The Design Phase
Building a model kit from scratch is one thing. Building one that actually works — where the landing gear retracts, the cockpit opens, the weapons detach — is something else entirely.
This is the first post in a series where we walk through everything that went into creating the Flight Model Store F-15E Strike Eagle. The full process: design, prototyping, testing, manufacturing. No marketing, no polish — just the real story of what it took.
We start at the beginning: the design phase.
Starting in CAD
Everything started in a CAD program. Using reference photos, technical drawings, and every piece of media we could find on the F-15E, we built a rough 3D shape of the aircraft. From there, the real work began.
We already knew what we wanted the model to do. The feature list we had in mind from day one:
• Movable flaps and ailerons
• Deployable airbrake
• Opening cockpit canopy
• Ejectable ejection seats
• Fully working landing gears and landing gear bay doors
That last one — the landing gear — was the most mechanically complex thing on the model, and it became the anchor around which everything else was designed.
The challenge was not just designing these mechanisms in isolation. It was designing them so they could all coexist in the same model, fit together cleanly, and — critically — actually be manufactured.
"It's not the case that if you can 3D print a part, you can injection mold it. Not at all."
The Injection Molding Problem
This is where things got complicated fast.
Most people designing a product for the first time think in terms of what the part looks like. Injection molding forces you to think about how the part comes out of a mold — and those two things are very different problems.
Here are the main constraints we had to design around:
No Undercuts
An undercut is any feature on a part that would prevent it from being ejected straight out of the mold. A simple example: if you have a hole in a wall that runs perpendicular to the direction the mold opens, that hole is an undercut. The mold physically cannot release the part.
The solution is usually to split the part into two pieces along the line of that feature. But every split you add creates new alignment requirements, new tolerances, new potential for things to not fit right. On a model with this many moving parts, undercuts were everywhere — and every one of them had to be solved.
Draft Angles
A part cannot have a perfectly vertical wall parallel to the direction of ejection. Without a slight angle — called a draft angle — the part grips the mold as it cools and cannot be released cleanly.
The standard is at least 1% draft, preferably more. That sounds small. In practice, on a model where adjacent parts need to fit flush against each other, a 1% angle on one part means you often need the opposite angle on the part next to it. Which means they need to be molded differently. Which affects the tooling. Which affects the cost and complexity of every mold.
Change one wall angle by a single degree and you can end up revisiting a dozen parts around it. The whole model is a connected puzzle — pull one piece and others move.
Wall Thickness
Injection molded parts need to stay within a fairly tight thickness range — ideally between 1mm and 3mm.
Too thin and the part becomes fragile and hard to fill consistently. Too thick and the cooling cycle extends dramatically, which slows production and introduces a defect called a sink hole — a depression on the surface where the plastic contracts unevenly as it cools. On a visible exterior surface, a sink hole is immediately obvious and completely ruins the part.
No Sharp Angles — Everything Filleted
Every sharp internal corner on a part needs to be replaced with a fillet — a small rounded transition. This is not aesthetic. It is structural.
Sharp corners create localised stress concentrations as the plastic cools and contracts. That stress can warp the part, crack it, or in severe cases make it completely unusable straight out of the mold.
On a mold that costs tens of thousands of dollars — and that will be used to produce thousands of parts — a warped part is not a minor inconvenience. It is an expensive mistake.
"A mold responsible for more than ten thousand parts. If you make a slight mistake, it's going to be very costly."
Why We Had to Learn This Ourselves
None of us came into this as injection molding experts. We learned as we went — through conversations with manufacturers, consultations with specialists, and a lot of trial and error.
The honest reason we had to become semi-experts ourselves: we simply could not afford to hire someone who already was one.
A model like this has never been made before. There is nothing truly comparable on the market to use as a reference. That means any experienced engineer we brought in would effectively be doing the same research and iteration we did — but billing for it. The hours required to design something this novel, at the level of detail we needed, would have cost far more than a startup at our stage could spend.
So we did it ourselves. It took longer. It required more iterations. But we came out the other side understanding every single part of this model in a way that would not have been possible otherwise.