20, 12:28 PM
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Keep the paramedics on speed dial, just in case. That is some serious damage to that top tube and I wouldn't feel safe riding it like that.
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Old 11-19-20, 01:05 PM
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Originally Posted by veganbikes View Post
Keep the paramedics on speed dial, just in case. That is some serious damage to that top tube and I wouldn't feel safe riding it like that.
Well I am looking for feedback one way or the other and I appreciate your view. Also, your profile indicates you either own or work at a bike shop so you have experience. Can I ask is there something in particular about the fix that you would call a weak point? Do you think the structural integrity of the carbon fiber would not hold up? The naval engineer in the video giving the instructions said they have been fixing aluminum on naval ships like this for 25 years and that the several bikes he has fixed for friends and even one racer have never failed. The bike he fixed in the video was actually cracked almost all the way through in two spots. Appreciate you taking the time to help, thank you!

Last edited by Yellowlab; 11-19-20 at 01:11 PM.
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Old 11-19-20, 01:15 PM
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I suggest asking a moderator to move this thread to the framebuilder's subforum. You're likely to get more reliable responses there.
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Old 11-19-20, 01:21 PM
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The transition from CF (being ultrastiff) to alu (not that strong) could be a problem. I don't think a couple of layers is enough to spread out the force enough, even though you did taper the CF and therefore spread the load when it goes from CF to alu. You might have it buckle where it goes from CF to alu again.
I would have more layers and I'd have it the entire length of the top tube (but still tapered). Not least because CF is really bad in compression and the top tube is mostly in compression.

Last edited by CargoDane; 11-19-20 at 01:26 PM.
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Old 11-19-20, 01:25 PM
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Originally Posted by Yellowlab View Post
Well I am looking for feedback one way or the other and I appreciate your view. Also, your profile indicates you either own or work at a bike shop so you have experience. Can I ask is there something in particular about the fix that you would call a weak point? Do you think the structural integrity of the carbon fiber would not hold up? The naval engineer in the video giving the instructions said they have been fixing aluminum on naval ships like this for 25 years and that the several bikes he has fixed for friends and even one racer have never failed. The bike he fixed in the video was actually cracked almost all the way through in two spots. Appreciate you taking the time to help, thank you!
The big difference is the Navy is that there's some engineer who's worked out exactly how many wraps you need and how far they need to overlap. And there's a 57 page procedure detailing every step. In principle it should work, but there's a lot of ways for it to go wrong. If the layers don't properly adhere to each other, it's much more likely to fail.
Riding it entirely up to how you feel about it. When you do decide to replace the frame....please please please take a hacksaw and cut this frame up. I'm all for people repairing things, but please don't pass it along to others.
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Old 11-19-20, 01:39 PM
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A followup report after ~1000 or so miles of riding would be appreciated. Thanks very much for the well documented repair.
I would have no real concerns about riding the frame with provisos that the bike is not raced or subjected to high speed
descents *. Catastrophic failure seems unlikely and would be preceded by, I feel, obvious changes in bike handling that would
clue the rider in.

* eg:
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Old 11-19-20, 01:40 PM
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I'm a retired boat builder and have worked with composites, both glass and carbon. That is a fine job and I would not worry about it. Nevertheless, it costs nothing to keep an eye on it.
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Old 11-19-20, 01:44 PM
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Well, it’s definitely badly damaged. You didn’t say how you did it, but your repair will at least keep the rain out You recognized this is a structural member and given the circumstances took a shot at repairing, which is definitely to your credit. At best the repair is a “stabilizing repair” not a permanent repair.

For anyone afraid it will fail, it might but there will be warning signs before it does. The OP seems to possess more than a modicum of “garage logic” and will do the right thing. Time might present options to replace the frame so he’s not left stranded.
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Old 11-19-20, 02:41 PM
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Originally Posted by CargoDane View Post
The transition from CF (being ultrastiff) to alu (not that strong) could be a problem. I don't think a couple of layers is enough to spread out the force enough, even though you did taper the CF and therefore spread the load when it goes from CF to alu. You might have it buckle where it goes from CF to alu again.
I would have more layers and I'd have it the entire length of the top tube (but still tapered). Not least because CF is really bad in compression and the top tube is mostly in compression.
HI CargoDane, thank you for the feedback. It was actually two seperate "treatments" or "wraps" of several layers each. The first wrap had 4 layers of carbon and the second wrap had 3 for a total of seven layers of carbon fiber over the damaged area. You used the term "a couple layers" and I just wanted to see if your opinion would change at all based on there being 7 layers. Thanks again! Cliff
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Old 11-19-20, 02:46 PM
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Yes, certainly changed. It should still have been more spread out, so to speak, but the worry about the CF strength I believe is over. Now it's a question on whether the edges will make the top tube collapse where the CF stops.
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Old 11-19-20, 02:53 PM
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Originally Posted by gsa103 View Post
The big difference is the Navy is that there's some engineer who's worked out exactly how many wraps you need and how far they need to overlap. And there's a 57 page procedure detailing every step. In principle it should work, but there's a lot of ways for it to go wrong. If the layers don't properly adhere to each other, it's much more likely to fail.
Riding it entirely up to how you feel about it. When you do decide to replace the frame....please please please take a hacksaw and cut this frame up. I'm all for people repairing things, but please don't pass it along to others.
Well, I did exceed the number of layers he used for his repair and also spread the tapering out beyond the ratio of repair area that he recommended. I'll post the video here so others may view if they wish.

