Canopy vacuum forming.

[jerry v]

What material to use for sealing a canopy plug made from basswood? Temperature of the vacuum molding process is 400 - 450 degrees Fahrenheit. Clear plastic canopy shows the wood grain.

Jerry

[Dan Berry]

Plaster of Paris will solve your problem.

[Roy DeCamara]

Use polyester resin and sand with 320 and 400 girt sandpaper.  Usually 2 coats of resin will suffice with the final coat sanded with 400 grit.

[Dan McEntee]

  I have used several coats of dope, sanded and polished smooth between coats. When you get the grain filled, sand it and biff it like you would a dope finish. The same when using resin or epoxy. The plastic gets heated by the mold shouldn't be. When the plastic is applied to the mold the cool down is very rapid. I have also used hydrocal, a construction material much like plaster but much harder, to make a mold from an existing canopy. Clean the original canopy and wipe free of any dust. Spray in a light coat of PAM from the kitchen cabinet, then after mixing up some hydrocal and water to a pancake batter consistency, fill the canopy as far as needed.. You need to support the canopy securely during  this process. It takes about 30 minutes for it too set up completely, then I like to let it sit for 24 hours before using it. I have never had to seal a hydrocal mold.
   Type at you later,
    Dan McEntee

[frank williams]

If I remember correctly, Al Rabe said that he would pull one canopy and then use it as a surface for the part.  Then he would pull a second canopy over the first.  This second one would be the one used.  I seem to remember he was concerned, like you, with imperfections in the canopy mold.

[Dan Berry]

Plaster of Paris is used as a filler. Sand it smooth, then seal it. It will stand up to the heat and pressure. It is easy enough to work with as a filler for the purpose.

[Gary Dowler]

When I had the canopy made for my scale PT-26, I carved the plug from balsa, then applied and sanded off multiple coats of automotive sandable primer.  When I had it completely smooth, I applied pin striping tape to form the framework and sent it off.  the result was superb.  It was good enough that I was asked if it could be used for a new catalog offering. 


Gary

[fred cesquim]

What material to use for sealing a canopy plug made from basswood? Temperature of the vacuum molding process is 400 - 450 degrees Fahrenheit. Clear plastic canopy shows the wood grain.

Jerry

2 layers of thin CA sanded smooth with a final 1200 sandpaper run through would make it as an option

[Paul Wescott]

If I remember correctly, Al Rabe said that he would pull one canopy and then use it as a surface for the part.  Then he would pull a second canopy over the first.  This second one would be the one used.  I seem to remember he was concerned, like you, with imperfections in the canopy mold.

Larry Renger told me that the pro’s at Mattel would make the wood plug a tiny bit undersize, then mold one sheet of plastic over the mold and leave it in place as described by Al Rabe via Frank’s post.  If Mattel could run production quantities in this fashion it must be a decent method.  Also seems like less work than sealing and sanding and such.

PW

[Curare]

If I remember correctly, Al Rabe said that he would pull one canopy and then use it as a surface for the part.  Then he would pull a second canopy over the first.  This second one would be the one used.  I seem to remember he was concerned, like you, with imperfections in the canopy mold.

This is how I've done it for a while, carve your plug undersize, pull a canopy and LEAVE IT ON THE PLUG, zap it down if you have to, then sand with 600 till it's all matt, and pull another over the top, it'll be clean and clear.

[jerry v]

Thanks for all replies!
I used dope to seal the wood, and first layer of thin plastic stays on the plug. This is Checkala Roma canopy, it was removable on the original. I was planning to have one layer of clear plastic as windows, and one layer on top of that as a cockpit “body” - clear or white, painted to the color, with windows frame/opening  cutouts. Plug has extra 1/4 in “skirt “, but front and back flat areas are made to size, with almost zero degrees draft, and they will be the part of the external structure. I was planning to use minimal internal structure in the canopy, because it’s a battery hatch. Layers of plastic make corners more and more round, and I would like to keep corners as sharp as possible.
I would like to post the Checkala Roma building tread here, I’m just not sure- in OTS or in the Building section.

Thanks again.

Jerry

[Warren Wagner]

Jerry,

As expected, the forum had viable solutions to your canopy issue.  Stunt Hanger is
a valuable resource.....thanks Sparky.

As far as posting is concerned, you might consider putting the 'build'
information in the "Building" sub forum, and including a link to the
"Old Time Stunt" sub forum.  I think that ideas picked up from your build,
would be exposed to more modelers if it is posted in the "Building" forum.
However, vise versa would work also, if you choose.

Thanks for sharing your project with us.

Cheers.

Warren Wagner
Clay, NY   AMA 1385

[jerry v]

Warren,
Thanks for your support! I will start the tread in the “Building “ section.

Jerry

[MikeyPratt]

Use polyester resin and sand with 320 and 400 girt sandpaper.  Usually 2 coats of resin will suffice with the final coat sanded with 400 grit.

Roy is correct,
But it really depends on how intricate the finished canopy is.  I made more canopy’s than I care to think about for Sig production models and other people.  Basswood or pine worked best covered with polyester resin and sanded down super smooth.  The first pull should be a piece of .010 ABS and leave it on the wooden mold, then pull the next mold out of PPG clear.  If you want a defined canopy frame, make a hollow mold out of aluminum epoxy (Rein), add a plywood base with vacuumed holes and drill small holes (.015”) in the corners of the framing then when vacuumed formed the vacuum will pull the plastic into the corners around the canopy frame.  That gives the canopy an awesome professional look when finished.

Mike Pratt