Big Van airdam/side-skirt design suggestions

[mwilliamshs]

So freebeard, thanks for posting about curving my front edges or covering things with pipe. Thanks to everyone else too!

Here's the 3 questions I originally shared. Any help on answering them?

The questions for me are:

1) should the airdam be straight across the bumper or be curved inward from the center toward the tire on each side?

2) Should the side-skirts start inboard of the front tires' rear edge (closer to the centerline of the body) or be straight inline with the body itself?

3) what should the skirts do behind the rear tires? I know freebeard says they should taper out to be inline with the outside edge of the rear tire but race car rear end diffusers don't do that. Neither do those seen on insights or prius(es) (prii?). They all taper inward. So anybody else got an idea?

[mwilliamshs]

Originally Posted by freebeard

...(water-pumper Vanagons do have a front radiator)...

are the vans pictured air or water cooled? Are their engines running? Are any front-mounted fans (radiator or AC condenser) running?

EDIT: NEVERMIND. Not relevant. Just a couple questions that popped up and needn't be answered.

[oldtamiyaphile]

Originally Posted by kach22i

Custom Trailer Aerodynamics | Freight Wing

Is there any reason why the ends are open? I want to do something like this on my trailer, and if the ends should be open it makes things a whole lot easier.

[kach22i]

Originally Posted by oldtamiyaphile

Is there any reason why the ends are open? I want to do something like this on my trailer, and if the ends should be open it makes things a whole lot easier.

It makes a nice home for bees and wasps, but I think it was done that way for simplicity.

It may give cross winds one less surface plane to push upon as well.

On second thought, once that trailer cranks all the way over you may not want anything extra sticking out which could interfere with the turning radius.

That is the reason for the angled cut at least. And if not for turning clearances to the cab I assume they would have went all the way to the corner edges at 90 degrees blunt.

Closing those ends might be nice but an unnecessary complexity.

[aerohead]

Originally Posted by mwilliamshs

So freebeard, thanks for posting about curving my front edges or covering things with pipe. Thanks to everyone else too!

Here's the 3 questions I originally shared. Any help on answering them?

The questions for me are:

1) should the airdam be straight across the bumper or be curved inward from the center toward the tire on each side?

2) Should the side-skirts start inboard of the front tires' rear edge (closer to the centerline of the body) or be straight inline with the body itself?

3) what should the skirts do behind the rear tires? I know freebeard says they should taper out to be inline with the outside edge of the rear tire but race car rear end diffusers don't do that. Neither do those seen on insights or prius(es) (prii?). They all taper inward. So anybody else got an idea?

1) the majority of the central portion of the airdam can be as straight as the bumper and valance,but the outer edges should roll into a radius,then extend straight back to the edge of the outer tread line to kick the air onto the sidewall of the tires,leaving as small a gap as will accommodate wheel flop from lock to lock.
2) The rocker panel extensions should pickup where the sides of the airdam leave off,at the outer edge of the tread at the tires rear,again,minimizing the gap.You want the tire face essentially even with the new 'sides' of the van.
3) If the rocker panel extension behind the tires begin at the outer tread edge,then gently taper inwards,they become the vertical equivalent of a diffuser,allowing the air to decelerate without separation,and by the time this flow breaks away at the rear,it's imparting a higher pressure to the wake region,reducing pressure drag.
--------------------------------------------------------------------------
Later on,if you add a belly and diffuser,you could add actual wheel fairings below the diffuser to streamline the turbulence behind the tires,as land speed record cars,SAE and Shell Eco Marathon racers,and Solar race cars use.

[aerohead]

Originally Posted by mwilliamshs

are the vans pictured air or water cooled? Are their engines running? Are any front-mounted fans (radiator or AC condenser) running?

EDIT: NEVERMIND. Not relevant. Just a couple questions that popped up and needn't be answered.

The Vanagon with the box-cavity/boat tail is a Wasserboxer Westfalia converted to Subaru engine.It has a Ford Model T radiator out front with no electric fan backup.A mechanical coolant pressure gauge was mounted in front of the windshield so system conditions could be monitored.There was never a overheating problem with the van.

[aerohead]

Originally Posted by oldtamiyaphile

Is there any reason why the ends are open? I want to do something like this on my trailer, and if the ends should be open it makes things a whole lot easier.

If they close the ends they're infringing on another patented deflector.It's not as good a design,but cheaper to make and sell.

[mwilliamshs]

Originally Posted by aerohead

1) the majority of the central portion of the airdam can be as straight as the bumper and valance,but the outer edges should roll into a radius,then extend straight back to the edge of the outer tread line to kick the air onto the sidewall of the tires,leaving as small a gap as will accommodate wheel flop from lock to lock.
2) The rocker panel extensions should pickup where the sides of the airdam leave off,at the outer edge of the tread at the tires rear,again,minimizing the gap.You want the tire face essentially even with the new 'sides' of the van.
3) If the rocker panel extension behind the tires begin at the outer tread edge,then gently taper inwards,they become the vertical equivalent of a diffuser,allowing the air to decelerate without separation,and by the time this flow breaks away at the rear,it's imparting a higher pressure to the wake region,reducing pressure drag.
--------------------------------------------------------------------------
Later on,if you add a belly and diffuser,you could add actual wheel fairings below the diffuser to streamline the turbulence behind the tires,as land speed record cars,SAE and Shell Eco Marathon racers,and Solar race cars use.

THANKS A TON!!! EXACTLY WHAT I WANTED TO KNOW AND THEN SOME.

[mwilliamshs]

Originally Posted by aerohead

If they close the ends they're infringing on another patented deflector.It's not as good a design,but cheaper to make and sell.

For a DIY solution to closing the ends, some careful cutting and a little origami would turn this quickie sketch into a nice foil I think...
...then caulk or plastic-weld (depending on material) the seams and you're set.

[aerohead]

If you have,or have access to a metal brake,she'd come together fast!
GE makes a great 100% silicone gutter sealant that's UV stable and remains elastic.It's not paintable but comes in colors.If you haven't used it yet,it's worth checking out.