My Carbon Fibre 280z!

[OldAndyAndTheSea]

Without a cage, or monocoque design, quite frankly, I wouldn't.

 

But if you want to go down the rabbit hole, you must include some sort of load bearing/dispersing core within the laminate. Most F1 racecars are constructed from a combination of aluminum, and nomex, honeycomb core. Aluminum is best used for crumple zones, and is highly structural, while nomex is designed for excellent fire resistance, but isn't as structurally robust. Nomex is significantly lighter, and subsequently more expensive, than aluminum, so it is used only where advantageous. So the survival cell (Monocoque) sees this type of core most often.

 

 

I'd build a totally composite version, with aluminum honeycomb (3-5mm) core. Imagine if you were to take an s30 door and cut the inside skin off. I'd make that idea, and then build a semi structural door panel that goes over the inner workings of the door, because I also would want to retain window function and such.

 

Horrible description, but eh I'll roll with it.

 

 

I really dislike the idea of making some bastardized door hybrid out of 40+ year old existing shells and single skin, hand laid, laminates. That's not safe. Nor is it truly using these materials as intended.

 

It's like if someone decided to build a carbon fiber house...and they start by making a bunch of carbon fiber 2x4s.....sure that will work, to some extent I suppose, but it isn't using the materials to their advantage.

 

Unless the person really knows these materials (at an Aerospace / ISO 9001 level) you really shouldn't be making your own doors, in my opinion.  

 

Not the task for the average body guy.

 

I feel this is an aesthetics game, hidden beneath a "weight savings" veil.

 

 

Edited March 26, 2018 by OldAndyAndTheSea

[miky360]

So the official weight of the car is 2231lbs. 99lb weight reduction from all the carbon. I’ll get to my goal of 1000kg from the lightweight brackets, bumper and battery!

[rturbo 930]

How in the hell did you get a late model 280Z to weigh 2231lbs? Without carbon parts it weighed 2330lbs? That's on the light side even for a 240Z, with a full tank.

[seattlejester]

Having played with that honeycomb aluminum, that material is pretty interesting. Lots of structure in the comb direction, you could stand on the material. Super trippy standing on the edge of aluminum foil thick material. Any side load though and it would collapse to the couple sheets thickness of aluminum foil that it was. It used to be pretty prohibitive to find, our supplier was a friend's dad who worked at boeing who bought it from their surplus section. 

 

It can support a ton of weight in the tubular direction. The question we had in our application was getting it to fit around curvatures, how to make it thin enough without shredding it, and how to try and keep the resin out of the combs as that would be overall additional weight. Thoughts of adding foam to keep the combs from collapsing, but in the end just a fiber glass structure core was used to support load. 

 

Huge aside, but you don't get a chance to talk about that material too often. 

 

For the doors, is it because to do it right there wouldn't be much weight savings? Add carbon, add core material, add resin etc. Therefore people who consider it as a weight savings aren't really planning on doing it right?

[Neverdone]

A thought to consider.

 

Singer, a car modifier who creates some of wildest 911's out there, remove all of the exterior body panels that are made of steel and replace them with carbon fiber...EXCEPT for the doors.

 

Their cars are well into the 6 figures, so it's not like they just didn't get around to it. 

 

I do not know  the reason for them not do it. It could be a safety thing, or possibly a legal issue, But even they don't.

 

Personally, I wouldn't. There's a lot of other areas to lose weight on the car if that's what you're after.

[miky360]

@rturbo 930 No idea lol. We're thinking its the T3 suspension that help load things off a bit. But yeah, full tank, all fluids in, and I still have sound deadening at the front (Trunk was cleaned up). 

 

@seattlejester Didn't think much into it. Just grabbed the doors as soon as I was told about the ridiculous cost to paint the car.

 

@Neverdone They definitely came up to mind. It's due to safety but a customer can still order the doors in carbon if they wish. Carbon was just the route to go to, funny enough, to save money lol.

