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Old Mar 08, 2006, 06:53 PM
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J Morgan's Avatar
Chapel Hill, TN USA
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Simple & Easy Clear Canopy Making........

I've had several requests, PM's, etc. for a thread on vac forming a clear canopy, most recently from Cecil, so here it is.
Some people are happy with a painted black, silver, blue, etc. canopy and that's fine but I myself feel that a clear canopy and some cockpit detail adds alot to the look of a model. It won't make it fly any better but does help the looks.
The way I do mine is good for a few pulls on the vac former before the mold degrades and affects the finished product. It is not for commercial use or use with a strong or very hot plastic. But it does work for me.
This will be a canopy for Philippe's(GGRN) Rafale that I'm presenting building.
I start with a good, repeat, good 3 view of the canopy. I need top view, side view and front view. Sometimes pics will work but 3 views are better. I measure the length , width, and height that scales to the model. Then cut a block of pink foam that is oversize. After making tracing paper templates, I transfer the side view to the foam. Then hot wire it leaving an excess around the outline. This allows some room for carving and shaping a little later.
After cutting the sideview I trace the top view on and hot wire it.
This leaves me with a chunky sort of canopy form. I then take my handy dandy sureform tool and carve the mold to shape. Keep checking against your pics to get as close as possible. Trial fit it on the plane to see how close it is and when satisfied sand it with med sandpaper. It doesn't need to be perfect just pretty smooth.
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Old Mar 08, 2006, 07:02 PM
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J Morgan's Avatar
Chapel Hill, TN USA
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So now we have a foam canopy but can't vac form it because the hot plastic will melt it. If you want to use the mold for several pulls, then now is the time to use some heavy FG and fg/epoxy the mold. Doesn't have to be neat or anything but do use epoxy and heavyweight glass on it. The next step will get it ready for the heat.
I don't see me making many pulls on this one so I just gave it 2 coats of 15 min epoxy.This is to protect the foam for the next step, auto bondo. So after 2 coats of epoxy, I sanded lightly and applied the auto bondo.
The bondo will provide a nice smooth surface, filling all the weave on the glass if you glass, and protect the foam from the heat. If you neglect the epoxy or epoxy/FG then the bondo will eat the foam. Enough said.
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Old Mar 08, 2006, 07:27 PM
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Chapel Hill, TN USA
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The bondo....if you've never used it be aware it's tough stuff. Us old guys have owned cars that were mostly held together with this stuff! I use what the auto parts places call a bondo cream. It is in previous pics. Comes in a tube with a tube of catalyst. Great stuff, sands better than any bondo I've ever seen. Don't get the old blackish colored stuff. You'll be sanding forever! It is hard to get smooth when applying and you will wind up with hills & valleys that have to be sanded smooth. Start with 40 grit, that's right 40 grit sandpaper. You probably don't even own 40 grit do you?
Sand it smooth as you can with 40 grit, there will be many scratches from the rough paper, but do the best you can. Then start going to finer grits until you are at 400 grit. You might find that you still have some dips that need to be refilled. Mix more bondo and refill. Do it to any bad spots you find and then sand again. We need this to be as smooth as possible because that will be the surface that the plastic forms to and if it is imperfect then so will be the plastic.
Now take a good filling primer and give it a heavy coat. This will show you how well you did sanding and filling. Inspect the painted mold. Not as good as you thought huh?
Paint shows EVERYTHING! You'll find some small spots and pinholes probably. Quck and easy, use some lite spackle to fill the pinholes. And in worse case scenarios, mix a little more bondo and get it right. Let dry and sand again. If necessary, give another coat of primer, dry, and sand again. After satisfied with the mold, give it a LIGHT coat of auto wax, dry, buff and you're done.
Now we have a mold that is ready to vac form!
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Old Mar 08, 2006, 07:40 PM
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OK, where were we? Oh yeah, the mold is ready for the vac former. Well, almost. I also glued a 1/4" piece of fanfold to the bottom of the mold and then sanded it flush with the canopy mold. This makes sure the plastic pulls down past the bottom of the mold and I can cut it right where the mold meets the fanfold. Damn, hope you can undstand this gibberish! We need to decide what thickness plastic to use. .020 usually is best for medium to small models. I used it here but it was very marginal. I probably should have gone to .030 or .040 plastic ( Vivak) but was too lazy to get it from the box. I had .020 laying right in front of me. But i got away with it so no harm done. The reason I should have used thicker plastic is because this is a pretty large canopy, 15" long, and fairly tall which means the plastic needs to stretch quite a bit. You also need standoff for the mold to sit on so the plastic can pull straight down past your mold and suck right up to the bottom. I found that I needed about 3/4" so I used 3 layers of fanfold stacked to get the mold off the vac form bed. Make sure the stapes and plastic are on the bottom when you form, just thought I better add that!
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Old Mar 08, 2006, 07:41 PM
GPT
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J,are you going to cover the actual vacforming process next?

