Big Van trashcan grill block

[mwilliamshs]

Good thinking on the tape. I'd also considered turning 32 rectangles into 8, of 4 small rectangles each, and covering them in big tiles that fit within the grid of the grill. Could be done so as to not look totally butchered that way and would be less labor to both reinstall and remove if temperatures so demanded. Might do that for the center portions come winter time if I think of a clever reversible means of attachment.

[freebeard]

The step inside each rectangle makes it work. Each piece will be flush with the others.

When I saw the thread title, I thought of this:

[elhigh]

Originally Posted by mwilliamshs

The picture aerohead posted, is that just my wake as-is, or is that the shape a tail should have, etc? I'm interested in a kamback and have started designing it but don't know the correct angles. Any help would be appreciated!

It's approximately the shape a kammback for your vehicle should take. You'd want it to taper in from the sides, too.

In the Aerodynamics section of the forum there's this: http://ecomodder.com/forum/showthrea...ower-6341.html

That will allow you to paste a translucent image of the idealized aerodynamic profile over a photo of your vehicle. Match the overlay's highest point to the rearmost high point of your vehicle, and you can see how a kammback should extend behind your vehicle to fill in its pressure wake.

For the side taper, you would use mirrored versions of the profile overlaid on a top-down photo of your vehicle. That can be a little tricky.

I don't remember where the cutoffs are and I'm a little pressed for time right now to look them up, but there's a point where extending the tail further doesn't contribute meaningfully to further improvement in the vehicle's aerodynamic performance. It will improve, but those improvements are small enough to be lost in the noise of tire alignment, carb jetting, etc. The good news there is that it means you can make a big improvement without having a ten-foot-long tail sticking out. A much shorter tail might be sufficient.

It's worth checking out TrailerTails: TrailerTail | ATDynamics – Fuel Efficiency Aerodynamics Technology for Tractor Trailers saving over 10% with TrailerTail and Side Skirts They're getting useful improvements with not subtle sculpting of the tail's contours. It helps to be an aerodynamicist and make things really perfect, but it isn't crucial. And like I said about tail length, TrailerTails are available as short as 36" - long enough to make a useful difference.

[mwilliamshs]

Thanks for the info.
Here's a shot of MY van. As you can see the fiberglass top adds about 4" of height but's flat on top (has ridges just like a truck bed but is level side to side and front to back other than that). I think that makes my point of "maximum camber" the upper rear corner right?



Here's an idea of what I'm contemplating up front but think a curved air dam, from flush with the front bumper's foremost bottom edge at the center to flush with the inner fenders at the rear, and reaching from 1-2" inboard of the tire's outer edge on each side would be a better bet. I'll likely extend it an inch or so below the lowest point of the suspension which is quite low on the twin I-beam Ford suspension but thankfully my front overhang (from tire to bumper) is very short so the reduced ground clearance shouldn't matter much and it will likely still be 4-5".

Here you can see the minimal OE air dam. It's cut about 2" short on each side of reaching the tires at all, much less their outer edges. I think keeping the width about 2" narrower than the overall tire width (passenger outside to driver outside) should cut down drag without adding to wake. I can't decide if curved or straight would be better. I'd normally think curved but with such a square front-end there may be more to it...?

I used the aero&rolling resistance calculator. Tell me what you think of my inputs and the output. 5000 lbs is a rough guess at this point but not too far off I'm afraid as shipping weight for this guy is 4300 or so and the top adds a couple hundred and the interior has some insulation and paneling added. I modified the Cd from .48 due to the top and lowered both the engine efficiency and drivetrain efficiency due to the truck-like components here. Big heavy C6 automatic chief among them. Rolling resistance is due to heavy load range E tires (not in pics, appointment for installation is Thursday) that I did actually choose for their efficient design and the fact that I'm a religious pressure-checker.

[oldtamiyaphile]

Originally Posted by aerohead

The newer design is around Cd 0.38.A padded bra for the nose would really help.

I wonder how much comes from detailing and underbody.

My VW T5 has a .33Cd



The profile difference isn't really that great and there's noting really special happening out the back, no taper, no box cavity, not even trip strips. It does have a pretty smooth underside, though.

Newer vans are around 0.31 like the Iveco Daily:



These have a sort of shallow box cavity out the back, I don't think the underbody aero is all that great though.

[mwilliamshs]

The 4th gen Ford vans got way more rounded corners, flush mounted glass, composite headlights, more integrated bumpers, a better grill to hood to windshield transition, more inset wheels, flag style mirrors, tighter panel gaps, less pronounced body character lines, flush door handles, scroll AC compressors, MAF fuel injection, much less pronounced door hinges (not kidding, you can hear mine in the wind) and all of that improves fuel mileage.

My neighbor has a 95. I parked next to him just now.

Check that angle. His front end is about 5" longer overall.


His side is much smoother.


My bumper is undamaged but like a parachute. His is actually bent out but still more streamlined.



These door hinges are ridiculous aerodynamically.

[freebeard]

The 4th gen Ford vans got way more rounded corners, flush mounted glass, composite headlights, (etc.) and all of that improves fuel mileage.

One option would be to trade up, but the 'for sale' sign and the new tires suggest this is a new purchase. If you look at the template overlay you see that to get a 100% boattail would double the overall length of the vehicle. The only practical way to do this would be with a trailer. IMHO better to follow the practices for a box van.



Ignoring the drag of the cab to van gap, there is 30%+ occurring under the vehicle. A belly pan (w/ diverter) and four-wheel skirts alone would put you past the 4th gen Cd.

Instead of an airdam, why not replace the whole bumper, following aerohead's suggestion for a 'padded bra'. It could push out to the profile you see on the VW LT5 and have clear headlight covers with a nice sideways radius. Add a bump on each side of the hood and let the center and the grill area be recessed.

Add fillets behind each exposed hinge on the side doors.

[mwilliamshs]

The van stays. Shopped a long time for the right one. The top alone is over $3k.

I'm willing to extend the back a couple feet or so with a tail but do not want to lengthen the front. The rear overhang is already a hassle so a bigger hassle there is small potatoes but the front snubness is a saving grace daily and to compromise that would make parking at work and school major issues.

A bigger front air dam, skirts from front tire to back tire with spats on both ends, rear skirts from rear tires to rear bumper, a kamback, and a belly pan are the plans. Gonna finish this grill block project and have the AC tuned up then start working/spending money on the motorcycles. Best way to save fuel is to ride the bikes but having a dry rig with AC will be a blessing this summer.

[drainoil]

I'm down with full size vans to. Glad to see you doing this.

[freebeard]

Do you have a plan for access to the rear doors? What about those rear-view mirrors?

Skirting the whole length of the vehicle would be awesome.