A Practical Guide to Pickup Truck Aeromods

[greengeeker]

Originally Posted by skyking

Another TDI fan here, I have a couple of beetles.
Your ranger is a good candidate for an aeroshell. how you build it depends on your skills and time.
One method that I'd do for the fun of it is wood strips, like a cedar strip canoe.
Instead of removing the plywood formers, plan on cutting most of them away and leave a 2" bulkhead there. This does a couple of things. Now you can glue and fasten the strips to that for easier construction, use less formers, and it will be stronger. It also give you attachment points.
If you want a lift lid, cut it out and build a gutter down each side of the fixed part for the lid to rest on and to carry rain to the back.
4 oz fiberglass is invisible and will show the wood perfectly. 6 oz is not too bad either.
coupled with a few other mods it should net 10% MPG improvement. That is where my beetle is at, around 45 or so.

Thanks for the response. I'm not necessarily following your description of the construction of the aeroshell but the visualization of the "canoe method" paints a picture.

During the summer months I'm averaging 54mpg in my 5spd Jetta - no mods, no hypermiling, standard 50/50 (city/hwy) commute. With the same engine and same commute in my truck I can just hit 40mpg. I'd like to bridge that gap some.

[skyking]

Originally Posted by greengeeker

Thanks for the response. I'm not necessarily following your description of the construction of the aeroshell but the visualization of the "canoe method" paints a picture.

During the summer months I'm averaging 54mpg in my 5spd Jetta - no mods, no hypermiling, standard 50/50 (city/hwy) commute. With the same engine and same commute in my truck I can just hit 40mpg. I'd like to bridge that gap some.

get a shape using the template overlay tool and a picture of your truck.
Aerodynamic Streamlining Template

Using that shape, cut 5~7 bulkheads from plywood, reduced by the thickness of your planned strips. These can be pieced together if you do strong scab patches with glue and fasteners. You can do as much or as little as you want in regards to curvature. The more it is rounded (side to side), the better it will do. The trick is that transition from the relatively square truck cab, and back again to the tailgate ege.
Set it on the truck bed and fasten it together with a couple of longitudinal boards so it is rigid and secure.
Then loosely follow this build method.
Building a Cedar Strip Canoe
Note that the builder used MDF formers and did not fasten directly to them, and had to strap everything down. This is tedious and not necessary. You get to glue and even finish nail to your bulkheads, since I propose that you leave 2" of them in the finished shell.
This method lets you form beautiful smooth curves quickly. when smooth and ready, overlay with 4 oz glass and epoxy. I use resin research 2000, it is UV stable, but I don't trust even that. More on that later.
If you want a lift hatch, cut that out after glassing, then build a gutter that will carry water and hold the hatch, on the inside of the fixed part left right and front. Glass all that in.
flip it over and cut out all but the 2" of bulkhead, and glass and epoxy the inside to seal it up.
I would shoot the finished structure on the outside with system three WR-LPU.

WR-LPU Topcoat - System Three Resins, Inc.

If you want to show off the wood, use clear. If you want a cooler canopy shoot it white.

Edit: you don't need to use cedar, any straight grained softer wood will do. No Kiln dried. The wood's stiffness will drive the size of the strip you can bend.

[aerohead]

Originally Posted by greengeeker

Thanks for amassing all the information together into an article - very helpful to have this all in one place.

I've put together a TDI Ranger and have been driving it for the last two years with the intentions of improving on the rock steady 39mpg (stock aero) with some aero mods. What I haven't seen (not necessarily directed at your article) is a list of priorities as far as aero is concerned. Which heavy hitters do you need to tackle first to make aero gains so that subsequent aero mods are actually beneficial. On a truck, which has the highest impact on aerodynamic drag? Is the airflow over the bed? Airflow under the truck? Yes, the answer is likely to be different for each truck but the order is going to be different for a truck than it is for a car.

Anyway, on my truck I've tried two things to improve the FE: 1) removed the 3.73 rearend and installed a 3.08 dropping cruising 5th gear rpm by 450rpm. 2) installed a hard tonneau cover on the bed

Neither of these showed any impact on my long term mileage.

I'm considering moving forward with some underbody mods (dam, belly pans) to see if this has a more significant impact.

