Silverado aerocap build thread

[MetroMPG]

Wouldn't a fence would just trip the flow and form a vortex?

FYI, Bondo has posted a video of his aerolid's tuft test, and there appears to be less upward flow on the side surface:

http://ecomodder.com/forum/showthrea...ell-12390.html

[aerohead]

Originally Posted by Big Dave

Are climbing tufts a good thing or is this the "C" pillar vortex climbing upwards on its own?

I would think that anything lifting mass would require energy.

Would a "fence" cut off the climbing vortex? You see fences a lot on STOL plane wings to control vortices.

That's a good question and I don't have a scientific answer.I believe the fences on the wing is to discourage spanwise flow which is exactly what is happening with the aeroshell.
And Darin nailed the cause down precisely as being due to the delta-P caused by the delta-V between top and sides.
"poco-loco' the sailboat derived cover that I have on the T-100 now doesn't do this due to the plan-taper and radiused tumblehome,but I do get a bit of it up over the rails,spilling over alongside the shell.
It's all pressure driven and the only solution is a completely integrated Kamm style truck bed which has plan taper to match the roofline.I started this on the Dodge but that's on hold for probably years.
Fences might discourage comingleing of the two airstreams but it would not remove the root cause of the problem.

[Bajascoob]

Originally Posted by Fubeca

Update:

I'm not sure this black plastic, shrunk with a heat gun is going to be a good medium-term solution when there are large temperature variations.

The weather has been pretty cold since I initially built the cover and the plastic remained tight and looked pretty good.

Last week we got some more warmth and the heat from the sun the plastic started to expand and wrinkle. I'm now pretty concerned about what it will look like after things really heat up.

I wonder if it was shrunk using the heat guns used for boats if it would have worked better as it would be a more uniform shrink.

However, this is not likely to be a great method for any type of long-term use.

I think I'm headed back to the drawing room to figure out version 2.0. I'm also considering doing some testing to determine how much difference there is between a snugtop style topper, a tonneau, and this topper for this particular truck. I may end up going a different route if there is not a significant difference.

On a positive note - I did just get my second highest tank ever at 19.04 MPG for a whole tank. I'm definitely excited to see what happens when things really warm up

Being black do you think it is more effected by the sun...thats why the boat guys use white? How about clear?

[Fubeca]

Yes, I'm sure the fact that it is black exacerbates the issue. After seeing Charlie's (who did a much better, more consistent job of shrinking) next to mine, I think I can do a little remedial shrinking and it will work okay.

[Bajascoob]

Is this stuff the "painters sheeting" 4 mil, black? I was thinking of using 6mil clear.

[Fubeca]

I don't really remember exactly what it was called. I may have posted it earlier in the thread. It was a basic heavy-duty black plastic from ace hardware. It came in a roll.

[Fubeca]

So - I finally got a little more time to run some numbers.

I did several bi-directional runs between freeway exits at 70 mph. A with the topper, B without, and A again with. Ambient temp at 45F and small perpendicular crosswind (less than 5 mph)

I don't have my book with the numbers and I can't remember the details - but it did manage a 7% improvement over the open bed (tailgate up) at 70mph.

Again the test wasn't great - there was moderate traffic and I had to throw out a couple of runs due to proximity of other vehicles.

I may run the test again in later in the year when I can do it at night or early in the morning when traffic is minimal.

I'm satisfied so far!

[Fubeca]

Ok finally got a chance to grab my notebook.

Average A runs 19.47
Average B runs 18.18

Difference of 1.29 MPG or 7%

[ECONORAM]

Originally Posted by Fubeca

Well Charlie (ChazInMT) stopped by on his way out East and we had a good time chatting over lunch.

Funny - neither of us really seems to get much interest in our caps while out and about. But it was kind of interesting to see a few people react when we were parked next to each other and running up and down the freeway together.

Anyway - we decided to do a little tuft testing to make Darin happy

We went up and down the highway about 3 miles - the first video is much better than the 2nd.

I could be wrong, but I suspect the gap between the cab and the sloped cover is causing some airflow ruckus. Did you consider filling the gap with some foam and trying some ABA runs?
I think your second test sounds good. I am still surprised you are only seeing a 7% improvement. I had anticipated more than that. I think am getting 10% from my belly panel install based on some extended road trip data, but am waiting for my MPGuino to show up so I can confirm this.

[Bajascoob]

Does the plastic covering lay down or balloon up...high v low pressure?
I would think that it would balloon up.

.I have my cap built, have to fabricate some mounting hardware, hopefully test it today or tommorow. The test would be a structual test . I am doing a 2k mile trip this weekend.