Conference vmszoo::rc

    Going back to my Vac-u-form days and extrapolating...
    
    The reason why they typically call it "pulling a canopy" is because you
    use vacuum to pull the air out between the warmed plastic and the mold.
    You can either use a male or female mold and a vacuum pump. You hold
    the plastic sheet in a frame that can get sealed to the area around the
    mold. You warm up the plastic so that it starts to sag and becomes
    quite pliable and then you quickly put it over the mold and evacuate
    the air between the plastic and mold. It is easier to pull the plastic
    into a female mold than to pull it over a male mold since the female
    mold allows for a good seal check before the plastic is heated. The
    vacuform that I had as a kid used a grooved insert that the male mold
    fit onto and the grooves allowed the vacuum to get all around the  mold
    (from an under the mold hole).
    
    Understand that I've never done anything larger than a two inch square
    in this manner but I've seen machines which cut game parts out of
    larger sheet in this manner at Milton Bradley. A female mold puts the
    detail on the outside while a male mold puts the detail on the inside
    (in case it matters)

    There was an article in either Model Aviation (MA) or RC Modeler
    (RCM) in the last 2-3 months on how to make wheel pants out of
    opaque white styrene.  This guy just used gravity and a typical home
    oven for heat.  He'd just make a male plug, mount the styrene in a
    frame and place it over the plug and put it in a preheated oven. 
    The part would form over the mold in a few mintues.  He stressed
    that the temperature had to be EXACTLY xxx degrees.  (280 deg F ???) 
    Too high or too low of temp. wouldn't work.

    I don't know if this process would work for clear plastic, but I
    think it would...  You should at least check out the article.

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    RCSD had an article specifically on molding canopies without vacuum.
    It's been 2-4 years ago but I'll see if I can dig it out. 
    He used basically the same method as Dan's note.
    
    FWIW the toy vacuum molding  setup that Mattel used to sell, are
    now rare and highly prized for just this purpose. If you ever run
    across one, bribe the toddler and confiscate it.
    
    Terry

    Gee, and I've been saving it all these years for the creepy crawlers
    you could also make with it.
    
    I would think that you could do a pretty fair job with a heat gun to
    warm the plastic over the male mold. You'd certainly be better able to
    tell how it was doing and more selective about where it needed just a
    little more.

By coincidence, I have just copied an article on vacuum forming
from  an old magazine.  Send me your mailstop offline and I'll
shoot you a copy.

I'm planning on trying this out soon, as a current project has a
cowling that is a perfect candidate for vacuum forming -- a
radial cowl for a 1/6 Curtiss Robin.

I've tried to find the ABS plastic, but the only stuff I can find
locally is 1/16 (.062) at $30 something a sheet.  I'd like to
find a smaller quanitiy of slightly thinner material for my first
experiments.  Anybody have experience with the 1/16th stuff?

At the club meeting this week I got the name of the local expert
on the subject and I'll be calling him soon for info.  Last year
he molded a bunch of cockpits for a club project T-28, looked
real professional.  I understand he goes to Denver for his
supply, anyway I'll post some info when I get it.

Can we change this note, or move it to, a general topic on vacuum
forming?

When I built my Jet Ranger, I had to make the front window myself. I built a 
male mold and then a female die to hold the plastic. I tried several different
clear materials but found that the clear plastic that Balsa USA sells for window 
material works best.

The procedure I used was to attach plastic to female die. Throw die in oven set
to a suitable temperature. Remove die from oven 30 seconds before plastic glops
all over bottom of oven (guess how I figured that one out 8^(  ).  Quickly pull
die over male mold. Nothing to it.