(I don't have enough posts to include links or pictures so if you want to see info on my truck just google "tdi ranger build tdiclub")

In rough figures,you might anticipate a 5-mpg gain with :
*grille block
*aeroshell
*full belly pan with diffuser/rocker panel extensions/wheel skirts/gap closures
------------------------------------------------------------------------
To get another 4-mpg on top of that:
*a 'significant' length of boat tail (think 48-inches ).
------------------------------------------------------------------------
So you'd be looking at 48-mpg highway.I'm getting 43-mpg hwy TDI equivalency in the T-100 which has a larger frontal area than the Ranger.

[greengeeker]

Originally Posted by aerohead

In rough figures,you might anticipate a 5-mpg gain with :
*grille block
*aeroshell
*full belly pan with diffuser/rocker panel extensions/wheel skirts/gap closures
------------------------------------------------------------------------
To get another 4-mpg on top of that:
*a 'significant' length of boat tail (think 48-inches ).
------------------------------------------------------------------------
So you'd be looking at 48-mpg highway.I'm getting 43-mpg hwy TDI equivalency in the T-100 which has a larger frontal area than the Ranger.

Are these figures you experienced on your T100? Nice work btw. You guys take this aero modding to a whole new level.

[deejaaa]

Originally Posted by skyking

.......
One method that I'd do for the fun of it is wood strips, like a cedar strip canoe.
Instead of removing the plywood formers, plan on cutting most of them away and leave a 2" bulkhead there. This does a couple of things. Now you can glue and fasten the strips to that for easier construction, use less formers, and it will be stronger. It also give you attachment points.
.....

Originally Posted by greengeeker

.........I'm not necessarily following your description of the construction of the aeroshell but the visualization of the "canoe method" paints a picture........

starting with step 6 will give you a real good visual of the formers.
Building A Cedar Strip Canoe

[freebeard]

aerohead is too modest to explain that his T-100 has been tweaked to within an inch of it's freakin' life. I mean, it's in supercar territory. Take a look at his albums or older threads like these twelve pages.

What I haven't seen (not necessarily directed at your article) is a list of priorities as far as aero is concerned. Which heavy hitters do you need to tackle first to make aero gains so that subsequent aero mods are actually beneficial. On a truck, which has the highest impact on aerodynamic drag? Is the airflow over the bed? Airflow under the truck? Yes, the answer is likely to be...

It's a cumulative effect. The only thing I can see is start at the front (upstream) and work your way downstream. That full length boattail is a drag to haul around, but it's like the cherry on top.

Or start with the simple fabrications and work up to the more complex ones. A popular thing here is to make a flimsy test panel and when it gets blown off, come back with something stronger.

The canoe strip idea is a good one, but be aware that even cedar or redwood will add weight. And there is a lot of shaving strips into tapers. If you do this you might make your 2" formers and attach them to a removable brace so you don't have to do finish cut inside the shell.

Personally I like Polymetal, it's a 3mm aluminum skinned recycled plastic core. I can't afford whole sheets of it but I have done some test joinery



That angle braked on the rolled edge should have been scored beforehand. It ruptured the outer aluminum skin. But that way you get to see how it's made. The strength of 5/8' plywood at 1/10th the weight. And here's a construction in redwood benderboard. It's a landscaping material 1/4" thin by 4" wide. You can soak it, bend it and dry it. It would cover a lot of surface fast. This was just a test to establish dimensions.

[skyking]

darts and slices and slivers are the only way to get those beautiful compound slippery shapes. TANSTAAFL

[aerohead]

Originally Posted by greengeeker

Are these figures you experienced on your T100? Nice work btw. You guys take this aero modding to a whole new level.

Yes,the grille block,aeroshell,and belly/rocker/skirt mods got me from 25,to 30-mpg.
Adding the tail pushed it to an average 34 mpg @ 65 mph.I've seen almost 40-mpg @ 60 mph on three occasions.
Going from 10% ethanol gasoline to a TDI powerplant is said to be a 30% mpg boost.So the 34 mpg would be expected to go to 44 mpg with the oil burner.
I think that the Ranger is aerodynamically similar to the T-100,and should react similarly.
Must be nice 'starting' at 39-40 mpg!