does anyone know if moebius will be offering a "clear upper hull" for the J-2 to show off the interior?

thanx

Definitely not going to happen....
Clear styrene is very brittle and the breakage in shipping would be unacceptable...Handling replacement parts would be a nightmare!
We send out plenty of replacemant parts now, I don't think we want to produce something like this that is a sure fire source of requests for replacement parts!

Dave

Sorta O.T., but why is clear plastic different? Is there something in the coloring checmical(s) that give the styrene more "plasticity"? I'm really quite curious, as I've heard for years now that clear styrene is brittle (and I've proved it time and time again, to my poor luck!), and wondered why.

Larry

I'm no Plastic chemical engineer -
I suspect that clear styrene is brittle because there is nothing added to keep it from being brittle...
I suspect that adatives that would prevent it from being brittle also prevent it from being crystal clear..
I have a good friend who owned both a palstic tool making operation and an injection molding plant as well, next time I talk to him I'll ask why clear styrene is brittle

Dave

Also, I've noticed that clear syrene tends to "yellow" after a number of years.

Ive never seen clear styrene yellow. Clear vac plastic (which is rarely styrene) will yellow. My dad has some kits that are pushing 50 years old and the clear parts are still quite clear.

Thanks for the clarification; it was the clear vac plastic from Lunar Models that I was thinking of when I wrote that.

Well, hopefully I can "clear" up some of this.
I am no chemical (or plastic) engineer. But I did work in injection molding for 17 years.

First of all, not all styrene is the same.
There are differerent grades, and types.
Most stryene is opaque in nature. Meaning, even with no colorant added, you can't see through the parts. It looks almost like it is white, thought it is actually pretty much color neutral. Parts ran with no colorant would appear white, though you would be able to sort of see through it.
Much like this new mug I got for Halloween.
http://www.tylisaari.com/me/halloween/2009/stuff071.JPG

Clear styrene is a special grade of styrene.
All styrene gets it's properties from how it bonds on a molecular level. In this case by lining themselves up end-to-end and forming striations.
This is what makes it stiff, rigid, and allows it to be chemically bonded (you know, melted together with glue) That is also why it is suseptable to breaking and cracking. It has built-in fault lines all through it because the way the material is bonded on a molecular level. It will only flex so much before one of those faults gives out and breaks or cracks.

Clear styrene gets it's clarity by lining those molecules up in even straighter, and more even lines. To allow the light to pass through it without being affected by it.
That is why clear parts are even stiffer then regular parts.
And why they crack and break easier. Less flexibility before one of the faults gives out.
And why they are even more affected by chemicals. Crazing and fogging from glues. Basically those long straight strands of molecules on the surface get bent and contorted. Which in turn causes the light to not pass through them properly.

Yeah the Lunar stuff would yellow badly. Most clear vac plastic is more of a vinyl or acetate type stuff versus styrene. I can't say I have seen real clear styrene sheets. Im not sure what makes it yellow but its not UV light as I have some boxed up kits with brown clear parts due to just age and not sunlight.

Trevor,
Thanks for the explanation.

Dave

Not a problem.
That's the point, to share information. :)

You could do it as clear polycarbonate, but good luck working on it with your average model tools. :-)

Not to mention it'd be significantly more expensive.

Always learrn something new!!! Thanks!!!

You could do it as clear polycarbonate, but good luck working on it with your average model tools. :-)

Not to mention it'd be significantly more expensive.


Also, it probably wouldn't work.
We did work with polycarb. And the molds have to be specially designed to run the stuff.
It shrinks like the dickens when it cools. And if there is not enough draft on the part, and the cycle times aren't set right, the parts seize right into the mold cavities.
And depending on the shape of the part, and the mold cavity design it may require a trip to the tool shop to remove the part.

Also, it probably wouldn't work.
We did work with polycarb. And the molds have to be specially designed to run the stuff.
It shrinks like the dickens when it cools. And if there is not enough draft on the part, and the cycle times aren't set right, the parts seize right into the mold cavities.
And depending on the shape of the part, and the mold cavity design it may require a trip to the tool shop to remove the part.

True, depending on the materials used in the mold, the number of complex pins on the inner surface and any other ribbing, this would be problematic for polycarbonate. Plus you have to account for pellet dryers in the manufacturing process (to reduce the moisture content, thus eliminating some of the issues you've mentioned above). It's not impossible, after all the upper hull is basically a gigantic potato chip bowl - but it would make for a very pricey option.

Lexan and PC are usually vacuuformed versus injection molded, at least for kit use.