Write-up: Project E46 seat back

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#1

I actually started working on this project back in February. It’s been a long long long process and I think I’ve all the kinks worked out. So I’ll make a little tour to show how I made the seat back. There isn’t going to be a lot of pictures but I’ll do my best to explain the little details.

BTW, the seat backs are going to debut at a show next wednesday on an E46 M3. Other than that I have one E36 M3 entering in Wheel Power Fest show tomorrow in Huntington Beach, CA. A second E36, the main carbon-werks car, can’t make it tomorrow so oh well.

I’ll start the “tour” tonight when I take some pictures.

#2

Before pictures. I’m basically using the stock seatback as a plug to make a fiberglass mold using: Tooling gelcoat, resin and glass


#3

Ok I didn’t get a chance to take any pics over weekend. But here’s basically how I started.

  1. Remove seatback from the car (duh). (30 minutes, yeah it was kind of tricky with the clips and all)

  2. Remove the mesh bag thing on the seatback. The carbon fiber seatback is not going to have this storage thing so I wasn’t too worry about breaking it. It’s plastic melted onto the other side of the seatback so I had to do some breaking anyway. (5-10 minutes, just to make sure I am not doing any damage to the seatback)

  3. Rip the leather off of the fibreglass body. This was a bitch to do because it was glued on pretty well. The seatback is now completely stripped but there is still a thick layer of foamy adhesive stuff that I need to get rid of before I can start sanding the surface. (30 minutes)

  4. I thought about using some kidn of adhesive dissolvant but luckily I only tried it in a small spot. First of all it doesn’t work and the liquid soaked into the body which made it soft and that’s BAD. So I tried scraping it with a putty knife instead. That works ok for a little while when I start to notice that I’m also scraping off part of the surface, which is also BAD. Lastly, I resorted to using a sander. So I popped in an 80-grit and went at the sucker. It works best but the process was quite slow. I finally finished removing the foamly surface. (6 hours, yeah, 6 hours)

  5. The foam is not completely removed and I wasn’t going to spend anymore time sand it so I decided to ignore it. Besides, I’m going to bondo over the entire surface anyway so it’ll be ok. Next step is using bondo to fill in the valley that’s caused by removing the basket section of the seat. NOT EASY. Not sure how long it took me to do this. I filled in the gap, spread on a thick layer of putty over the entire seat back and sand everything down smooth. ( 1.5 days or about 12 hours)

  6. A little bit more sanding. Now I’m ready to apply a coat of primer over the whole thing. (1 hour)

  7. Light sand, and 2 more coats of primer. (1.5 hours)

  8. Clear coat (1 hour)

  9. After a day of letting the clear coat cure, I started waxing the seatback with Meguires’ #8 Mold Parting Wax. I did a good 5 layers of wax (2 hours)

  10. Time to apply PVA parting spray. I applied 2 layers with 1 hour wait in between each layer (2 hours)

As you can see. It took me almost a week to just prep the surface of the core. I haven’t even made my mold yet.

to be continued…

#4

So much for a write-up since the thought of taking pictures during the process never even crossed my mind. Then again, I would not want to encourage copy cats.

So I made my 90 degree angle flange all around the plug using modeling clay (the kind that does not dry). NOT EASY. I need to figure out a better way next time. I don’t remember how long this it took since I did it over a course of 2-3 days.

Now to the mold making part. I got some orange tooling gel as my gel coat for the mold’s surface. This is a polyester gel coat so I added the recommended amount of catalyst and applied my first coat over the plug. I waited for about 20-30 mins and repeated the proces. I did a 3rd coat just to be sure it’s thick enough.

Now it’s time to apply the glass backing. I ran out of glass so I just got whatever that stuff they had at Home Depot. $5/package of 9square feet of woven glass. Seems like it weights about 2-3 oz which is kind of light. I used up about 3 packages. I chose to stick with polyester resin for this process since my gel coat is also Polyester.

A day later. Now it’s time to remove the mold from the plug. Crossing my fingers hoping that there’s no bubbles/voids on the surface of the mold. The mold came off very easily thanks to the wax and PVA. The surface looked very good except for minor hairline cracks and whatnot.

#5

pretty intresting so far… got any pics of the mold as it is now?

#6

Sorry I don’t. I have since gone back and made another plug and another mold. I’ll take some pictures of that soon.

#7

yea my car has a hard seat back like that and i’ve thought about doing it in c/f but thats a long way off… Gotta get good at the small things 1st… besides i’d be worried i try it and end up wasting a lot of good materials…