pic: Wood Coast Drive

[carpedav000]

Then why NOT use it for the front/side panels? I've gotten a lot of the benefits of using plywood, but no answers as to why polycarbonate would or would not be better.

[EricH]

Originally Posted by carpedav000

Then why NOT use it for the front/side panels? I've gotten a lot of the benefits of using plywood, but no answers as to why polycarbonate would or would not be better.

In this case, plywood takes impacts at least as well as polycarb, and is faster by far to cut and install.

Here are some more possible reasons: Wood is lighter than polycarb for the same size of piece (though it's quite possible that you might need a thicker piece). Wood is actually stiffer than polycarb--take a sheet of birch ply and a sheet of polycarb, hold at one end, shake. Wood is immune to loctite spidering... and it's a lot easier to drill without cracking if you forgot to CAD the holes for the laser.

Note: The above specifically applies to birch plywood, ideally Baltic birch plywood.


That being said, there ARE teams that build chassis out of polycarb: 1714 has been very hard to see for many years because their primary building material is polycarb (or is it acrylic? think it's polycarb). But they have to be very creative in terms of material attachment and stiffening.

[mman1506]

Originally Posted by EricH

In this case, plywood takes impacts at least as well as polycarb, and is faster by far to cut and install.

Here are some more possible reasons: Wood is lighter than polycarb for the same size of piece (though it's quite possible that you might need a thicker piece). Wood is actually stiffer than polycarb--take a sheet of birch ply and a sheet of polycarb, hold at one end, shake. Wood is immune to loctite spidering... and it's a lot easier to drill without cracking if you forgot to CAD the holes for the laser.

Note: The above specifically applies to birch plywood, ideally Baltic birch plywood.


That being said, there ARE teams that build chassis out of polycarb: 1714 has been very hard to see for many years because their primary building material is polycarb (or is it acrylic? think it's polycarb). But they have to be very creative in terms of material attachment and stiffening.

I think your mixing up polycarbonate (lexan) and acrylic (plexiglass). Polycarb is extremely impact resistant but cannot be cut on a commercial laser cutter. Acrylic is very brittle and can very easily be cut on a laser cutter.

[EricH]

Originally Posted by mman1506

I think your mixing up polycarbonate (lexan) and acrylic (plexiglass). Polycarb is extremely impact resistant but cannot be cut on a commercial laser cutter. Acrylic is very brittle and can very easily be cut on a laser cutter.

In what way? I happen to be comparing WOOD and polycarb, thank you very much. The comment about the laser cutter was in a statement about WOOD.

[mman1506]

Originally Posted by EricH

In what way? I happen to be comparing WOOD and polycarb, thank you very much. The comment about the laser cutter was in a statement about WOOD.

I believe you are comparing wood and acrylic.

Originally Posted by EricH

In this case, plywood takes impacts at least as well as polycarb, and is faster by far to cut and install.

Polycarb is much more impact resistant than baltic birch.

Originally Posted by EricH

it's a lot easier to drill without cracking if you forgot to CAD the holes for the laser.

It's very difficult to crack both polycarbonate and baltic birch while drilling. Out of the two baltic birch is easier to crack.

Again you can not laser cut polycarb with a commercially available machine.

[EricH]

Originally Posted by mman1506

It's very difficult to crack both polycarbonate and baltic birch while drilling. Out of the two baltic birch is easier to crack.

My understanding was that acrylic is easy to drill, polycarb needs a special drill bit or it'll crack, and birch merely splinters if you make a mistake--not crack.

Again you can not laser cut polycarb with a commercially available machine.

I never, EVER, said you COULD cut polycarb on a laser. If you can show me where EXACTLY I said that, by QUOTING, then I'll retract this statement. Otherwise, leave any discussion of cutting polycarb by laser out.

[mman1506]

Originally Posted by EricH

My understanding was that acrylic is easy to drill, polycarb needs a special drill bit or it'll crack, and birch merely splinters if you make a mistake--not crack.

As I said earlier you are mixing up polycarbonate and acrylic. Acrylic is difficult to drill, polycarbonate is very easy to drill.

[EricH]

Originally Posted by mman1506

As I said earlier you are mixing up polycarbonate and acrylic. Acrylic is difficult to drill, polycarbonate is very easy to drill.

Ah. (Makes me wonder why acrylic is found with FRC teams--and their "unskilled" drillers--around, but that's beside the point.)


Now, for the impact resistance: polycarb vs birch. Polycarb deflects, birch absorbs. They're about the same, but I'm going to have to give that to the plywood on strength-to-weight ratio. The main issue with birch ply is that it absorbs by getting dented or, eventually, splintering. (Acrylic never even enters this discussion, as the "standard" test for identifying unknown clear plastic is to clamp firmly and hit with the biggest hammer in the area--if it doesn't break, use the polycarb, otherwise it was acrylic.)

[MichaelBick]

Originally Posted by carpedav000

Then why NOT use it for the front/side panels? I've gotten a lot of the benefits of using plywood, but no answers as to why polycarbonate would or would not be better.

Polycarb is denser and less rigid