Cargo trailer conversion

[SandRdr]

Weird Alice again. Exterior.

Aero is a thing. Flying models childhood. Small sailboats counterpoint to bikes. Best bud is seven time SSA open class champ…

Found a used Demco DT6000HD I could afford and started from front building enclosure in 3ft 4ft 5ft 4ft sections bolted together and to bed. That is longer than the bed cuz first box extends front. The tilt up front beak was last. Took months so the trailer was on the road in between each section going to the mtns or to TD. First version was too light and did not weather well. Dis assembled. Rebuilt. Gross with TD load is 3920 Cat scale. Two bikes, gear, tools, ez up paddock stuff yada yada.

Most trips include a five mile interstate down grade. Coastdown test numbers every trip, each configuration. Beginning hit a mark at top at sixty and lift. Rig would stabilize at about 65 open trailer two bikes junk strapped on. Now same exact load except weight of the box. When it touches 70 back shift sprinter to fourth. 75 back shift to three and brush brakes every half mile. Pretty sure aero matters. LOL

Never seen a VG that was closed on the end.

Seems like it would induce drag.

 

[EGR]

Never seen a VG that was closed on the end.

Seems like it would induce drag.

This video contains good illustrations and explanation.

Airtab | Aerodynamic Fuel Savers | Airtab Videos

Airtabs are small powerful devices that reduce vehicle aerodynamic drag, save fuel, improve stability, visbility, safety. Airtabs™ are designed to perform on tractors, trailers, straight trucks, cargo vans, RVs and Buses.

www.airtab.com

VG will do different things in different locations and applications. Bluff body applications are different than aircraft applications.

This rear edge of trailer VG opposed pairs does induce a bit of drag. But they eliminate the big laminar flow separation bubble on the back side of the box. Trades a small amount of controlled drag for elimination of a much larger uncontrollable drag. Net reduction overall.

The VG in the photo eliminate crosswind and big truck buffeting and trailer feed forward wobble. They have been on and off several times while the trailer stayed in service. Maybe 50,000 miles in the rig. Completely eliminate trailer feed forward wobble.

 

[SandRdr]

This video contains good illustrations and explanation.

Airtab | Aerodynamic Fuel Savers | Airtab Videos

Airtabs are small powerful devices that reduce vehicle aerodynamic drag, save fuel, improve stability, visbility, safety. Airtabs™ are designed to perform on tractors, trailers, straight trucks, cargo vans, RVs and Buses.

www.airtab.com

VG will do different things in different locations and applications. Bluff body applications are different than aircraft applications.

This rear edge of trailer VG opposed pairs does induce a bit of drag. But they eliminate the big laminar flow separation bubble on the back side of the box. Trades a small amount of controlled drag for elimination of a much larger uncontrollable drag. Net reduction overall.

The VG in the photo eliminate crosswind and big truck buffeting and trailer feed forward wobble. They have been on and off several times while the trailer stayed in service. Maybe 50,000 miles in the rig. Completely eliminate trailer feed forward wobble.

Did you design them? Getting airflow to stay attached to a flat surface perpendicular to travel would certainly require some compromise!

 

[EGR]

LoL. The attached flow on any object moving through air is front to back along the sides of the object. On a box the flow detaches abruptly at rear edge. Full stop. It becomes a turbulent low pressure mess. A VG in such place reshapes, “combs” it so it wants to continue straight line behind the object and not add to the low pressure object trailing drag turbulence.

The research was NACA, 1930s, 1940s. Public domain forever.

Have a look at the little video…

 

[SandRdr]

LoL. The attached flow on any object moving through air is front to back along the sides of the object. On a box the flow detaches abruptly at rear edge. Full stop. It becomes a turbulent low pressure mess. A VG in such place reshapes, “combs” it so it wants to continue straight line behind the object and not add to the low pressure object trailing drag turbulence.

The research was NACA, 1930s, 1940s. Public domain forever.

Have a look at the little video…

A bit of a different application than what I used them for (homebuilt AC).

 

[EGR]

A bit of a different application than what I used them for (homebuilt AC).

Radically different. AC by design will almost never have trailing turbulence drag. Everything out there rolling down the road will have. Lots.

 

[SandRdr]

Radically different. AC by design will almost never have trailing turbulence drag. Everything out there rolling down the road will have. Lots.

I made my own and it lowered the stall speed significantly

 

[TravelinLite]

The lip is actually a rain shield for top of ramp when it is closed. There is no seal. About inch gap actually.

The vortex generators reshape the attached flow off the trailer sides to prevent formation of large wrap around vortices in the low pressure on back of the box. In bluff body aero those big trailing vortices are major drag source. All the research was NACA in the ‘30s ‘40s.

Google Air Tabs. A Canadian company selling primarily to otr freight people. They have exceptionally good tech presentation online.

Great presentation on the Air Tabs. Intuitively I would have put them on incorrectly. Thanks. That trailer certainly is a one of a kind.