Gaia Has Aired Out Long Enough
 

I have a goal to increase my average MPG up to 25. Right now we've been averaging between 15.2 and 16.7 depending on the mix of driving. Yes, I realize that's a 50-60% increase which would be insane. But I think I can do it with a few modifications I have in mind. Also, according to my garage, I used to get 19.8 average so I'm already halfway there! :p

First aero mod is to fix up the belly. A nearly-full belly pan to cover up the engine bay and front half of the vehicle. I have tons of cloroplast from a store liquidation I was a part of years ago that I specifically saved for this project so I'm finally going to get to use it!
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The middle seems pretty straight forward. There are two crossmembers that I can attach to spanning the frame (didn't get a good pic of the second one, but you get the idea).
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The belly pan will also go full width from side step to side step, wherever possible. The underside of the side steps have little brackets that I think I'll be able to attach to and then the frame on the other side.
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Where I'm seeing a problem is how to do a belly pan in the rear. I'm just not seeing anywhere I can attach to between the gas tank on the driver side, the monstrosity of a muffler on the passenger side and the spare tire in the middle behind the rear axle. Not to mention giving space for the suspension to move.
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I would also like your guy's advice with the cloroplast distance from the exhaust. If I attach to the cross member, I would only have about 1-1/2 to 2 inches of clearance between the hot stuff and the plastic. In your guy's experience is this enough space or should I leave a cut out around that area?
I know if I ever upgrade to a metal pan, I can just go all the way across.
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I've read through many threads and online articles, but any insight, advice, do's and don'ts, don't forget abouts, anything is always helpful and welcome! :thumbup:

Use a metal frame across the rear suspension to hold the panelling in place.

My video on bellypans (and be warned, I don't like coroplast):

https://www.youtube.com/watch?v=L9WCVlWPcys&t=1s

So you know about the durability of Coroplast. Okay for cutting templates, but not a lot else.

If you want to use it for test purposes, at least wrap the edges with your favorite tape to seal the corrugations.

Consider swapping out the tires for more economy focused ones.
A lower rolling resistance is often underestimated, but it makes a significant difference, especialy in heavier vehicles.

Also:
Holy ****, that underbody looks like an aerodynamic nightmake in stock configuration.

Maybe also consider a different vehicle for daily driving, yours will never be efficient.

Maybe not *quite* that bad, but yes, the general point is correct.

Let's agree that a flat undertray should be rather effective here.;)

coroplast for belly pans
 

I have had a coroplast belly pan on my VW Golf for 10 years. I have some things for you to consider, some Dos and Don'ts.

1. I believe coroplast is suitable for a belly pan if it is well supported. It is used seal up the bottom of modern camper trailers here in the U.S. It is cheap and doesn't rust. However, it can sag and is not particularly heat resistant near exhaust systems.

2. As Julian has stated, I recommend building a supporting framework to attach the coroplast to. Build it stronger think you think you need to. Sudden wind gusts at highway speeds can generate a lot of force on your attachment points. Julian has measured downforce on his car from his belly pan. The curved pan is sucking the car down to the road. You don't want this thing coming loose on the highway. If you do not weld you can use aluminum angle and rivets or locking nuts and bolts. Riv-nuts are great for attaching the framework to the vehicle and coroplast to the frame using fender washers and Lock-Tite. You can purchase an inexpensive Riv-nut tool from Harbor F. Design the framework so it can be removed for servicing. A belly pan can accumulate water, snow, mud or dust over time. You may want to have some places for it to drain itself.

3. Manufacturers usually leave the cat and the muffler uncovered. A full belly pan can trap heat between the pan and the floor of the car. The muffler can be fairly flat. Make your supporting frame flush with the bottom of the muffler and surround it and leave it open to the bottom.

4. There may be places where metal is better than coroplast. On my car I have a rigid aluminum "Panzer Plate" under the engine and radiator as a skid plate. Looking at your photos, covering the front part in this way may be time and money well spent. This will be more durable in the event of an impact with road debris.

Click on my avatar and you can scroll through some photos of mine. I feel that a belly pan can be some of the lowest hanging fruit for aero gains. Also, I just switched to LRR tires and the early results look very promising. If you could afford a second set of lightweight rims with narrower LRR tires, that may help too.

Like this from another thread.

The back end is trickier on rear wheel drive. The fuel tank is pretty smooth and the driveshaft needs some room to move up and down. You may have to stop the front part of the belly pan at the back axle and build another frame and belly pan section behind the axle. Try to seal this section all around the sides to keep air and mud/slush/snow out.

Thanks for the tips guys! Julian, that is an excellent video!
The coroplast is definitely short term for testing, or at least until I can get the funds to use some sort of sheet metal. I'll be sure to seal the sides when I'm done fitting it.

