AP9engineering

19/10/2026

Practicing resin infusion

I'm usually making parts with prepreg, but it has its significant downsides such as tooling costs, size restrictions based on the autoclave or oven and layup time is some cases. Also - infusion lets you select from way more variants of resin systems and fabrics.
So I took this somewhat complex geometry panel to practice making a vinylester mould and infusing a part.

I made this panel in 3 stages:

1. ⁠infusing the first carbon skin with 4x4 twill + biaxial. Cured in oven
2. ⁠adhering 2mm honeycomb core. Cured in oven under vacuum again
3. ⁠wet laminating backing ply of 4x4 twill + biaxial separately on a release film while trying to get the resin fraction close to 50%. And adding that on top of the core. Then bagging and curing it the third time

Final cure was done at 200c out of the mould as the mould service temps was only around 80c. Ramp rate to 200c was 0.1 degree per minut I might add to minimise the risk of the matrix softening too much while the part doesn't have support from the mould. So the post cure took about 48hours alone.

All in all I'm very happy how this came out and how I was able to avoid many of the potential issues that I had in my mind. As this part is potentially in a high heat environment, then next step is to try out using Basalt fibers and phenolic resin. Not looking forward to working with phenolics that much... But exciting at the same time.

12/10/2026

I’ve wanted to sculpt a Saab 900 Carlsson for years. Finally started this weekend. Now it’s filing, sanding and shaping all the way to Christmas. 🎅

08/10/2026

09/09/2026

🚨 TESTING ONLY. THIS WILL NOT BE A PRODUCTION PART 🚨

Before anyone reaches for their keyboards: This is not a good idea

This is a Saab 900 front axle bump-stop buffer - a rubber buffer attached to a metal cone (usually).

As I’m producing the rubber buffers, it would be way nicer to be able to provide a full replacement assembly to the customer. If only I had those metal cones available and all cleaned up...
So, that put a question in my head - It’s easy to make it out of carbon. What if I did??

Within a few hours I sketched up and printed the mould that would hold up to elevated temperatures and pressure that it’s experiencing during prepreg cure cycle.

I’ve made multiple samples of 3 versions of these in various thicknesses (3mm, 3,5mm and 4mm). It is not going on any car. But instead they’re all going to my local university for testing. There are many tests that could be done for these parts, but mainly what I’m interested in is Static compression to failure and Cyclic compression (fatigue). Multiple samples will be crushed until they fail so we can see how they fail, when they fail, and how the failure changes with thickness. The original steel part will be tested as well, giving us an actual comparison rather than a bunch of opinions from the internet.

Let’s break some parts and find out just how questionable this idea really is. 🔬💥

21/08/2026

Sometimes you just need to finish something.

I’d been meaning to replace this little Lucas pipe since 2015.

Ten years later, I finally did it. A few hours in Fusion 360, 4 hours on the printer, and 150 grams instead of nearly a kilo.

But the weight saving wasn’t really the main point anymore.

Sometimes, when all your big projects seem to have another six steps to go, you just need to finish something.

Wrote a blog post about exactly that.

https://ap9engineering.com/sometimes-you-just-need-to-finish-something/

28/07/2026

A rare Saab part is now a CAD model.

This started as an idea to preserve the original Carlsson intake duct, but it quickly turned into a full reverse engineering project.

✔ 3D scanned
✔ Rebuilt from scratch in Fusion 360
✔ ~7 prototype prints

The best part isn’t the print - it’s having an editable model that can evolve into future designs like brake cooling or oil cooler ducting.

The full project is now up on my website (link in bio).

ReverseEngineering 3DPrinting

28/07/2026

I finally finished a project that's been on my list for a while: reverse engineering the Saab 900 Carlsson front bumper intake duct.

The goal wasn't just to make another copy. I wanted to recreate the original as a fully editable CAD model so I can reproduce it whenever needed and build on it in the future.

That meant:
• 3D scanning the original duct and bumper with an Einstar Rockit
• Rebuilding the entire part from scratch in Fusion 360
• Around 7 prototype prints before I was happy with the fit

One thing I didn't expect was discovering that the original ducts and even the bumper itself aren't perfectly symmetrical.

I wrote a full article covering this process

👉 https://ap9engineering.com/saab-900-carlsson-intake-duct/

I'd love to hear what you think. If you own a Carlsson, would you keep it as is or be interested in some actual ducting to the brakes or oil cooler? Or you prefer the fog lights entirely?

One of the things I enjoy about reverse engineering is that, once you’re finished, the part isn’t just another reproduction but it’s a design you own. That’s what led me to the Saab 900 Carlsson air intake duct. I’m planning to produce a small number of carbon fibre Carlsson bumpers, and r...

06/07/2026

The shop is open!

After a few years of selling parts through messages and emails, AP9 Engineering finally has its own website.
First of all, thank you to everyone who’s supported my work so far. Your trust is what made taking this next step possible.
The website is more than just a shop. I’ve also started a blog where I’ll be sharing the engineering behind the parts, ongoing Saab projects and the problems I’m trying to solve along the way.
If you’re restoring or maintaining your own Saab 900, I hope you’ll find something useful there.
🔗 Link in bio

06/07/2026

The shop is open!

After a few years of selling parts through direct messages and emails, I've finally launched the AP9 Engineering website.

Before anything else, thank you to everyone who's supported AP9 Engineering so far. Your trust and encouragement are what made taking this next step possible.

It's more than just a shop however. I've added a blog where I'll be sharing what goes into developing some of these parts, along with other ongoing Saab 900 projects - the problems I'm trying to solve, the design decisions behind them, and the engineering process. I wanted to share the thinking behind the work, not just the finished product.

Some parts have stayed simple and practical. Others have grown into much bigger projects, because once I get into a problem, I can't stop until I've found a solution I'm happy with.

That's really how AP9 Engineering came to be, and now it has a proper home online.

If you've been restoring or maintaining your own Saab 900 and have run into the same challenges I have, I hope you'll find something useful there.

www.ap9engineering.com

02/03/2026

This part started as a problem on my own car.

Original rear hatch trims for the Saab 900 Classic are almost always warped or shrunken — so I developed a proper reproduction to OEM standards.

After testing and installing it myself, I decided to produce a small run.

Saab 900 Classic Hatchback – 3 & 5 door

Available now.
DM for info.