Aeromoding my truck ('95 Chevy S10 pickup)

[BamZipPow]

Originally Posted by aerohead

Don't forget that a cab-wing/half-tonneau can perform almost as well as an aeroshell.It's wind tunnel proven,both in model and full-scale testing.Good bed utility aspects as well.

How would a full tonneau and cab wing/ducktail perform?

[bennelson]

I imagine it would perform pretty well.

One of my objectives though is to have something that is lockable, keeps the rain and snow out, and has enough height.

I have noticed several times where I was transporting gear that I had the leave the partial tonneau off because what I was carrying was just a little too tall.

An aerocap would be lockable, weatherproof, and have the interior cargo height that I need.

Some sort of sidewings would be pretty slick for the times that I carry a motorcycle in the bed of the truck.

[aerohead]

Originally Posted by BamZipPow

How would a full tonneau and cab wing/ducktail perform?

I never tested a full tonneau so I can't share anything empirical.
My gut feeling is that it must be an improvement as the length of the wing provides some pressure regain before separation ( good!) and also 'tailors' the wake behind the cab,perhaps a benefit to the locked-vortex circulating above the cover.
When Gilkison had the T-100 he ran the 1/2-tonneau with cab wing and registered the numbers as promised by Texas Techs R&D.The full cover might cost some efficiency but you would have complete security and weather protection for all your gear,so maybe not such a penalty in the bigger picture.
P.S. The back portion of an aeroshell attached to a half-tonneau was tested by us for good effect.If memory serves me,we picked up 8% mpg HWY all by itself ( no wing ).I have photos of this and will post when I can.

[KamperBob]

I think I read somewhere that a half tonneau outperformed a full tonneau. Do we already have a thread on that here somewhere? If so, a convenience link would be great.

Did I recall correctly that some automaker (GM?) patented the half tonneau?

Cheers
KB

[COcyclist]

Originally Posted by bennelson

i have been using a real simple half-tonneau on the truck much of the time.

The only trouble with it is that it doesn't keep the rain and snow off the other part of the bed!

I work with enough valuable tools and gear that I sort of need some type of locking cap. If I am going to have a cap anyways, I would like a cool aerodynamic one!

I just started reading this thread and I have struggled with how I might do this on my seldom driven S-10. I need to keep snow, rain and leaves out of the bed. Inspiration! What if I were to build a telescoping tonneau? The front half could slide back over the rear for access to the bed or tall items. The back half could be mounted to the bed rails. This would leave me the visibility and much of the versatility of the truck and still shed rain and snow. I'm thinking coroplast over a contoured OSB framework.

I hope you find the time do do your fiberglass top but life gets in the way sometimes

[bennelson]

Originally Posted by COcyclist

. Inspiration! What if I were to build a telescoping tonneau?

Sounds interesting!

Can you make a sketch?

[aerohead]

Originally Posted by KamperBob

I think I read somewhere that a half tonneau outperformed a full tonneau. Do we already have a thread on that here somewhere? If so, a convenience link would be great.

Did I recall correctly that some automaker (GM?) patented the half tonneau?

Cheers
KB

KB,we got into this a while back and I thought I posted on it,don't remember.
GM did receive a utility patent on the 1/2-tonneau,and within the patent they provide a metric of delta-Cd vs tonneau percentage coverage from 0-100%.
The 1/2-tonneau does demonstrate the lowest drag for their test truck.
A Gale Banks modified S-15 set an LSR of 211 mph at Bonneville,using the 1/2-tonneau along with some other tricks,sporting a CD 0.31,lower than Corvette of that time period.

[cyclist916]

I've contemplated an aero cover for a pick-up also, but it seems to me that the angle directly from the top of the cab to the top of the tail-gate is too steep.

[aerohead]

Originally Posted by cyclist916

I've contemplated an aero cover for a pick-up also, but it seems to me that the angle directly from the top of the cab to the top of the tail-gate is too steep.

You could limit the slope to respect the geometry of your trucks bed,not allowing it to go as low as the top of the tailgate.
In a way,you'd have more usable space inside and a nice vertical rear windshield back there.
And if you do some plan taper,bringing the sides in,you might gain back some that your losing in elevation.

[KamperBob]

Phil, thanks.

Cyclist916, here's my understanding. It's not just angle. Smooth flow is key. For most trucks I suspect a simple wedge from cab to tailgate is better than open box by stuffing the wake. It still leaves room for improvement via sudden change of slope. That discontinuity in shape detaches flow. Arch the lid for clean transition to keep flow attached. Keep the front tangent to the cab. On a long bed the top might be able to arch all the way down to the tailgate without detachment. On a short bed the top may have to stay somewhat higher than the tailgate. It really depends on the truck. Other factors include shape of the cab, hood and grill, plus how well the aerocap fits the cab. The cleaner the transition, the better. Tuft testing of a cheap prototype should reveal max curvature for your truck. Also round edges for smooth transition between top and sides to minimize vortices. No one design (shape, curvature, angles) can be "best" for all conditions (wind speed, direction) so generous trailing radii make it robust, forgiving, tolerant. This is my understanding. It may not be perfect. Hopefully others with more experience can correct these guidelines. Good luck, and please keep us posted on your project.

Cheers
KB