Swede's AeroLid build thread
 

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 :thumbup:)
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.
http://ecomodder.com/forum/attachmen...1&d=1272581704http://ecomodder.com/forum/attachmen...1&d=1272581817http://ecomodder.com/forum/attachmen...1&d=1272581817http://ecomodder.com/forum/attachmen...1&d=1272581817

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.

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.

Continued

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

http://ecomodder.com/forum/attachmen...1&d=1272763510

http://ecomodder.com/forum/attachmen...1&d=1272763510

http://ecomodder.com/forum/attachmen...1&d=1272763510

http://ecomodder.com/forum/attachmen...1&d=1272763510

http://ecomodder.com/forum/attachmen...1&d=1272763510

http://ecomodder.com/forum/attachmen...1&d=1272763510

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.
http://ecomodder.com/forum/attachmen...1&d=1272764200

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.
http://ecomodder.com/forum/attachmen...1&d=1272764200

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.
http://ecomodder.com/forum/attachmen...1&d=1272764200

http://ecomodder.com/forum/attachmen...1&d=1272764200

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.
http://ecomodder.com/forum/attachmen...1&d=1272764200

http://ecomodder.com/forum/attachmen...1&d=1272764200

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

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).

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.

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.

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.

The long bed truck would stand to gain more from an aerodynamic cover than a short bed if I am not mistaken. This is due to the fact that the air has more chance to get caught in the box and hit the tailgate rather than flow past the cab and over the tailgate. There are gains to be made in both cases however. I have a short bed as you can see.

It's too soon to post results yet, but my first run in very windy and cold conditions were netting me almost the same mpg's as I was getting in warm relatively calm weather.

More results to come......

Swede

Light weight, and looks great, I'll give it two thumbs up:thumbup::thumbup:

Side hinge ??
 

Swede, I've been hoping to build a similar cover for my truck. My thought was to hinge it on the driver's side, and open from the passenger side. That way, the weight will be on the bed, not up near the roof line, and I believe it will be a much easier build. Also, if you ever go to a rear camera, wiring along that side will be simple too.

I hope if/when I ge around to building my cap it comes out as nice as yours.

As long as the pivot point of the hinge is lined up with or in front of the front edge and at the top of the cover, I think it will be physically impossible for it to hit the bed rails or the cab.

Thanks for the compliment. The important thing to remember is to use light wieght materials. I doubt that I will have any issues with an upper hinge as the cap is less than 30 lbs. That's probably less than the hatch on a metro!!

I find that the huge Dumbo ear mirrors on the truck, while creating drag, do give an excellent veiw to the rear. I havent missed the rearview mirror that much yet, but then again I'm not the type to use it much anyway;)

Swede

Lid
 

Swede,Sorry! This is my first look at your project.
I like what you're doing.From an airflow standpoint the only hitch I might think of,is how the sides 'tumble' aggressively from the cab back,falling at an ever steeper angle in such a short distance to the back.
Tuft-testing will reveal if flow is good there.Hope so.
Otherwise,you should be rewarded for your efforts at the pump.Nice work!:thumbup:

Thanks for the comment aerohead.

The first real highway run I did was this weekend and I had no way to see air flow over the top of the lid but the drivers side I could see out of my side mirror. I attatched tufts and observed the air flow that followed the contour from the b pillar of the cab and around the leading edge of the cap. I observed a little flow disturbance right at that edge and as the air continued along the cap it had a definite upward flow toward the top of the cap. I'm not sure if this is normal or even desirable on an aerodynamic cap like this. The other factor that may have skewed any real flow observations is the fact that I had a 90 degree crosswind coming from the passenger side of the truck during my drive.

I know that the angle looks steep but when measured from the beginning of the curve to the end at the tailgate with and angle meter, I have 11 degrees of slope. This is well within acceptable limits from what I understand.

The radius of the angle change from the top plane of the cab roof to the slope may be a little on the steep side but tuft testing with a chase/observation vehicle will tell.

One Question:

When tuft testing, are the tufts supposed to flow straight back with no movement along the surface of the substrate, or do they sometimes move side to side along the surface while still laying parallel to the substrate?

tufts
 

Swede,thanks for the heads up.Sounds like she's okay! The pressure is lower on top so the side tufts will be attempting to 'go' there,As long as they are not oscillating wildly from side to side you should be in the money!
Dr. Kamm's car did the same thing.:thumbup:

On a side note....

Unfortunately I am a smoker, but it can lead to some interesting observations. When I used to toss a butt out the window, (I don't do it often) I would notice the wind grab it and wildly toss it around right out of the window. Now I tossed one out and it flew smoothly along the side of the truck and dropped down to the rear smoothly in the trailing wake. A huge difference in the smoothness of the airflow along the side and into the trailing wake seems to be the answer to that.

What do you all think?

Not being seasoned like the others, sounds like you did something right.

Do you hear less wind turbulance at speed?

Seems to be quieter than it was, yes.

I just took a few more pictures to better show the side profile of the cap while mounted on the truck for those who are interested.

Here is a side profile

http://ecomodder.com/forum/attachmen...1&d=1273185812

And detail of the rear

http://ecomodder.com/forum/attachmen...1&d=1273185812

Question:

What do you do when you have some leftover coroplast, some spare time, and a gaping air hole in the front of you're truck?