I have thought about putting some LRR tires on my old rims and saving these snow tires for... snow. Just haven't pulled the trigger yet. My daily driver is actually my Corolla. My problem, though is that the car is too small for me and is physically hurting me so I need to start driving this, hence the need to improve the MPGs. Back when I was driving hundreds of miles a day, I was using the Corolla, but now that I'm down to about 40 a day I need to bite the economy bullet to save my health!

Thanks for the tips! At this point getting the proper support is my biggest issue...

I got phase 1A done of the front belly pan. It's by no means perfect, but I can work with it as I move along.

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The only way I can get it attached using factory mounting points/holes is to use four screws, two in the front and two in the back. I know on the back I could get two more bolts, but that would only be in the middle. You guys said to go more than I think and I think I need more as it is! Plus they are only towards the middle of the pan, the edges are completely unsupported spanning the length. I just don't see how I can attach anything without modification. I don't really want to be using rivets or screwing into the bumper/"air dam". And I would also like to keep the pan frame approximately level with what's already there, I don't want to bring the pan down lower than it has to be.

I'm thinking about cutting the pan in half and covering the whole span so that the bumper section in the corners gets covered and I have a better support throughout. I'm just not sure if I'll be able to get the approach angle to match up with the middle section. More tinkering on that...
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But I still need to find a better way to actually attach it. I can screw in through the bottom lip of the air dam, I just don't really want to do that unless there's no other way. I wonder if I could somehow "glue" a nut onto the inside of the air dam lip so it won't be noticeable. Although now that I think of it, that would mean screwing in from the top which I wouldn't be able to access. *thinking cap on*
I was thinking something like this which is how I attached to the front of the pan, just with an inverted bolt.
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It's a good thing it's night, I'm going to have to shower and sleep on this. My best thinking times!

A few more thoughts I should have mentioned...

I want this to be a template for an eventual metal skid plate. With that being said any "frame" work I do to support the coroplast I would prefer would be setup to accept the plate without modifications.

I did test run this guy on a windy, hilly backroad approaching 60 MPH and there was no discernible movement. I was listening with the window down for anything. Also, the bolt in the previous post is well into the nut with no signs of movement.

Even though it's not secured, the middle of the pan does have a resting support so it doesn't flop as it rests against the radiator lower support.

I work for an electrical contractor, I wonder if I can utilize some strut in some way.

Rivnuts. Might need reinforcing washers to prevent tearout. Otherwise building adhesive on "T" nuts.

Strut is incredible for reinforcement.

work for electrical contractor
 

1/2-inch EMT is a great low cost material for panel frame and sub-frame fabrication. I prefer oxyacetylene with a small tip, however, a wire-feed will certainly work.
Mounting ears can be attached wherever needed, including those for Dzus fasteners.
Also, 'stacked' metal, multi-level heat-shields, with dead-air voids spaced between sheets, can be attached between coroplast and heat sources to protect against thermal 'creep.'
Scrap, EMT cut-offs make great vertical spacer material.

Regarding using the coroplast as a future template, do not wait 10 years to do the second phase.

I used this material on the tonneau bed cover, and every year it was wrapped a little more and now looks like a wave you could surf on.

2012
Replacement for Tonneau Fabric - Coroplast
Poor man's Tonneau Cover - Replacement - Pelican Parts Forums

I hope you grind off the zinc coating first. Otherwise, not at all good for your health...

^ X2 (You can get really bad fumes even if you grind or sand. Do this in a really well ventilated area)

"Speed Nuts" work for attaching to the edge of the airdam etc. It slides over one edge like a paperclip with a nut on the back, pre-drill a small hole and the screw draws it tighter.

Thanks for the advice and tips everyone. A little update since installing the pan. With only those 4 bolts and the lip of the air dam holding/securing the pan, the pan has shown no signs of movement. I'm still going to install more attachment points, but for everyday use it seems to work well. I had one scare this morning when I had it on cruise control on the highway and I suddenly lost power and it felt like I was carrying a parachute. I turned off the cruise and the problem went away (I've had a feeling the cruise control has been going out for some time now). When I got to work, I checked the pan and it's still firmly secured.

With that being said, I filled up for the first time last night and my MPG for the tank was 17.3! Not bad considering that's working off of an average 16! That also included about 40 miles of "no mods" and 20 miles of (12) 3x3s on the roof (long drive, story for another time). So 60 miles of a 260 mile tank were "different". I have a feeling I should do an A-B-A test, I'm just dreading having to drive with it off for a few days! :D


After a bit of research I had a "duh" moment when I realized these U-nuts/speed nuts would work perfectly. I found a pot full of them on Amazon for a couple of bucks and ordered them. When they got here, I opened the box and before I could even touch the bag I realized my mistake. The hole/nut is on the open end which means when I clip the nut onto the air dam I would need to drill a hole through the air dam which is what I was trying to avoid. If the hole/nut was closer to the hinge side rather than the open side it would work perfectly. Alas, I had to go back to the drawing board...

