Silverado aerocap build thread
 

Teaser :thumbup:

http://ecomodder.com/forum/attachmen...1&d=1262183906

Nice work on the radiused side-top transition.

Added to the project library & looking forward to the progress.

Any plans to A-B-A test the finished work?

I'm not sure I've got my scangauge quite calibrated. I'll probably try to do some testing in a few weeks.

I'm very curious to see hard data.

I like it too. Looks like a very sturdy rib cage and a good start.

Sweet!
 

I can already see the air slipping over it.I believe you'll be pleased at the pump.Nice fabrication!

Looks really good so far.

OSB - the rich man's cardboard.....:thumbup:

Looking forward to more. :thumbup: so far.

Good luck, It reminds me of all the balsa wood airplanes I built as a kid.
Dave

:D

Total investment:

4 2x4s = $7
2 OSB = $12
2 1/4" Ply = $17
Aluminum Tape = $11
Shrink Plastic = $15

Grand Total: $62

This is really just a test to make sure I can to it and work on perfecting the shape. If I can get the kinks worked out and if I see enough of an economy improvement then I'll go for something a little more permanent and better constructed.

Update:
Done for now. I've got a couple hundred miles to drive during the next couple of days so I'll report back on my experience.

I might do some tuft testing to see if it is too high - I'm a little concerned about a couple of the edges. I'm also concerned about the gap. I may need to come up with some kind of filler.

http://ecomodder.com/forum/attachmen...1&d=1262241744

One more:

http://ecomodder.com/forum/attachmen...1&d=1262244102

Looks good.

Be careful about it blocking the 3rd brake light.... that might cause a legal issue in some areas.

If you want to fill the gap, just use some auto body masking tape and black plastic for now. In fact, that could be a 2 minute addition to test if the gap is really hurting you at all!

How do you intend to test your design?

Well - it was a terrible day to do any real testing but it was the only time I'll have for a while.

I warmed the truck up and drove back and forth on a 1.5 mile stretch of straight rural highway.

I ended up doing a B-A-B-A test. Each leg was 4 sets of out and back.

B: avg mpg 19.6
A: avg mpg 18.8
B: avg mpg 19.4
A: avg mpg 18.8

So it looks like a lackluster improvement of ~.7 mpg or ~4%

The ambient temp was 10* and there was a NW wind at 10-15 mph. The road was East to West.

So I don't think the test is really all that valuable. I'll be interested to see how my mileage looks over time.

I'll take some more pics and maybe you all can let me know if you see any areas that may need improvement. I was really hoping to get 10 - 20% improvement.

(EDIT: testing speed of 55 mph)

weather
 

I suspect that if you had immediately yanked the cover and did the same runs "naked",that you would not have seen your 17.58mpg baseline.
I've been looking back over the logbook on my truck and it will lose almost 9 % mpg between winter and summer.
I really think that 10-degree temp is slamming your numbers,that's why I posted the general temp/mpg chart.Your 19.6 might become a 21.364 mpg in August.
It takes 22-miles of continuous driving at 50-mph just to bring a vehicle up to it's equilibrium temperature for any given ambient condition.Any parking time between runs,even a stoplight can cost you in heat transfer.
I like your cap a lot.Please spend some time with it and see that,when things warm up again,she doesn't go even further between gas pumps.
I tore my hair out the winter of '05/06 hoping to see my bellypan show up on the radar.It wasn't until spring that the numbers emerged.

The "B" numbers above are with the topper and the "A" numbers are without. I'm not concerned about the overall numbers, as the cold does really effect it. I was just hoping to see a little more differentiation between the numbers with the topper and the numbers without.

I'm happy to see any improvement though and it keeps the snow out of the bed :)

WOWOW!!!!!!
The black is shrink plastic???
There is some really lite foam in the marketplace that would fill the gap and not scratch the cab or be attached to the cab.

It isn't really meant to be a shrink plastic - but it works. It is just standard construction film. The stuff they use around here to provide a vapor barrier between the insulation and the living space in a house.

I was looking for something cheap and easy to cover the topper with and thought about boat shrink wrap (the stuff they use to protect boats in the off-season). It was kind of hard to come by at cheap prices so I tested this stuff since it was made of basically the same plastic. I picked it up at the local hardware store in a big roll.

Up close you can see a lot of imperfections - but it looks great from a distance and it was cheap and easy. I just wrapped the whole thing, stapled it to the underside and shrunk it up with my heat gun.

I'll try and pull another picture off my camera tonight that shows it a little better.

It is hard to get the images to show detail - the snow/light kind of washes it out.

http://ecomodder.com/forum/attachmen...1&d=1262311781

very impressive...... very clean.......

Maybe Darrin should think about this stuff for his bumble bee tail......

Thanks to everyone for all the encouragement! It was fun to build and I think it will serve its purpose well. If I can find some time on a day without wind (we get one or two each year), I'll try to take some video of tufts and see what the air is doing.

Fubeca, that turned out really well. I'm impressed with the finished look. Wish my handiwork was that polished.

About your test results: what speed were you driving? I didn't see that mentioned.

You likely realize the percentage difference between A & B runs increases with increasing speed.

Brett (bondo) reports a ~20% change with his cap on the highway (here and here), but with all due respect (and I mean that), he hasn't yet done a "controlled as possible" A-B-A test. Also worth noting: he drives at 70 mph, which would show a greater percentage increase than I would see, for example, because I tend to test around 90 km/h / 56 mph.

