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carbon fiber fans: check this out!(13 posts)

carbon fiber fans: check this out!JohnG
May 4, 2002 9:25 PM
My LOOK KG281 frame is toast, or at least in need of some major TLC. Bike got rear ended by another rider and somehow taco'd the rear wheel and cracked the carbon seatstay. It was really a "nothing" deal but damn.... all that damage. Somehow the wheels got locked together in a death spiral.

Damn..... these LOOKS seatstays are pretty fragile. I'm more than a little miffed. LOOK says $450 and a "maybe".

Since the frame is junk value now, maybe I'll fix it myself. ??? Where's my can of bondo.... ;)

Sucks to be a fragile carbon
JohnG
re: carbon fiber fans: check this out!dustin73
May 4, 2002 11:03 PM
isn't the frame shot? i was always under the impression that once carbon cracks, it's toast.
It is, but...Ian
May 5, 2002 12:28 PM
... it is a lugged frame, so you pull out the broken piece and stick in a new one.

Ian
just curiousJohnG
May 5, 2002 9:42 PM
Is it unreasonable to expect a repair of the "tube" to hold up over time? I'm thinking of a tapered grind on the cracked section and a wrapped carbon/epoxy lamination over the ground down area. ?????

BTW: I wouldn't attempt this type of repair on a highly stressed tube section but I suspect this part of the frame is under relatively low stress. The "splint" area would likely end up a fair bit bigger than the original tube. I wouldn't really care re the looks of the tube at that point as this frame would be the new "beater" in the fleet. Any comments???

JohnG
Ahhh...Ian
May 6, 2002 5:39 AM
... now you have went a little beyond my expertise. But, the original carbon where it is cracked would not be supporting any stress. The new carbon would need to be as strong as the original tube, while also bonding to that tube. Not something that I see myself ever attempting, I would always worry about it when riding.

Ian
re: I've fixed chainstay andcyclopathic
May 6, 2002 7:08 AM
it hold up a couple years still going.

you need J&B Weld (Walmart) it's better then regular epoxy, and fiberglass or better CF cloth. Hardware stores sell fiberglass, you can find carbon fiber in boat repair places or on net. 3-4" tape seems easier to work with.

Basically you're building a "custom" lug around crack ;) and that's what you do:

take fine sandpaper and remove finish 2-3" around crack (be careful not to damage fibers), then put epoxy layer and wrap one layer with overlap, put another epoxy layer, repeat. Need 3 layers 2 minimum. After you're done with last layer coat it epoxy and let it dry (~24hr). Sand lightly, paint and it will be hardly noticeable, unless somebody is staring at it.

CP

PS. also check for cracks in other areas, they may show up later good luck
re: I've fixed chainstay andJohnG
May 6, 2002 11:36 AM
Interesting....... I would have thought that the repair area would be stronger if it was ground down at bit first.

JohnG
I second the JB weldDave Hickey
May 6, 2002 1:04 PM
That is one strong epoxy. I've used it for a lot of different applications, and it's the strongest I've used
Guess there are some things you just can't see coming.Leisure
May 5, 2002 12:24 AM
Sorry to hear your bad luck. Will the other guy's insurance cover anything? What are you thinking of getting now?
Guess there are some things you just can't see coming.JohnG
May 5, 2002 6:05 AM
This bike was actually on-loan to a friend but it does impact the 'stable' in that it's one less bike available for use.

I'm NOT a carbon expert but I have been told by several people that a carbon structure once cracked is unrepairable. ???? I think that the jetliner that crashed in NJ had a repaired carbon tail that failed again. :(

Craig Calfee said he would take a look at it and see what he thinks.

JohnG
duct tape? :-) nmDougSloan
May 6, 2002 5:31 AM
the 386 is repairable, seat stays are screwed on, and the carbonPaul
May 6, 2002 5:36 AM
lug can be broken at the wishbone. I can only guess at the cost and time to repair. A lot to be said about the low cost beer cans.
question for youJohnG
May 6, 2002 6:35 AM
I noticed the screw at the dropout area also. If I remove that screw will the seat stay come loose from the dropout "plate"????? If so, that would facilitate a way to internally "sleeve" the cracked area.

Let me know what you think
JohnG