Mold pattern for a new glareshield

[carusoam]

Some of the coolest thermoformed molds I have seen were low volume and made out of wood... picture craftsman plastic tool boxes with all those different sized sockets...

Some quick copy molds for parts are often made using epoxy... to make a mold of a cup shape... use a cup and fill it with epoxy... or use a container full of epoxy and sink a cup into it...   positive /negative type molds for the same thing...

Keep in mind the finish on this part is not really a requirement is it?

Depending on size... add some big wave ribs to add strength / rigidity...

There is a good chance you can make a much better product than was made the first time....

Talk to the guy who is going to make the leather or euro-pleather cover for it... to get any dimension adds or subtracts.... depending on the thickness of the finishing covering material...

For safety reasons, be thinking about using flame retardant materials along the way... always ask when you are acquiring plastic sheet.  It often comes in several varieties...

Best regards,

-a-

[Yetti]

I find these guys have a large array of FAA certified plastics.  https://www.professionalplastics.com/ROYALITER57SHEET

 

I have always been intrigued by the english wheel.   I think when I redo my glareshield it would be a fun project.

[larryb]

If you do ever make a mold for the top section, maybe you can figure out how to get the raised section over the annunciator panel to sit flat. Mooney never could.

Both of my Mooney’s (current Encore and previous J) raised sections sit flat. But I have seen so many pictures of others that don’t sit flat that I have wondered why they don’t.

[BrianW]

Here are the photos of the mold, the vac formed part and the part trimmed:

[BrianW]

I believe the vac formers heated the abs too fast causing the bubbles, non-uniform heating, and poor surface finish.

The high heat also blistered and bubbled my mold.  I can do bodywork to repair the mold, but later for that!  At least I got a part that's good enough.

Since it's the underside of the glareshield,100% cosmetically perfect isn't necessary. I was able the smooth out some of the bigger bubbles with a heatgun and wooden blocks.

Today I was test fitting the upper and lower glareshield in my Mooney.  I did the adjusting with the heatgun again, and trimming with dremel.

It lays flat, follows the panel and windshield contours, and looks quite acceptable. I'll bond the upper and lower parts together using the same oem methods.

I can't wait until it's done, and get all my sign-offs, so I can fly the plane again.

Edited April 8, 2019 by BrianW

[carusoam]

Nice work, BW!

1) Bubbles are hard to identify the source... often drying the plastic sheet in an oven for hours can drive out some moisture....

2) heating it too hot may generate bubbles from degradation...

3) to get the middle of the sheet equally heated as the surface of the sheet... lower the oven temp 10°F and raise the time seconds longer...

4) Time vs temp can be exchanged one for the other... it’s called time temperature super-position....

5) If you have visibility to inside the oven... you watch the behavior of the plastic sheet while it is heating.... you can watch as stress relieves (wiggling)... or the sheet loses its tensile strength... it begins to sag....this is the hint it is near ready to form...

6) when the sheet sags into the heaters below... that was the sign you waited too long, or the oven was too hot... 

7) an IR thermometer is great for knowing if there is a hot spot in the middle or near the edges.... if you can get access to the sheet just before forming... seconds count... it is cooling quickly.

8) you only get a couple of tries before it’s time to cool the mold... a plastic bag with cold water in it, can transfer a lot of heat...

 

You did a great job! Thanks for sharing the details...

Best regards,

-a-

[PT20J]

Wow, great job. 

I used Permatex 81158 black silicone adhesive. It adheres well to clean ABS and it’s easy to get the two parts apart again if you ever need to by working a long blade between them to cut through the adhesive. 

Check that the metal piece that holds the lamp holders is assembled correctly - mine was upside down and backwards - and rivet it to the bottom plastic part with black pop rivets per the IPC. Otherwise, it’s really difficult to replace the bulbs after assembly.

Skip

 

 

[BrianW]

Here's the completed glareshield!

Edited April 20, 2019 by BrianW

[Marauder]

Here's the completed glareshield!

That looks GREAT! Nice job! Care to make one for an F model?


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[steingar]

Color me mightily impressed.