Project-Scuderia

I acquired an OEM carbon fiber decklid from a fellow FerrariChat member just before Christmas 2015 to incorporate into the project. As usual, the first order of business was to weigh the old parts and the new parts.

Rear Decklid, aluminum & Lexan = 12.660 kg (27.84 lb)

Rear Decklid, carbon fiber & Lexan = 9.470 kg (20.91 lb)

Considering the entire assemblies, the combined weight savings is 3.190 kg (6.93 lb)
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Each decklid is made up of several components: frame, Lexan transparency, two vents, two cross braces, and hardware. Wanting to know how each of the components contributed to the overall savings, and what their relative efficiencies were, I had to disassemble the decklids to collect the component weight data.

First up were the carbon fiber cross braces. The cross braces on both the stock aluminum decklid and the carbon fiber decklid are carbon fiber, but are of different construction and appearance. The stock braces are basically ‘square tube’ construction, while the optional braces are ‘C-channel’ construction. Removing the braces from the carbon fiber decklid revealed the OEM part number on a foil label.

Rear Decklid cross braces (stock CF) = 0.355 kg (0.78 lb) total for the pair

Rear Decklid cross braces (optional CF) = 0.405 kg (0.89 lb) total for the pair

While the difference is a minor 0.050 kg (0.11 lb), the optional braces are actually heavier than the stock braces, and they are unfortunately not interchangeable. The top surfaces of the optional braces have a gloss resin, whereas the stock braces have a satin finish. The undersides of the C-channel optional braces are unfinished and not very attractive. The stock braces are finished equally well on all sides, given their square tube construction.
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Next up were the vent grills. At first glance, all of the grills appeared to be the same on both decklids. But removal led to an interesting discovery. One of the vents from the carbon fiber decklid was noticeably lighter than the others, so much so that I noticed it just by handling it, even before putting it on the scale. Some additional testing for stiffness and magnetism revealed that it was, in fact, made of aluminum. However, all of the vents are powder coated identically, are the same size, and none have part numbers. I started a new F-Chat thread a couple months ago to investigate further, and made some inquiries to suppliers, but no information was forthcoming. So far, this aluminum vent appears to be a unicorn, and its origin an unsolved mystery.

Rear Decklid vent, steel = 630 g (1.39 lb)

Rear Decklid vent, aluminum = 260 g (0.57 lb)

If a manufacturing source is discovered, the potential weight savings of a pair of aluminum vents is 740 g (1.64 lb)
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After stripping off the braces, vents, and all the hardware from both decklids, I was finally down to the decklid frame and the Lexan transparency. Although there are four black cap screws through the four corners of the Lexan, these are not the primary fasteners. In fact, they don’t actually contact the Lexan and are there as a safety mechanism to retain the Lexan should it break loose. The Lexan is actually bonded to the frame with adhesive, and is not easily separated.

So, determining the mass of the Lexan required more creativity on my part: volumetric analysis!

Rear Decklid Lexan (calculated) = 1520 sq in area x 0.2 in thick = 304 cu in = 4982 cu cm x 1.2 g/cu cm = 5.978 kg (13.18 lb)

Using the calculated weight of the Lexan, and assuming both transparencies were identical, I weighed both of the frame/Lexan assemblies, and subtracted the weight of the Lexan to derive the bare frame weights. Note that in both cases, the lower ‘body panel’ of the decklid (where the Ferrari logo is attached) is bonded to the frame and is not removable. The Ferrari logos are also attached with ‘booby-trap’ fasteners, so I included them in the assembly weights.

Aluminum Rear Decklid (calculated) = 6.682 kg (14.73 lb)

Carbon Fiber Rear Decklid (calculated) = 3.492 kg (7.70 lb)

The weight savings of the frame is 3.190 kg (7.03 lb).

This corresponds closely to the initial weight of the two decklid assemblies; the minor difference being the cross braces.

Dividing the carbon fiber frame weight by the aluminum frame weight yields the Carbon Fiber Decklid weight ratio of 52%; slightly better performance than the carbon fiber rocker panels. Effectively, the carbon fiber frame has twice the strength-to-weight ratio of the aluminum frame. Extrapolating this to the rest of the car, which is mostly aluminum, there are huge opportunities for significant weight savings throughout the car, where there are aluminum structural components.
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With all of the data collected, and some bonus discoveries along the way, the last step before installation was re-assembly of the decklids. The photo below shows all of the parts that attach to the bottom of the decklid assembly. In addition, there are hinge bolts and shims for the top of the assembly, and a stamped aluminum water shield and fasteners.

The electrical assembly for the third brake light, and the warning sensor for an ‘open decklid’, is a fascinating example of engineering design. The assemblies are identical on both decklids, showing some forethought in the design of the car, suggesting the carbon fiber decklid was in the original product plan. Both assemblies complete an electrical circuit to the vehicle without using the decklid as a ground conduit (easy to do with aluminum, but not a good idea with carbon fiber), and without running a wire up the length of the decklid as most manufacturers do. Instead, Ferrari closed the circuit with a spring-loaded positive contact and used the latch as a ground contact. Very elegant.
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Here are a couple more shots from the car show. The Scud did relatively well in the competition. The key to winning this year was showing up. The threat of rain kept the real serious competition away, so there were only about a third as many cars as last year. So, I was awarded this massive trophy for best car overall!
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Psych!
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After removing the front bumper, I stripped off the accessories and hardware, with the exception of the headlight washer assemblies. The headlight washers are attached to bonded brackets such that they are likely to be damaged if removed, so I elected to leave them in. I weighed the stripped-down bumper:

Front Bumper w/headlight washers, Fiberglass = 13.435 kg (29.61 lbs)

Using the data collected from the fiberglass and carbon fiber rocker panels, I derived the following target weight for a carbon fiber bumper assembly:

Front Bumper, Carbon Fiber (theoretical) = 7.121 kg (15.69 lbs)

Roughly, a carbon fiber front bumper should conservatively save about 15 lb. There are a number of opportunities for weight savings in the front bumper, beginning with the elimination of the headlight washers, which have minimal utility in the US. Other savings could be gained in the reinforcing structures bonded inside the bumper, switching the marker lights to LEDs, and down-sizing the mounting hardware, which is heavy enough to support a 4,000 pound bumper. A more aggressive target would be a 20 lb reduction.
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Similar to the front bumper, I removed the rear bumper, stripped off the accessories and hardware, and weighed it:

Rear Bumper, Fiberglass = 10.255 kg (22.62 lbs)

Using the same data collected from the fiberglass and carbon fiber rocker panels, I derived the following target weight for a rear carbon fiber bumper assembly:

Rear Bumper, Carbon Fiber (theoretical) = 5.435 kg (11.99 lbs)

So, a carbon fiber rear bumper should conservatively save about 10 lb. There are fewer opportunities for weight savings than in the front bumper, but similar savings could be gained in the reinforcing structures bonded inside the bumper, switching the marker lights to LEDs, removing the rear reflectors, opening the vents behind the mesh, and down-sizing the mounting hardware. An aggressive target would be a 14 lb reduction.
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Removing the front and rear bumpers required removal of the under body panels along with the rear diffuser. While they were off the car, I used the opportunity to refurbish scuff marks on the panels, weigh the panels, and assess them for designing improved replacement parts.

Front under body aero panel (fiberglass) = 3.065 kg (6.75 lb)

Rear under body aero panel (fiberglass) = 5.830 kg (12.75 lb)

Unlike the aluminum under body panel that has structural stiffness, the front and rear under body panels are very thin and flexible. They function aerodynamically, but not structurally. There does not seem to be sufficient margin for weight savings in a re-design using a different material, but especially with the rear panel, a re-design as a multi-piece panel would yield big benefits in easier maintenance and replacement parts shipping. Having to remove a 30 sq. ft. panel for an alignment, engine service, or transmission service adds unnecessary delays and expense. A re-design could separate the panel into smaller sections that could be removed faster and easier to access specific components.
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No, they were refurbished by a paint & body shop. It was a multi-step process that took [them] several weeks. But yes, the final product is a finish comparable to the topside of the car, and requires similar maintenance.

 

After removing the front under body panel, you need to remove the forward front wheel well liners (the ones with the vents).

You also need to pull four rubber plugs from the front bulkhead of the trunk. Then you can access all the front bumper hardware.

There are 4 nuts to remove inside the bonnet. Be sure to count the washers that come off of each stud, and record their locations.

There are 2 nuts and 1 screw to remove inside each wheel well. The screw is an alignment adjustment that matches the top corner of the bumper with the fender at the wheel opening. Record its position before removing.

Then disconnect the electrical pigtails to the marker lights.

Slide the front bumper off partially, until you can reach the connector on the headlight washer hose. Have a rubber cap handy when you disconnect it, because it is not a self-sealing quick-disconnect fitting.

After the hose is disconnected, you should be able to slide the bumper off the rest of the way. Again, count the number and thickness of the spacers/washers on the 4 main studs from the bumper into the trunk, and record that data.

 

Thanks for the photos. They do help determine which parts of the bumper reinforcements are US-spec crash attenuators. If the bumpers and reinforcements could be purchased separately, without the reinforcements installed, that would make modification and removal easy. Once they are bonded to the bumpers, it would be 'less easy'.

 

Yep - Rey and David have done a couple jobs for me. They are becoming the go-to guys in Austin for paint & body and resto work. Especially British makes.

 

One of the reasons for removing the front bumper was to install skid plates. Texas roads aren’t the worst, but they aren’t the best either, and have plenty of steep aprons, drainage dips, and speed bumps. I picked up an NOS skid plate set in the FerrariChat Classifieds. With the front bumper already off, installation took about an hour. Before drilling any holes, I took a lot of time to properly position the skid plates, tape them down, mark the holes, and mask the painted bumper surface to ensure the paint would not chip around the drilled holes.

The skid plates are somewhat flexible, but are naturally flat. The bottom of the bumper is not perfectly flat, so there is tension on the stainless steel hardware to conform the skid plates to the bumper surface. I would not consider installing the skid plates without using the mounting hardware, and I certainly wouldn’t warranty such work.

Most of the hardware was easy to install, but a few of the bolts close to the nose have very little clearance on the inside between the bottom and the radiator ducts, so getting the washers and nuts started took some practice and patience. Non-magnetic stainless steel just made it that much more challenging/rewarding to get it installed correctly.
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Here's a skid plate with the hardware installed. The kit came with nicely finished stainless hardware; essential for any fasteners under the car.

Also is a shot of the front bumper assembly, fully re-assembled with the skid plates added. I painted the ducts facing the side vents on the bumper satin black to match the radiator assemblies inside the bumper. That way, you don't see any body color over spray when you look in the side vents. I should have done the same at the rocker panel vents to cover the over spray you can see when looking inside the lower vents.
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