underbody belly pan DIYing, rust from bolt/screw holes?

[danwat1234]

I 'took' a few large choroplast election posters and have been thinking about using them to enhance the aero of the underbody of my car. But, I am very hesitant to drill holes in the underbody, even if I prime it afterward because that will be a weak point for rust to occur. This is on a 1999 Civic DX, steel body.

What have you guys done to reduce the chance of rusting? I use Krylon primer in the spray can on any chipped off paint on the body, and any rust spots after sanding, cleaning and drying.

With what little MPG benefit underbody panels do, doesn't seem worth it. Luckily the grille and bumper is all plastic so I can drill that without worry.

[turbovr41991]

I have seen where some people build frames out of aluminum or another material and build frames for the cloroplast to sit on. I guess that would reduce where it needs to mount. I would like as minimal holes in metal as possible when I do mine.

[JRMichler]

I've been thinking about the same thing and for the same reason.

I plan to first squirt on a shot of primer, let it dry, then glob on some roofing tar. I have previous experience with roofing tar. That stuff seals against water so well that I have never seen rust under roofing tar. In one case, the roofing tar was about ten years old.

[Fat Charlie]

Even a small mpg gain counts for a lot against "this spot might rust earlier than otherwise." Keeping drilling to a minimum is obviously the best thing to do and protecting any holes you make only makes sense, but a car burns a lot of gas over its lifetime. The fuel log here keeps track of how much money you're actually saving over EPA, and a little bit of savings adds up a lot.

I'd protect any holes I drilled, but any measurable fuel savings would add up long before potential rust made me drill new mounting points, much less caused real problems.

[Pandaf]

I use cavity wax for hollow spaces like doors and the body of the car. After drilling apply it, and again a bit after you fitted the screw. First it is very liquid like penetrating oil, but it dries quickly to a waxy greasy stuff that blocks oxygen from affecting the bare metal. I wouldn't use paint as that is likely to damage more easily.
Depending on how much you drive and in which conditions I would check it maximum once per year.

[Sven7]

Do an air dam and add pans under the engine bay and behind the rear axle. The minimal gains you're likely to see by doing a full belly pan instead of the former aren't worth it in my opinion. Use only existing holes when mounting stuff.

Roofing tar sounds promising but I still wouldn't chance it.

[mcrews]

Originally Posted by Sven7

Do an air dam and add pans under the engine bay and behind the rear axle. The minimal gains you're likely to see by doing a full belly pan instead of the former aren't worth it in my opinion. Use only existing holes when mounting stuff.

Roofing tar sounds promising but I still wouldn't chance it.

I built a full body pan the first time....because I wanted to MAX the effects.
I now run as sven says.
I didnot notice a drop off.

(see the link in my signature)

[Cd]

Rust ?? What's that ?

[Sven7]

Originally Posted by Cd

Rust ?? What's that ?

screw you man!!!

[mcrews]

Originally Posted by Cd

Rust ?? What's that ?

teee heeee heeeee.......

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