Free-blowing a bulged bubble canopy?

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

geosnooker2000

Well-Known Member
Joined
Mar 30, 2019
Messages
188
Location
Somerville, TN
Sourcing is a majour pita, that's why companies have full time purchasing departments, and it's getting worse. I buy from a few suppliers in Toronto, one is Laird Plastics. I called them and they said the closest Laird to you (Geosnooker2000 Somerville TN) is Louisville, KY, or Atlanta, GA . You could call them and ask if they have a closer dealer or one of their customers you could buy from.
Yeah, I figure when the time comes, it's gonna be, get on the phone with a sales rep and tell them what I want, all the while being carful to describe my "project" as an "off road vehicle". I learned that lesson when I went asking around about turbocharges. It was all "let me tell you about this and that, etc." until the word "airplane" came out of my mouth. "Nawwww... my liability insurance won't let me sell to YOU..."
 

geosnooker2000

Well-Known Member
Joined
Mar 30, 2019
Messages
188
Location
Somerville, TN
You can practice with Home Depot acrylic. Might take too or three tries.
I wonder if you could buy the UV protective film, apply it to regular clear 1/4" acrylic first, heat them together before forming over the form... (the issue being, there will likely be compound curves in my windshilds.)
 

BBerson

Light Plane Philosopher
HBA Supporter
Joined
Dec 16, 2007
Messages
15,067
Location
Port Townsend WA
This thread is about free blowing with no form other than end forms.
What are you hoping to do with UV film?
 

Vigilant1

Well-Known Member
Lifetime Supporter
Joined
Jan 24, 2011
Messages
6,501
Location
US
The acrylic sheet appears to be available in "UV-resistant" (the plastic itself is resistant to yellowing/milkiness/crazing) and "UV filtering" (the plastic protects the materials behind it from UV damage). For a plane that will be hangared and which might see the equivalent of 100 hours of peak direct sunlight exposure in a year, is the UV filtering stuff worth finding and paying for? The UV resistant acrylic appears to be widely available.
 

Orange4sky

Well-Known Member
Joined
Apr 14, 2020
Messages
53
Good quality straight cast acrylic is already UV resistant and it filters a lot of UV. Coatings are nice but expensive to get in single sheets IF you can find a supplier. Please post if you do find someone. Aircraft windshield makers are your best bet but you will notice that they all offer plain cast acrylic windows.

Grimco is a good source. In Canada they stock good quality papered cast acrylic for $100 3/16 x 4’ x 8’. Cheaper than my plastic wholesaler: Polyshapes.

As for insulation, I prefer one inch thick by 24” wide fiberfrax, an alumina based wool that is softer and thinner and much easier to work with than fibreglass. It is also good for 2500F I hang it with a few stainless screws and fender washers. I get it from a local pottery supplier for a few bucks a linear foot. Or cheaper by the roll. Expanded sheet metal is a good option for backing. It’s stiffer and lighter than straight sheet and can be bent into boxes easily. You can also use stainless safety wire to hang the insulation.
 

Orange4sky

Well-Known Member
Joined
Apr 14, 2020
Messages
53
This is my heater. It’s a dual infra red and convection style. Controller is from an old kiln. It has two SCR solid state relays. Once it’s up to temp, there is little infra red heating, so it’s pretty even temp. Glas is supported by 1”deep by 3” wide #4 paper clips hanging on 3/4” x 1/8” stainless flat bar. Convection is by a small squirrel cage fan stripped of paint with the motor protruding outside of the oven. There is a duct cobbled together from fiberfrax and aluminum heater duct that takes hot air from the top and circulates it along the bottom.
 

Attachments

1Bad88

Well-Known Member
Joined
Jul 18, 2012
Messages
620
Location
Bellville, TX
Did you try Cope Plastics? They have a location in Memphis. Since you are looking for a low quantity of sheets you will probably have to talk to distributors.
 

Orange4sky

Well-Known Member
Joined
Apr 14, 2020
Messages
53

Attachments

Last edited:

rotax618

Well-Known Member
Joined
Oct 31, 2005
Messages
1,209
Location
Evans Head Australia
A friend used to blow (suck) gyrocopter bubble windscreens and doors 93578630-E68C-4012-8479-A96B959DB661.jpegfrom polycarbonate (lexan) sheets, he used an insulated box (metal ute canopy) with an element from a fan forced oven (including the fan) and an accurate thermostat.
 

Clark Hinds

Member
HBA Supporter
Joined
Feb 26, 2020
Messages
11
Location
Memphis, TN
I'm no expert by any means but don't get carried away with the oven part of this project. I used foil faced OSB board and built a 4x4x8 oven heated by propane turkey fryer burner and an elevated piece of metal to distribute the heat.
Viewing port on the end covered with a piece of glass and a couple of thermometers.
Bottom line, heat it till the box smokes and you think you have gone too far. Then all of the sudden the acrylic becomes pliable and do you thing. Do it on a hot day and you need no insulation.
 

GTX_Engines

Well-Known Member
Joined
May 17, 2013
Messages
45
Location
Columbia, SC
I used to make rocket style gumball machines from scratch in the '90's. Drape molding acrylic sheet is simple, and can be accomplished with nothing more than a "salamander" kerosene space heater. Just put the plastic in the hot air stream and let it drape over a cylinder. Cylinders for concrete pouring work very well, even though they are fiber - since you don't need much heat and not for very long. Free-form drape shaping is also possible, this is how I make gyrocopter windshields.

Polycarbonate must be cooked at 220° for 24 hours before heat forming. It is hygroscopic and the moisture inside it will boil and you'll wind up with a sheet of bubbles if you don't evaporate beforehand. Acrylic does not need to be pre-cooked.

Vacuum forming is lots of fun. Just heat the sheet until it droops in the frame and it's ready to go. Use Pam cooking spray as a release agent so the plastic won't stick to the mold. You only need 320-350° for vacuum or blow molding.
 

geosnooker2000

Well-Known Member
Joined
Mar 30, 2019
Messages
188
Location
Somerville, TN
This thread is about free blowing with no form other than end forms.
What are you hoping to do with UV film?
Sorry about my participation in this thread. I am always leery of starting a new thread for a question and then getting beaten about the head and neck because "why don't you use the search function to see if this subject has already been discussed?" Which, I get that. Should we ask a Mod to see if he can separate my subject matter out into a new thread? I wouldn't mind.

As far as the UV film, I think it has been answered pretty well that "Good quality straight cast acrylic is already UV resistant and it filters a lot of UV", Which, I did not know. So now I know. BUT.... It would be nice to add a slight tint to help with eye strain and cabin overheating.
 

1Bad88

Well-Known Member
Joined
Jul 18, 2012
Messages
620
Location
Bellville, TX
I have read that acrylic can be tinted with clothing dye by submerging it in heated water (below the softening temperature of the acrylic)
It works, I have done it with RIT dye but I don't know how it holds up to UV. Also, you would have to have a big container to fit a windshield. It doesn't look all that great. There are places to save money but this isn't it IMHO. Buy the real deal and don't have regrets.
 
Top