You make a grille block of course:D:D

Here's the grille :eek:

http://ecomodder.com/forum/attachmen...1&d=1273186120

A few minutes of cutting later.....


http://ecomodder.com/forum/attachmen...1&d=1273186120

And the finished product...

http://ecomodder.com/forum/attachmen...1&d=1273186120

http://ecomodder.com/forum/attachmen...1&d=1273186425

I'm pretty sure that the lower opening will be more than sufficient to provide airflow unless I tow something. If needs be I cut a few zipties and I have full airflow back immediately.:thumbup:

if you'd have used black zip ties it would have been perfect :D

and if you hear less wind turbulance, then there is less wind turbulance, and that's bound to be a good thing.

Results.....

Well, I had the first decent weather to test the effectiveness of the AeroLid and grill block. No major head or cross-winds and no tailwind to give false high numbers.

Speed was kept around 100-105km/h and highest average about midway through the trip peaked @ 23.1mpg US. Overall average was 22.4 mpg US.

Thats an average increase of 12% over my usual FE numbers.

On a side note, the 24mpg in my sig was calculated in IMP mpg.

Gotta love trucks, getting a 12% increase isn't hard.

Hey Swede, Sorry I been out of it for a while. Your cap looks great, good job on it. I had about the same result (12% gain give er take) with my 2000 GMC. I'd vote for side hinge too, you would have to remake something on your current lid if you try to front hinge it.

Again Good Job....Welcome to the club.

you should do a ABA test. there are allot of variables from day to day. the only true test is a ABA test. i thought i was getting around the same increase until i did a ABA test.

My truck has an onboard fuel efficiency computer and it shows total gallons of fuel used/avg FE/ ODO/ etc. Based on that I am getting a lifetime city/hwy average of just over 16mpg. I am hoping to see this number start to move up as better weather and new mods impact my overall FE.

I want to do some ABAB tests one of these days but that will have to be on a hwy trip on the same day for true accuracy, correct????

If you have instantaneous fuel economy readings on your onboard computer, it is possible to do it on a flat stretch of road. Warm up the truck, drive between 2 landmarks using cruise control at a constant speed. Leave the truck running and cruise "on" between runs. Disengage cruise by tapping the brake. It is best to do both directions in light traffic and no wind if possible. Remove Kamm, repeat. Replace Kamm, repeat. It takes some time to get accurate results and higher speeds will show bigger differences in Aero mods.

Very sharp - nice work. I suppose folks with trucks, especially big engines always loafing along find this mod appealing. My truck is for towing so I prefer to let the engine and transmission coolers breathe easy. I appreciate your craftsmanship though. :)

Cheers
KB

First time perusing this thread.

Looks good, swede & thanks for documenting the build. Added to the project library. The more the merrier!

Swede, great job on the aerolid and the grille block. :thumbup: Thanks for taking the time to document the build as it progressed and share it with the rest of us. This is yet another inspiration to the rest of us!

Cool looking aerolid!
 

Nice work Swede on your aerolid. I have missed this post and want to comment on the crafty job you have done. It has an F-117 flavor to it.

Good job on the grille block also. I see where it fits right on the "M" of GMC.

I read you noticed a reduction in cabin wind noise. I noticed this also. Reduction in wind noise = reduction in turbulent air = reduction in aerodynamic drag. Hope you show some positive results in fuel efficiency improvement.

Keep up the good work!

Bondo

Coming from you Bondo that means a lot. Thanks.

I have noticed a definite positive effect on FE and it looks like the lid will be on for good unless I need the extra space in the bed. Next step is to incorporate a hinge system that allows me to flip it up from the rear like a solid tonneau cover with gas strut supports.

The coroplast really doesn't like the heat and tends to sag and buckle when the temps hit the 30 C range. Any lightweight alternatives out there that you can think of?? (I'm not good at all with fiber and resin so that is out)

Thanks

Swede

Bajascoob used 4 mil plastic sheeting for his. It shouldn't flap around too bad. Or it could be the black heating up in the sun, so white coroplast might not sag as bad.

Results..........

I finally had an opportunity to do some A-B-A testing and had some very exciting results. I took the truck on the same route that I normally do every weekend, a 230km trip each way. The data is from the on-board trip computer.

Here's what I came up with...

1- no cover, with wind, 230km traveled, average FE 20.5 MPG us
2- no cover, against wind, 230km traveled, average FE 19.5 MPG us
3- Aerolid installed, with wind, 230km traveled, average FE 23 MPG us

The results show a 13% improvement!!!!
There may be some variables that I am unaware of that swayed these numbers but the total 690km was traveled during the same day with the same weather, wind, speed, etc.

There was a very definite improvement in amount of wind noise and the feel of the truck stability wise with the cover installed. Wind buffeting seemed to be reduced compared to an open bed. I'll be sticking with this for sure and looking at some practical functionality improvements now.

(very well traveled today)

Swede

That is excellent -- good work!

Excellent results swede!
 

Your hard work is paying off. Thanks for sharing your test results.

12-15% improvement in fuel efficiency with the installation of an aerolid seems to be the rule. I tend to see around a 15% improvement as does round.boater who has one of my Aerolids on his Ford F-150. He has a nice fuel log posted here on ecomodder.

I also notice my truck being much more stable with the lid in place and the interior wind noise is much less.

You guys who build your own aerolids have my respect. I do hope someday things will work out to where I can get my product to market. People as yourself who see positive fuel saving results with their lids definitely helps with the marketing aspect.

Thanks,

Bondo

Today.....

Going against a 33km/h headwind/crosswind @ 105km/h I got 20.5MPG us during a 230km stretch.

I'd say that's a pretty solid result. Maybe I should start a fuel log on this thing!!!

Swede.

BTW, where do I get those ecomodder stickers so I can start spreading the word??