Build Update: The Plastics Department Is Now Operational

Somewhere between the last race and this update, Black Flag Racing quietly opened a manufacturing division. It occupies one corner of the house, runs on filament and stubbornness, and answers to the name Ender-5 Max. This is the story of how we are teaching ourselves CAD, negotiated what we hope to be a lasting peace with a 3D printer, and started producing actual aerodynamic parts for the #86 car, including a few we're genuinely proud of.

Learning CAD by Arguing With It

First, the design side. The aero program, which includes the splitter, ducts, louvers, and the rear wing we've been developing under the Project Zephyr Prime banner, needs real geometry: airfoil profiles, contour-matched surfaces, mounting bosses that line up with holes that exist in the physical world. That means CAD, and CAD is a skill nobody on this team had when the season started.

Our approach has been the same one we apply to everything: learn by doing, keep what works, document the failures so they at least earn their keep. We've been pairing traditional modeling with generative AI tools: describing a part, letting the model rough in geometry, then correcting its confident nonsense by hand. The workflow is genuinely useful, with one caveat: the AI does not know what a car is. It knows what cars look like. It will produce a beautiful bracket that intersects the hood, mirrors a duct into the wrong side of the airflow, or cheerfully suggests a wall thickness best described as "decorative." The human's job is to be the one in the room who has met physics personally…

…but as a way to get from napkin sketch to printable STL in an evening instead of a week? Its pretty awesome. The revision loop is now: model it, print it, hold it against the car, discover the car disagrees, revise, reprint. Iteration used to be expensive. Now it's overnight. Well overnight-ish.

The Ender-5 Max: A Character Study

The printer itself deserves an introduction, because it has become a personality on the team. The Ender-5 Max is large, capable, and possessed of two recurring moods.

Mood one: the clogged nozzle. A clog announces itself the way most mechanical failures do: quietly, hours ago, when you weren't watching. The extruder keeps politely clicking, the toolhead keeps sweeping its paths, and the printer air-prints an elaborate ghost of your part, committed to the performance long after the material stopped showing up. We've learned the maintenance rhythm: cold pulls, needle files, not letting filament sit hot and idle while we wander off to look at the car and daydream. The nozzle rewards attention and punishes optimism, which makes it a natural fit for this team.

Mood two: heat migration. Heat creep is the sneakier one — warmth wandering up the hotend into territory where filament is supposed to stay solid, softening it early and jamming the works. It took a few failed prints to diagnose, because the failure looks random until you realize it always happens on long prints, in the afternoon, when the shop is warmest. The fix was a combination of cooling airflow, temperature discipline, and accepting that a printer in the summer is technically operating in a hostile climate. We manage engine cooling for a living now, so managing it for a machine the size of a mini-fridge felt almost relaxing.

Between those two moods, the printer works, and works well. Big, clean prints, night after night. We just had to learn its love language, which is maintenance…begging…and occassional pillow talk.

Actual Parts on the Actual Car

Now the good news, which is genuinely good.

NACA ducts for brake cooling: printed, successfull.y These are the low-drag inlet ducts that will feed cool air toward the front brakes — the same brakes we lavished attention on in the brake bedding article, and which run hard all day carrying our front-heavy Accord into braking zones. The NACA profile is a proper piece of geometry, all curved ramp and diverging walls, and it printed beautifully. Holding a finished duct that started as an airfoil reference and a rough AI-generated draft, and now fits the bodywork it was contoured against, is the moment this whole capability paid for itself.

Hood louvers: printed, successfully. Heat has to leave the engine bay, and louvers give it a formal exit instead of forcing it to seep out through gaps like a rumor. Our cooling philosophy has always been that temperature management wins endurance races, and the louvers are that philosophy in physical form. They came off the bed flat, clean, and consistent — a batch of identical parts, which for hand fabricators is a small miracle.

Rear wing pylons: initial sections printed. The pylons (the vertical supports that will carry the Zephyr Prime rear wing) are the most structurally serious print job yet, so we're proceeding in stages: printing the initial portions, checking fit, geometry, and stiffness before committing to the full pieces and their metal reinforcement. Early sections look right and measure right. The wing they'll eventually hold has lived in CAD long enough. It's ready to start existing.

What's Next

More pylon sections, fit checks against the trunk, and then the slow graduation of parts from "printed prototype" to "raced hardware" — which for anything structural means validation, reinforcement, and a fastener strategy the tech inspectors will smile upon. The ducts and louvers go on the car ahead of NCM in September, where they'll do their jobs in front of an audience.

The larger point is this: the team can now think of a part and then have the part. That's a new capability, built the way we build everything: by starting before we felt ready and taking notes the whole way down. The nozzle will clog again. The heat will creep. The parts pile grows anyway.

The Ender-5 Max was not consulted for this article. Its busy humming away printing the first section of the front splitter.

All The Way