Also, I took it for granted that this bike, should the repair hold up, be a "forever bike". I'd not pass it on to anyone else for what I would assume are the same reasons no one would want to take it on as their own. I would not be comfortable with someone else's repair having no knowledge of what went into it. I know that I spent a week or better researching the process and at least another week meticulously and painstakingly putting all of the layers down with as much care and responsibility as I would know how. No one should take it for granted or assume the risk and I would not let them should they want to.
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Old 11-19-20, 03:03 PM
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Originally Posted by reconnaissance View Post
Well, it’s definitely badly damaged. You didn’t say how you did it, but your repair will at least keep the rain out You recognized this is a structural member and given the circumstances took a shot at repairing, which is definitely to your credit. At best the repair is a “stabilizing repair” not a permanent repair.

For anyone afraid it will fail, it might but there will be warning signs before it does. The OP seems to possess more than a modicum of “garage logic” and will do the right thing. Time might present options to replace the frame so he’s not left stranded.
Hi reconnaissance, thank you for the feedback. I was backing the tractor into the shed and looking behind me to do so. When I cut the wheel slightly to adjust, the bucket which sits way out in front swung over enough that the tooth of the bucket was able to do this damage. Normally the bike is hanging on a rack out of reach so it usually isn't a concern. One of those situations where I forgot to hang the bike and the bucket was just at the exact right height and everything came together just right. Not my finest moment for sure.

Appreciate the comment regarding apparent garage logic, I would like to think you are right but my ego isn't such that I wouldn't get a second opinion which is why I'm posting here; to get the opinion of folks like yourself. Also, this bike will primarily be used as trainer bike during the winters on Zwift. I suppose I should have mentioned that in the OP. I have other bikes that I ride on the road so this one is likely to see very little if any real riding.

Thanks again,
Cliff
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Old 11-19-20, 03:08 PM
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Originally Posted by berner View Post
I'm a retired boat builder and have worked with composites, both glass and carbon. That is a fine job and I would not worry about it. Nevertheless, it costs nothing to keep an eye on it.
Berner, thank you for the feedback! I appreciate very much hearing from someone that has a lot of experience with these materials saying you think it is a fine job. I wouldn't be able to say so definitively since it is my first go at it so it goes a long way with me to hear that from you. Thank you again!
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Old 11-19-20, 03:10 PM
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Originally Posted by sch View Post
A followup report after ~1000 or so miles of riding would be appreciated. Thanks very much for the well documented repair.
I would have no real concerns about riding the frame with provisos that the bike is not raced or subjected to high speed
descents *. Catastrophic failure seems unlikely and would be preceded by, I feel, obvious changes in bike handling that would
clue the rider in.

* eg: https://www.youtube.com/watch?v=fJSpgRIVw78&t=199s
sch, thank you for the feedback. I should have mentioned in my OP that this bike is only used on a trainer in the winter for Zwift. I have two other road bikes I use during the summer so this repair will likely see very little if any road riding. Thank you again!
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Old 11-19-20, 03:35 PM
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Originally Posted by Yellowlab View Post
sch, thank you for the feedback. I should have mentioned in my OP that this bike is only used on a trainer in the winter for Zwift. I have two other road bikes I use during the summer so this repair will likely see very little if any road riding. Thank you again!
Oh, in that case, two pieces of broom handle and gaffer tape would probably have sufficed!
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Old 11-19-20, 03:44 PM
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Re: etching
Aluminium spontaneously react with air by forming an oxide layer. Getting stuff to bond well to that layer is tricky. The etching is supposed to remove that oxide layer to let whatever you’re applying bond to truly bare metal.
One option to etching is to mix up a small batch of resin, then use that to wet sand the area about to be treated. The sanding breaks through the oxide simultaneously as the resin fills in the scuffs before the metal has had time to re-oxidise.

I think you’ve done a good job and I would be quite content to ride a bike with that kind of repair. A good amount of overlap.

