t_vago's compound curve foam board pickup aeroshell

[MetroMPG]

Hmmm...



from: http://ecomodder.com/forum/showthrea...ans-15417.html

[t vago]

Originally Posted by KamperBob

Originally Posted by MetroMPG

These two shells illustrate something that I think is not adequately addressed whenever people think about aerocaps for trucks.

It's not enough to shape the cap so that air from the top travels downward smoothly. It must be remembered that air also travels around the sides of the vehicle, and so it is important to shape the cap so that the air travels back to the center smoothly.

I hope that tomorrow I can complete my idea of having a quick-release feature for this aerocap I'm going to make. The cap will have an aluminum base frame that will actually secure the cap to the truck. The foam frame will be securely glued to the aluminum base frame. The foam skin will then be applied on top.

[NeilBlanchard]

The shape at the tailgate would seem to be very important, too. The black Italian-designed unit appears to have a *rising* wedge on the sides? The cap I modeled has a downward curve on the sides:

[KamperBob]

Neil, I agree with your concern about those wedge shoulders.


Your design is interesting. I like your down-arch shoulders over the tailgate in terms of direction. I just hope flow will attach to it since that club-cab Dakota has a pretty short box. Do you have any plans to find out?

My truck box is 2-3 inches higher in the back than front over a length of 78 inches so ~2 degrees. That probably helped my previous hard tonneau with reattachment.

[BamZipPow]

I would guess the reason why the Italian cap has high rear shoulders is fer the locking mechanism. The single turn handle is under the middle hatch and uses the center locking system with rods that go to the sides.

[d0sitmatr]

I still say that is one of the sexiest aerocaps Ive seen.

[jamesqf]

Originally Posted by t vago

It's not enough to shape the cap so that air from the top travels downward smoothly. It must be remembered that air also travels around the sides of the vehicle...

This reminds me of an idea I had, which is to make some air from the sides flow through the bed. Have a NACA-style inlet forward of the wheel well, and louvers in the tailgate. Any thoughts?

[Varn]

I wonder how effective the tailbox design is on trying to recover some energy after the flat windshields and sides of the vehicle has created a ton of shear over the front and sides and hence turbulent flow from near the front of the vehicle. Perhaps the tail box needs to be made bigger so that the flow has a chance to reattach and stay attached. Similar to the Toyota truck that was for sale on ebay a few months ago.

[aerohead]

Originally Posted by euromodder

It's been mentioned before that you can get away with a steeper angle if the sides also taper in smoothly.

The streamlining template used is only 2D - the ideal low speed aero shape is an ice-cream cone (with only one ball of ice-cream ) where there are no sides, only taper.

The Aerodynamic Streamlining Template is based on a streamline body of revolution( Jaray's Zeppelins ) and is intended to be used for 3D streamlining as you can see on the T-100 and trailer project.

[KamperBob]

I have two different designs.

A) Split with a hinge in front. The top lifts up. The sides are wedges bulged slightly at the front. All convex - no concave.


B) One piece that slides back and tilts forward. The bottom gutter edges would have a couple inch fillet (hard to draw).


Notes:

• Both match cab shape at the front for smooth transition.
• Slopes are all less than 22 degrees from normal.
• Compound curvature using fiberglassed (similar to T's).

Which would you prefer and why?