Mountain Bike Reviews Forum banner

1 - 17 of 17 Posts

·
Elitest thrill junkie
Joined
·
35,025 Posts
Discussion Starter #1
But not as expected.

Doing trailwork a few days ago I was foolishly attempting to ride a few feet with a rake to take it back to the tools car and somehow caught it in my rear seatstay. Loud cracking noise that sounded like rake handle, but was unfortunately my seatstay.

The new layup is curing right now and should be ready for sanding tomorrow...which will be a big job.

013b2bf2dc8d2aa4934b511e12d9326e9121ffc771.jpg

01c431c606a9b033ba37e9180d17235002f49fbfa9.jpg

01e24ff5cee638481f0509e504205b074a334fa321.jpg

01926a2ed6c90d900ee5f986b8b5552c950172bc50.jpg

011487b21cc5bb93a625e7bafcbd295421c3cc9f1b.jpg

01f5ccf343f6f9ccddd544fcc559d4c5939548cd55.jpg
 

·
Elitest thrill junkie
Joined
·
35,025 Posts
Discussion Starter #2
Making progress.

013078e0054d15fa74e37a8edbc84ebf8940835da7.jpg

019a5a6d88bded9fc3b09bd2ce4fdbe2b34272347c.jpg

0174c19e9a929c2d0bc8ee496f9b663621f37ab1b3.jpg

01fa2c8857c375fa63b2316d9b1319a8ec2f9569f9.jpg
 

·
Registered
Joined
·
6,024 Posts
So you overlayed over the crack or cut out and spliced in? Hard to tell from your pic.

Sent from my moto g(6) forge using Tapatalk
 

·
Elitest thrill junkie
Joined
·
35,025 Posts
Discussion Starter #5
So you overlayed over the crack or cut out and spliced in? Hard to tell from your pic.

Sent from my moto g(6) forge using Tapatalk
Lots of sanding, the structure was pretty much toast when I got down to it (last picture in the first post). Can't really "cut it out", it just kept sharding off at that level, so overlayed helical strips above and below. You can't make a "tube" anymore, but helical strips are kind of the next best thing, in opposing directions for each layer. I think I ended up with 4-5 structural layers and then a layer on top to cover it all. I'm kind of lazy though, it took half a day just to sand it down to the 2nd to last picture, so while I could go further and get it looking nicer, I'm just going to clear coat and paint over it and make it matte black.
 

·
Elitest thrill junkie
Joined
·
35,025 Posts
Discussion Starter #6
No pictures of laying the carbon though, it's just too damn messy to even try. As soon as you get the CF out and start cutting it, it's full PPE time and you might as well get it all laid up in one big swoop.
 

·
Registered
Joined
·
2,682 Posts
Ouch! Good reminder to use my steel hardtail as the trail-tool-mule!

Maybe you could start up some similar Turner-V.-Ellsworth type banter by posting this in the Yeti forum as a handy how-to guide....
:lol:
 

·
Elitest thrill junkie
Joined
·
35,025 Posts
Discussion Starter #8
Ouch! Good reminder to use my steel hardtail as the trail-tool-mule!

Maybe you could start up some similar Turner-V.-Ellsworth type banter by posting this in the Yeti forum as a handy how-to guide....
:lol:
Yeti doesn't appear to need any help, the video the guy posted of his SB100 carbon layup was absolutely mind-blowing.

Black in Black and riding today.

01bae68d13e298a790ba30c80941254aed7c1845c0.jpg

010d613a9136f511df62e66eab5b2f98787c39e82e.jpg
 

·
Registered
Joined
·
1,354 Posts
The cost for that repair might be only 200-300 at some repair places. I would rather just have someone else do it.
 

·
Elitest thrill junkie
Joined
·
35,025 Posts
Discussion Starter #10
The cost for that repair might be only 200-300 at some repair places. I would rather just have someone else do it.
A full yard of CF only cost $40 bucks, I didn't have quite enough on hand to be comfortable with, so I got a yard. I still had plenty of resin and hardener left over from the last job. Apart from sandpaper, there wasn't much cost involved. Don't forget, on top of that $300 you have to still tear your frame down, package and ship it, risking further damage. Shipping ain't free and is especially problematic for bigger items like bicycle frames. Not an insignificant amount.
 

·
Registered
Joined
·
2,682 Posts
Yeti doesn't appear to need any help, the video the guy posted of his SB100 carbon layup was absolutely mind-blowing.
The one where they "forgot" the resin and he was squashing the tubes by hand?? I had a friend with an SB6 that you could do that to in a couple of places, I kinda figured it was just the frame but maybe not?! He now rides a Kingdom Vendetta and laughs at anyone on a carbon bike...
:lol:

Glad the repair worked well and the RFX is still out there fighting!
 

