Material For Belly Pan

[lacole725]

Planning out a belly pan for my 2010 Focus. I'm having trouble deciding on materials, my mind instantly goes to aluminum but I'm sure there are stronger and lighter materials that are of equal cost. I want to keep as solid of a piece as possible, not a bunch of pieces. I basically have a machinist and machine shop at my disposal, so fabrication shouldn't be a problem. Any ideas?

[botsapper]

Try:

PVC closed-cell boards (Sintra, Celtec,etc) - Inexpensive, lightweight, fire-resistant and very easy fabrication techniques.

Thermoplastic acrylic-polyvinyl chloride alloy sheet (Kydex) - Very tough and abrasion, chemical & fire resistant. Very easy to work with.

Low Weight Reinforced Thermoplastics (LWRT) - Lightweight plastic composites with low thermal expansion and good mechanical and high impact properties.

High-density polyethylene (HDPE -cutting boards) - High impact properties and low coefficient of friction. Already used as auto & truck underbody splash shields & skid plates.

General purpose ABS sheets - High impact & strength properties, Easy to work with and a common auto trim material.

Good luck on your material choices.

[lacole725]

Thanks!

[jime57]

Originally Posted by botsapper

Try:

PVC closed-cell boards (Sintra, Celtec,etc) - Inexpensive, lightweight, fire-resistant and very easy fabrication techniques.

Thermoplastic acrylic-polyvinyl chloride alloy sheet (Kydex) - Very tough and abrasion, chemical & fire resistant. Very easy to work with.

Low Weight Reinforced Thermoplastics (LWRT) - Lightweight plastic composites with low thermal expansion and good mechanical and high impact properties.

High-density polyethylene (HDPE -cutting boards) - High impact properties and low coefficient of friction. Already used as auto & truck underbody splash shields & skid plates.

General purpose ABS sheets - High impact & strength properties, Easy to work with and a common auto trim material.

Good luck on your material choices.

Botsapper, what is the relative costs of these materials.

I would mention a couple of other materials. One, coroplast, has seen wide use, is inexpensive, lightweight and does come from sign companies in 4x8 sheets. It has good weather resistance and can be cut with common boxcutters. Several folks have placed it a couple of inches from exhaust pipes/mufflers without ill effects.

Perhaps the most versatile approach of all is foam/fiberglass sandwich that was used by 3-Wheeler in fabrication of his Insight boattail. The beauty of the approach is that it is almost infinitely flexible as to how various bulges and odd shapes are accomodated. The down side is that the approach is very manual labor intensive. Take a look at the consolidated link here:

http://ecomodder.com/forum/showthrea...ect-13533.html

Keep us updated on your progress.

[lacole725]

My main concern is the heat from the exhaust. I won't be able to start this until at least next week or the week after. I am testing the result of my rear seat delete and I just don't have the money to buy material right now. I need to find a way to actually get under my car to take some measurements, it sits low to the ground and I am pretty big. So far I have only checked out HDPE, I will check out the others later. I was thinking I could do something in the shape of a skid plate up front to direct air flow, then that would transition to the bigger belly pan, then maybe a skid plate shape in the rear. I just have to check out underneath my vehicle to see what I can do and cannot do. I'm just glad I have a FWD and don't have to worry about a driveshaft or a rear.

On another note, has anyone looked into underhood air flow? Like the small amount of air that would enter through the grille and the gap between the hood and the grille? I was wondering how turbulent the air would be and its effect on the aerodynamics of the car. I have a mostly uncovered engine bay, no shrouds or anything. A Focus oriented company makes a spark plug cover that would smooth out some of the rough spots. It may not make a difference at all. Just a thought.

[jime57]

Originally Posted by lacole725

My main concern is the heat from the exhaust. I won't be able to start this until at least next week or the week after. I am testing the result of my rear seat delete and I just don't have the money to buy material right now. I need to find a way to actually get under my car to take some measurements, it sits low to the ground and I am pretty big. So far I have only checked out HDPE, I will check out the others later. I was thinking I could do something in the shape of a skid plate up front to direct air flow, then that would transition to the bigger belly pan, then maybe a skid plate shape in the rear. I just have to check out underneath my vehicle to see what I can do and cannot do. I'm just glad I have a FWD and don't have to worry about a driveshaft or a rear.

On another note, has anyone looked into underhood air flow? Like the small amount of air that would enter through the grille and the gap between the hood and the grille? I was wondering how turbulent the air would be and its effect on the aerodynamics of the car. I have a mostly uncovered engine bay, no shrouds or anything. A Focus oriented company makes a spark plug cover that would smooth out some of the rough spots. It may not make a difference at all. Just a thought.

When I did an Echo rear underbelly, I was also concerned about heat from the muffler. I used a combination of Coroplast and aluminum flashing. I ran a lightweight and small aluminum angle alongside of the muffler and used that to hold the joint between the coroplast and aluminum flashing stable, pop rivets holding it all together. I'll try to find the link. You might be able to borrow some ramps from a friend or neighbor. Even the plastic ones are getting expensive, IMHO.

I would stay away from underhood tinkering and concentrate on the "low hanging fruit." The German Aerodynamist Hucho studied engine compartment airflow and the gains to be had from "practical" changes are very small. A Grill block is the biggest improvement, but you will need to design something that is easily removable for LA driving. You can probably use a partial block for the cooler months but will likely need to remove it in a hurry for the summer months.

[jime57]

Here is the link I promised:

http://ecomodder.com/forum/showthrea...echo-7380.html

I certainly would not recommend the solid cinder blocks for support. My Echo was very light in back, so I was willing to take the risk, but the Camry is much heavier and much lower. Risk just to great in your case to use those supports.

BTW, coroplast can sometimes be picked up for free. It is one of the primary sign materials in political campaigns. We are in election season ;-)

[lacole725]

How about the thickness of the material? The thinner the better?

[jime57]

The thinner it is the more attachment/support points it will need. Too thin, it may also flutter, compromising some of the benefits, one reason I personally like coroplast. In addition to being light, it has internal reinforcement. I really can't speak to the stiffness of the other materials.

Too thick, it is sometimes difficult to bend as needed, and gets heavy. The area to be covered is the variable. A complete underbelly on that car will probably require more than a 4x8 ft. sheet.

Most of the materials mentioned here have specifications on various internet sites. You can get the weights and various performance parameters. Melting points would be important if you are going to cover exhaust parts. Catalytic converters in particular get very hot.

Sometimes you can make use of "natural" attachment points where a single self tapping screw and large washer will suffice. In some areas, where no further access is required, pop rivets work. In some extremely open areas, you may have to build a lightweight structure as I show in the Echo link. You need to think ahead to how service access will be obtained.

Sorry not to provide a direct answer, but I think there are too many variables to be more specific, and I don't know the underside of the car.

[lacole725]

My catalytic converter is one thing I dont have to worry about, I have a mani-cat. That means the converter is built into the manifold and is tucked up near the engine. The machinist I work with, whom has professional drag racing experience, said if I use some form of plastic I need to use o-rings when attaching it so the plastic can adjust itself when it heats up. He said he has seen racers just bolt it up tight and it ends up cracking. I was thinking I could attach it in a way that would be similar to the German cars, so changing the oil would be simple. That reminds me, I need to get one of those Fumoto oil drain valves. I may switch to 0W-20 when I get my oil changed next time, I'm approaching my 30,000 mile service.