Thank you guys!
As promised, I'll show how I vacuformed the fuselage parts.
These are the things I used:
Two wooden frames on the left, some claps and a wooden box. The frames should fit the upper part of the box quite closely. to increase tightness I added some foam rubber to the upper edge of the box
It is important, that the box is airtight, so I wasn't mean using carpenter glue...
I used thinner wood for the top where i drilled several holes. I drilled another hole into the side. This hole had the diameter of my vacuum cleaner's hose
to create the master moulds, I glued together two about 1.8 cm thick balsa wood boards. It is important to paint the inner sides red with a permanent marker before gluing them. And don't take too much glue in this case because you'll have to separate them again.
Then I cut sideviews and upperviews of my airplane fuselage in the propper scale out of paper, added them as stencils to the doubled boards and cut or sanded respectively everything away what didn't belong to the fuselage. Remember sanding a little more because of the thickness of the plastic material. The masters need to be a little smaller than the actual scaled down fuselage. The marked red line where both boards meet is the centerline for the fuselage halves. If the fuselage is sanded, you can separate the two halves again. Put them onto the holed top of your vacuforming box. Don't forget to put them on some thin placeholders, some thick cardboard or so. They shouldn't lie straight on the surface, just a little bit raised. I reinforced them there with double sided tape.
Take your vacuum cleaner and stick the hose tight into the sidehole of the box. I used some tape to seal it up. switch your vacuum cleaner on (it's important that it reaches its operating efficiency)
Then take your plastic sheet (I used 0.75 mm stuff), place it between your wooden frames and fasten it with the claps. Put the thing into your oven or use a heat gun to melt the plastic (like I did). In every case you should put the frame onto some thick wooden blocks. The plastic is hot enough, when the surface gets shiny and it starts to sag. Take it quickly out of the oven or switch off your heat gun (don't burn your fingers as I did...) and put the frames with the plastic sheet in between immediately over your box. The vacuum cleaner will do the rest:
If it looks like this, leave some time to get it cold and then treat it like a custom bought vacukit.
Te crucial point in the whole affair is to pass the right moment to remove the plastic from the heat (if it gets dark or starts to bubble it is too late. If you remove it too early, it won't lie down over the moulds.
Try it and have fun!
Best wishes
Borsos