easy DIY vac form canopies

[fred cesquim]

recently reading about canopy vac form techs i thought this would be interesting to share.
I have been building a lot of scale planes that demands taylored canopies, wing tip lights, plastic cowls and detail parts and even wheel pants.
After years of makeshift solutions i decided to build a home made small and simple vac form unit.

[fred cesquim]

first thing is to make a PLUG for the part to be vac formed. my method is to make a template from thin ply with the final profiles shapes, add balsa blocks and sand to final form. You can add a layer of thin CA and sand to smooth finish, or add epoxy resin and fiberglass cloth, sand, add more resin and sand to a shiny surface. if this is intented for canopy shiny achieve the best result

[fred cesquim]

i purchased a "shoe box" made of MDF. opended a side hole to insert my vaccum cleaner hose and holes on the top to suck the air. you can open the top and add a metal perforated sheet as well. leave a lip all around and add a sealing cushion with single sided tape ( felt, foam, rubber).
Then using a picture frame of wood ( both items i bought on local craft stores) you can clamp a sheet of transparent PET or PVC depending of the task. I have found out that transparent face shield mask are perfect for canopy (but opted to buy a full sheet to have more material to spare) here in brazil we call PET plastic. Donīt know the thickness but itīs exaclty the one of the face shields

[fred cesquim]

i tried 2 methods to fix the plastic to the frame> large masking tape and metal clamps, both works but the tape is faster and you have less chance to burn your hands
put your oven o the maximum power and let it heat.
i have added some metal support to the base grill on the oven to support the wood frame away from the oven.
when you have the oven ready, insert your vacuum cleaner hose to the box, turn on the cleaner ( must be a strong one)
rest the wood frame on the support inside the oven and close the door. watch it until the plastic sags down and when it reaches about 2" of sag, take it off and rest evenly over the plug pice. the vacuum will do a beatyful job now!
i use a electric oven, maybe a gas oven can be used but be carefull with the fire risk.

[fred cesquim]

you can play with different materials, thickness and ammount of exposition to the heat and learnt the trics
for the biplane canopy i had destroyed a lot of material because of the big size but found out a good solution.
one tip is to let the plug a bit raised from the surface like 1/4 so the air sucks the plastic innwards and make a better lip on the parts.
i have used the wheel pants sides as a mold for fiberglass wheel pants because i hate abs parts for that.
the transparent mold of the cowl shown is just me playing around with a moitle cowl that i eventually made up a fiberglass mold later.
hope this can be helpful

[944_Jim]

Mr Fred,
This is on time! I'm about to make a vac-box. The obsolete and broken  toaster oven needs to be fixed so I can cook my material.

Thanks for your notes!

[fred cesquim]

Mr Fred,
This is on time! I'm about to make a vac-box. The obsolete and broken  toaster oven needs to be fixed so I can cook my material.

Thanks for your notes!

thanks a lot Jim, glad helped you!
please donīt do the bread at the same time, tastes funny
regards from Brazil
Fred