Belly Pan on 1st gen RAV4

[myrefugeisintheLord]

This project has been under construction for about 2 months now. And though I wanted to wait until it was "finished" before making this thread, I don't want to go and forget important info either.

Spending several hours just looking, measuring, and deciding the plan of attack, it was apparent that there were places that would need a frame. I used aluminum angle and C bars.

I was able to acquire 2'x4' sheets of coroplast. A bit too small in places, so the frame reflects the size restraints.

Back end: I've changed my plan for that and will be working on revising it today. Originally I thought wrapping the muffler with aluminum would act as a heat shield for the coro, but it has turned out to be VERY annoying because of the extra noise. More of a rattle then a roar...
However, the driver's side of the muffler hangs lower then the passenger side, so to remedy that, I plan on holding it up with some plumbers tape.

The plan for the coro in the back is to either extend at a ~10 degree angle upward and just end slightly past the rear door. Or instead of cutting off the coro, I would bend it at a ~90 degree angle and have it attach to the place the aluminum is currently attached. I like that idea better, but I'm concerned the muffler will make it too hot with the "tent" effect.... Maybe some air openings on the vertical portion?

I made up a couple aero templates, and according to my guesses, and the template angles, the coro looks like it won't get really close to the muffler, so I might be okay! (A note on this template, I sized the template to the RAV picture for the top line, and then moved the template upward to line up the lower angles. I hope I did that the right way!)



Okay, enough talk, lets get some pictures in here!

Front little frame had to be removed, because it interfered with having a side piece to cover the belts. Rear perpendicular bar hadn't been installed yet.


A closer view of the middle part.


The back bar in place. (Tough job!) Also a couple pieces of coro installed.


Clear view of the back aluminum sheet that will be replaced.


I had added a couple more sheets of coro since then. And I can add a picture of those later today when I get her up on the ramps.

Here's a parallel angle. I did add one sheet, on the other side, that goes through the suspension bar. I cut long, narrow oval holes for the rod to go through and have room to move freely, and zip tied the coro together. I'll show a picture of what I'm talking about in a few hours.


If you guys have suggestions, I'd be happy to hear them! I'm pretty slow these days, and I never seem to do the right, or best thing the first time through. There's always LOTS of room for improvement!

Thank you guys for all the ideas, and info!! Couldn't have gotten this far without ya!!

[Otto]

We have an election coming up soon and, Lord knows, 4X8 sheets of coroplast would be much better used doing something useful like aero modding your car....

Consider use of framed aluminum window screen to cover the hot spots. Dissipates heat, lets cooling air out, still gives a comparatively smooth surface for the airstream beneath the car, vs. bumping along the sharp edges of mufflers, etc..

The coro will tell you if too hot from a tailpipe, etc., by discoloration and/or distortion. Either trim that area back and/or apply aluminum foil tape (like duct tape) to nearby areas to reflect and dissipate such heat.

[baldlobo]

are any of your cross members touching your exhaust? if they are i suggest you re-do those areas aluminum and coroplast melt; both need around 1" clearence or more.

with that said i'd try to get the belly pan cover your control arms or be closer to ride height.

[myrefugeisintheLord]

A couple more pictures of the way it is now.


Closer look at the suspension area.


There's not much to be seen on the front bumper area because that piece is off right now.


Otto: 4'x8' sheets of coro would be great! However they would be cut into 50"x 48" pieces because the RAV is 50" wide underneath.... As it is, I have to use one side lengthwise, and the other widthwise.

The idea of the mesh is a good one! I might incorporate that into the design.

Baldlobo: The cross member by the muffler is about 2 mm from the tail pipe... I'm trying to keep from "lowering" the belly area as much as possible. Plus the lowest part is the tail pipe going under the diff mount. I figured that part of the pipe could extend down past the pan, but trying to find a place to add a mounting point for the pan back there was VERY difficult. If it wasn't one thing, it was another.
With as soft a metal as the aluminum is, I'm not surprised that it can melt with the heat of the tail pipe. I will have to keep a close eye on it. Unless anybody has a better idea for mounting the coro back there!
I've been trying to keep the coro 0.5"-1" away from the exhaust.

As far as the suspension goes, the one set of bars extend pretty low. I figured going down around them would cause more wind drag then letting only one bar catch the wind. ??? But I'm still new to this whole aerodynamic realm.

Speaking of which! I did have an aero question regarding this. The belly pan is higher between the front suspension and the rear suspension. Would it be better to "lower" the middle part of the pan to make it level between both suspensions?

[mcrews]

Very nice!

from personal experience, don't underestimate the force of wind on exposed edges. You need to lay a 6 inch wide strip over that slot for the exposed suspension.
Or very sticky tape.

see about the third page of my underbelly thread (in my signature) I have a picture of gorilla tape being pealed back on the front.

[Sven7]

Nice job. One of the reasons for doing a pan in the first place is to cover suspension components so if you can drop the pan down a couple inches and still have suspension movement that would be ideal. Personally I cut it out around the wheel wells because I didn't want to deal with it.

Second, if those are aluminum bars make sure you're putting something between it and steel frame parts. Al and steel will react and corrode. Also, I know rust is not as prevalent in the PNW as here, but you might want to coat those metal screws with primer... it might be better than nothing.

The diffuser should be flat and level to the ground.



Keep it up!

[myrefugeisintheLord]

Thank you guys for the support! And suggestions!

mcrews, I read your thread last year, but wow, I should have read it again! I love the idea of using those lumber brackets! We have lots of those at the house we're trying to sell. Also I really like the idea of using U brackets to attach the lumber brackets as I'd rather not screw into the frame if I don't have to.

No tape for me. I've been totally burn out on that.

I will see about encompassing the lower suspension bar.

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?

[freebeard]

And lastly, I honestly can't interpret your diagram... I wish I could!!

I gave up, too; but I went back to look. The difference in A, B and C is the roofline, bubble top, notchback and K-back.

Read 'primer' as dielectric insulator and it all makes sense.

[myrefugeisintheLord]

Originally Posted by freebeard

I gave up, too; but I went back to look. The difference in A, B and C is the roofline, bubble top, notchback and K-back.

Read 'primer' as dielectric insulator and it all makes sense.

That's about the only thing I COULD understand. I have no clue what the symbols represent or are called to learn about them, and I wish I could look at those numbers and learn something. But it flies WAY over my head...

When I look at that diagram I interpret that the flat line is demonstrating the baseline, and the higher line is the angle you want. Clarification would be greatly appreciated!

I will have to look up "dielectric insulator" tomorrow, if I get a change at work. Thanks for the lead Freebeard!

[baldlobo]

cliff notes version
side; Delta Cx (or change in your cd)
bottom; of the graph is change in rear diffuser angle

and the difference in body types(a,b,c)