HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Jan 11, 2005, 02:59 PM
Registered User
mattuk's Avatar
United Kingdom, England, Dorset
Joined Oct 2004
50 Posts
Question
Pop Bottle Canopy

I have read articles about moulding canopies using pop bottles however I cannot see how they can work.
I have tried several times with different shaped moulds and I always find the same problem.




The front is not a problem (I push the plug right up to the neck of the bottle) but there is too much plastic at the back to shrink. Once it has shrunk a certain amount it wont shrink anymore. I think this type of plastic will only shrink 25%.

What am doing wrong?
mattuk is offline Find More Posts by mattuk
Reply With Quote
Sign up now
to remove ads between posts
Old Jan 11, 2005, 03:45 PM
B for Bruce
BMatthews's Avatar
The 'Wack, BC, Canada
Joined Oct 2002
11,524 Posts
It shrinks more than that quite easily. I've only shrunk one around a little box so far but was impressed with the results. I found that the plastic shrinks to about 1/3 of it's original diameter without too much trouble but I was using a serious hot air gun to do it. I think you'l find the key is to cut away the neck bell as well as the base and then to pack the sleeve that's left so it's quite tight at the largest point before you start shrinking
BMatthews is offline Find More Posts by BMatthews
Reply With Quote
Old Jan 11, 2005, 04:50 PM
Registered User
mattuk's Avatar
United Kingdom, England, Dorset
Joined Oct 2004
50 Posts
Thank you for your reply.

Quote:
pack the sleeve that's left so it's quite tight at the largest point before you start shrinking
That is the problem I am having, the canopies are very shallow at the back and 2" deep in the middle so even when the canopy is touching the plastic at the largest point of the plug there is still a 2" gap at the back.

I use a heat gun whitch I use for solar filming, maby thats not hot enough.
mattuk is offline Find More Posts by mattuk
Reply With Quote
Old Jan 11, 2005, 05:26 PM
Registered User
Staffs, UK
Joined Nov 2003
10,661 Posts
I use a paint stripping gun (carefully ) and usually cut off the neck and angle the plug into the base so it's as close as I can get it to the plastic all round. But for bubble canopies it can still easily take several attempts to get it right. The technique is great for typical WWII fighter canopies (e.g. Spitfire/Hurricane) but not too hot for bubbles. Proper vacuum forming (or just buying one) works better for those but it's a pain to get set up initially.

Steve
slipstick is online now Find More Posts by slipstick
Reply With Quote
Old Jan 11, 2005, 05:40 PM
Registered User
mattuk's Avatar
United Kingdom, England, Dorset
Joined Oct 2004
50 Posts
Thanks for that, I think thats probably the problem. Bubbles dont work very well with this method because they curve down on both sides so the plug cant be a tight fit at both ends. I have managed to make a hurricane canopy with this method.

I think I will have a look at making a vacuum former.
mattuk is offline Find More Posts by mattuk
Reply With Quote
Old Jan 11, 2005, 08:19 PM
Registered User
vintage1's Avatar
East Anglia, UK
Joined Sep 2002
29,703 Posts
I never got these blastd bottles to work,

Gave up and bult a vac form box. Took about three hours. First and only pull (got sidetracked) was ten times better than any pop bottle, so I know when I get it out again it will all be fine


Heres the story.
http://www.rcgroups.com/forums/showthread.php?t=161451
vintage1 is offline Find More Posts by vintage1
Reply With Quote
Old Jan 12, 2005, 10:11 PM
Registered User
Joined Jan 2005
13 Posts
I'm just finishing up a bi-plane that I drew up and, i'm using a pop-bottle canopy, but I didn't 'form' it. I just took a 2-litre soda bottle and used the front of it where the cap goes. From there I just kept trimming it till I liked it, and until it fitted right. It was easy since the back of it was flat, and didn't curve back down. It turned out good, and looks great with the rest of the plane. Could you make it into two peices, and put some trim where they meet in the center? Not sure if thats the look your looking for, but just a suggestion. Sorry no pics.
rziga2006 is offline Find More Posts by rziga2006
Reply With Quote
Old Jan 13, 2005, 01:49 AM
MSboy
John Threatt's Avatar
Rock hill, SC
Joined Sep 2004
48 Posts
2 liter PET Bottles

