In a year and a half to two years I am planning on replacing several body panels on a late ‘70s American coupe that could see up to daily use. This raises several concerned regarding the doors and the hood. The doors are fairly long and the hood is around 169mm long and 148mm wide. Since I’m in the planning stages, I figured I would ask now, rather than later.

I am planning on using your vacuum infusion process and will be finishing the body panels for a stock look, but much, much lighter.

As I stated, panels are going to be finished and painted so, should I concentrate on finding a source of carbon fiber wide enough for the entire hood, or should I use two pieces? If I’m using two pieces, how should they be laid for best finish and strength?

Ultimately, I want this to a nearly direct replacement, so... How many layers of carbon fiber should I use?

At what width or length should I consider using a core?

Should I consider using a core or simply make the parts entirely out of carbon fiber?

I’m planning on making an inner frame of steel to tie the hinges and latch for the door together as well as provide side support in the event of a crash. I’m also planning on embedding captive nuts to provide attachment points for the hood. Is the technique and epoxy in your video appropriate, or is there a better method?

I appreciate your consideration and any advice you can provide.

Thank you.

If you're painting the hood anyway, just use whatever width carbon is easy for you to source and have about a 1" overlap. That will be adequate strength wise, and you'll just have an ever so slightly heavier part due to the excess material - not something you'd concern yourself with.

For a street vehicle with an inner frame, I would recommend a 3mm core with a single layer of 200g carbon either side. It's also a good idea to include some Kevlar to create a 'soft failure' in the event of an accident - razor sharp shards of carbon fibre are never nice to have on the street.

For your doors, you really want to have that crash structure engineered. For the street cars I have done, we simply had moly intrusion bars inside the carbon inner and outer skin's and this was engineered for those specific vehicles. But best to check this out with an engineer, as you really don't want to under-do that side of things.

+x

 

Hanaldo - 4/18/2019 4:32:00 AM

If you're painting the hood anyway, just use whatever width carbon is easy for you to source and have about a 1" overlap. That will be adequate strength wise, and you'll just have an ever so slightly heavier part due to the excess material - not something you'd concern yourself with.

For a street vehicle with an inner frame, I would recommend a 3mm core with a single layer of 200g carbon either side. It's also a good idea to include some Kevlar to create a 'soft failure' in the event of an accident - razor sharp shards of carbon fibre are never nice to have on the street.

For your doors, you really want to have that crash structure engineered. For the street cars I have done, we simply had moly intrusion bars inside the carbon inner and outer skin's and this was engineered for those specific vehicles. But best to check this out with an engineer, as you really don't want to under-do that side of things.

Thank you for your response. In regards to the Kevlar, is it be better to replace one of the layers of carbon fiber with Kevlar, or would it be better to use a lighter weight carbon fiber with a Kevlar liner on the inside?

For a street car I would just add a layer of ~200g Kevlar either side of the core. So 200g carbon > 200g Kevlar > 3mm core > 200g Kevlar > 200g carbon.

It will be a little bit heavier, but it's a street car - a kg here or there isn't much of a sacrifice, and it's nice to have a slightly more rigid bonnet on a street car, doesn't feel as cheap or flimsy when you open it.