Very nice work!
 

December 31, 2009 at 3:37 p.m. Fubeca wrote:

"So I don't think the test is really all that valuable. I'll be interested to see how my mileage looks over time."


The A-B-A tests are best in warmer weather with calm wind. Wind tunnel tests are the best do to controlled conditions and refined calibration. Mileage records over time do create a real world average for that specific driver and that specific vehicle.

That said, you did one fine job of fabricating you aerocap. Very nice lines! I wish I had a full scale wind tunnel we could park your truck in with your aerocap on it and do some testing of it's performance toward cd reduction.


Keep up the good work.

Bondo

Even if it's a 4% gain at your typical speeds, it's still a significant gain that'll pay for itself in no time.

If you drive 10,000 miles a year at speeds that will net that 4% improvement, that's 19 gallons not burned: 513 gallons vs. 532 gallons. (19.5 mpg vs. 18.8 mpg)

@ $2.75 a gallon, you save $52.25.

So your mod starts giving a healthy return on your investment early in year 2.

And that's a conservative estimate of fuel prices. I'd be willing to bet it's going to be much more than $2.75/gal in the US in 8 or 10 months.

This is true of course. And in that case, the more data the more convincing it is.

Sorry - I forgot to mention speed. It was at 55mph. I do expect to see better improvements at higher speeds.

I'd love to see what it looks like in a wind tunnel too!

This is a pretty awesome looking cap! I can't believe you got it done so quickly. :thumbup:

Thanks again for all the compliments. I am satisfied with the result for the time that I put into it. I only spent about 12 hours total on the project (I already had all of the materials).

It is a great proof-of-concept for me that will allow testing. If I really like it I may work on doing something more permanent along the lines of Bondo's very nice creations. Who knows, he may be producing them soon and I'll just be able to buy one.

It does look really good in pictures - but it has more than its fair share of imperfections up close. It really was a quick and dirty build.

If you plug your truck's numbers into the aero & rolling resistance tool, you could project what the 4% improvement you saw at 55 would translate into at different speeds.

There's always the poor man's wind tunnel! On-road tuft testing, eg. http://ecomodder.com/forum/showthrea...per-11522.html

Thanks again for sharing the project & for the time put into testing (I appreciate the effort it takes).

I will probably try tuft testing if I get a reasonable day and some time. Today we had no wind but the high was -4F. I decided not to try any testing :eek:

fubeca your cap looks great. how did you attach the 1/4" plywood to the osb so it did'nt split it? how did you get 1/4" plywood to bend around that corner? the shrink wrap really looks great where did you get it? what did you use the aluminum tape for?

i will not be able to work on my cap till the end of january. i was going to paint mine with exterior paint but the shrink wrap looks way better.

I used a 1/4" crown pneumatic stapler with 1" staples to attach the plywood. I ran the plywood to the edge of the curve on the top and the sides, then I ran 1" strips along the shoulder curve. This left some fairly large gaps at the corner, so I used the aluminum tape to cover the gaps in the curve to make it continuous and provide support for the shrink plastic. I used aluminum because it wasn't effected by the heat of the shrinking. I was concerned duct tape would melt and adhere to the plastic and mess up the shrink.

I got the plastic at the local Ace Hardware - I think it is called heavy duty construction sheeting, it came in a 10' x 25' roll.

Looks AMAZING I just have to do this to my Dakota.

Fubeca -

Impressive execution. I hope this isn't and odd request, but can you take a picture of the interior, looking up and into the structure and the plastic sheeting?

CarloSW2

Carlos doesn't like transparency?

Ok, I'm going to have to ask that you explain yourself here... odd fetish?

It doesn't sound odd - I'll try to get something. I kick myself for not taking more pictures of the progress showing the construction methodology.

I'm not sure what the longevity of the plastic will be - but it only took about an hour or two to shrink the first time - I'm sure I could do it once a year and not feel too bad about it.

Christ -

I just like seeing "structure". I agree with dwestmodesto. It looks soooo much like balsa wood airplane fuselages.

Fubeca -

I understand not taking pictures. When you have the idea in your head, you're eager to make it into reality, so pictures seem like a distraction ... until you get all those odd questions later on, ;) .

CarloSW2

Yeah, it's kinda like those cool little 3d balsa wood puzzles that you put together to make dinosaurs and such. I love to see "under the skin".

Here is a picture looking toward the front driver's side from the back.

http://ecomodder.com/forum/attachmen...1&d=1262660607

You can see the strips of 1/4" plywood used to provide support for the curve, and the back of the aluminum tape that spans the gaps providing support for the plastic on the outside. The top and sides are solid pieces of 1/4" ply, the corners are strips.

The plastic is wrapped around the outside, then stapled to the 2x4 frame and you can see some of the excess hanging and tacked up out of the way in the image. It could be trimmed down to the 2x4 - but I was in a hurry. The osb board along the side was used to provide support and structure to the osb ribs before the plywood was attached.

The 2x4 in the middle of the image just ties the two sides together at the midpoint and provides strength when taking it off and on.

PS - it is pretty stout - during the ABA testing, a ramp I was trying to use to climb up to the bed came loose and I had to stop its fall with my head. It ended up bouncing off the ground (and leaving its marks on my head :eek:). The structure didn't suffer, but a bit of the plastic was worn off the bottom.

i wonder how much having sharp edged on the corners instead of rounded corners would hurt aerodynamics?