[OldAndyAndTheSea]

19 hours ago, seattlejester said:

Having played with that honeycomb aluminum, that material is pretty interesting. Lots of structure in the comb direction, you could stand on the material. Super trippy standing on the edge of aluminum foil thick material. Any side load though and it would collapse to the couple sheets thickness of aluminum foil that it was. It used to be pretty prohibitive to find, our supplier was a friend's dad who worked at boeing who bought it from their surplus section. 

 

It can support a ton of weight in the tubular direction. The question we had in our application was getting it to fit around curvatures, how to make it thin enough without shredding it, and how to try and keep the resin out of the combs as that would be overall additional weight. Thoughts of adding foam to keep the combs from collapsing, but in the end just a fiber glass structure core was used to support load. 

 

Huge aside, but you don't get a chance to talk about that material too often. 

 

For the doors, is it because to do it right there wouldn't be much weight savings? Add carbon, add core material, add resin etc. Therefore people who consider it as a weight savings aren't really planning on doing it right?

 

 

yeah, getting aluminum honeycomb, or honeycomb in general, to lay nicely over complex compound curves is inherently a challenge. It has massive compression strength. Shear, not so much, like you mention. Depending on the complexity of the geometry, you can sometimes carefully scarf, and bevel, core to make them flex, bend, or conform better. Sometimes you must cut the core into many sections and lay them side by side, instead of one continuous piece. It definitely can be tricky.

 

Getting resin within the combs themselves shouldn't happen, if you're using the proper materials that these were designed around. Prepregs. If you're using these types of cores, you should NOT be using hand layup. That defeats the purpose. Very much like a laminate that includes both chopped strand mat, and a carbon fiber skin. That is not a "carbon" laminate. That's mostly fiberglass and the carbon is doing very little, if anything, to the structure of the layup. You see virtually no weight savings over the "fiberglass" versions...and the carbon isn't even allowed to do its job... It's simply a more aesthetically pleasing cover, which there's nothing wrong with...just stop calling it a "carbon X".

 

If you're using prepregs and honeycomb it is a breeze. The prepreg fabric only has enough catalyzed resin for itself, so you must use a sheet of "film adhesive" (a literal sheet of catalyzed resin) to join the fabrics to the core. The film adhesive is just enough resin to, in a perfect world, form a little meniscus over the top of each of the combs, holding a firm and uniform bond between the skin and core. If it is too resin rich, the laminate becomes heavier (like you said) and brittle. Resin rich comes from hand layup.

 

In a perfect world, when you test the physicals of the laminate, the core itself will fail, and the skins will not delaminate.

 

high density foams are a wonderful material, and work well in combination with honeycombs, but as you can see from even my brief touching on the topic...there is a lot of variability, and tailor-ability to composites....which is one of its greatest advantages. If you understand the materials, and how they are designed to be used, you can customize the laminate to do exactly what you want, where you want. Only robust in those areas that need it, or strong in a certain force, while others areas that don't need said requirements can be as lightweight as possible.

 

I think the main reason behind most doors being metal is simply it's the best bang for the buck. It's wonderful at dispersing load, and provides good intrusion protection. You will absolutely see a weight savings with a carbon, cored, door over its metal counterpart - but doing so would add exorbitant cost and effort. As far as physical performance, the carbon door would be superior in virtually every way, but only if properly constructed. If not properly constructed, it could be devastating.

 

I was extremely lucky to learn from, quite frankly, one of the Composites wold's leading authorities, Henry Elliot. Now a head consultant for the Oracle Team USA Americas Cup team. 

 

I oringinally had planned to make full carbon, FIA legal, composite doors while at school. When I told him about the project, he raised his eyebrows big time...

 

Basically told me not to do it....he told me that the juice was not going to be worth the squeeze.

 

"if ten pounds is what makes or breaks your race, you're on an entirely different level of skill.....Don't sacrifice safety for weight, that's not how composites are supposed to work."

 

"don't sacrifice safety by chasing numbers."

 

is essentially what he told me.

 

 

 

 

If you aren't going into making doors with these thoughts in mind, you shouldn't be making doors.

 

That's my humble opinion.

Edited April 10, 2018 by OldAndyAndTheSea

[seattlejester]

That is super interesting. Our core was pretty thin to start with, but if it was a thicker height I can see how you could shape it instead of trying to curve it with the right tools.

