Polycarbonate

[Marty_d]

Hey all,

 

I was in a plastics place the other day buying some polycarbonate for the windscreen and top window.

 

I asked how it was with bending, as the windscreen curves around the bonnet/instrument panel but also bends in a different direction.

 

Instead of answering, the lady just grabbed the sample I'd brought in and bent it over until it was almost folded in half. 

 

She said "If that was acrylic, it'd just snap.  But polycarbonate can bend as much as you want it to.  The guys out the back got a piece of 6mm, stuck it in a bending brake and put a 90 degree bend in it."

 

So there you go - if you're worried about bending poly, don't.  It can take it!

 

 

[nomadpete]

There is one little trap to watch out for with polycarbonate, as I discovered after replacing my aircraft windscreen.

 

When the Lightwing factory built the aircraft, they sprayed about an inch wide strip of white paint around the perimeter of the screen, on the inside. It does look neat.

 

So I copied this, only to find that spray paint can cause shallow crazing of the plastic. This showed up after I fitted the screen. I don't think it is affecting the structural quality of the plastic, as there have been no actual cracks anywhere. Just that annoying slight sparkle in a couple of places.

 

 

[djpacro]

So there you go - if you're worried about bending poly, don't.  It can take it!

 

When building an aeroplane back in the ‘80s, I’d say “treat it like steel”. 35 years later it is still going strong in serious aerobatic competition.

 

 

[kgwilson]

Polycarbonate is incredibly tough, can be bent to shape easily and is easy to drill whereas Acrylic isn't as strong, doesn't bend much and cracks easily.  Acrylic though is cheaper, can be easily blown to form bubble canopies, doesn't yellow with age (UV exposure), is more scratch resistant than Polycarbonate & these can be polished out (You can't do this with polycarbonate) and has better clarity than polycarbonate. It is just horses for courses

 

 

[Old Koreelah]

Polycarbonate is the safest defence against striking birds, etc, but needs to be replaced every few years due to scratching and crazing. It can be heat-formed with care, but (I found out the hard way) only after it's been cooked at 60C for 24 hours to dry out all the absorbed water. 

 

An all-lexan cockpit might be a safety hazard in a crash; you won't be able to smash your way out. Best to have side windows of acrylic.

 

 

[M61A1]

Hey all,

 

I was in a plastics place the other day buying some polycarbonate for the windscreen and top window.

 

I asked how it was with bending, as the windscreen curves around the bonnet/instrument panel but also bends in a different direction.

 

Instead of answering, the lady just grabbed the sample I'd brought in and bent it over until it was almost folded in half. 

 

She said "If that was acrylic, it'd just snap.  But polycarbonate can bend as much as you want it to.  The guys out the back got a piece of 6mm, stuck it in a bending brake and put a 90 degree bend in it."

 

So there you go - if you're worried about bending poly, don't.  It can take it!

 

 

 

Don't spill fuel on it, especially where it is stressed from bending.

 

Try that on a scrap piece.

 

 

[Marty_d]

That could be a problem, especially as the wings slope down to the root which slopes straight on to the top window.  Any overflow or splash would trickle straight on to it.  

 

The only good thing is that the top window is not stressed at all, it's basically flat.

 

Guess I'll just have to take a lot of care with fuelling.

 

 

[Old Koreelah]

That could be a problem, especially as the wings slope down to the root which slopes straight on to the top window.  Any overflow or splash would trickle straight on to it.  

 

The only good thing is that the top window is not stressed at all, it's basically flat.

 

Guess I'll just have to take a lot of care with fuelling.

 

Have a look at Ollie Hartman's Hornets. Their "wing fences" don't have an aeronautical function- they're there to divert spilled fuel away from the plolycarb screen.