heinzboehmer's 2002 Topaz 6MT Coupe

[karter16]

Interesting. I didn't think it was very hard to get mine in and out through the door when I did it - only minor flexing / squashing of the corners required and that was with the CSL bucket seats in place. I did the headliner in my 318i sedan many years ago and that was horrible to fit through a sedan-sized door.

[bigjae46]

For sure.

But honestly, I think finding someone local with a CNC router and routing it out of pink insulation foam is gonna be way easier and way, way cheaper. That's how most of the RC plane people build their stuff, so maybe someone in that space can help out.

Random video pick, but jump to 4:20 for an example: https://www.youtube.com/watch?v=o6FMjOl0TRA

How did you get to the 33% lighter figure? Scan measures in roughly at 1.5 m2 for surface area of the part. A layup with 4 (to make the part thickness ~1mm) 210g 2x2 3k layers would weigh ~1260 g dry. Leaves very little margin for the weight of the resin + fabric, unless 4 layers is way overkill.

Also, the part is made opposite to what you're describing (and what I expected originally). The thickness is ~5 mm throughout most of the part (sans fabric), but the edges are "crimped" down to ~1 mm to fit under the other trims in the interior. I'm guessing the increased thickness in the middle is for either stiffness or NVH. If the carbon part is stiff enough, it could likely be made at 1 mm thickness throughout. NVH is easy to address with the "recycled jeans" insulation (51488229733 + 51488229734) that you can get from BMW.

Got it...I'll see what I can find

My mistake, I was thinking the normal aluminum to carbon conversion.

It could still be a lot lighter than the fiberboard. With the edges being thinner then that makes it much easier. Since it will be upholstered, the part could be laid up with a 1k carbon which is less dense, a 4mm soric core with an extra layer of 3k around the edges. One side will have the exposed core but who cares. Not sure how much lighter. I don't have my soric core math lined up with reality well enough quite yet to make a close guess.

[ac427]

I'll ask my metalurgist father, but I think it would apply to all or most alloys, not just copper. Some crush washers provided in various kits look to be aluminum at times, not always copper.

What did your Dad say about aluminum and annealing?

[Obioban]

Got it...I'll see what I can find

My mistake, I was thinking the normal aluminum to carbon conversion.

It could still be a lot lighter than the fiberboard. With the edges being thinner then that makes it much easier. Since it will be upholstered, the part could be laid up with a 1k carbon which is less dense, a 4mm soric core with an extra layer of 3k around the edges. One side will have the exposed core but who cares. Not sure how much lighter. I don't have my soric core math lined up with reality well enough quite yet to make a close guess.

Suspect you'd have to take out the windshield or black glass to install it, if it were completely rigid.

[bigjae46]

Suspect you'd have to take out the windshield or black glass to install it, if it were completely rigid.

Should be a little bendy but not much. Can't get it in through the door opening with the seats removed?

[Obioban]

Should be a little bendy but not much. Can't get it in through the door opening with the seats removed?

You can get the the stock one in that way, but it’s quite bendy.

[bigjae46]

You can get the the stock one in that way, but it’s quite bendy.

Maybe that's why the 2M one never took off? The headliner would need to be installed when the roof is installed and most that would buy it already have a roof installed.

[heinzboehmer]

Yeah the stiffness of the part will be an interesting thing to figure out. Too stiff and it won't fit through the door, too bendy and it'll flop around when driving, since it's not really held by anything in the middle.


Also, have started working on the CAD model and wow, it's been a struggle.

For the previous scan, I hung the part vertically from the ceiling, thinking that that would allow it to keep its shape. Unfortunately, mirroring the part along its short axis in the digital world made it very apparent that this assumption was incorrect.

I messed around with it for a while, thinking that I had my coordinate axes slightly tweaked, but eventually came to the conclusion that the part was deformed when I scanned it. This is as good as I could get it:



That gap is roughly 20 mm across. Nowhere near acceptable.

So, I gave up on that scan and redid it. This time, I built a professional fixture so that the part could lay horizontally on the ground without distorting:



For anyone following along at home, you'll need exactly these parts for max precision:

• 4x Dinner plates
• 1x Flooring sample
• 2x Varied candles
• 1x Folded over MF towel
• 3x Assorted rolls of tape

I set everything up so that the headliner was juust barely resting on the plates. They're not there to provide any support, but rather to provide flat references for plane alignment in CAD.

Newest scan is muuuch better (have updated the previous link):



Gray is the scan and yellow is the mirror. Not entirely perfect, but I didn't expect it to be. Can absolutely work with though.

Now it's just a matter of getting lost in surface land and coming out the other side with a model.

[0-60motorsports]

Thats excellent.

[George Hill]

I think it'll go in even being completely rigid, I don't recall ever having to bend a coupe. The door frame is larger on a coupe than a sedan and they come out a sedan without bending as well. Worst case you take the door off, 3 bolts and a wiring connector, bingo bango.

[YoitsTmac]

I've definitely replaced a headliner on a coupe without removing the door. I MAY have removed the seat or laid them all the way back, but I've done it without a door removal. For whatever it may be worth

Also on the e46 m3 Facebook group, someone said they were going to make slick top headliners at about $1k soon. But I didn't pay too much attention to it

[George Hill]

I've definitely replaced a headliner on a coupe without removing the door. I MAY have removed the seat or laid them all the way back, but I've done it without a door removal. For whatever it may be worth

You don't need to on a stock headliner, lay the seat back and open the door and it goes out the passenger side no problem.

What I meant was that IF you needed to bend it to get it out and a rigid headliner wouldn't fit then you could take the door off easier than pulling a windshield. Again, I don't think that is necessary but some people were concerned in the various headliner threads present right now.

[heinzboehmer]

I've definitely replaced a headliner on a coupe without removing the door. I MAY have removed the seat or laid them all the way back, but I've done it without a door removal. For whatever it may be worth

Also on the e46 m3 Facebook group, someone said they were going to make slick top headliners at about $1k soon. But I didn't pay too much attention to it

The 2M one? I'm very curious to see what they managed to pull off, how they made it, how much it weighs, etc. Staring at this part has made it very obvious that it's not trivial to get it right.

You don't need to on a stock headliner, lay the seat back and open the door and it goes out the passenger side no problem.

What I meant was that IF you needed to bend it to get it out and a rigid headliner wouldn't fit then you could take the door off easier than pulling a windshield. Again, I don't think that is necessary but some people were concerned in the various headliner threads present right now.

Yep, I like your line of reasoning. Feels safer to go for max stiffness in the part and remove the door if necessary during install. Seems like much less hassle in the end than trying to live with a floppy headliner.

Unless you make it too stiff and it resonates at highway speeds 🙃

If that ends up being an issue, it might be worth looking into redesigning the motion sensor bracket so that it double-sided-tapes to the roof, to constrain the part in the middle. Hopefully that drives the resonant frequency way up into a range that a street car will never see in practice.

[bigjae46]

The 2M one? I'm very curious to see what they managed to pull off, how they made it, how much it weighs, etc. Staring at this part has made it very obvious that it's not trivial to get it right

What I would do is apply a layer of surface veil with epoxy on the original part to create a good surface to pull a mold from. That is how I made a mold for the fiberboard E9X M3 panels that go behind the front bumper.

The bad thing is you have to destroy the part.

[heinzboehmer]

What I would do is apply a layer of surface veil with epoxy on the original part to create a good surface to pull a mold from. That is how I made a mold for the fiberboard E9X M3 panels that go behind the front bumper.

The bad thing is you have to destroy the part.

Bryson sent me this: https://www.instagram.com/reel/DYAGESosIlI/

Looks like their strategy is similar?