I want to make the cheapest cf bumper possible

I will start by saying i have very little knowledge of carbon fiber part making but have done some basic research. I would like to make a front bumper for my 2002dad silverado. My theory for doing this is going to be basically like skinning the outside of the factory steel bumper and then separating the carbon fiber from the factory bumper without vac bagging.
Basically remove bumper from truck
wax alot and spray pva
apply resin and 2 layers of 3k or 6k twill
separate
sand down and clearcoat

What i really want to know is will this work the way ive described and come out being at least a decent looking final product.
From my research everything except skinning uses expensive vac bagging. Infusion. Prepreg. And so on.
My funds are extremely limited and im desperate to get some weight off this truck especially the nose. But i dont want to severely damage the original bumper incase i ruin the cf one also. And dont want to spend alot of cash making a mold either.
Also not exactly looking for extreme strength here just want to be able to ride down the road without it flying all to pieces thank you so much for your help and any recomendations will be appreciated

Prepregs are better to handle…
Good Luck

Thanks i appreciate the lightning fast reply and i have read that but dont you have to put prepreg in an oven to cure? That was my understanding anyway. If not i would imagine it would be easier. Am i incorrect on that assumption? And what kind of money would i be looking at differing from reg cf and resin

With the requirements of your project, buying a low quality fiberglass cover from eBay or other resources would be better suited for what you are going for.

Like this for example.

http://www.andysautosport.com/chevrolet/1999_2006_silverado/exterior/body_kits/street_scene/strs00067091.html

The problem with building it on top of the original steel unit is that you will end up with an oversized part that may not fit the dimensions required for your application.

To make a bumper with just 2 layers of a 200g carbon will barely be much bigger so fitting is probably not an issue.

Having just two layers is the problem because it would only be about 0.5mm thick and this is too flexible not only for use on a car but also to sand and work on etc it would just be very floppy and twist etc.

If you add more layers it will become stronger for use and working on but also really expensive.

As the last poster said if you can buy a fibreglass version of the part then this could be wrapped with just one layer and refinished.

Prepreg is 3 to many times more expensive than just dry cloth and unmixed epoxy resin. You’d probably need at least 6-7 yards for 2 layers of a truck bumper that would be seriously lacking structural integrity. You could add structural integrity with a honeycomb sandwich core; as a rule composites, especially carbon fiber, perform best when sandwiched. Using a core will require you to make a female mold though.

Not sure what year you have but isn’t there something already available on the market? I saw bumpers and a hood for about $1k. Making a cheap bumper might be more trouble than it’s worth if you can buy something.If your new to this material, you might want to get a bit more practice on smaller projects. Especially if you are on a ‘tight budget’, this stuff is expensive and mistakes cost accordingly. If your concerned with looks and cheap, then you’ll have an even harder time on such a good sized first project.

Thank you all so much for your help . I do understand that it is a large project for a first try. The bumper is almost 8 feet long ( all the way around) and 24’’ wide on the ends and roughly 10-15’’ through the entire center section so i was going to just buy 3yds of 3k or 6k (probably 6) at 60’’ wide and spit the material long ways to have 2you layers worth with extra. But the bumper will be mounted on all 4 front outer corners. I was going to use factory steel mounts cut down as much as possible for weight also.
The fiberglass covers save a very small amout of weight i appreciate your reccomendation but its just as expensive as me giving the carbon fiber a whirl and ive not seen a factory style unit either… some of the fiberglass units are actually heavier than the factoy bumper.
And as far as thickness and oversized product fitment i agree with the above i dont know this 100% i dont think you will be able to look at this few mm of thickness ( or oversize) and notice it by eye. Or cause any unusual fitment.
And it is a 2002 silverado
has anyone tried this method. And if i need another layer or 2 thats easier still than making a female mold vac bagging and all that
thanks again though everybody

You’ll want to add stiffening ribs to the back of the part and laminate over them to give the piece flexural strength.

While I don’t think it’s a great idea as a project, you might look into core materials as well to have enough strength in your end product. also, with the curves of the ends, you may have a tough time pulling your skin off the existing bumper.

(I think you are too excited to do this project to listen to people with more experience who can think a few moves ahead on how this will work, but, that’s how we learn, so maybe just have at it and see what happens.)

If it’s not a silly question why are you so desperate to loose weight (off the truck)?

Not a silly question. I thought the same… It’s a truck firstly, so it’s gonna be heavier right? Second, what does the bumper weigh and how much are you gonna save?

What is the goal here? Just to say, “yah I saved 55 lbs” or whatever. Not to detour you from this project, but sometimes you’re better off spending your time (and ca$h) on something more worth while. Especially when you’re poor. THat’s how I started off with this stuff.

As far as weight savings… you might want to really think about how, where, and why you wanna save weight. There may be other components that would save more? Maybe the hood? Maybe an aluminum smaller sized radiator? Lighter wheels and tires?

For the price you’ll spend on materials for a bumper and then huge amounts of time and the failure, it’s gonna be long and hard won. A great way to learn if you can afford it.

Asking questions here is a good way to start. We’ve all made some seriously stupid mistakes in our past :smiley:

I don’t know how much a 12 year old truck is worth but it would probably be cheaper to sell it and buy a lighter truck.

Since he mentioned the stick bumper isn’t all that heavy (it’s not, pretty thin) I’m thinking the maing goal is for looks.
This is where you will have a problem. Your plan us to lay up, then sand down. This works with bondo and similar undifferentiated matetals, but it’s not going to work with carbon fiber.
You will sand right through the resin layer and into the carbon fiber, which will show visually , even if you clear coat it.
You’ll end up painting it to cover it, so you could have just used regular glass and gelcoat. This is assuming you can even get it in shape that looks good.
Nothing wrong with experimentation, but unless you are planning to develop your composite skills further, using this project as a learning experience, it will be a big waste of time and money.
My first experience in building composites was hand shaping surfboards. There was a kernel of wisdom given to me by every shaper I talked to.
They all said “great , you’re learning to build boards, it’s a learning process so your first board will be a coffee table.” As it turns out, it wasn’t even good enough for that. It made an ok workbench.
The point is that if you are just doing this to make the one part and that’s it, don’t bother cause it won’t be anything you want to use until you make a few bad ones. Especially considering you’re doing it the most difficult way possible.