Where to find cheap corrugated plastic to make my own undertray?

As the title states I am looking for somewhere to get corrugated on the cheap. 

Looking to make a custom under tray for my car. If you can suggest a  better material I am all ears for that as well.

The day after any election

Oooooo...... election signs. That sounds good. I might have to go scope out a big one or two.

Talk to your local independent sign shops.  We used to order the stuff in 4x8 sheets and often got stuck with big pieces left over of some weird color that was ordered for a single job.  about 10 years ago we were ordering the 4mm thick white stuff by the pallet and paying less than $5 for a 4x8 sheet, so it's cheap even if you have to buy it. 

Be aware, it's available in a 10mm thick version too that is damn strong but still fairly light. a few scraps of that make excellent reinforcement bits.

In reply to Daeldalus :

https://grassrootsmotorsports.com/forum/grm/more-awesome-craigslist-photos/58179/page20/

5th post down.

Walls of a portopotti.

They had some at Home Depot last I checked. Don't know the price.

RossD said:

They had some at Home Depot last I checked. Don't know the price.

Home Depot price was 168$ and change for a 4x8 sheet

Dude, are you looking at the right stuff? The Summerville store lists the 4mmx4'x8' sheets as $20 - https://www.homedepot.com/p/Coroplast-48-in-x-96-in-x-0-157-in-White-Corrugated-Plastic-Sheet-CP4896S/205351385

For a better material, consider sheet ABS or Alumalite (aluminum-coroplast sandwich).

In reply to ultraclyde :

I was looking at the right stuff. I was just looking at the 10-pack price. Whoops

In reply to GameboyRMH :

Any good places to obtain those?

Daeldalus said:

In reply to GameboyRMH :

Any good places to obtain those?

Hardware stores sometimes carry sheet ABS, Alumalite you'll probably have to order online, although a sign shop might have it.

I've been using both thicknesses to build a tray system for one of my cars. The 10 mil stuff allows wider spans with less support structure so overall weight is less. Depending on your dimensions it may work out better to use thicker stuff. Here's what I'm working on. The whole diffuser section will be the thinner stuff. I got mine in 4 X 8 sheets from a sign shop around the corner.

Be careful about heat. I used aluminum where headers and side pipe exhaust might melt plastic.

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Undertray or undertray and splitter? 

If using a splitter and going to the track, most guys just use plywood since it's cheap and easy.

There were piles of it for free at the county hazardous waste drop off site.   Also free windshield washer fluid, oil, trans fluid etc.  Just had to know someone who worked there to set it aside for you.

In reply to z31maniac :

Just under tray. Engine swap and skid plate makes it so I can't use a stock tray

Would FRP work? https://www.homedepot.com/p/4-ft-x-8-ft-White-090-FRP-Wall-Board-MFTF12IXA480009600/100389836

I've bought Coroplast from Piedmont Plastics for some industrial projects.  They're a big national company.  Last time I bought, it costs $15 per 4 x 8 sheet, and they have it in a bunch of colors.  My local guys do fabrication too, but I've never had them do anything.