Journal
Dispatches from the engineering floor. Read our build logs, painting techniques, and update notes on modular developments.
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.
Sourcing
Finding the Right Suppliers Part 3: Paint, Decals, and Everything in the Box Design and prototyping get most of the attention when people talk about building a product. But running parallel to all of that — quietly and persistently — was another challenge entirely: finding the right suppliers for everything that goes in the box. Screws. Screwdrivers. Paint. A filler substance for the screw holes. Decals. Every single item had to be sourced, tested, negotiated, and in some cases co-developed with the supplier before it was good enough to include. Some of it was straightforward. Most of it was not. The Easy Part: Screws and Screwdrivers Fortunately, one of our team members has direct experience in supplier sourcing — communicating with manufacturers, managing samples, handling transportation logistics. That background made a significant difference. The screws and screwdrivers were covered relatively quickly. Standard hardware components with established suppliers, manageable tolerances, and a straightforward sourcing process. We moved on. The paint was a different story entirely. The Hard Part: Paint [ IMAGE: Row of paint sample pots from various suppliers being tested ] A fraction of the paint samples we tested across more than 12 suppliers. We tested paint from at least 12 different suppliers. Every single one failed to meet our standards. The requirement sounds simple: a paint that works without a primer, covers consistently across all colours, on white plastic. In practice, finding a paint that does all three of those things — reliably, at an acceptable price point — turned out to be one of the most time-consuming parts of the entire project. "It's very difficult to find a paint that works without a primer and covers sufficiently for all colours on white plastic." No primer is a deliberate choice. Adding a priming step makes the build process longer, more technical, and less accessible — exactly what we were trying to avoid. But removing primer means the paint itself has to do more work, which narrows the field of viable formulas considerably. Working With Suppliers to Get It Right Eventually the search moved beyond off-the-shelf products. We started working directly with suppliers to adjust their formulas — sending back samples with specific feedback, requesting modifications, waiting for new batches to be shipped, testing again. Sample shipped. Tested. Feedback sent. Formula adjusted. New sample shipped. Repeat. It was slow. It was iterative in exactly the same way the prototyping phase was. And it had to happen while everything else was also in progress. The Price Constraint Finding a paint that performs well is one problem. Finding one that performs well at a price that keeps the final box affordable is another. Every component in the box has a cost, and that cost ultimately determines what we charge. If the paint alone pushed the price up by €10 or €20, a meaningful portion of potential buyers would walk away — not because the model isn't worth it, but because price sensitivity is real and we have to respect it. So the search was never just for quality. It was for quality at a price that made the whole thing viable. That combination is harder to find than either one on its own. "It's an option to go for a very expensive paint that works well. But then fewer people would want to buy it." We got there. A supplier that could produce the specific colours we needed, to the standard we required, at a price we could work with. It took longer than we wanted. But the paint in the box is something we're genuinely proud of. The Decals: Rethinking the Standard Traditional model kits use waterslide decals. You soak them in water, slide them off the backing paper, and position them on the model. In theory it works. In practice, for anyone without experience, it is a frustrating process — the decals tear, they fold, they go on crooked, and fixing a mistake is nearly impossible. It also requires a pencil to burnish them down properly. Which is a tool most people building a model for the first time do not own and would not think to buy. "Waterslide decals are not beginner friendly. And we want our model to be accessible for everyone." We wanted something better. So we researched the alternatives. UV Printed Decal Stickers There are subcategories within the decal and sticker world that most people are not aware of. One of them is UV printed decal stickers — a technology that produces sharper detail, more durable colour, and a significantly easier application process than waterslide alternatives. The challenge with this technology is resolution and scale. Some of the decals on a 1/48 model are very small. Finding a supplier capable of printing at that size without losing detail — and doing it consistently across a full production run — required its own search process. We found the right company. The decals in the box are the result of that. Applying them is easier. They look better. And you do not need a pencil. Next up: Manufacturing. The molds, the factory, and what it actually means to commit to producing something at scale for the first time.
