Partial Bed Cover- '98 Frontier

[Bow]

Don't be sorry.. I'm learning!

The Sail Panels for my setup...

Probably make them extend back as far as the top Shelf?

Roughly follow the contour of the side of the Cab and taper them in 12 degrees from the cab...

Am I understanding this right?

I have some scrap aluminum, a shear, a bending brake, and very few morals...

[Christ]

Originally Posted by Bow

Don't be sorry.. I'm learning!

The Sail Panels for my setup...

Probably make them extend back as far as the top Shelf?

Roughly follow the contour of the side of the Cab and taper them in 12 degrees from the cab...

Am I understanding this right?

I have some scrap aluminum, a shear, a bending brake, and very few morals...

You lucky....

Yeah, that's the basic idea. Any ideal shape only becomes ideal after lots of tweaking, ya know? Even a brick can be aerodynamic with enough refinement.

[Bow]

Originally Posted by Christ

You lucky....

Yeah, that's the basic idea. Any ideal shape only becomes ideal after lots of tweaking, ya know? Even a brick can be aerodynamic with enough refinement.

Bricks are great... with enough power behind them...

[Christ]

Yeah... just ask my Ford.

As soon as I get it inspected, I'm gonna get some pics and put 'em in my thread along w/ a fuel log entry for it.

[aerohead]

Originally Posted by Bow

Don't be sorry.. I'm learning!

The Sail Panels for my setup...

Probably make them extend back as far as the top Shelf?

Roughly follow the contour of the side of the Cab and taper them in 12 degrees from the cab...

Am I understanding this right?

I have some scrap aluminum, a shear, a bending brake, and very few morals...

I wouldn't go over 7-degrees on the side.The air there is moving slower than that air over the roof due to the windshield dividing the airstream.
All curvature must begin almost unnoticeably at first,growing steeper as the flow slows and regains pressure.
This is the reason for the templates.They can be used for top and sides.

[Christ]

Originally Posted by aerohead

I wouldn't go over 7-degrees on the side.The air there is moving slower than that air over the roof due to the windshield dividing the airstream.
All curvature must begin almost unnoticeably at first,growing steeper as the flow slows and regains pressure.
This is the reason for the templates.They can be used for top and sides.

I think this is contradictory to my memory (which wouldn't surprise me, lately.)

Is the side flow slower, or faster? Logic seems to say that with a faster flow, the angle should be shorter, because there is more kinetic energy keeping to flow following a constant direction, which would suggest that a more shallow angle is necessary in a higher speed fluid environment.

Please, correct me if I'm wrong about this, or if you have some information that suggests otherwise?

Also - If we use the same teardrop template shown on an overhead view of the truck, where do we align the widest point? At the widest point of the truck, or at the aft edge of the cab?

Bow -
I'd listen to Phil before myself, if I were you. He's got ALOT more experience and years in the field.

[ccrider]

bow did you use a tank of fuel yet? you haven't entered any fuel logs in a while. i am curious if your results will hold on a full tank. i went through allot more work building a aerocap and i am not seeing the results you are.

[MetroMPG]

Another thought on side flow considerations: it will be dirtified (how's that for technical language!) by the side mirrors. Turbulent flow would suffer earlier separation than clean flow.

[aerohead]

Originally Posted by Christ

I think this is contradictory to my memory (which wouldn't surprise me, lately.)

Is the side flow slower, or faster? Logic seems to say that with a faster flow, the angle should be shorter, because there is more kinetic energy keeping to flow following a constant direction, which would suggest that a more shallow angle is necessary in a higher speed fluid environment.

Please, correct me if I'm wrong about this, or if you have some information that suggests otherwise?

Also - If we use the same teardrop template shown on an overhead view of the truck, where do we align the widest point? At the widest point of the truck, or at the aft edge of the cab?

Bow -
I'd listen to Phil before myself, if I were you. He's got ALOT more experience and years in the field.

Christ,this is a tricky one.Typically,due to a windshields slant,it will divide the airstream such that more air is channeled over the roof than down the side over the A-pillars.
The ave velocity over the roof might be 1.25-1.35 the rad speed because of the roof eruption.
Air blasting around the A-Pillar might have a local velocity near the side-view mirror of 1.65 road speed but overall,the flow down the sides is at road speed,'slower' than over the roof.
This is why attached-vorticity on fastbacks can be a problem if careful attention isn't paid to the greenhouse of the car.
Two airstreams colliding at different velocity will wrap up into vortical flow creating very high drag potential as this vorticity causes tremendous interference drag and also cannot transfer kinetic energy in the form of pressure regain at the tail,making for a wake of lower base pressure (greater form drag).
On the pickup,the roof has some downward curvature already,which the sides do not always share.The top air will have greater ability to feed the boundary layer of more curvature whereas the sides are just beginning their camber and are all velocity pressure.
As the template suggests,the further back you go,the more curve you can support,up to 22-degrees.
So the 'sail panel' area requires very subtle curvature to begin with or there'll be separation.The 'shooting from the hip' convention has been,keep it to around 7-degrees.
Using the template would be more accurate but it also requires compound curves,very resource intensive to fabricate.
The template would be aligned to match the maximum cross-section when viewed from above (plan view) at the point of maximum camber if it exists.
If top and sides begin at same point you get Kamm's roof.

[aerohead]

Originally Posted by MetroMPG

Another thought on side flow considerations: it will be dirtified (how's that for technical language!) by the side mirrors. Turbulent flow would suffer earlier separation than clean flow.

Hey,if others can get Ginormous in to the dictionary,I think 'dirtified' belongs there too!
As to side mirror turbulence,good call!
Can anybody figure out how single-task oriented I am?
Macro Phil!,not Micro!!!!!!!!!!!!!!