At first, I thought... there is not enough resin in here. Did I squeeze out too much? I was all set to try again, but decided to run some tests on it.
I can't crush it with Channel-lock pliers, or break it, holding on with pliers.
It is VERY difficult to score with a razor knife.
With all my might (I'm a cyclist, that is not a lot of might), I can't break this by hand.
In wrestling with it, the only damage I could do was to snap the pipe, where it meets the repair.
I finally stuck a steel rod in each end of my little carbon fiber "pipe". Laid the works over a 2x4 board, and stood on the ends of the pipes. It finally broke at the point where I joined the pipe together. I'm confident that a pristine seat-stay would have failed the same test. So... instead of more testing... I'm just "going for it" on the bike. Worst case, I need to sand it back and try again.
The seatstay, with a layer of epoxy. I stressed the stay a bit, to get the epoxy to flow in as best I could. I'll let this set up for the next 10 minutes while I cut my sheet.
BTW, I mixed the epoxy by weight and not volume. I learned later, that isn't ideal. It seems to work just fine, so far.
Here's my sheet of plain-weave. I honestly didn't put a ton of thought into the length/number of wraps. My logic went like this.... my test was plenty strong. My seatstay is thinner than my test-pipe. I'll just cut a length of fabric longer than I used for my test. I'll have more wraps than my test... it will be strong. I forgot to count the wraps, so I don't even know how many there are. If anyone wants, I can figure it out, since I put a ruler in the picture.
Ready to tape. Make sure the tape is wrapping in the direction of the fabric wrap. This is a place where doing a test was very valuable in doing a good job. I found that wrapping the fabric tightly is difficult, because the epoxy is slippery. getting the first wrap tight sucks. It wasn't tight on my test.
On this, I wrapped all the wraps as best I could, then just kept tighting the roll over the stay. I probably turned it in place 5 times before it really snugged up. Once snug, I didn't much care where the fabric ended on the outer wrap.
Sorry for the focus. it happens a lot in this project. This is the tape, wrapped tightly, epoxy oozing out as I go, but locked-in once wrapped.
This is really out of focus. it's a shame, because you can really see the value in the pin-hole method of this technique.
The first stop was this Instructable: http://www.instructables.com/id/Repairi ... cle-Frame/
Very well done, in that he talked about what he liked and didn't like about his process. I didn't follow his method exactly, but this was the number-one inspiration that I could do this myself.
Next up, several YouTube videos. There's a bunch of questionable stuff out there.
The one most closely related to what I've done: https://www.youtube.com/watch?v=0OZxeGNnSIU
That video is good, because it is professional, but geared to the home DIY person (no vacuum needed). Good info about temp for curing.
Speaking of temperature for curing.....good information. What convinced me I really want to get the temp up. https://www.masterbond.com/interview/q- ... e-industry
Sure, this stuff will cure at "room temp", but as mentioned in the Predator Cycling video, and verified in the masterbond tech docs.... above 80*F is better, stay below 150*F
This picture is a mess. If you look at it long enough, you can see what's going on....
Heat lamp faces seatstay. Foil-faced insulation panels as reflectors. The blue glove and plastic-wrap are pretty good indications that the temp isn't too high.
Fortunately, I did use a little science:
With the non-contact thermometer, I kept the temp of the repair area to around 110* F. Not bad, since this is a garage, with room temp at 50*. Should I have moved my wife's MTB tire further from my work area? Yes. But you can easily stick your hand between the frame and this heater, without feeling the urge to pull it away.
Side-story... the last time I used this heater was in this garage, heater on the hood of my Jeep, pointed at the windshield. I was using it to cure the epoxy for mounting a rear-view mirror. SCIENCE!
It gets cold in the garage, so the whole works came indoors later. It spent 10 hours under the heat, and and a full 24 hours before the unveiling. The brush I used to apply this batch is under the heat, too. Easy gauge of how well things are progressing.
I intend for this repair to be thicker than the original profile. It will always look like it is "wearing a cast".
See that bare spot on the right side? That is where I sanded the finish off, but didn't get good coverage with fiber or epoxy. That bothers me. The point is certainly as strong as stock, but now it's a spot right next to my repair. It's now a weak-link, because the repair is so much less flexible than the original seatstay.
