Building aero cap for dodge truck with ?'s

[nubbzcummins]

I'm about 45 minutes from mooresville.....where is the wind tunnel and what are the rates? Version 2 is still not like I would like it so Version 3 is in the works which will be adding a little more positive arc to the roof and altering the design of the rear. If version 3 looks good then it will go through some testing before fiberglassing an aerocap.....

[bondo]

Here is a link to the A2 wind tunnel. Thier rates were about $300.00 per hour. You get a nice readout showing all the data.

A2WT HomePage

Bondo

[cons]

Hello Nubbz, I put a similar top on my pick-up and wow what a difference! I think one important component you might want to look into it how to maximize a clean airflow separation at the back. I extended my cap 8 inches from the end of the truck and I think that helps a bit. On the Volt video on this website, a designer talks about putting a thin, 5mm? dimple across the back for better separation, and said that little feature went a long way. I've also heard on this site, 10-12 degrees should be the angle you're seeking. If you go straight from the cab to the gate, it'll be more, maybe 15, and those few degrees cause are detachment over the topper, increasing drag. If you measure the lengths of all the sides, you can type it into an internet angle calculator to get your precise angle.
Cheers,
Cons

[406pat]

I'm new here so feel free to let me know if this is a dead horse.

Has anyone considered using a rough surface on a truck topper rather than a smooth one? Having a rough surface would create a turbulent boundary layer and this could possibly allow a greater angle on the truck topper due to the effect a turbulent boundary layer has on separation.

Any thoughts on this?

[aerohead]

Originally Posted by 406pat

I'm new here so feel free to let me know if this is a dead horse.

Has anyone considered using a rough surface on a truck topper rather than a smooth one? Having a rough surface would create a turbulent boundary layer and this could possibly allow a greater angle on the truck topper due to the effect a turbulent boundary layer has on separation.

Any thoughts on this?

All the air is already in turbulent boundary layer,as the critical velocity for this with vehicles occurs around 20-mph.
Turbulators would allow a steeper cap angles without separation,but then you'd be losing valuable space inside the bed underneath.
22-degrees is the magic number.You don't want to exceed it.