truck aeroback

[kitcar]

I've got a new idea for Stinkerbutt. We've all seen Phil Knoxs' truck. I've got an idea that I'd really like to try. I don't know how many of you have seen a Dakota (2nd generation) in person but the rounded fenders and front end really lend themselves to aero mods; look at me, 26 mpg on the highway. Now I want to take it to the next level.

Picture this:

The truck currently has a soft cover. Take that off. Get one piece of Lexan the size of the rear window. Get another two in a triangular shape, the point of which will be at the tail gate.

Now mount the triangular pieces of the Lexan to the bed. Mount the piece the size of the rear window at the...rear window. Mount the bed cover to that. The front of the bed cover will be just below the top of the cab, the bed end will be where it is now, even with the top of the tailgate. What we're going to do is simply raise the front of the bed cover.

So the Lexan allows one to view over the shoulder out the bed for traffic and safety purposes, the current bed cover mounts to that. Now we have the "ice cream cone" shape for the back of the truck.

I'll shoot a short video of this concept tomorrow night.

To review: the current bed cover will be (at the front) about at the height of the cab. It will end at the tailgate where it is now. The sides and front of it will be Lexan which will allow seeing traffic while driving. What I'm proposing is just raising the front of the bed cover to the the level of the cab; instant ice cream cone shape.

Now, because the cab curves in at the top on this model, I'll have to add some canards to direct the air flow past the new top as it rises to the top of the cab. Again this will be in my video presentation.

[Telco]

How will you see out the back? If you are installing a large piece of Lexan already, just leave the bedcover in place and set this on top. The bedcover won't stretch from the top of the cab to the back of the bed anyway, if I understand what you want to do, the bedcover will be about a foot short.

[GasSavers_BMac]

It will be 3" short

[GasSavers_BMac]

Mine was very easy to make. Too bad my fiberglass didn't cure lastnight, it'd be on the truck right now.

[MetroMPG]

It's not truly a cone shape - more of a wedge.

Ideally, you would round the "shoulders" of the aeroshell to soften the transition from "top" to "sides".

That said, we have to compromise sometimes, and your plan is surely an aero improvement over just the stock tonneau cover.

[kitcar]

Originally Posted by Telco

How will you see out the back? If you are installing a large piece of Lexan already, just leave the bedcover in place and set this on top. The bedcover won't stretch from the top of the cab to the back of the bed anyway, if I understand what you want to do, the bedcover will be about a foot short.

That's the purpose of the Lexan; so I can see into the blind spots. Rear views are not required on a commercial vehicles in Michigan.

My calculations show that the existing cover would be about 1.95 inches short of meeting the edge of the tailgate; a deficit easily made up with aluminum stock.

[brucepick]

I say go for it. Looks like a decent plan.

[kitcar]

Originally Posted by brucepick

I say go for it. Looks like a decent plan.

Well, yeah. But we don't know if it will actually make any improvement. I mean what if the shape of the front of the Dakota (admittedly pretty darn smooth lines for a truck) negates the need for a cover like this. Yeah, I know Knox had great results and data says that this is the best shape but this ain't a square front design. But the math of adding a spoiler to the roof of the thing said that the air should spill over the tailgate and it didn't. I knew the air dam and side skirts would make a difference - it'll help with on any vehicle. But once you get to the top, well all bets are off.

And lets not forget; The 2000 was the first year that they left off the wheel well flairs. Not from a styling standpoint but because a Dakota gets better mileage with the tires sticking into the air stream. The mileage went up 1 mpg without them, via the EPA.

As an aside, did you guys notice that the EPA has updated all the mileage estimates for years past to the '08 mileage? Mine went from 14 city/20 highway to 13 city/18 highway. Which makes my garage entries look that much better.

[GasSavers_BMac]

Well, even though it was a windy day, I got 22 going to Detroit and 20 coming back.
That was with my aero cap, cam advanced 4 degrees and Halo plugs.
My Dak is a 98 with those fender flares, flairs... whatever. Should I take them off???

[jwxr7]

Nice mileage kitcar! I'd like to see some pics of your aero mods. When did you add the cab spoilers? Did it make a difference in FE? I didn't see that your gaslog.

Originally Posted by BMac

Well, even though it was a windy day, I got 22 going to Detroit and 20 coming back.
That was with my aero cap, cam advanced 4 degrees and Halo plugs.
My Dak is a 98 with those fender flares, flairs... whatever. Should I take them off???

Pics please . I want to do something for my gmc soon. Describe a little bit of your construction steps and materials.



thanks