I have read in numerous posts of the “experts” on here talking of rolled edges. What are they and what do they look like? Thanks.
it is when the mold has the edge of the part molded in to it, unlike some molds that are made to the part size, *usually has no flange or has scribe mark on the mold for trimming
a cut vs. a finished edge. A rolled edge does not show the cut marks. If you look at a cheap/medium priced cf hood, you can see where the hood was cut. look at a pricy one and the edge will be ‘rolled’; the edge will look finished rather than raged like it was cut.
How would one incorporate rolled edges into their moulds??
either directly into the mold or by sanding a fiberglass part to the finished edge then overlaying with carbon. The second is how the cheaper hoods are done.
does anyone have any pics of their rolled edge molds? I’m curious to see what one would look like.
Would the rolled edge not make it more difficult to pop the carbon part out of the mold???
would it not be very difficult to get the carbon to roll into such a tiny sharp angle?
Think of it as an exact replica edge rather than rolled.When a hood is closed…what does the edges look like ?
Thats it. It can complicate removal with some designs.
And you do have to engineer the back substructure to fit tighter tolerances as well when bonding the upper and lower .
You also have to bodywork out any reliefs/undercuts which is also more work with the plug.
Vinny
so the mold would just curl back on itself to give this rolled look once the carbon was layed in there right?
how in the hell would someone get the rolled look if they had several layers of carbon in the mold?
these rolled parts can be infused right?
Your basically trying to copy the factory edge all the way up to 90 degrees, or just before it becomes a negative.
You defintely dont want to have anything in your mold curve back on its self.
And you can definitely infuse a hood with a rolled edge. Its the finish work when you combine the two shells that makes a good rolled finish or a crappy one.
This is the way i was working to build the mold for a carbon fiber motorcycle fender. It will have a rolled edge for the front leading edge of the fender. Looks much better. I was hoping to get it past 90 deg. and try for like 120deg or 60deg, whichever way is right to say it. I may put a piece of roving in there so the carbon fiber doesn’t just flop over under vacuum/cure.
several layers of carbon should roll over just fine I would think. it’s not very thick if your using less than 6oz c/f.
ok so you don’t want the mold curling back… so to get the rolled edge do you just fold the carbon back on itself along the edge that you want to look good?
that makes more sense to me. It would be tricky to get the carbon to stay putwhen it’s creased like that… how would you do it?
doesn’t the mold have a trim part. aka: a 2+ part mold where the edge of the part is made by some sort of layup, with a clamped on edge piece, to give it definition?
How do you get the carbon to sit and pull into the rolled edge? When i have tried to do it the part has a air void all the way around the rolled edge and either has to be filled or cut out.
Someone suggested to me to lay a few layers of CSM around the perimeter above the peel ply an it puts more pressure on the carbon to get into the rolled edge an not leave air voids.
That would work. Even some tacky tape maybe…like a pressure plate for the inside that can be taken out. I never did anyhthing like that, but I figured bagging would take care of it 
I agree… the only way you are going to get it to roll back is to have a tooling plate that fits along that entire edge… and the tooling plate ( whatever you make it out of ) must fit perfect.
I would try making it out of something liquid that will harden… perhaps rtv silicone. You don’t want something hard that causes print through while under the vacuum bag.
I should mention that when i tried this bonnet it was under a vacuum and i still had voids. I saw a picture on here that someone put up with carbon vacuumed to make a bonnet brace ( under bonnet frame) you sir are a master!
How much vacuum over time should i be putting on a bonnet mold to allow the carbon to pull into the mold 100%? I have a feeling i blast the vacuum too fast and the peel ply and breather grab real fast but then don’t allow the carbon to pull in.
well use your fingers to move all the layers around and push it in. You can also try cycle debulking. Vacuum, release, pull vacuum, release, at least 10 times. That might help nest everythink together.
first you should make sure that you have as little as possible material going on to the flange. more surface area means more force required to move it. My suggestion is you purposly leave a couple darts open with small holes in it. This will regulate your vacuum pressure. as the bag goes down slowly, use a rubber squeegee(thalco brand works good) to press in the corners with all your weight. seal up a hole in a dart when you feel ready and repeat the process until you have full vacuum pressure.
good suggestion ^^
It has worked for me… if you are working with epoxy you will have plenty of time to debulk. or if you use polyester or vinylester just kick the resin with half as much mekp. to extend the gel time.
I would suggest making a plastic polyethelene paddle tool that has the same radius curve shape as your rolled edge. After vacuum bagging immediately go to work with the tool and debulking.