If you want to form a canopy without a vacumn mould, you should take a clean bottle and cut the neck and base off. Split the side with a knife or sissors. Now, look at the canopy you wish to form and see how to get the best fit out of the curve below the bottleneck. Cut the plastic so that there is about an inch or better oversize on the canopy. start on the front and staple, screw or nail the edge to the underside of the wood mold. The biggesr error is letting the plastic "slip" while its contracting. Pine is a good choice for molds. Slowly warm the plastic with a heat gun, Even a hair dryer will work although more slowly. When the plastic has formed, let it cool it will be suprisingly faithful to your mold shape
before removing the fasteners and cutting the bottom edge of the canopy free. You may want to make the canopy an extra 1/4" high to allow for trimming the base to fit the fuselage, Learning to form canopies was easier than finding a glue that would adhere strongly to that incredibly tough plastic. Just to show you that it can be done, heres a picture of a bottom protective cover formed from a PET bottle. It is used to protect a PPE foam fuselage from Rocks and mud and latched in place by 3 N50 magnets.
John Threatt is offline Find More Posts by John Threatt
Reply With Quote
Old Jan 13, 2005, 07:34 AM
MSboy
John Threatt's Avatar
Rock hill, SC
Joined Sep 2004
48 Posts
Mattuk,
after you cut the plastic, tack it to your form and heat the base first. this will pull the plastic down on the form and prevent movement. then work towards the top of the canopy and the plastic will fit the form snugly. Remove by cutting the base free. Trim to fit.
John Threatt is offline Find More Posts by John Threatt
Reply With Quote
Old Jan 13, 2005, 06:02 PM
Registered User
mattuk's Avatar
United Kingdom, England, Dorset
Joined Oct 2004
50 Posts
Thanks for all the info on your vacuum former, hope to have mine up and running soon. Could you tell me what type of plastic you use and where you can get it in the UK?
mattuk is offline Find More Posts by mattuk
Reply With Quote
Old Jan 13, 2005, 06:33 PM
Registered User
vintage1's Avatar
East Anglia, UK
Joined Sep 2002
29,703 Posts
I have no idea what it is. I went into Galaxy Models and bought a sheet of every sort they had

LHS should stock something. Get thick as it stretches right?

I made windows for my latest creation out of the packaging from a RipMax Xtra ESC..

Not vacformed (by me anyway): The package was the usual 'bubble'
vintage1 is offline Find More Posts by vintage1
Reply With Quote
Old Jun 16, 2014, 02:16 AM
Crash Test Dummy
Brunei, Brunei-Muara, Masin
Joined Nov 2013
130 Posts
Its an old thread, I know, but I thought I would add in my 2c.

I cut out the cleanest section from a 2L water bottle - so take off the neck and base, slit the cylinder and flatten out - you get a decent sized sheet of PET.

I then warm it to get it to lie flat and trim it to usable size.

Working quickly is the key - Heat your oven to 160C (320F), place the sheet of PET you made from the clear water bottle on a baking sheet - Itwo baking trays back to back - and put them in the oven. I get my vacuum bagging machine from the kitchen and make an appropriate sized bag, put the form in the bag and a little sprinkle of talc. Shake it all around to coat the inside of the bag. When the PET sheet is warm and pliable, slip it in the bag and quickly put it in the vacuum bag machine. My bagger has a setting for vacuum without sealing, so I can reuse the bag without having to cut it open.

I have found the best results if you make sure your bag is big enough that the sheet and form can sit flat on the bench when the bag is in the machine.

It's important to let the sheet reach the proper temperature - the 'forming' temperature for PET is 149C/300F - at this temperature you can leave it in the oven for ages without it degrading, so if you were going to make some canopies, make a bunch at the same time - its as easy as just pulling the sheet out as you need it - leaving the remaining sheets at the right temp until you do.

If you leave the sheets uncovered, they will start to shrink and shrivel... you need to press them between the two baking trays to stop this happening.
immike is offline Find More Posts by immike
Last edited by immike; Jun 16, 2014 at 03:15 AM.
Reply With Quote
Old Jun 16, 2014, 05:52 AM
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
Joined Mar 2003
13,614 Posts
Interesting sounding method, any chance of a few pictures ?

It's difficult to visualize how the PET wraps around the form.
eflightray is online now Find More Posts by eflightray
Reply With Quote
Old Jun 16, 2014, 12:53 PM
Registered User
Canada
Joined Nov 2000
7,154 Posts
Fascinating to read about.
Couple of points that I've tripped over ..
Bottle plastic shrinks ..a lot.. when heated into a semblance of a sheet, it reverts to being surprisingly thick (often unusably) in my few experiments in that direction.
How does one manage to get the heated plastic sheet into a Vac Bag?
Then seal it.. Before.. the plastic cools into unusability.
For me it's a frantic rush from heat source to Vac Platten .. Extra steps? unlikely.
Reads as more theory than fact.
Bare is offline Find More Posts by Bare
Reply With Quote
Old Jun 16, 2014, 01:37 PM
B for Bruce
BMatthews's Avatar
The 'Wack, BC, Canada
Joined Oct 2002
11,524 Posts
I have to agree. I can't imagine the thin sheet staying hot and pliable even during the few seconds it takes to get it into the bag. Let alone into a bag and correctly placed over the plug and then held stable while the open end is clamped in the machine and the air is drawn out. It would be back down close to room temperature from passing through all that air and handling and touching the bag plastic and mold.

I've worked with heavier sheets of Kydex that simply did not stay hot enough for long enough when I heated them in the oven and then tried to transfer them to a forming mold. And we're talking roughly 6 to 8 times as thick.
BMatthews is offline Find More Posts by BMatthews
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Aldi's juice bottle canopy kramer Micro Helis 7 Feb 09, 2005 03:00 AM
The incredible shrinking pop bottle - not! vintage1 Electric Plane Talk 26 Jul 25, 2003 03:32 AM