After continuing to live my life laying on the ground with 3500 pounds above me, I kept looking for an option that I like that I think would work in the long run. I think I have a plan that will work. There are several bolts with extra length and holes in the frame not being used. I think I can tap the holes for a bolt and use the existing bolts to install a vertical support piece out of flat bar and then either attach some sort of strut frame or attach the belly pan directly to those vertical pieces. I think I have found a hole/bolt in just about every area so the support should be good around every edge (and the middle I already have covered).

On a side note that is marginally related, what do you guys think of brazing? I've never done it before, but I got the brazing tools needed for a previous project that didn't pan out (no pun intended) because I left that company and didn't need to work on that project anymore. I might use it in this project for the vertical brackets if/when needed.

Brazing (at least with oxy acetylene equipment that I use) is very easy and can give a really neat job on thin gauge material. (It can be used for thicker material but MIG /arc welding is much quicker.) Tobin bronze sticks are fine for most brazing but if strength is needed, use nickel bronze.

I brazed this bicycle carrier together that I made. Thin wall, high tensile steel tube.

https://i.postimg.cc/bvTC58dj/7-9.jpg

High-end bicycle frames and Morgan trikes use brazing preferentially. Here's a reference:

www.mig-welding.co.uk/.../how-strong-is-brazing-compared-to-welding.42160/

zinc
 

Good call!
The Los Angeles Public School system, in the 1960s, was thoughtful enough to hire master metalsmiths for their vocational-oriented classroom curriculum.
Safety was paramount, and the zinc issue was not lost on the instructor.
Soldering, stick-welding, aluminum casting, etc., were all conducted under forced-air exhaust and well ventilated workshop environments.:)
Neighborhood workshop, father-mentor-supervisors, wouldn't let our ignorance get the best of us either.:p

Finally got around to moving forward with the belly pan. Added another piece to the driver side between the rear of the front tire to about 3/4 back to the rear tire. There's still plenty of spots to clean up, but excited to see how this comes along. I'm hoping I can get the mirror image on the passenger side this week/weekend. We'll see how the schedule works out...

From under the engine. You can see the front pan covering the engine bay.
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Closer to the front
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From side, just behind rear of front tire. I had to cut a significant notch in the front corner of the coroplast for tire clearance.
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Side view, towards the back
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One of these days I want to get a gopro under there to see what the material is doing with airflow on it at speed. Not sure how stable it is. It might be firm, it might be wobbly and pulsating. No idea at this point.

Images don't display. I bolded the part I would delete but there is no file type suffix (as .jpg or something). The remaining string is unsearchable.

Changed link techniques. Hopefully it works this time.

In an effort to complete this thread by posting in the correct one...

Third piece, passenger side mid section.

Behind front tire:
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From the front, inside the wheel:
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In front of rear tire:
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I had to fabricate my own brackets to attach the outside edges of the board to the underside of the steps. This really stretched my working knowledge as I've never fabricated anything metal before. I used a L bar from the hardware store, drill and tapped, used an angle grinder to cut them to size and and belt/disc sander to clean up the edges (just so there were no sharp burrs). I offset the holes so the bolts don't hit each other when installed.
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Now that I have a significant portion of the belly pan done, I'm going to go back and adjust a few things.

1. Install a full-width front section. I skipped this originally because I didn't see how to attach on the outer edges of the bumper. I think I found a way to do it so I will play with that. I might end up doing a two piece driver half/passenger half so it's easier to work with.
2. The rear edge of the wheel well is still open which allows air to move down the vehicle *above* the pan, defeating the purpose! There's only one spot to attach a piece of something there, so want I am planning is to slit and fold up the chloroplast. This will force the air down and across the bottom of the pan.
3. I need to get a gopro and watch the pan at speed. I have a feeling the pan is reverberating. I will need to figure out a way to install more attachment points. I think I have an idea that will work, I'll use some threaded rod and some accessories to "drop" the attachment point from the frame up high to the pan closer to the ground.
4. Better integration of the front pan, the stock pan under the oil pan, and the two mid-section pans to keep better air attachment across the whole system.
5. I'm not sure how to put a pan further to the rear of the truck. I'm starting to get into the rear end that has the muffler, gas tank, axle, differential, spare tire, etc. We'll see if I can make something work back there.