·
Elitest thrill junkie
Joined
·
35,025 Posts
Discussion Starter #12
The one where they "forgot" the resin and he was squashing the tubes by hand?? I had a friend with an SB6 that you could do that to in a couple of places, I kinda figured it was just the frame but maybe not?! He now rides a Kingdom Vendetta and laughs at anyone on a carbon bike...
:lol:

Glad the repair worked well and the RFX is still out there fighting!
I didn't want to add fuel to the fire, but hell my compromised RFX seemed far more structurally intact than that Yeti. I got a pretty good appreciation for the carbon layup on the RFX doing this work and it appears pretty high quality. Sure, carbon can be thin and you shouldn't be clamping some of the structures hard in things like stands, but damn, that Yeti was crazy.
 

·
Elitest thrill junkie
Joined
·
35,025 Posts
Discussion Starter #13
Repair looks better without the nasty tape

01fabe3ce5adb534cce91d67f3e31fc00f96c5a40c.jpg
 

·
Registered
Joined
·
672 Posts
So you're saying the rake handle got caught up in your rear wheel and did that damage to your chainstay instead of snapping a spoke or two? Yikes!

Your DIY repair looks pretty good though, hopefully it holds up. Nice handy work.
 

·
Elitest thrill junkie
Joined
·
35,025 Posts
Discussion Starter #15
So you're saying the rake handle got caught up in your rear wheel and did that damage to your chainstay instead of snapping a spoke or two?
Yeah, it was hard to see exactly while it was happening, I think the rake got more wedged between the stay and wheel rim or tire possibly, where the leverage distance made it easy to crack the stay, but it was in tall grass and obviously happened rather quick (not traveling fast though). Once the rear triangle was unbolted, everything else seemed to check out fine, lots of little nicks and scratches over the years, but only the seatstay seemed to be affected. The cracking noise when it happened was pretty loud though, unmistakable, except it sounded just like the wooden rake handle snapping.
 

·
not so super...
Joined
·
11,465 Posts
Did you cure it under vacuum and heat? If you didn’t draw out all the air bubbles the new layers you added will most likely have too much porosity and not add the strength you are seeking.

That doesn’t even begin to account for the proper fabric (weave, weight, material) and epoxy compound (mix ratio, fabric to epoxy ratio, cure method.....).
 

·
Elitest thrill junkie
Joined
·
35,025 Posts
Discussion Starter #17
Did you cure it under vacuum and heat? If you didn’t draw out all the air bubbles the new layers you added will most likely have too much porosity and not add the strength you are seeking.

That doesn’t even begin to account for the proper fabric (weave, weight, material) and epoxy compound (mix ratio, fabric to epoxy ratio, cure method.....).
It depends on what resin system you are using. The resin I'm using will cure at 40 degrees, recommended was something like 50 or 60, but I was well above that (waited for a nice warm day). The mix ratio is dependent on the resin system you are using (and provided).

It depends on how fancy you want to get and how complex the structure. If I don't have any remaining structure, it gets much harder to lay down fabric and not have porosity/voids. I've heard of people using wood dowels or other shapes for this, but it's really going to depend. So, since i had remaining structure, I could just use peel ply and absorber cloth on top after wrapping to "squeeze out" any voids/air. Then yes, we aren't using UD like the original, so what I end up doing is making circular helix's out of strips. You run a strip in a helix in one direction, then run another strip in a helix in the opposite direction. This is because you can't make a continuous "tube" out of UD or even 2d, unless you have far more complex means. But the helix shapes give you the ability to get similar structural strength, as in just cutting a rectangle and drooping it over the broken part is NOT going to give you the strength, or just making a "patch" is not going to give you the strength. What I an generally doing is re-building and over-building the damaged member with multiple helixs in opposing directions. It's not as obvious in the pictures, but the "new" stay is significantly built up, I think I got either 4-5 helix strips in before a "top-off" rectangular wrap. Depending on the weight of the CF, I could vary the number of strips, as in use less or more, but again, for this, I would just tend to over-build it and who cares if it ends up larger than before.

I've done this before, I repaired my fat-bike that I accidentally took a hammer to the chainstay and it turned grey (de-laminated). I had to follow a similar process and that was kind of my prototype experience.

For more complex structures, this method would not work and eventually you'd need a vacuum system, but for simpler stuff, this has worked fine and several of us (on the site) have done it. The biggest issue is simply the messy nature of CF during cutting and laying and the monotonous sanding before and after.
 
1 - 17 of 17 Posts
Top