Forming a windscreen for a Piper Cherokee 140 by Gwillows.

[OldBrampton]

I am in N.Z. Please can someone help me with advice about making a windscreen for this model. I followed the plan instructions but had great difficulty in fitting the screen. I used different types of plastic sheet, from packaging etc; In the end I did purchase a packet of styrene sheets made by Evergreen Scale models. 015" or 0.4 mm in thickness. I made a form to scale using a balsa wood block and shaping it to fit the opening and then using a heat gun to soften the styrene sheet and pulling it around the form as I have seen done in video clips on Youtube.

Now of course the problem is in the angles, a flat sheet to form a curved screen!! I am thinking of trying to build a vacuum unit to see if that will work but I thought there may be a simpler method that someone knows about or perhaps even where I can purchase a screen already made from a model shop.

Please can someone offer some advice? Kind regards from N.Z., Old Brampton.

[Bill Gaylord]

You almost need 3 hands when trimming and test fitting the clear windscreen sheet to fit, but it can be done. It works well if you can first install the side windows, and then trim the front to butt perfectly against the front edge of the side windows. Now there is no ambiguity in locating the window, positively locating it for final installation. Next tape is used temporarily to secure the windscreen, ran across the window pillars and the side windows. The Sterling Citabria windscreen I recently fitted was a bit testy, as the acetate I had was a bit thicker than desired. Thinner is better when it comes to fitting. The sheet can carefully be "worked" to create the curves, but it also tends to kink, which is difficult to avoid. I tack the windscreen down using very small amounts of thick CA using activator for rapid curing. You have to be careful doing this, as too much will bleed and whiten the windscreen around the edges. Once tack glued in place, Pacer canopy glue is used along the full seam of the windscreen.

[OldBrampton]

Hi Bill, Thank you for replying so promptly and posting the photo of such a lovely model. First of all my christian name is Bariss. I hesitated to use it as I am very new to this forum, although I have been a member for some years this is the first time I have asked a question.

The model I am working on is kit no307 which is a low wing Piper from the 1960s. If you have a Gwillows catalogue, mine is 2007, it is shown on page three. I understand this probably should not make much of a difference, although the shape of the screen is such that it does not have any flat angular edges as in your model. I have had five tries until now and you are bang on when you say you need three hands! My plan has a thin, central support running from top to bottom of the screen. I was using this as 'fulcrum' to work from, setting the screen in the center and then trying to work around the edges but as I am a bit disabled in my hands I found it to be very frustrating indeed. I will try again by following your instructions. One thing. Please can you enlighten me. What is Pacer canopy glue?

I will have to learn how to upload photos so that it will make it easier for people to see what I mean. Thank you once again for your help, Bill,

Kind regards, Bariss.

[Bill Gaylord]

You're welcome. The Cherokee has some compound curve, but may look reasonable if simply made from a flat sheet pattern. I was thinking Cessna somehow, when I recently build a Comet Cherokee.
Pacer canopy glue is a glue that dries clear, for canopies. I'm convinced it is basically like Elmer's white glue, but with a plasticiser mixed in. The reason I use CA and activator for tack gluing, is so that I can simply tape the sides in place as was described to hold it in place, and tack a few spots to fix it in place. When the CA is hit with a drop of activator, it will cure withing 10 seconds. From there, I can remove the tape and glue the entire seam using Pacer.

One thing you could try is heat pulling. The idea is to make a mold and then draw a heated sheet of plastic over the mold. The process will waste a bit of sheet, as the piece needs to be oversized, to give you something to grip, using a heat gun. What I've found works best is to heat the sheet over the mold, set the heat gun down while running on a concrete surface, and then slam the sheet over the mold. There's literally no time to shut off the heat gun, as the sheet will cool during that time period. The mold needs to be blocked up a bit, to provide room to pull the heated sheet over the mold. I've made numerous plastic parts using the method, where smaller is obviously better. After pulling a number of these, something the size of the Guillow's Cherokee would be easy. Just make the mold a bit larger than you need, and trim out the center portion that will be the size of the required windscreen. These below are some of the larger I've made using the process, for a Miles M38 and Miles Aerovan. For smaller canopies, I use scrap clear plastic from packaging, as a few are often scrapped until I get the process down pat. I used a one of the scrapped Miles Aerovan canopies for something very similar to the Piper Cherokee windscreen recently. I was able to use a smaller portion cut out of the center of the spare Aervan canopy and use it for a recent Sipa Minijet top cocpit glass section.

[dirk gently]

What I did recently in the same situation:

1. cut a form from styrofoam and sanded to the shape of the windscreen
2. laminated the form with glass fabric and epoxy
3. covered with automotive filler and sanded smooth
4. removed the styrofoam with nitro thinner
5. filled the form with plaster
6. got a plastic bottle, put the form inside and shrunk to shape over the form using a heatgun

[Bill Gaylord]

The pop bottle method does work. There's a number of Google results that come up under canopy pop bottle, or canopy 2 liter bottle. For something small like this windscreen, I would use the simple "leverage" method versus vacuum. Always make the mold a bit oversize, to allow for trim adjustment.
http://www.murocmodelmasters.org/canopy.pdf

[dirk gently]

Also: http://www.ffscale.co.uk/page4f.htm

[Coloradoken]

I had a similar problem with the super cub (303). The canopy sheet provided with the kit was too small to use. Also the plans only had half the windscreen. I assumed the sheet was supposed to be cut out for the left 1/2 and then turned over for the other 1/2. Would not work. I got a thin sheet of clear plastic made for dividers. It was perfect, Flexible , clear and cheap. Cut it out after laying out sheet -not to easy to get the proper curved shape from a flat sheet- but doable, You can see the result in my posting of about 6 weeks ago. Good luck.

[OldBrampton]

Thank you all for your advice and encouragement. The photo's are great, Bill.

Obviously there are a number of different ways to get to the same end and I am going to enjoy trying them all out!! That really is the thing that gives making models it's 'bite', solving problems and making a success of a project. I will let you know how I get on and hopefully there will be some pictures.

Kind regards to all, Bariss.

[davidchoate]

popular problems.