Yoav's Mirage 3C 1:33 scale

[McTschegsn]

Originally Posted by Erik Zwaan

Hi Chris,

Thank you for your kind offer but I'm building the Mirage on scale 1:33, so at 91% size of the original and I'm not sure what the size of your mold is.
I'm currently making a vacuum box and see if it leads to something. To maintain some sort of progress I'm working the air intakes as well.

If I screw up, I may gladly take up your offer and will let you know!

By the way, how's your Kfir coming along? Thought you were still in the final stages of completion?

Cheers,
Erik

Hey Erik,

the Kfir is resting at the moment because of our move to a new house... Plenty of work to do and almost no time for papermodeling.
The first R/C meetings are upcoming and I have plenty of things to prepare for that, too. She is not forgotten :D

[Erik Zwaan]

Thanks guys for your valued and very useful comment regarding the vacuum process!

Today was our national day, the King’s birthday, with a lot of flags around in our neighborhood. The weather was not as bad as had been predicted but it was simply too cold, barely 5°C and in the late afternoon some showers. In other words: A good day to test the vacuum box.

I cut out a square of overhead sheet and pinched it in the frame. Then used our table barbecue (gourmet set) with two stones placed on top for the frame to rest on. I connected the vacuum cleaner to the vacuum box and placed the mold on a base to keep it free from the board (thanks for the tip Knife!). Switched on the heater to maximum and waited to see what happened next.

I expected the plastic sheet to sag during the heating up but despite the fact that the plastic softened up, it pulled itself tight in the frame. In the end I put the frame on the barbecue but the plastic remained tight. Switched on the vacuum cleaner and after almost five minutes being heated up I put the frame quickly on the box and immediately the plastic shaped itself over the mold, driven by the vacuum.

The result was a very acceptable canopy but somehow the edges had not folded sharply around the mold so I made a second try. This time I pinched the plastic sheet very loosely in the frame but still the sheet tightened during the heating process. Immediately after placing the frame on the vacuum box I pressed a small wooden spatula around the mold to get sharp edges. This time the result was an almost perfectly shaped canopy.

It took quite some time to prepare the tools but the vacuuming process itself is a matter of seconds, and the heat-up only a few minutes.

So this is my recipe for the process. Besides putting the mold on a base and pinching the plastic loosely in the frame, the other very important thing is to make the mold as smooth as possible for a nicely shaped and smooth canopy. The result is not 100% perfect but for a first time, 95% is more than acceptable!

Ok, that's it for now. No more modelling for the next two weeks or so, next week I’ll be away for a short holiday in Paris .

Erik

[Isaac]

Erik.

I usually add a small extra pice of wood under the mold to raise it up. This way, the plastic forms the entire mold


Enjoy Paris


Isaac

[alzictorini]

Erik

What a top looking Vacuum Box. You mention a YouTube video, could you proved the link please buddy?

Best regards

[hyair]

Hi Erik - your canopy fit to the fuselage of YOAV's mirage is looking very good !
It will certainly add to the model appeal . Sometimes small imperfections
of the canopy can be covered by the outside frames so it should look
very good. I hope to build this model in 1:48 scale sometime as it's already
printed and ready for building.

Regards - Yair

[YOAVHOZMI]

hi Erik

the clear canopy is loooking good, but i think you have to polish more the mold, especially where was the joint strips on the paper canopy....i marked them in the attached pictures.




keep on your wonderful working

YOAV

[Erik Zwaan]

Morning guys,

Thanks again for your feedback. Just a quick reaction during a coffee break in the office:

@ Isaac: I used a small base but next time will use a bigger one of let's say 1cm high, to make sure the vacuumed foil fully follows the shape of the mold. This time it was still just a little bit off.

@ Al: Here are the links. There are many others but I found these ones very useful.
How I Built a Vacuum Forming Machine
https://www.youtube.com/watch?v=JS8ETVtKpCA

@ Yoav: You're absolutely right regarding the lines that you see in the canopy but it's not that pronounced as it may look like. The mold in the picture was still sanded a bit afterwards to smooth out the joints. What I basically did is that I made the mold using the inside frames of the cockpit, used white glue on the seams and smoothed them out with my finger as much as possible. Then applied white glue on the inside and outside surface and let it dry. This already provided a stiff "shell" to use for the vacuuming although I later on added a bit of wall filler on the inside to make the shell even stronger. I also used a former on the inside, based on the frame with the rear view mirrors. This way of making the mold differs from the usual process as shown on this site, where the outside canopy is used, filled with wall filler or gypsum and later on sandpapered away, to leave the hardened core as basis for vacuuming. Perhaps this will give a smoother canopy, as it's likely easier to polish. Something to consider for a next project! You learn as you go and it's great to pick up the experience from others.

@Yair: Looking forward to your build of a 1:48 scale Mirage!!

Alright, coffee finished - back to work

Erik

[YOAVHOZMI]

another thing Erik that i forgot, the front of the canopy must be flat(the place that you put the front oblong frame)

YOAV

[Erik Zwaan]

Hi Yoav, the canopy is indeed flat on the front side. I dry-fitted the frames already and they seem to match perfectly. Thanks for your attention .

Erik

[alzictorini]

Erik

Thanks buddy for the link, looks like I'll be busy building this weekend!

Enjoy