Side Skirts: First Prototype Complete
 

I got my first attempt at side skirts done:
http://ecomodder.com/forum/member-di...-prototype.jpg
http://ecomodder.com/forum/member-di...-prototype.jpg
For right now, they extend down about 9 inches, leaving about 5 inches of clearance. I only did the driver side for now, I want to see if that's enough clearance before making the final versions. After seeing this one, it's also clear to me that I want to extend it a little more in the front and quite a bit in the back. The reason this one is the length it is is that it's 8 feet (the length of the thermo-ply panel I had).

I attached the panel via some fender washers and the pre-existing holes on the inside of the body panels:
http://ecomodder.com/forum/member-di...-prototype.jpg

I should be able to get the passenger side skirt done tonight. Eventually, I think I'll make some nicer, painted version. The nice part was that I had everything except the fender washers lying around already.

Nice and clean and secure. One pointer to think about. The side skirts under semi trucks sweep outward as they go back so that they are about even with the out plane of the rear tires when they reach them. Maybe that's an advantageous design for you too? Also, can you take it back a little further, closer to the rear tire?

Yeah, I definitely will take them back farther.

Actually, I've lloked at the skirts are trucks are fairly flat--but so are the body panels of the trailers. Plus, the tires are fully under the trailer. Unfortuantely, on my truck the body pansle slope inward and tehy go towards the ground, leaving the bottom side of the tires sticking out. So far I haven't come up with a good, clean way of flaring the skirt out.

That looks good and I hope that you see good results!

Are they flush with the outside of the wheels? I have been thinking lately about people who make boat-tail fairings and wonder if it would be better to just build something the width of the tires in between. That seems much simpler than trying to craft the perfect boat tail.

I guess that would be like what you have done, but with an inner skirt. I am not sure that a bottom would really do any good, except for rigidity, and that might be unwelcome.

No. Ideally they would be, but they fall about in the middle of the tires.

Looks like a nice start.

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You could look for some old school full length Aluminium running boards.
Put them on the truck, then attach the skirts to them. It would make it easier to get in and out of the truck and also keep the truck cleaner. If you couldn't find them, you could have them fabricated to meet your specs.
(height, length, width and flair)

Or.

Before going through all that trouble. You could find a home siding contractor that has a 10' brake and have them brake some of the aluminum coil that they use for corner and fascia trim into the shape needed. It even comes in white.

Then if you wanted to, you could reinforce the back side by gluing or pop riveting or bolting coroplast or some other material. Add a few diagonal struts, fill the ends in with some mud flap material and done.

The last option could be had as cheap as a $20 bill and a 12 pack of suds at quitting time.


Anyways, just a few ideas.

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What do you think about taking it to the ground, but the lower portion being brissels? I noticed on a few tractor trailers recently, but I wonder why it doesn't meet the ground. I mean, the portion that is too long will just wear down...its not metal or strong to damage anything.

As it hits the ground and wears down, it adjusts to the perfect height. Just an idea. I look forward to following.

If I'm not mistaken, the brissels are used to reduce road spray when it's raining and not for aerodynamic mpg reasons.

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IIRC basjoos' Civic has double sidewalls flushed to the inside and outside of the tires.

What do you think about crosswind performance?

Aircraft Hanger Door Brush Seal. Available in 2-6" length in 6' sections.

Update.

I got the passenger side done. I made it ~7" longer and I like it a lot better:
http://ecomodder.com/forum/member-di...ture5235-a.jpg

I also took this pic that shows the construction better (from the back side):
http://ecomodder.com/forum/member-di...ture5234-a.jpg

Thanks for all the ideas and suggestions

Is the material water-proof, not just water-resistant? I'm thinking that it may need that protection plus gravel/sand protection; all of this from the tires. Some sort of fender flare at both wheelwells? Maybe a formed metal cap for a few inches and/or along lower cut edge.

The front end doesn't move too much in comparison to RR axle up & down. Might also consider an angle cut to accommodate this; RR to FF. I imagine you could use a load of gravel. Shovel it out until at RR axle rating.

BRISTLES, fellas, ain't no brissels out there . . but, then, I can't speak for FORD.

One or another of us is going to need to measure the air flow delta across the heat exchangers at some point with these aero changes (blocks, dams, pans, skirts, etc).

http://ecomodder.com/forum/showthrea...ood-26028.html

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No, it's not. That's why I'm calling these "prototypes". The material I used will hold up for a year or so (based on what my belly pan has done).

The purpose of these was to get something in place so I can see ways to make a better, "final" version, or some more durable materials.

Had you not done the belly pan first, how well would it work to use your side skirts as the base for an undertray?

My belly pan doesn't go back as far as where the side skirts start. I think that is a definite posibility.

I tried this.

I think you are being too aggressive for practical use. Your skirts look to be 3-4 inches above grade.

Mine were six inches above grade (on a similar vehicle) and they caught every bump in the road and eventually tore up even my indestructible ripstop conveyor belt material.

But they did have a positive effect on MPG.

Mine are 5-6 inches right now (~1" farther in the rear than the front).

So far I haven't had any issues with them hitting the ground. That's part of the reason I made these prototypes, to try to decide how low I can go.

BTW, where did you get your conveyor belt material?

5-6" is close. Drive it over some railroad grade crossings and what is left will tell you what will work. My guess is that 8" is probably A-OK.

I got my 3/8" ripstop conveyor belt from an industrial supply house in Naptown.

It is not a bit cheap. An air dam and two side skirts set me back $100. You are doing this right in one respect. Run one made of cheaper stuff and use it as a pattern for the more durable material. The ripstop conveyor belt is darned near indestructible, but the flip side is that durability makes it a bear to fabricate.

Take your "pattern" and pay the shop rate to get a good professional product that will last for years. Save yourself the agony of sawing/drilling this stuff. Ask me how I know it is hard to work.

Another piece of advice from having done this: clamp the front and rear edges firmly. Your skirt will try to vibrate like an oboe/bassoon double reed. If not clamped firmly even ripstop will wear through .

I have one RR crossing on my commute, but it's very level & smooth. There's another one not far from my house that's awful that I go over once & a great while. I should go see how they do on that crossing.

That's why I constructed them the way I did. As you can see from the pic in post #11, I made a "spline" of 3/4" thick wood that's drilled & bolted on. The sheeting is sandwiched between the spline and the sheet metal.