Paper-mache and/or plastic cowling?
 

One of my current projects is a small O/D parasol wing sport plane. The motor, OS 26 FS, will be inverted and fully cowled. I amjust about ready to make the cowling.

I had in mind to try and make one from paper-mache or maybe a 2-piece one made from one or two plastic bottles.

I've never tried either of these methods before.

To attempt the paper-mache one I considered making a plug from modelling clay, plastering it with pieces of wet tissue paper applied with aliphatic glue, and then digging out the clay when the glue has dried.

For the plastic one I considered making a wooden plug and trying to mold the plastic over it with plenty of heat from either a heat gun or small gas bottle.

Has anyone out there had any experience using either of these methods, or can point me in the direction of some information that may help.

Thanks in advance.

Alan W

Great Endeavor!!
 

It's been soooo long since I made a plastic cowl, but I would be more inclined to go that way, then the papier mache...I would use a wood plug, sanded perfectly smooth, and use the stove, to finish it...I can't remember the temp I would use, but if I remember it wasn't very high...if you email me and remind me, and give me a few days, I will experiment a bit, since I still have some plugs, and the plastic....I do remember it was a LOT lower temp than I would have expected....

I have since graduated to fiberglass, and it's really easy, since you are making a wood plug, anyway.

There's a good site on fiberglass cowls, on one of the other forums, here:

http://www.rcuniverse.com/showthread...threadid=28248

Good luck, and most of all, have fun!!!

FG Cowl
 

Another way is to make a styrofoam(or balsa) plug, then cover it with a low temperature covering like Econokote. Next lay up a layer of fiberglass mat and/or add layers of fiberglass cloth over it as needed for strength.

You can use polyester or epoxy resin. Thin cloth (3/4 to 1.5 oz) is easier to work with than the heavier 6 oz cloth. The smoother you can get it on, the less sanding you will need to do.

When it's hardened, sand the bumps off with 80 grit paper. Try not to sand into the cloth too much. Brush on another coat of resin and sand with 100-180 grit. You can use automotive "spot putty" to fill rough spots. Prime with sandable primer and finish sand.

Fellows use different variations of this technique such as brushing hot paraffin wax over the plug, or coating the plug with water based polyurethane etc, adding wire for stiffness etc.

Some don't coat the plug at all and just dig the foam off or dissolve it with gasoline when done! If you don't coat the plug use only epoxy resin because polyester eats foam :)

Paper-mache and/or plastic cowling?
 

I have made cowlings from plastic cups formed over a form with a heat gun. You know, those red or blue plastic cups used at picnics. I have used them for electric airplanes. I have also formed 2 leiter soda bottles to make naceles. Cheap materials so one can experiment a lot.