Don Terrill’s Speed-Talk

what material do most guys use to block off grille and openings? how is it fastened?

Don't know where it comes from (I used to pick up scraps from work) but there's a black corrugated plastic material, constructed exactly like corrugated cardboard. It's easy to cut, strong enough to stand up to 150 MPH and easy to tie-wrap to grill bars or whatever.

The local trade name for the plastic MadBill is talking about , is CorPlas. It's used to protect walls in clean rooms during consturction/remodeling and in water jet beds.

MadBill wrote:Don't know where it comes from (I used to pick up scraps from work) but there's a black corrugated plastic material, constructed exactly like corrugated cardboard. It's easy to cut, strong enough to stand up to 150 MPH and easy to tie-wrap to grill bars or whatever.

-ok, was thinking of something, a method not too hard on the eyes
-but something like that will work
-also heard of guys attaching something to the backside of grill....not visible and maybe doesn't have to be pretty etc..
-thinking of something a little more permanent...do it and forget..

CorPlas! Yes, that's the stuff. I use it on the back of the grill, so it just sort of disappears. Also to seal the grill better to the rad, so that all the air goes for cooling.

Here is what we did:



And here is what we used:
http://www.estreetplastics.com/1_8_x_12 ... 251248.htm

It is hard to notice that it is there from just a few feet away, unless you look real close.

Confused wrote:The local trade name for the plastic MadBill is talking about , is CorPlas.......

It is also used a lot in the sign making business.

Ken

Having seen the remnants of at least one "I'll just screw in a sheet of 0.03" aluminum with five or six sheet metal screws" to block the grill, I think it is worth pointing out just how much force will be on that plate . A worst case assumption is a flat plate with nothing around it, which will overestimate the force since on a car there will be lots of stuff diverting air and shielding the plate. The total force in pounds = the area in sq. feet * 0.00512 * (speed in mph) * (speed in mph), from http://www.arraysolutions.com/Products/windloads.htm which is just the first hit in my search. So, at 150 mph and a grill opening of 1' tall by 3' wide, the total force is 0.00512 * 3 sq feet * 150 mph * 150 mph = 345 pounds, distributed evenly over the blocking plate. The actual force might be as little as half of that depending on the aerodynamics, but if you design for a little over 345, say 400+ pounds, you shouldn't drive over the plate on the first pass with this area and speed . Support the edges well, and put one or two vertical pieces of thin 1"x1" angle across the back to stiffen the middle so it doesn't turn into a bowl and shear the edge fasteners. Note the force goes as speed squared, so whatever the force is at 100 mph it will be double at 141 mph and double again at 200 mph.

good info thanks guys!

-handy formula...easy to get 300-400 pounds of force!