E46 Carbon Roof - The Ultimate Sunroof Delete

[Cement 875]

General Bla

I've been researching whats required to do a carbon roof on the E46 coupe and might document here in case others want to follow the same path including the required LVVTA certification etc. One or two might think this is over capitalising somewhat on the ex 318 so will also document my reasoning 🧐

• Got sunroof, don't want sunroof
• Weight savings (mostly in the sunroof delete)
• Want black interior so would need to do a new head liner anyhoo ... yes, the tail wags the dog
• It's within the realm of the DIY'er
• Have the opportunity to help manufacture the roof itself via vacuum infusion
• Just looks cool !!!

On Certification

I'm always keen to do things properly so I got in touch with the LVVTA to see if there is any certification interest in replacing the skin. As there is no definitive information for this procedure they took it to their Technical Working Group (TWG) for consideration. After a bit of back and forth the below statement was arrived at which provides the framework for doing the job.

"Based on the information provided, assuming that the procedure involves removing only the sunroof cassette and single layer of roof skin, that any spot-welded areas (particularly along the roof seams and apron areas) are either unaltered or restored to OEM specification using a compatible repair process, that the central roof bow is attached in a way that replicates the OE method of attachment, TWG are happy with the principle of this idea. However, the final approval must come from an LVV Certifier, and in addition to the above, they must be satisfied that the structure of the vehicle has not been altered by this modification beyond a safe tolerance of OE. They must also be satisfied that the bonding agents used to reattach the new roof skin are appropriate for the intended use."

I've been in touch with my certifier and he has outlined the inspections he would need for this:

• After the steel skin has been removed and the hood bow fitted
• After the new roof goes on but before glass installed
• Once everything is completed

 

The Process

There are many videos on YouTube of people doing the procedure, some of the better ones are linked below.

• Showing the roof skin being a single layer coming off the structural members: https://youtu.be/GhTOA7Cl9fk?t=140
• Showing a bit more of the overall process: https://www.youtube.com/watch?v=wmC-gooNM0M

The official procedure from BMW for replacement of the M3 CSL roof can be found here, which will be the process of installation for me: https://www.newtis.info/tisv2/a/en/e46-m3-csl-cou/repair-manuals/41-body/41-31-roof/4K9opCv

 

What Next

Need final confirmation the mold is indeed to suit the E46 coupe then I need to locate some spare cash. May take a little while until the next update but that's where things are at currently.

Edited June 12, 2023 by Cement

[Eagle 1662]

6 minutes ago, Cement said:

• Got sunroof, don't want sunroof

Is your car a ticked up Japanese import or are 318i coupes without sunroof hard to find?

[Cement 875]

It's NZ new but sunroof was not part of the priority list when I purchased... Just a good straight car for project base was the order of the day.

[polley 916]

I have a friend under taking this at the moment. Mold is done and i think production will be starting in not too long.

Edited March 8, 2023 by polley

[Cement 875]

1 hour ago, polley said:

I have a friend under taking this at the moment. Mold is done and i think production will be starting in not too long.

Awesome, any details to share on how one gets a hold of, manufacturing technique and price etc ?

[polley 916]

6 hours ago, Cement said:

Awesome, any details to share on how one gets a hold of, manufacturing technique and price etc ?

Its carbon fiber, pretty sure he is going to use infusion. Not sure what price will be. Will keep you updated.

[Cement 875]

Have given the go-ahead to make the roof and will be able to help out over a weekend in 2-4 weeks time ... exciting !!

[Cement 875]

Saturday is the day we shall get everything layed up and in the bag, pump it down and if all is well it shall infuse on Sunday

Got the parts list together for the fitment, adds up more than the roof itself !! Then there is certification expense etc etc ... probably another venture where could have spent better else where buuuuuut ... should be pretty cool right 😎

[Cement 875]

So no resin flowing this weekend but some sound decision making which should lead to a better / more certain result. Essentially it's pretty difficult to get the fabric right into the corners so we had to change approach after getting the first layer of fabric down (the most important one) using spray adhesive ... it was too aggressive and was not allowing the needed movement of the fabric causing all sorts of weirdness. So that layer was removed and is now the last layer instead where it will not be seen.

In the end the best method was to lay in all of the fabric (1x200gsm, 2x400gsm, 1x200gsm) and pull a partial vacuum, then massage into the corners nicely through the bag where you could move the fabric in from the outer edges, leaving the large flat part of the roof alone. The vacuum will be left on it for a few days so the cloth takes on the needed shape ... we'll then de-bag and add in the breather fabric, resin pipe work, flow media etc ready for the actual infusion.

To the pics ...

[polley 916]

Cool, be intersting to see how it comes out. Is Will giving you a hand ?

[Cement 875]

1 hour ago, polley said:

Cool, be intersting to see how it comes out. Is Will giving you a hand ?

That's the one yep

[Cement 875]

Phase 2 of 3 for the manufacture complete ... temporary bag removed and all of the proper steps completed ahead of infusing on Saturday. So cool to see it done in the flesh just like so many of the great vacuum infusion videos on YouTube etc. Steps done now and pictured:

• Layer of peel ply added
• Flow media added
• Flat channel for encouraging resin flow
• Spiral tube for feeding in resin
• 3x bungs for resin and 1x bung for vacuum pump

 

[Cement 875]

Had some delays with the infusion as the bag was not holding the vacuum well enough. Will says we need about 3 hours of good vacuum holding so the resin can gel and we get a good part out.

