t_vago's compound curve foam board pickup aeroshell

[NeilBlanchard]

I do like the look of the Nissan cap, and it may be fine aerodynamically -- only tuft testing will tell.

I made a quick attempt in SketchUp (after downloading a free quad cab model from the Google 3D Warehouse -- there is a Dakota there, but not for download), and it lacks the arch all the way back to the tailgate (a little more trial and error would get it there):



In my estimation, the departure angle of the whole trailing edge would be better with a downward slope.

[t vago]

That looks like a 2005+ Dakota quad cab. Nice!

Steep angle aside, you can see that if you were to look downward on Neil's drawing, that the sides kind of curve in toward the centerline anyway. I think I am going to go with my 12 degree sides anyway, though. Trying to do that drawing in real life looks to be beyond my ability.

[NeilBlanchard]

Here's a slightly better version:




I could email you the SKP file and you can work on it -- there is a section tool that can show the surface contour.

When you reconstruct this, is your plan to skin it with fiberglass? Or, just toughen up the ribs, etc. so you can run it as foam and see how it changes the FE -- and then finish it?

[t vago]

Originally Posted by NeilBlanchard

When you reconstruct this, is your plan to skin it with fiberglass? Or, just toughen up the ribs, etc. so you can run it as foam and see how it changes the FE -- and then finish it?

The plan is to run it as foam and see how it changes the FE. Once I am satisfied with it, I'll likely use it as a mold for a fiberglass shell.

[JasonG]

Just put a fiberglass layer on it.
The foam weighs so little it wont make much of a difference and it will add strength.

[JasonG]

Just put a fiberglass layer on it.
The foam weighs so little it wont make much of a difference and it will add strength.

[ChazInMT]

Neil, give up on making the cap end at the top of the lift gate, this is NOT an an optimal aero design, it is far too steep and departs radically from the "Ideal" template which is discussed, have a 1 foot tall lift gate. Look at current design SUVs for inspiration. Do curve in the sides, about 6" each gradually, and only drop the top 7-8". And the trailing edge should be sharp, not radiused.

[ChazInMT]

T Vargo, tweek the sides of your V2 cap, you have fallen into the trap of creating a sudden change in air direction right behind the cab on the sides....do you see it? Just copy the line you have for the top (when viewed from the side) and put that line on the sides too, if looked at it from the top, otherwise, the top profile is GREAT. Keep up the good work. I like the flat area above the tailgate.

[NeilBlanchard]

In the light of the Aero Cap Thesis thread, I'll try to do a 12 degree main slope with the 3D side taper, and see how that looks.

How long and how wide is your bed t_vago? (I wish the Dakota SU model was available, but the GM one I got will do...) I'll adjust it to be the right dimensions.

[t vago]

My bed opening is 53 inches across by 63 inches long.

Let's see what you come up with.