Me, I might have tried to get away from that huge chunk of filler some way. And maybe cut the CF more at a taper the whole way to create a smoother transition from the aluminium to the repair and back to the aluminium.
Not that I think it’d be hugely important.
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Old 11-19-20, 05:20 PM
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Originally Posted by dabac View Post
Re: etching
Aluminium spontaneously react with air by forming an oxide layer. Getting stuff to bond well to that layer is tricky. The etching is supposed to remove that oxide layer to let whatever you’re applying bond to truly bare metal.
One option to etching is to mix up a small batch of resin, then use that to wet sand the area about to be treated. The sanding breaks through the oxide simultaneously as the resin fills in the scuffs before the metal has had time to re-oxidise.

I think you’ve done a good job and I would be quite content to ride a bike with that kind of repair. A good amount of overlap.

Me, I might have tried to get away from that huge chunk of filler some way. And maybe cut the CF more at a taper the whole way to create a smoother transition from the aluminium to the repair and back to the aluminium.
Not that I think it’d be hugely important.
Thank you dabac! That is great info about the etching. I wish we had conversed a couple of weeks ago :-) It is nice hearing the opinions of everyone but I appreciate most getting feedback from someone like you with first hand experience with this type of thing. Thank you again for taking the time and for the great vote of confidence in the repair!
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Old 11-19-20, 05:34 PM
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I've no idea how well it'll stay bonded to the aluminum, but as long as it does, ride it. You'll probably know if it ever gets to failing well before it is an immediate issue. But I'd say you did a good job. I wouldn't sell it though. Especially not without full disclosure.

What you did is not unlike how you patch up fiberglass boats and other things made with fiberglass and epoxy or polyester resin. And they hold up as good as new.

Let us know in a year or two how it's holding up.
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Old 11-19-20, 06:04 PM
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Originally Posted by Yellowlab View Post
Appreciate the comment regarding apparent garage logic, I would like to think you are right but my ego isn't such that I wouldn't get a second opinion which is why I'm posting here; to get the opinion of folks like yourself. Also, this bike will primarily be used as trainer bike during the winters on Zwift. I suppose I should have mentioned that in the OP. I have other bikes that I ride on the road so this one is likely to see very little if any real riding.
In that case, it's fine. Honestly, it's a very through repair. I don't know that I'd trust it to last thousands of miles with various potholes and irregular impacts, but as a trainer it'll never see those loads. The primary risk is aluminum corrosion at the joint, due to sweat from the trainer. So as long as it's properly painted, it should be fine.
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Old 11-19-20, 07:17 PM
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Originally Posted by Yellowlab View Post
Well I am looking for feedback one way or the other and I appreciate your view. Also, your profile indicates you either own or work at a bike shop so you have experience. Can I ask is there something in particular about the fix that you would call a weak point? Do you think the structural integrity of the carbon fiber would not hold up? The naval engineer in the video giving the instructions said they have been fixing aluminum on naval ships like this for 25 years and that the several bikes he has fixed for friends and even one racer have never failed. The bike he fixed in the video was actually cracked almost all the way through in two spots. Appreciate you taking the time to help, thank you!
I work at a shop and am a general bike nerd. I find a lot of home-brew fixes to be a bit sketchy. You may have good luck and it may work out but the idea of it doesn't sit well with me. People do it and sometimes they have great luck but I personally wouldn't do it. If I had to do something I would go to a professional frame builder who works in that material.

People on the internet may have qualifications out the wazoo because it is the internet and you can do what you want. They may get lucky with a fix they did heck they may do it all the time but stuff like that you gotta be extra careful of. They can take their own life into their hands but are they prepared to handle things if someone says yeah try this at home kids and it doesn't work out as well?

Whatever you do stay safe and sometimes it is best to say "I have a cool Specialized wall hanger". I had to do that to my beloved Langster but in that circumstance it was a frame failure and they replaced it so I was covered. If mine failed like your's did I would have said ok now time to get that custom bike I have wanted at least these days. If bikes were in supply I would say ok let's see what I can replace it with.
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Old 11-19-20, 07:34 PM
  #23  
79pmooney
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I did a somewhat similar repair to the chainstays of a Reynolds 501 steel Peugeot sport bike 15 years ago. I picked up the frame "as is" after it was hit hard by probably an SUV from the side. Trashed fork, dented top tube and both chainstays about to break behind the support. (Cracks totaled a full circumference.)

I built and raced sailboats in a former life and happened to have a few feet of unidirectional CF as well as Gougeon Bros. boatbuilding epoxy and years of wet laminating skills. I stripped the paint from above and forward of the BB shell back to several inches behind the chainstay support. Took the CF and cut it to several narrow strips. Masked off the tubes beyond the paint stripping. Taped the ends of the fiberglass strips firmly to the painted portions of the seat and down tubes.

