Good all-around unidirectional CF for bike repair

[Colin]

Hello! 

I've devoured...a lot...of YT and forums on carbon bike repair. My repair is a fracture on a flat section of my non-drive seat stay, and most CF repair kits include a 2x2 3k twill (wet laminate and heat tube method), but nearly every repair person says that it's best to try and layer along similar UD patterns. I've yet to sand down the area, and I don't have calipers to measure tow thickness to match weaves — I'm really not that crazy — but I'd like to at least have one or two UD layers running in the load direction or on slight angles, and then put the 2x2 as my top layer for aesthetics and overall strength. 

I'm not an engineer, but I have a feeling that I'm vastly underestimating just how strong this stuff is. I'm probably overthinking it. But I'd love a link to a Rock West product that is a solid UD prepreg that is flexible enough for slight bends. Like, is 3k standard modulus a good choice? 

[Colin]

I see also that I've made several mistakes even in asking my question...

Since I'm doing wet laminate and heat tape*, I probably want a dry UD, perhaps like this?

[lo_0l]

29 minutes ago, Colin said:

Hello! 

I've devoured...a lot...of YT and forums on carbon bike repair. My repair is a fracture on a flat section of my non-drive seat stay, and most CF repair kits include a 2x2 3k twill (wet laminate and heat tube method), but nearly every repair person says that it's best to try and layer along similar UD patterns. I've yet to sand down the area, and I don't have calipers to measure tow thickness to match weaves — I'm really not that crazy — but I'd like to at least have one or two UD layers running in the load direction or on slight angles, and then put the 2x2 as my top layer for aesthetics and overall strength. 

I'm not an engineer, but I have a feeling that I'm vastly underestimating just how strong this stuff is. I'm probably overthinking it. But I'd love a link to a Rock West product that is a solid UD prepreg that is flexible enough for slight bends. Like, is 3k standard modulus a good choice? 

Do you have a picture of the damage?

[Colin]

Yes! Specialized FACT 10r frame. 

[lo_0l]

28 minutes ago, Colin said:

Yes! Specialized FACT 10r frame. 

I would buy a new fork. I don't think you're going to repair this at home in a manner that would be safe.

It might be worth contacting Specialized to see if it's covered under warranty. They might at least sell you a fork at a cost. Worth asking for sure.

[Colin]

21 minutes ago, lo_0l said:

I would buy a new fork. I don't think you're going to repair this at home in a manner that would be safe.

It might be worth contacting Specialized to see if it's covered under warranty. They might at least sell you a fork at a cost. Worth asking for sure.

Oh, I do appreciate the concern, but I think the situation changes significantly because this isn't my fork — it's the seat stays on the back of the bike. It's a pretty common place for people to do DIY carbon repairs online, and several repair companies even have videos devoted to just that location. I'd never touch a fork DIY. 

[lo_0l]

2 hours ago, Colin said:

Oh, I do appreciate the concern, but I think the situation changes significantly because this isn't my fork — it's the seat stays on the back of the bike. It's a pretty common place for people to do DIY carbon repairs online, and several repair companies even have videos devoted to just that location. I'd never touch a fork DIY. 

The pictures you shared appear to be a fork. Perhaps you shared the wrong pictures? 

[BenCarbonNovice]

 

I am a novice with composites, but I have a lot of experience with bikes.  I agree that at a glance, it looks like a fork, but that is because the orientation of what is up and down is lost.  However, that is but it is clearly the rear wheel. 

Colin,  Your photos are fine.  I bet you can fix it, but I must admit that I'm not qualified to give you sound advice. 

[lo_0l]

On 6/29/2024 at 10:06 PM, BenCarbonNovice said:

 

I am a novice with composites, but I have a lot of experience with bikes.  I agree that at a glance, it looks like a fork, but that is because the orientation of what is up and down is lost.  However, that is but it is clearly the rear wheel. 

Colin,  Your photos are fine.  I bet you can fix it, but I must admit that I'm not qualified to give you sound advice. 

 

Ah, I see the chain now. Thanks!

Still wouldn't do this personally. I'm just not sure they're going to be able to prevent it from breaking all of the way through. It already looks to be cracked through and through, and it's just not something I'd personally want to be flying down the trail on and have fail.

That said, there are people who specialize in this stuff like Appleman Bicycles. You could try getting in touch with them @Colin 👍