Quote:
Originally Posted by myrefugeisintheLord
Sven7, What would you suggest putting between any metal and aluminum in contact with each other? I'm thinking there isn't going to be any place that the two metals are actually touching, because the previous owners had a thick protective undercoating added. I don't like thinking of how much extra weight we're carrying around because of it, but at least future rust will be prevented or at least slowed.
I'm unsure as to what primer you may be referring to. I've heard it mentioned in a couple other places, but honestly, the only primer I know of is paint primer. And that doesn't make sense to me.
And lastly,  I honestly can't interpret your diagram... I wish I could!!
So basically, the end of the belly pan is best when it's level with the ground? That would be easier then trying to figure out this 10 degree angle thing.
Probably the further out the back, the better?
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Since aluminum and steel hate each other you have to put a non-reactive metal in between them. I use zinc coated bolts, but galvanized should work as well. With an undercoating you should be fine, but just be careful.
Just Rustoleum or whatever. Get some that is meant for bare metal, spray the drill hole and screw before putting it together, and it should coat most surfaces. Not perfect, but better than nothing.
The diagram shows drag numbers for diffuser angles on several body styles. You have the wagon type, "c", so follow the C line on the graph. It says that any angle more than 0 degrees is going to increase your drag, so keep your diffuser at 0. (ΔCx means the change in drag for X. You want to be below 0)
If you're going to do a boat tail it wouldn't be as important because you'd be managing the flow all the way back, but here you need to be mindful of what the air might be doing after it leaves your car.
As for the angle, I found it helpful when building the boat tail to cut a 10* wedge out of plywood. As long as the bottom of the wedge is level with the ground you've got a concrete 10* angle to build from. You can just cut out a rectangle!