The good news is the bag is holding well now so we are good to go tomorrow to get the resin in

Also went with BMW NZ for the require parts which I've listed out below ... prices were not THAT much more than Schmiedmann after a little back and forth. Got the adhesives and a few of the other bits today that are not ex Germany ... only to find that 1 out of 3 window adhesives and both of the structural adhesives were past their best before dates 🤬

Not awesome when one is ... wait or it ... $300 and the other is a relative steal at around $200. INSANE prices but as I want to get this certed I must stick to the OEM products, one of which is clearly a Sika product. If anybody else wants to do a roof any time soon hit me up for some of the more expensive K1 adhesive which I only need to apply to exposed metal where spot welds are ground down etc as corrosion prevention.

Shopping list if anyone is interested:

51318208468    E46 Window moulding front
51318208471    E46 Window moulding rear
83192211217    R1 Cleaner
41328242075    E46 Roof bow
83190413015    Body adhesive K1
83190417144    Body adhesive K3
83192289286    Window adhesive

[Cement 875]

Got the resin infused today !! There were a couple of microscopic leaks identified during the infusion process which were sealed with mastic, crossing fingers there is no air against the mold side.

[polley 916]

Hope all goes well! Just have to be patient now.

[Cement 875]

Have not seen it in the flesh yet but its out of the mold and looking good

[Cement 875]

Got the glass removed today so I can start drilling out the spot welds this weekend to get the lid off.

[Cement 875]

I'd say I'm fairly committed now 😁 Removed the sunroof cassette (let me know if you need one !!) and got prepped for making a mess ... don't forget to tape off around the window trims to prevent future rust nuggets getting lodged in there !!

Next up it was time to start separating the many many spot welds around the perimeter. I started off using my little spot weld cutter (sprung pin in the middle, like a mini hole saw) but this proved pretty average ... pin rounded off and cuter tries to walk all over the place.

In the end the ideal method for the front and rear seams was to:

• Use die grinder to cut a small track around the edge of the spot
• Generally thin out the material around the weld
• Split the skin using a chisel, it basically just shears at the spot weld
• If not fully separated use the chisel ... like a chisel It goes through the thinned sheet metal easily

For the sides I might opt for a better drill, have seen some which look like a brad point wood drill which I might use. Must wait until Tuesday to get a hold of one though

[Karter16 407]

Looking great! This is a very cool project and certainly no mean feat! I am very much enjoying following this!

Keep up the great work!

[Cement 875]

Thanks @Karter16 ... I've not really stopped to reflect on what the hell I'm doing, but with tin snips in hand just now it dawned on me 😂 What a weird thing to be doing haha. Happy to show the 'warts n all' process here, very much a case of it getting wore before it gets better through this phase !!

Decided to remove the main part of the roof leaving only the strips at the edges so its more obvious when I've gone deep enough to release each spot weld. The alternative is going deeper than necessary on them so the entire piece can be lifted off in one great movement. Looks a hell of a lot worse but I reckon its the more gentle approach.

[Cement 875]

I have successfully removed the lid form the tin can Like anything new, the second side was a lot faster based on changing up the approach:

• Prepped all spot welds at once
• Started from the front and worked backward prying gently with a nail puller
• Using the heavier skin thats attached to the roof itself (adds strength around sunroof), pry up and over rolling towards the middle of the car
• Used a hardwood wedge to split a few problematic welds and lift the skin enough to grab with the vice grips. These are super useful, doing it again I'd probably make a half dozen longer ones (maybe 200mm) to use since they don't scratch and add a lot of splitting power.

Waiting on my Aliexpress belts to use with the finger sander to clean everything up nicely. Can't wait to get the drop cloth out and ensure there are no filings anywhere near the car !!

Picture of the tools used included for reference.

[Cement 875]

Have got all the spot welds ground down (used little finger sander, not pictured above) and removed the remains of the sealer.

Spoken to the certifier and he is happy for me to apply the K1 adhesive (as corrosion inhibitor) on the exposed metal areas ... was going to weld in the roof bow then do this and have him over to inspect but alas the bow has been delayed so I'm keen to get the metal covered asap.

Spot welds all look pretty happy 🤣

Edited June 6, 2023 by Cement

[Cement 875]

Popped three heaters in the garage for a few hours to raise the temp a bit and applied the K1 adhesive all over the areas where metal had been exposed. Used maybe 1/3 of the tube by the looks of it ... thats only $100 worth of this ridiculous goo 🤣

[Cement 875]

Still waiting for the roof bow (maybe another week) but some progress on the roof itself !! A little pictorial tour below ...

The roof as it came out of the mold after rough trimming, 2.5kg 😍 There are a few imperfections (small air pockets on the corner ridges and resin build up where the fabric has not gotten right into the tight corner) but overall its pretty awesome !!

Just a nice glamour shot during wet sanding, who doesn't like carbon !!

Basic setup for spraying ready to go

The setup at NZ Fibreglass in the booth. The item at the back is roof #1 from the mold; mine with the sanded finish ready to clear.

3 Coats of Upol clear coat on ... my first time spraying anything critical, and with a proper gun. Pretty happy with the result but an obvious orange peel going on. Will let it harden fully from here then sand it back flat and give it another two or three coats ... if we can't get it perfect off the gun (highly likely) we'll then safely have enough material to sand flat and buff to beauty.

[Cement 875]

Got to confirm its for the right model car at last 😃 Hopefully the window moldings come up onto the roof slightly to hide the most noticeable pieces of deep resin, else might run a small strip of black vinyl perhaps ... will see when we get there but safe to say its going to look pretty sweet !! I can see why people might go with a plain 1x1 weave as the twill is fairly intense ... then again so is all the sh*t in the garage at the moment !! All back together with some light window tinting and it should look mean.