The side closest to the wheel. This is where the worst damage was. You can see my barespot on the left in this pic.
Discussed earlier, I'm concerned about the repair being much less flexible where it meets the exposed original seatstay. To deal with this I sanded my repair to taper on each end. This would have been a good place to integrate antonioiglesius' suggestion of a diagonal meeting point, but getting that diagonal edge done was beyond my skill of getting a good clean edge to lay down.
I tape further up the seatstay, get a smooth coat of epoxy on there, wait about an hour and peel the tape while the epoxy is still not solid.
It looks kind of cool.
Well.... I didn't receive what I ordered, I got 2x2 twill. You keen folks are still saying... I don't see 2x2 twill.
My original thought looked something like this:
My plain-weave would only be the top-coat. My plan changed when I was happy with my test-pipe, and didn't want to deal with a return and wait for new fabric. I also decided that running several direction-changes of unidirectional can only lead to me making a huge mess of things. That layup lends itself well to vacuum bagging.
The next steps were not planned. It all came together quickly and would definitely had come out better if I had planned for it. I'm not displeased, but I'm not thrilled.
As we saw in my last pics, I have a top-coat of epoxy drying. I hadn't used heat, so it was drying slowly. It's two hours later, still tacky.
I decide "I'm going to put a final dress-coat on this". Something that is not there for strength, but instead to protect my repair. I grab my 2x2 twill (that I had decided not to use).
When people think of what carbon-fiber "looks" like, the image is usually 2x2 twill. While it has compromised in strength/weight ratio, it is easy to wrap around contours....
close-up of my stuff
I want this to look nice. This layer is all bout looks. And covering up that bare spot we discussed earlier. But mostly looks. I've decided I am going to leave this repair visible (no frame-matching paint). It will be a "conversation piece". I'll lie and say I left it exposed so I can do a regular visual inspection, but really, I am leaving it visible as it's part of what this bike is, now.
This layer of fabric needs to be sized just right, with good clean edges. I decide to not use my roller-resin method. Instead, I'll lay electric tape on the edges of fabric, cut the fabric to the tape, lay the fabric on the tacky epoxy (from earlier) and peel off the electric tape. That was a mistake. Peeling the tape made a mess.
If I were to do this again, I'd use the roller-resin technique from earlier, and roll the crap out of it, leaving it resin-dry. I'd then put a very thin layer of new resin on top of my tacky resin, and wait 40 minutes for things to get good and tacky. THEN, I'd cut my fabric (while still sandwiched in the plastic).
Well, I didn't do all that. I laid my fabric on the tacky seatstay, pulled off the tape, made a mess that I tried to dress up using scissors, and ended up with frayed ended at each end of my repair. I'll get over it.
No pics of those steps. I then wiped on a decent layer of epoxy, wrapped with parchment paper, and taped. This time the tape is not pulled tight. Just snug and form fitting. Back into the heat for a day. Once out, I sanded it with 100 grit, and applied another layer of epoxy. This layer was just to give me a nice smooth surface to sand. No wrapping of any kind on this layer.
The result. Don't let those long lines fool you, they are reflections of the black-railing you see in the background. The reflections do show you the countours, but this is glass-smooth. Those aren't brush-strokes.
Remember when I wrote that there was no wrap on this layer (of course you do, it was in this post).... here's another angle. You can clearly see what way I had the frame laying while this step was drying.
Now, we are up to date. When I started this thread, I already had several days worth of pics. This is the current state of things. What's next?
Sand off the drips. Ride the bike.
Sure, There's more I can do. I could sand and polish the epoxy to make it look better. I could clear-coat it for UV protection. I could hit it with steel-wool or fine sand-paper to give it a matte look. But I think I will put it together and ride it.
Thanks for watching. I'll keep you posted with details. If I'm a good person, I'll come back to this thread in upcoming years, and tell you how it's holding up. It's not good if there is a carbon-fiber repair, then you never hear from the guy again..... doesn't inspire confidence that this is something you should try yourself!
Over the last year, I've ballooned into a super-Clyde at over 250lbs. I had no worries during the ride. I can't detect a difference in ride, but I've done almost no riding in a year, and the additional 50 lbs is the biggest change in my ride feel.
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