Swede's AeroLid build thread

[swede]

Following in the footsteps of others here I have decided to build an aerodynamic cover for my 2009 GMC Sierra. The truck has a 4.8L engine, automatic transmission and 4wd. Current HWY average is 20-21 mpg US.

Highway cruising speed is consistently 105 km/h and terrain is varied on my weekly round trip that totals 550km. This is a 225km one way trip from my hometown to work.

The idea for the aerolid is following along design that Bajascoob used. I bought 100' of 1/2" tubing for $29.00 CAD and will try using some leftover 6mil vapour barrier plastic that I have.

Total costs so far:
1/2" EMT $29
1/2" EMT bender $50 (Gotta have the right tools )
Angle indicator $22

The basic layout will be similar to Bajascoob's unless there have been any inherent faults with that design so far. A basic tapering down and in towards the tailgate will offer a rudimentary "boat tail" to the lid. I plan to have it hinge up at the front like a solid tonneau if a good strong design comes together.

So far it looks like I'll have a 12 degree slope from cab to tailgate. I'll have to hump it a little just after the cab to prevent a sharp angle change and cause airflow separation. Here are some pics of what I've started with.

[rbrowning]

Looks like a good start. Do you think it would create too much turbulence if you lower the front top edge enough to allow those behind you to see your third break light? Or will it be visible through the plastic? Or could it be relocated to the top center of the tailgate?

I've seen so many cases where one break light has burnt out and when the driver pumps the brakes it looks like a turn signal. I really appreciate the third light.

[swede]

Plans are to have a third light on the rear deck lid of the cap. There will be more pics of construction as the weekend progresses.

Initial tests of 6 mil plastic were disappointing, less shrink than expected but good self welding characteristics. Too bad.

I'm now looking at clear coroplast or lexan. I may have a hook up for a skid (pallet) of lexan and umhw plastic cut off's from a family hookup, (brother in law).

If this works out I am hoping for a Lexan shell. If I cant get the plastic soon enough I will go to Home Depot and get white or clear coroplast for the test run.

[swede]

Continued

Pictures of the framework construction. All joints are welded, no connectors used.

[swede]

Sourced some black coroplast for 30 dollars for 2 4x8 sheets. Covered the frame with it and riveted it on. The rivets tended to pull out of the plastic a little too easy so I made washers out perforated strapping and uses the strapping to edge the major stress areas around the corner bends. 1/8" pop rivets are used to fasten the entire perimeter of the covering.

More pics.....

Interior view showing framework. Pipe insulation keeps the box rails from getting beat up.


Exterior showing coroplast. My first time working with it. I found that a heat gun and carefully bending the radius of the corners prevented major kinks.


A few pics of the back showing the fastback style raised edge. This was done in an attemt to "boat tail" air flow. Some bubbling issues with the plastic on the sides. I may add additional braces and fasten it on the sides.




Here it is on the truck. There are four stakes that drop into the trucks stake pockets. Ratchet straps fasten it down into the the bed from the cargo tiedowns in the box.




If it works well I will design a hinge from the front to allow it to raise up like a solid tonneau cover.
I will be very closely monitoring fuel consumption for the next while and will post results here as I get them. Barring no major headwinds, typical fuel consumption ranges from 19-21mpg hwy most times.

Total cost to date for supplies (not including tools) $70.00 tax included.
Comments and suggestions welcome!!

Thanks

Swede

[COcyclist]

Looks great. Nice work, I hope you see some positive results. For anyone welding EMT, be sure to wire brush off the galvanized coating and/or weld in a ventilated area.

Do you have a rough estimate of the weight of the AeroLid?

[swede]

Looks great. Nice work, I hope you see some positive results. For anyone welding EMT, be sure to wire brush off the galvanized coating and/or weld in a ventilated area.

Do you have a rough estimate of the weight of the AeroLid?

Welding galvanized steel is not something to be undertaken by someone who is not aware of the dangers of zinc poisoning. When I welded the skeleton together I was in a garage with a good crossbreeze and I didn't hover in the path of the welding smoke, rather staying back a bit and letting the smoke get blown away.

The AeroLid wieghs in at less than 30 lbs, probably around 20lb. I havent weighed it yet but I can lift it up with one hand and mount it on the truck easily myself (two hands).

[autoteach]

it is probably a good suggestion to use a respirator or exhaust system. If you avoid contact with the smoke, its reasonable, but precautions never hurt anyone. By the way, I teach high school shop.

[vskid3]

Nice job. How do you plan on making it hinged? I was thinking it would be best to have the hinge at the top with a frame to support it while it's up.
I wonder if there is any difference in gains between a longbed and shortbed with a cover like this.

[swede]

I was thinking it would be best to have the hinge at the top with a frame to support it while it's up.

That's exactly what I had in mind. I plan on making a "headache rack" type frame with hinges at the top and gas struts to support the lid while it is up. The only challenge will be figuring out how to prevent the bottom front edge from hitting the box rails due to the lower swept arc as the lid opens. I'll have to think up some fancy hinge geometry for that I guess.