Let’s say I have a rear fender on my bike that I would like to replicate in carbon fiber.
I now have a mold made from fiberglass, But I can’t get the mounting indents perfect. Since the mold doesn’t have the right copy of the mounting indent, then the carbon fiber version won’t have a good mounting point either.
Im talking about those mounting holes.
How do I correctly make those holes? I can’t figure it out, since the material stretches and it won’t be perfectly aligned inside the hole.
If I have well understood: you have the mold without the indents ? if so you can place your fender inside the mold ,trace the centers of the holes on the mold, place there three inserts with the right height and diameter,fixing them with adhesive. Choose the right fabric style.I believe you will have some problems in replicating the indents with plain weave… twill2x2 would work better
I currently have the mold with the indents, but they are far from perfect
btw: this is the mold, but it’s just to showcase where the item belongs.
For the mold i started with 25grams of fiberglass, then 160grams
But even with a light material as 25grams, it’s difficult to reproduce the indents. How do others do it?
I mean carbon is even more rigid so im not sure how that would turn out. Is there a trick to it? Cut the hole or something, and press some loose material in it or ? should i use chopped strand mat in the hole to make an exact replica?
Cut the holes in your carbon fabric in precise location of the indents and slightly undersized. This will allow you to place your fabric in with minimal disturbance then cover the indents with extra small pieces.
You can use a little filler mixed from resin and silica to make a little fillet and keep the pieces around the indents stuck in place
For the mold the same or just use a lot of filler around the indents to make a big fillet
on your application why not shave the indents backdrill your mounting holes and use some nice chrome hardware. then use phenolic spacers to make up the difference.
spacers are real cheap too
Many of our parts have similar shaped holes for bolts. All we do is cut, “x” shaped slits in the fabric so when we place the fabric down the, “x” shaped slits just fold over those pillars. When I say pillars, I’m talking about those lumps in the mold that represent the mounting areas of the part. Often when making carbon fiber parts that require the look as well, cutting of the fabric in strategic areas is necessary to keep a properly straight weave. Otherwise, you’ll have pleats, folds, pulls, distortion, and zigzagging.
Thanks, im gonna give it another go, it will be my fourth mold. Im getting there.
For the mould itself: Use a blob of resin mixed with aerosil and glass fibers (for sale at www.polyestershoppen.nl) in the mounting point. After that you can laminate over it without having to force the fabrics into the indent. Moulds can be thick, usually some 3-5x laminate thickness of the product. If you are doing the mould in polyester, then CSM is your friend for thickness.
I have glass strand mat, im going to make my fourth mold this weekend and im first going to use a very thin 25grams fiber glas cloth to start with, fill the holes with loose fibers, continu with a thicker grams and up the weight to have a strong mold.
i forgot to lay the fibers 45 degrees and 90 degrees so my third try of making a mold was a bit too flexible.
i also only used 3 layers in total, not enough. And the fiberglass mold is still a bit sticky on the outside. Perhaps i should use a tad more of hardener.
Alright, So i’ve made a new mold, #4.
I was finally able to copy the indents.
but i still have issues
Especially around the corners it wouldn’t stick and the fiberglass wouldn’t copy the contour. How do you get around this and have it copy the item as close as possible?
And as i’ve already asked previously. I now have a mold, im going to clean it up. It’s the best one i have so far out of 4. And i think it’s useable to make a first version of a fender. But how am i going to lay up the carbon around the mounting holes. Im going to either make a cross and have it drape around the strut, or cut a hole. But then what? How am i going to cover the rest of the strut? And have it stay there? It will just come off the strut as it won’t stay nice in place around the strut? Someone said make a combo of resin and silica. But what should i do with that? First add a layer or 2,3, around the strut and then smear the filler over it ? or? And what type of silicia should i use? any brands or types?
im doing wet layups, without vacuuming or anything because this is my first time using the material etc. And chance on pulling this off and making a okay decent part?
Try this method. Do a small sample section of the most difficult section of your mold.
Apply your release to the whole thing an get it nice and slick. Get some spray adhesive and mighty spray it onto the mold. Start laying your fabric dry. It should hold you fabric in those tight corners and you can wet it out from the back side. Vacuum would greatly help you out but it should do the trick. Worst case you’ll end up spraying some gel coat after you remove the part from the mold.
hmm, good tip.
what i normally do now, is, put epoxy on the part, let it cure for an hour it get’s sticky and then i start applying the material. The big downside to this is that if you have difficult parts of and you start stretching the fibers than it will look real messy.