Guys looking for some help. Don’t know what I’m doing wrong. I made a set of eyebrows for a cub several years ago with the cores I’m using. Now trying to make another set and they will not work. As in the past I use the clear sheets from Sig. I think it is butyrate. I have tried the .015, .030, and .040 thicknesses.
The setup. Plug made from hard balsa block. I have a frame that is just a little larger then the plug. I attach the plastic to the frame with the spring paper clips. Heat the plastic over a stove burner and then swing to the plug. Problems I’m running into now is in the circled are, the plastic becomes to thin, it is like the thickness of a photo.

Cub Man, I also had that problem, there are three things that might be wrong, First, make your frame a little larger, there is not enough plastic to go around, Second, turn your pastic over before you put it on the buck. Third, if you can, heat the top of the buck a little just before you put the plastic on.I spent several several tries before I got mine correct. Hope this helps.

Gary

Well guys,
gave it a try again pulling a canopy. I made a table like the one at the beginning of this forum. Then I heated my plastic in the oven until it was just starting to sag, took if out and put it over the form, and presto, perfect canopy. I like it so much I decided to make another one. The second one I let sag a inch and darn if I didn't get folds in it so I tried a third time. Just as it started to sag, I took it out and it sucked down perfect. I was getting the plastic to hot and letting it sag to much. Thanks guys, without your help I be without a canopy for my Jemco Hellcat.
Larry

Thanks for that info... I never would have thought about the material getting too hot... Thanks for the tip.

Bob

I have found that I get "folds" when I suck the plastic down too quickly. Years ago I bought a vacuum forming machine with an electric heater at the top of it. Since you just slide the hot material straight down onto the table, I let it sag 2 or 3 inches first.

Steve,
I couldn't do that. Everytime I let it sag that much I get folds but again, I didn't have a heater like you said you have. Now another question for you guys, how heavy of a material can you form. What I used was .020. Could .040 be as easy to form?
Larry

I have used the .040 with my homemade vac former with no problem

Do I understand this process right? Heat up the plastic till it sags, push it down on the mold until it reaches the the vacuum table and turn on the vacuum . How much of the thickness of the plastic do you loose on something that has height to it. And how do you get a good seal on the frame holding the plastic to the vacuum table? pub

This thread hasn't been posted on in a while but I wanted to thank all who have posted and contributed, without it my Herr P-51 would still be without a cowl. I made a small machine and use my Shopvac for suction. I made 3 attempts and the final was perfect. The first didn't pull tight enough and I had to drill small holes for added suction in the chin area. I tried to use thin "blister pack" material but the end result was far to flimsy. The final pull was done with approx .040 clear plastic, unknown type as I had it laying around my shop for over 10 yrs now.

Thanks again for all who posted!

God Bless,

Jay

Thanks for the shots. They said that a shop vac wasn't strong enough to pull that kind of suction. It looks like it'll work after all... nice job on the cowl. I've never tried Vacuum forming but have been interested in it for a while. Thanks!!

What temp & how long did you heat it for that .040 plastic?

Bob

Thanks for the compliments. The Shopvac had plenty of power to do the job. The plastic I used was 15"x15" but my plug and base was at least 6" tall so I had to stretch the plastic quite a bit and it sucked it down fine. I tried 325 then 350 and finally went with 400 degrees. @ 400 the plastics started to distort and slight sag after maybe 2-3 minutes. I immediately pulled it out and threw it over the plug and machine. It was a blast just doing it. It sure opens the hobby up for a lot of scratch building. I'm glad I tried it. I made my machine out of a desk top shelf that I was going to throw out.

God Bless!

Jay

Thanks for that info, Jay.

Bob

Vaccum forming is fun, isn't it?! I've made quite a few parts with my homemade machine using the same book pictured at the beginning of this thread. My 5HP shop vac has always had plenty of suction to pull just about anything I would want to make. The key I found was finding the sweet spot during the heating process. Too cool or too hot was what would cause problems. Attached are a few pics of things I've formed and their molds for my Space Shuttle project. The shuttle main engines and OMS engine bells as well as the heat shields and engine nozzles on the SRB's are all vac formed.

Dan

That's awesome!

Blessings,

Jay

In my quest for easily available plastics I came across some, ( not sure what kind or name) .050 used for picture frames @ Menards. I spent $3.50 for a 11x14 pieces. It sagged and I pulled it over my mold fine but when I tried to release it from the mold pieces shattered. It was as brittle as glass after being heated and not a good solution. I stop by Menards soon to get the name of the plastic. Not recommended at all[] It was still fun doing the vacuum forming process Can anyone point me to some cheap plastic in the .040-.050 range?

Blessings!

The last time I bought plastic for vacuum forming, I got it from Balsa USA. I am pretty certain that it was PET-G which is very good for molding. Give them a call and see if they still supply it.

theradioflyer,

I use US PLASTICS, they have the correct plastic for thermo forming (PET). for around $10. See past forms.That is where I got my info, there is some really fine craftmen out there.

Gary

Thanks for all the good information. Dan.

Thanks Guys!

Blessings,

Jay

This thread is GOLD!!!
Thankyou guys!

Good evening
I have been looking for a windsheild for my old 1/4 Scale Cub and can't find one, would any of you gentlemen be interested in making one. My old one has a few cracks in it. I have been looking for months with no luck.

Thanks Morgan

this is a good store for sheets

http://www.indplastic.com/index.cfm?...oduct=358http:

//www.professionalplastics.com/contact

love this thread
just wondering if any one has used plaster of Paris to copy a part for forming I have a old canopy that I want to copy and was thinking of using plaster poured into the canopy to make a form, sealing the plaster of course with polyester resin before the pull just wondering if there might be any problems using that material, rather than carving a canopy from wood which would be a challenge.

I've also had good results with PETG. For cowls I am using ABS and it pulls like a dream, of course it's not clear.

One trick that I came up with on my last cowl I pulled was to have my heat gun handy. After placing the heated thermo-plastic over the plug, I use the heat gun to keep it soft to help complete the pull. It made much deeper parts possible than I'd ever done before.

Dave

I used plaster of Paris for this canopy (see pic), unfortunately the table I built was not large enough for it. That canopy is 18"L x 8"W x 7"T, it took 3galons of mix to fill it with and that was with using foam fillers. Worked great.