Vac Forming a Canopy

Vac Forming is a great way to make a very professional look canopy for your plane multirotor on anything you want to mold really. The key to vac forming something really neat, is having a really good mold to work from. if you put in the time to get a nice smooth mold you'll get great results.

Some stuff you need,

•  basic wood working tools

• sandpaper

• body fillers

• primer filler

• spray paints (cheap enamel paint works well)

• vacuum cleaner

• heat gun

• glues,

• gloves

• something accurate to measure temperature. hand held point and shoot temp gun is best.

• a sheet of 1mm polystyrene plastic or .5mm polycarbonate plastic (lexan)

• and a few other things that you pick out in the pictures.

Some things to know about plastics!

Working with polystyrene sheeting is the best place to start. its dirt cheap, requires no real special preparation and. molds super easy. Polystyrene sheeting molding temperature is ideally about 137C. This 'how to' will be based on polystyrene sheeting. If you choose to go down the path of using polycarbonate sheet, its wise to know that you must dry polycarbonate as it is hydroscopic, 1 hour for every millimetre of thickness at 100C. and then its best to use the plastic within the next few hours. Not drying the polycarbonate results in horrid bubbles along seams and bends and its also very weakened. Once Polycarbonate has been dried, the molding temperature is quite a bit higher, 190C.

Constructing a vac forming bed!

My Vac bed is 2 IKEA canvas frames originally, but its quite easy to make your own with some cheap pine from the hardware store. Modify or make frame that fit in your kitchen oven, this is important!! Back one of the frames in plywood or any strong material. As the vacuum bed use perforated steel panel or you can use plywood and drill loads of holes. Be sure to support the vacuum bed from underneath to prevent it from crushing.( look carefully at my pictures, you'll notice some pine blocks under the mesh). In the lower bed drill a large hole that fits your vacuum cleaner nozzle.

Building a Mold.

Building a mold is pretty easy. If your making a once of molding that only needs to stand up to a few runs, balsa-wood is nice. But its important that after your initial shaping you finish it of with, car body filler, filler paints, lots of sanding, checking, sanding, until its as good as you can get it. At my work shop I have a CNC router and I used that to make the first parts of my mold from just MDF wood board. It machines nicely but still requires lot of sanding, filler and paint to get in nice. In this instance im making a canopy for my hexacopter. NOTE- i've carved in some recessed letters on top of the mold and these need little airholes drilled in them for proper suction. Also i've added a slightly larger piece of MDF on the bottom of my mold, this gives me a nice edge to cut my canopy out against.

preparing to Form the Plastic!

first cut out plastic to be molded exactly the same size as your frame. Fasten the plastic with small wood screws to your top frame. Seal the edges with masking tape, this helps lots with leaks and a quick mold. Masking tape is fine for polycarbonate to, even at nearly 200c!

If your using polystyrene sheet, it needs to evenly heat to 137C. once your oven is preheated it only takes a few minutes. Be sure to measure the temperature of the plastic all over, it needs to be even. When polystyrene is hot it sort of tightens and only sags a bit in the oven, whereas polycarbonate at 190C will droop like a big soapy bubble when hot.

 Steps to Vac Form! (read carefully)

1. When the plastic is hot and ready, switch on the vacuum.

2. remove plastic on frame from oven and quickly lay the top frame on vac bed. (check video)

3. the plastic will suck down quickly, and it will also cool down very fast.

4. use your heatgun to help details to form better, be very careful, if you over heat the plastic it will suck a hole straight through it.

Finshing the canopy!

Cut the canopy from the cooled plastic. trim it up and paint it. you may have to experiment with what paints work on polystyrene but so far cheap enamel paint has worked for me.

Thanks

Sam