"In this Special Series, I'm taking another step towards the M5 CSL conversion. I document the development, features and conversion process of the E60 M5 CSL carbon roof kit.

In this entry, it's time: preparations are made, and the carbon panel finally gets glued and sealed."
- Matt

Understanding adhesion. 

Prior to applying any adhesives, the roof's chassis rails were inspected one last time and thoroughly cleaned for application of the adhesives. The carbon panel's underside was also inspected for any surface irregularities, and contaminants were chemically removed. 

The carbon roof panel installation process involves 2x different adhesive types that will vary on the area and surfaces upon which it is applied.

• 2 component, catalyzed epoxy. 
  • Extremely strong. 
  • Settles within one hour. 
• 1 component urethane. 
  • Flexible, strong. 
  • Settles within 4 to 8 hours depending on pressure, temperatures, etc. 

We combined the E46 M3's original instructions with common sense.The BMW instructions dictate for epoxy to be applied on the chassis rails and the front and rear transversal beams. 

The E60 M5's beams also had urethane applied on the inner sections. We identified and applied urethane on the same areas. We would also use this approach for the roof bar. 

The surrounding areas were masked and the interior was draped once more. The adhesives used could stain and destroy interior trims and materials should it unknowingly come into contact.  

The chassis rails, transversal beams and roof bar had their edges masked to ensure no adhesive would leak. 

The roof bar itself was first glued to the chassis rails using 2 component epoxy. It was spread across the upper and lower tabs. 

Urethane was first applied across the sections where BMW used on the original metal roof, in part because it takes a lot more time to settle.

We mimicked BMW's technique on the roof bar using urethane. 

The rear transversal beam also has sections of urethane. You'll notice urethane was applied first, and specifically on inner sections of beams as it is the lesser of the two adhesives.  

The urethane was applied in small sections, as BMW originally did. Urethane is flexible and spread under pressure during curing. 

Next, we begun applying the 2 component epoxy. It's a more intensive process. It requires more strength, and certainly more focus as the consequences of any errors are much higher 

The epoxy was first applied across the transversal beams as they are the harder to reach areas. 

The epoxy was then applied across the roof's chassis rails in a continuous section.

The front and rear beams did have slight indents that were left unglued by BMW. We retained the same method. 

With the clock running, I switched to video recording and did not take pictures of the last step. The epoxy was spread out to cover all sections of the rail uniformly prior to the roof panel alignment. 

With the adhesives properly applied, the roof panel was brought out and settled into position. 

We took a minute to fiddle and validate its alignment using the mechanisms described in the previous entry.  

With all corners in their position and the dimples aligned, we proceeded with the final step of the adhesion process.

These adhesives need pressure to reach their bond strength. Clamps were positioned across the transversal beams first. 

Pressure helps spread the epoxy through the surface. Additional attention was given to the corners of the panel. 

You want some spill, but too much would indicate excessive pressure.

Additional clamps were added to the chassis rails to ensure sufficient pressure across the roof panel.

The adhesives were left to cure for a minimum of 24 hours before we removed the clamps. At the shop's temperatures, the epoxy has upwards of 75% of its final adhesive strength within a day.

The final step to the adhesion process was to seal all edges. A film of urethane was applied. This eliminates water infiltration probabilities.  

As we awaited for the urethane to cure, we proceeded with fitting the roof antenna. 

It houses this antenna, it is your GPS navigation receiver, telemetry, and phone receiver.

AH! The cutouts were a little tight. This is common with composite panels.  We enlarged the cutout for the front tab of the shark fin. 

It had no bearing on the fitment of the shark fin. 

Fitment is spot on within the relief of the panel. This would be a flat section if you do not spec the cut-out for the shark fin.  

The shark fin is glued to the panel using urethane. The original urethane was still present. We removed and re-applied for final fitment. 

Unlike the title implies, this is not necessarily a permanent installation. In case of a crash, you could remove the roof panel with less hassle than the original metal roof to re-use on a new chassis. 

The most nerve-racking step of the conversion process was finally over with.

Up next: we take a pause from the paint shop and recondition the rear shelf prior to re-assembling the interior.