Q: what is "gum strip"?

I'm keen on your method.   You could layer with metal mesh- but the finishing/filling consequences might be unsavory- you might be better served by using fabric (canvas, cotton duck, etc).   I'm think'n do as you said (car+plastic wrap+PVA mache), then fill the negative space with expanding foam (GreatStuff, etc) embeded with a few pieces of armature and mounting brackets.   To do this, you will need to support the work while it is removed from the car; you could cut large pieces of cardboard to fit the major front profiles, like a slice form, with the edges away from the car terminating on a plane; remove the cast from the part, flip the whole onto the slice form to act as mother mold and staging table for the foam fill.   Tediously over complex.   A much simpler approach would be to frame the car (say, with 2 X 4's) where the imagined wall line would be and extend the plastic wrap from the car to the surrounding frame along the part line (a laser level would be handing for tracing the part line on the plastic); filling the space from frame to car with foam would be a great help; when papering the model, paper up the foam to the frame.   Remove the part from the model, cutting only as necessary for removal.   Attach legs to the frame and rejoin all parts on the frame.   The part will need to be supported- with sand, chunks of foam, packing peanuts, what have you -while you apply expanding foam and armature to the inside, then cut out any negative elements and free the part from the frame...

Hello, Parkage:

I discovered recently that using brown paper (from heavy-duty brown wrapping paper to brown-paper supermarket bags) makes for much stronger papier mache (for the strips and glue method). Newsprint has very short fiber, and therefore tears and breaks more easily. Brown paper has longer fiber, and behaves a bit more like a fabric. If you tear your strips rather than cut them, you will also gain strength, again because torn fiber has more tensile strength than cut fiber. The bull mask on my gallery was made using brown-paper grocery bags, about 5 layers. The result was quite strong enough to be worn and banged around, and it had minimal inner bracing. I formed the mask over a cow skull, using plastic food-wrap as a mould release like you described.

Best regards! Scylla

You can also use Bond (office) paper.  I have used alternate layers of brown (kraft) and bond to produce a very strong laminate.

Good morning Parkadge.

Glad you liked the "Bull Mask".

Regards acquiring brown paper bags...I bet your students will happily bury you in bags from home (smile). A fine opportunity to inspire the youth to recycle and repurpose materials.

I look forward to seeing your auto-project on this site!

Best, Scylla

I agree with the others that newspaper isn't strong enough to use for the wide spans in your project, except possibly as a lining material to protect the car.

For using the expanding foam: latex or nitrile gloves and old (disposible) clothing are crucial.

And be sure the owner of the car isn't going to need it for a while!

Sue

Have you seen Andre Willemsen's car front? He has used real headlamps for a realistic effect. http://www.papiermache.co.uk/gallery/item/3/

That looks amazing. Unfortunately we didn't have the time or the space to do that

In the end we only had access to the car for a couple of hours each session and then we had to remove  what we had done. So we lost the shape of the original. Each week we restretched it but it didn't really work out. We would have been better just making a chicken wire armature to work on. Great learning experience though.

Time ALWAYS seems to be the issue with papier mache! 

It's either the time it takes for enough layers for strength, the time it takes for smoothing the paper down properly, or the time it takes to dry.

Then you start it in hot, dry weather, and that seems to invite a cool, wet spell.

It's summer here in western Washington State, but you wouldn't know it by the weather.  It's raining now.  It's been raining since spring.  Spring was wetter than winter.  Even if it warms up to 70F (21 C), it's raining, and then a cold wind starts blowing.

The papier mache hates it.

The tomatoes hate it.

But the peas are as happy as clams at high tide.

Whooppee.

Sue