Coroplast undertray question (covering the control arms)

[Otto]

Since Coroplast seems to work well for undertray applications, and since it's flexible, why not make a chin undertray that is long enough to go from the bottom of the front bumper and attach to the aft edges of the control arms?

Most such undertrays end at the leading edge of the control arms, with cutouts to allow lock to lock steering travel of the wheels/tires.

However, given the flexibility of Coroplast, the inboard section of the control arms could be covered, to smoothen airflow as far aft as possible. As the contol arms move up and down with road contour, the Coroplast would flex, but have the smallest possible cutout for the wheels.

Why not?

[MetroMPG]

No reason why not.

When I made the tray for my car, I effectively did that. Front and rear control arms were covered, with allowance for suspension travel.

[cerdmier]

Do alot of you cover the exhaust pipe when make a undertray? I would think it too hot for coroplast. What kinds of issues do you run into with having a undertray? A lot of questions 'cause I'm new to this type of modding. Thanks.

[MetroMPG]

I used aluminum flashing rather than coroplast in the areas near the exhaust.

I didn't cover the catalytic converter though - I made a cutout around it.

[ModelE]

good call metro, covering the cat is a big no no. Can get a car lit on fire if your not careful. some truck fires on beaches start like that, guy digs in, covers cat, keeps trying to drive out, boom catches fire.

[Christ]

Hm. You'd think the sand would leach heat from the cat, rather than insulate it.

Sheets of dense plastic work OK for under trays? It's either that or sheet metal from an old water heater, for me, since I'm not really into buying new stuff for eco-modding when there is so much usable stuff around me.

[vtec-e]

Originally Posted by cerdmier

What kinds of issues do you run into with having a undertray? A lot of questions 'cause I'm new to this type of modding. Thanks.

When i put an undertray under the back of my civic, i upset the airflow through the cabin as the exhaust vent is behind the rear bumper and must have required a negative pressure in that area to work. Installing the tray blocked off that area so i cut a little vent there and put in some flexi duct with no improvement. My windows fogged up constantly right up until i retired my civic. So i'll have to watch that when i undertray my yaris then......

ollie

[Bicycle Bob]

I'd rather let the suspension occasionally push the Coroplast down than cut holes in it. If the mounting points are close to a flex area, you can use a flat spring for some offset and flex between the car and the pan.

[MetroMPG]

Coyote used stretchable rubber for the portion of the undertray over his rear control arms, if I'm not mistaken. Inner tube rubber, or the stuff used to line small ponds, I forget which.