 

That makes a lot more sense on how one is supposed to go about it. Do you cap the ends in any way or is it just a sandwich of sorts?

 

We played with this material maybe 13 years ago? There was only one shop that had prepreg sheets and they only sold it in 1x1 or 1x2 sheets locally we wanted like a 1x3 or a 1x4 with some curves so that wasn't really going to work, we didn't have credit cards being younger back then either meaning no online purchases, kind of interesting how things change. We ended up doing some fiber glass strengthening beams and some type of core mat and hand laid layers of carbon for our little project. 

 

I digressed a lot though, but I appreciate your thoughts. My only foray into this may be some hand laid carbon for a hood at some point, doors are way beyond what I think I am able or willing to do.

[OldAndyAndTheSea]

14 minutes ago, seattlejester said:

 

 

That makes a lot more sense on how one is supposed to go about it. Do you cap the ends in any way or is it just a sandwich of sorts?

 

I digressed a lot though, but I appreciate your thoughts. My only foray into this may be some hand laid carbon for a hood at some point, doors are way beyond what I think I am able or willing to do.

 

Typically any ends are covered by the laminate, exposed core is a risk to the core itself, not unlike any other circumstance, and should be thought about in the same way. The core is usually prepped, with beveled edges, at usually around a 45 degree angle (or at around a 2-5mm radius - material thickness depending) to allow for easy conformity of the fabric over the core's surface. 

 

Sometimes the ends aren't capped, but those situations are less common I find. ..but again, there's that tailor-ability coming into play. If you want caps, you can have caps. If you don't need caps, you don't have to have them. You have freedom of choice. Unfortunately freedom can sometimes be dangerous too. haha.

 

I love answering any composites related questions. Unfortunately there is a lot of misunderstanding of these materials. I'd like to help clear that up, to make the industry, as a whole, better.

 

I do apologize for any tangential trajectory that my comments may have taken things however. haha.

Edited April 10, 2018 by OldAndyAndTheSea

[miky360]

A little update on this car. I found a lot more weight (some obvious, some not so obvious) to remove. I should be getting the car back this week and I'm expecting it to weigh roughly 2130lbs or 966kgs. And I still have a decent sized list of weight saving plans. I also haven't touched the engine bay yet. I have dropped off an N42 bottom end to get built into a 3L. This build is really taking a long time. But when you can't wrench, nothing you can do except wait lol.

 

Once the car is in a presentable restored shape. I will go full Robert Linton on the car. If you don't know who he is, look him up with his Porsche 964 America GS build and currently building a 991 911R in the same fashion.  
 

Might make a spreadsheet with all the weight info I've gathered over the years. Will only do it if there is enough interest. 

[260DET]

Epic thread in the just cause of losing weight, great to see, just don't forget that Group 3 cars weigh up to 1,300 kg and do lap times that us Z punters can only dream about with modest power. 

[miky360]

 

Spoke on my friends channel a bit more on the car, future plans. What I forgot to talk about was my replacement plan for a cage. Unfortunately and not surprisingly, no local Line-X dealer was wanted to spray the interior and under carriage of the car for whatever reason. So I had it sprayed with Raptor Liner instead. I guess its easier to work with? The scales weren’t calibrating so I wasn’t able to get the exact weight of the car. Also spoke future aero plans. Because of how light the car is, I actually lose some mechanical grip and will have to make up for it in other areas. 

[260DET]

Seems like you have not made a decision yet on door area impact strength. My decision was to go with composite doors incorporating a separate light weight tube steel frame to connect to the hinges from the latch. The doors were then filled as far as practical with foam which cushions and spreads impact. Importantly the car has a basic cage which adds to impact protection and stiffens the body too. 
 

So what I suggest is deciding if the car is going to have a cage and go from there. I'm quite confident that my setup will provide excellent protection.

[jessejames]

Where did you get most of the carbon parts?

[phphung]

Hey what company makes those carbon fiber doors?

[ZT-R]

Yea i would love some real cf doors with oem inner shells. not just fiberglass with a layer or 2 over.