Manufacturing
No going back At some point the designing stops and the committing begins. Manufacturing was that point. Everything up until now — the CAD work, the prototypes, the supplier negotiations — had some degree of reversibility. You could reprint a part, retest a mechanism, switch a supplier. The moment the molds were cut, that flexibility was gone. Working With the Injection Molding Engineers We did not have the expertise to design the molds ourselves. Injection molding is a specialist discipline, and the tooling that goes into a mold at production scale is a different problem entirely from designing the parts that come out of it. After talking to a number of manufacturers we settled on a supplier whose engineers worked with us directly. They reviewed our designs, understood what we were trying to achieve, and made final adjustments where they knew better than we did. Which, in some areas, they did. That collaboration mattered. Handing a finished CAD file to a factory and hoping for the best is not how this works — at least not well. The people cutting the molds have seen thousands of parts come out of machines. They know what causes problems. Listening to them saved us from mistakes we would not have caught ourselves. How a Mold Is Made A mold starts as a solid block of steel or aluminium. The negative shape of your part — every surface, every detail, every tolerance — is machined directly into that block. What comes out of the machine is a cavity that, when filled with molten plastic under pressure, produces your part. For this model we ended up with a set of four molds. One of those molds runs a double cycle — meaning it produces two parts per injection rather than one. "If you want to know how much a mold costs, look it up. You will be surprised." The cost of tooling is one of the more shocking realities of physical product manufacturing. Each mold represents a significant investment — the kind of number that makes you sit with your decisions for a long time before committing to them. The Weight of a Decision You Cannot Undo The anxiety leading up to mold production was real. Once a mold is cut, changes to the design are either impossible or extremely expensive. You can sometimes add material to a mold cavity — but removing it, which is what most design changes require, means cutting into the steel again or in many cases scrapping the mold entirely and starting over. Months of prototyping, hundreds of iterations, all the back-and-forth with the engineers — all of it was preparation for a moment where we had to look at our designs and say: we are confident enough in this to lock it in permanently. "If you want to change something after the mold is created — it's not possible. Or at the very least, very limited." We were as ready as we could be. We had tested everything we could test. We had fixed everything we had found. We knew the designs were good. It was still nerve-wracking. And Then the Parts Started Coming Out The molds were made. Production began. And the parts that came out of those machines were — after everything — what we had designed them to be. That moment, holding an injection molded part for the first time and seeing that the tolerances were right, the mechanisms worked, the surface finish was clean — it is difficult to describe after the length of the road that led there. Next up: Assembly and Quality Control. What happens after the parts come out of the molds — putting it all together, checking every mechanism, and making sure what goes in the box is something we're proud to put our name on.
Prototyping
The Loop That Never Ends Part 2: The Prototyping Phase If the design phase was about solving problems on a screen, the prototyping phase was about discovering how many of those solutions were wrong. The process was straightforward in theory. Print a part. Check the fit. Test the mechanism. Go back to CAD, adjust the design, print again. Repeat. In practice, that loop ran for months. Print. Test. Repeat. Almost every single iteration ended the same way: back to the drawing board. A mechanism that moved smoothly in CAD would bind in reality. A fit that looked perfect on screen would be too tight — or too loose — the moment you held the parts in your hands. 3D printing is not the same as injection molding. The tolerances are different, the material behaves differently, the surface finish is different. But it is the fastest way to find out whether an idea actually works, and at this stage speed matters more than perfection. [ IMAGE: 3D printer running, mid-print ] The printer ran almost continuously throughout this phase. "In 99% of cases — back to the drawing board." We went through a lot of filament. More than we want to admit. The pile of discarded parts, broken supports, and failed mechanisms grew steadily. What you see in the photo above is about 10% of the total. Knowing When to Stop The strange thing about this kind of iterative process is that it never truly ends. There is always something you can improve. A mechanism that works can work more smoothly. A fit that is good can be tighter. A part that is strong enough can be stronger. At a certain point you have to draw a line. "If we keep doing this, it can go on forever. And forever is a very long time." That moment — when you look at the assembled prototype and conclude that everything is, genuinely, on point — is less a celebration and more a quiet decision. Not that the model is perfect. That it is good enough to move forward, and that the time spent chasing further improvements would cost more than the improvements are worth. We reached that point. It took a while. But we got there. [ IMAGE: Final prototype assembled and photographed ] The final prototype — the version that told us we were ready to move to production. Next up: Manufacturing. Where prototyping ends and the real pressure begins — tooling, molds, and the moment you commit to producing something at scale.