Wrap the wing with aluminium foil, taking it round all edges or taping it where it won't fold around an edge.  Use brown packaging paper, which is flexible but strong, also taking it around the edges.  Paste with a mixture of PVA and CMC or wallpaper paste (or in this case since it is not likely to be long lived, boiled flour paste . . did I really say that????)
Apply about six layers and allow to dry thoroughly.  Paint to the car colour.
Separate carefully from the car, cutting along the edges to release.  You may find that the shaping allows it to hold on to the real wing sufficient for your needs but otherwise you will have to work out a method for the particular situation.

What's the stiffening for?  Are they being handled by actors taking them on and off the car during scenes?  Or are they being handled by techies?  In my experience actors are rougher on props and sets than technical folk. (I've been both.)  Also, how are you storing them ... are they propped up on a wall so need to hold their shape with the weight of the others resting on them? If so, you'll want to reinforce the places where they'll be handled the most and where they'll sit when stored. 

I'd try it David's way first.  6 layers.  I do multiple layers at a time and let them all dry together (of course I've never done anything as big as a car!) ...  Keep in mind that since the inside of the paper mache is against the tin foil and car the outside will be dry when you take it off, but the inside will need additional drying time. 

Another option would be to create them out of chipboard or cardboard, with a paste made from glue and plaster.  There's a video on the Science Channel website discussing this technique for making dress forms. 

Here's the link: 
http://science.discovery.com/videos/how … -form.html

I've had a couple of notifications of new replies on this topic, but when I come here, there's nothing new...strange.

Well, I did a test piece and it's worked brilliantly! Thanks for the help guys.
I used decent PVA watered down about 6 parts PVA to 1 part water.

However, I'd like to know what people use on the top layer to smooth out the overlap lines? I used butcher's paper (thick white/cream paper) and tore the edges - not cut.
I even sanded before painting, and the lines still show up under the paint.

Do people use some kind of plaster jointing putty, or "builder's bog" as a top coat and just smear it over the top, effectively smoothing the joins?

Cheers!

Awesome - thanks for the detailed explanation.

What is the benefit of this recipe over say - what builders use to patch plasterboard walls?

Sweet, that sounds perfect then. The only probs with self levelling is I'm making these panels on the car itself (so vertical for the most part).  Although I guess I could just do that after its all dried and lie the panels flat.

Thanks very much.

Now I just have to find calcium carbonate.... Artist supply shops?

Oh to apply it on a vertical surface, just mix it to a consistency of a good paint. It will hang on just fine. Just apply thinner layers. I paint it on odd shaped pieces often.

When you're asking around to find a source, be sure to give them all its common names:  whiting, calcium carbonate, chalk.  Some people know it by one name and not the others.  You can ask for whiting and they immediately say they don't carry it, with their hand on a 50# bag labeled 'calcium carbonate'.  It's used with swimming pools, as an additive for art paints, stained glass artistry,

If you have a potters supply nearby, start there first.

Whatever your source, make sure it doesn't have any additives. 

Sue

Try Northcote Pottery Supplies -- website:  http://www.northcotepottery.com.au/home
142 - 144 Weston Street, Brunswick East 3057, Victoria  Australia
Tel 03 9387 3911
[see Prices, appears to be called whiting]

Clayworks -- website:  http://www.clayworksaustralia.com/
6 Johnston Crt, Dandenong 3175, Victoria, Australia
Ph +61 3 97916749
[see Prices, "Raw Materials", listed as calcium carbonate]

Walker Ceramics -- website:  http://www.walkerceramics.com.au
Phone 03 87616322          Email sales@walkerceramics.
[see Raw Materials, called Calcite (OMYA 10) "A purer form of whiting"

Some may be distributors, just ask who would sell to you nearest your location.

Sue

Yep pottery suppliers are your best bet, and the quality is usually good too. I'm fortunate to have one across town, which is a long way in Houston, but I buy in 50lb batches so I only have to make the trip once a year (maybe 2 since my projects keep getting bigger and bigger). Mail order is good, but the shipping gets prohibitive. Some of your better specialty paint stores (house type paint) do carry it, they call it whiting or sash putty, so if you have one in the neighborhood, you might want to give them a try before going out of your way.

Last edited by paper soup (2012-03-21 19:41:33)

Acrylic-based gesso may be better for this particular use, as it seems to have a bit of flex to it.  Paper Soup's recipe looks good for things that don't flex at all.

Sue

I would think that you could find it at most fine-art supply places, those that sell paints for artists (oils, watercolors, acrylics, etc).  The most common use is probably sizing framed painters' canvases.  It runs about $7 USD for 250 ml of an economy brand, but comes in all sizes.

'Acrylic gesso' should be the standard name.

Here's an American link and description:  http://www.dickblick.com/products/blick … ite-gesso/

Sue

I've added a bit of plaster to my glue when I want more rigidity with fewer layers.  (And by a 'bit' I mean 1tb per ~10oz of paste.) ...

As for covering up paper lines and still maintaining flexibility ... I'd suggest trying a thin version of monster mud, ie, add a little bit of drywall compound to latex paint to thicken it ... the latex should retain it's flexibility enough to not flake or crack.  (You could try just adding calcium carbonate to latex paint as well and see ...) ...

-- b