Top thread btw,I,ve been thinking about doing my own canopies.
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Old Mar 08, 2006, 07:42 PM
GPT
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Are you beat me,must of gone up,whilst I was typing.
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Old Mar 08, 2006, 07:59 PM
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Chapel Hill, TN USA
Joined Apr 2001
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The previous pic shows the vac former I recently built for these larger canopies. My older one was too small. Simple wooden box, nailed and siliconed together to prevent leaks. A plastic fitting that matches whatever shop vac hose you have is siliconed in the side. Then hose is duct taped on to prevent leaks.
Heat source.......By far, a oven is the BEST! I don't have room for one in my shop corner so I use the small hot plate you see in the corner of the prev pic. Not a good source and demands a learning curve , just like plastic does, to get good pulls. If you can use an oven then great. It provides even heat and makes your life simpler. It is VERY IMPORTANT to get even heat on the plastic.
This took two pulls to get one I could use. First one didn't have the plastic heated evenly enough. My second one as close but not good enough. So I left it on the vac former, turned on the shop vac, and used a heat gun carefully in a couple of places to suck it down till it was right. Be careful though, a heat gun can meltholes in the plastic and hurt your core if it gets too hot.
This left me with a useable canopy. Let it cool and leave it on the mold. Now take a felt tip marker and draw your canopy lower line on it. This helps alot when cutting it out. You can get rid of the black later with denatured alcohol. After drawing the line, remove the mold, pull the plastic gently off the frame and use you canopy scissors to cut away the excess plastic. Now take it and use mild soap to clean the wax , etc off of it.
There you have it, a clear canopy for that new build you've been working on for 2 months. And how long did the canopy take? I started about 10:00 am and worked on and off during the day. Probably about 3 hours, maybe 3 1/2 hrs tops. Well worth the effort. any questions?
BTW....I get good service for plastic at

www.indplastic.com

Try them.

J
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Old Mar 08, 2006, 08:08 PM
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GPT,
Had to describe the vac forming process without pics because using a hot plate like this and you are busier than a one armed paperhanger!

J
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Old Mar 08, 2006, 08:24 PM
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sweeeeeeeeeeeeeeeeet! Looks great.
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Old Mar 08, 2006, 08:39 PM
GPT
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Thanks for the process J.I have a 3Dfoamy on my Jetset44 F18 and they make all the difference in looks.
I'll try making one for my Formosa first,and then I'll try one for the next jet,probably the eurofighter.
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Old Mar 08, 2006, 09:09 PM
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A very big thanks J....

We need to get a sticky index with these types of threads....

Bob
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Old Mar 09, 2006, 12:14 AM
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Your welcome.

J
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Old Mar 09, 2006, 07:55 AM
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John,
Thanks for this thread. As usual its great. What plastic are you using for the canopies? I've pulled a couple (pull molding rather than vacuforming) and I think I was using K&S plastic I picked up at a hobby shop.
Dave
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Old Mar 09, 2006, 08:12 AM
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Great stuff J!

If you guys have not found this thread.. I suggest you read it front to back. It is also by John. It is how he finishes planes enjoy!
http://www.rcgroups.com/forums/showthread.php?t=161218
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Old Mar 09, 2006, 08:18 AM
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Chapel Hill, TN USA
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Thanks guys

Dave,
I used .020 Vivak for this one but could just barely make it work. It's pretty thin in places. If it gives me any trouble I'll pull one from .030 or .040.
The K&S is good stuff but expensive at the sizes they sell it. Also, few hobby shops have the large size I need. My new vac former is 12" x 24" so I order sheets sized for it. A 24"x48" sheet allows me 4 pulls with no waste.
Like I posted, check out this website, they have anything you will need.

www.indplastic.com

J
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