Then I mixed the epoxy, brushed it onto the stripped area going right to the masking tape. Laid pieces of CF longitudinally along the chainstays. Then wrapped the CF strips turn by turn, wetting it out as I went and pulling it tight.after wetout. I took turns around the support as well as the chainstays. Taped the still dry end again firmly to the painted chainstay. But things started going badly. The CF was too stiff and the epoxy resin wasn't breaking down the binder in the fabric so it was springing away from the metal. This as the epoxy was starting to set up.

Ran in side, grabbed my thinking cap and thought fast! An innertube wrap. A crude vacuum bag. Cut tubes into two strips each. taped them just like I did the CF and wrapped it tight! Lots of resin squeezed out. I knew it had set up enough that doing anything would be a disaster so I spread newspaper and left.

Next day, I returned fearing the worst. Unwrapped the innertube which came off nicely to see a finished job that looked vacuum bagged! Took a sharp knife to trim the CF right at the tape edge and pulled the tape. Nice and clean. Sanded it just enough to remove hairs and owies. (Later I had to grind the CF down to clear the chainring but that was well past the crack so the cut fiber didn't matter. The point was to not cut or jeopardize any of the CF strands to keep full strength.) Finally I painted the repair black. (On a red bike.)

End result? It turned the typical loosey-goosey Peugeot BB into the stiffest Peugeot ever made. Never worried about that crack (or anywhere else around the BB) again. Rode it 8000 miles. (I did not take it into the hills, but not because of that repair. I had no idea what else on that frame was compromised when that SUV hit it and had no interest in finding out going downhill.) The frame is now retired. I've suffered two hard crashes on it (not its fault and it came through far better than I) plus I wanted a bike that much fun I could take into the hills so my avatar was patterned after it to take its place.

Sorry, no pics.

Ben
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Old 11-19-20, 09:04 PM
  #24  
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Your repair seems well thought out. Bravo. Keep an eye on it though.
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Old 11-19-20, 09:23 PM
  #25  
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Originally Posted by 79pmooney View Post
I did a somewhat similar repair to the chainstays of a Reynolds 501 steel Peugeot sport bike 15 years ago. I picked up the frame "as is" after it was hit hard by probably an SUV from the side. Trashed fork, dented top tube and both chainstays about to break behind the support. (Cracks totaled a full circumference.)

I built and raced sailboats in a former life and happened to have a few feet of unidirectional CF as well as Gougeon Bros. boatbuilding epoxy and years of wet laminating skills. I stripped the paint from above and forward of the BB shell back to several inches behind the chainstay support. Took the CF and cut it to several narrow strips. Masked off the tubes beyond the paint stripping. Taped the ends of the fiberglass strips firmly to the painted portions of the seat and down tubes.

Then I mixed the epoxy, brushed it onto the stripped area going right to the masking tape. Laid pieces of CF longitudinally along the chainstays. Then wrapped the CF strips turn by turn, wetting it out as I went and pulling it tight.after wetout. I took turns around the support as well as the chainstays. Taped the still dry end again firmly to the painted chainstay. But things started going badly. The CF was too stiff and the epoxy resin wasn't breaking down the binder in the fabric so it was springing away from the metal. This as the epoxy was starting to set up.

Ran in side, grabbed my thinking cap and thought fast! An innertube wrap. A crude vacuum bag. Cut tubes into two strips each. taped them just like I did the CF and wrapped it tight! Lots of resin squeezed out. I knew it had set up enough that doing anything would be a disaster so I spread newspaper and left.

Next day, I returned fearing the worst. Unwrapped the innertube which came off nicely to see a finished job that looked vacuum bagged! Took a sharp knife to trim the CF right at the tape edge and pulled the tape. Nice and clean. Sanded it just enough to remove hairs and owies. (Later I had to grind the CF down to clear the chainring but that was well past the crack so the cut fiber didn't matter. The point was to not cut or jeopardize any of the CF strands to keep full strength.) Finally I painted the repair black. (On a red bike.)

End result? It turned the typical loosey-goosey Peugeot BB into the stiffest Peugeot ever made. Never worried about that crack (or anywhere else around the BB) again. Rode it 8000 miles. (I did not take it into the hills, but not because of that repair. I had no idea what else on that frame was compromised when that SUV hit it and had no interest in finding out going downhill.) The frame is now retired. I've suffered two hard crashes on it (not its fault and it came through far better than I) plus I wanted a bike that much fun I could take into the hills so my avatar was patterned after it to take its place.

Sorry, no pics.

Ben
Awesome story! I love hearing about stuff like that. That inner tube idea sounds pretty brilliant to come up with on the spot. Not sure I would have thought of that one. Might even be easier to apply as a wrap and also come off easier and cleaner than the heat shrink tape I was using. That stuff was kind of a pain. I can picture what you're talking about but wish you had pics none the less. Can't fault you though, I probably won't have these pics in 8 or 10 years. Glad to hear you got so much use from it after the repair! Thanks again!
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