Aerodynamic Streamlining Template: Part-C

[drmiller100]

Originally Posted by jimepting

I can understand your impatience to get started, but your building effort will be long, and expensive. Why not try to understand the aerodynamic principles first.

if we keep doing things the same way we always have, we will continue to get the results we always have.

I started building things.

The first thing I figured out is the side template is about 1/4 of the opportunity.

Every aero device has ONE top. Every aero device has TWO sides.

If I fix something to take advantage of his template, I'm getting about 1/3 of the potential benefits. And tapering things from the sides can be a LOT easier if you choose your starting point.

But, my point is the numbers are misleading. And I believe the template is a disservice as I believe in the real world there will be big problems with separation.

Airplanes do the opposite of the template - they get a lesser angle the further you go back to ENSURE the air stays attached. Aero's template tells you to increase, and I think in the real world that will be bad.

I did not mean to be mean in my post. It is pretty important to understand the theory, as it leads to opportunities.

But it is also important to take the theory and apply it.

With the cancellation of the NW Vetter show, I'm taking a deep breath, taking out a few loans, calling in some favors, and am going to push for Carmel.

[NeilBlanchard]

Maybe you missed this part of this thread where we discussed the plan taper and how it can reduce drag significantly?

[kach22i]

Originally Posted by drmiller100

Airplanes do the opposite of the template - they get a lesser angle the further you go back to ENSURE the air stays attached. Aero's template tells you to increase, and I think in the real world that will be bad.

Could you post an image or to which illustrates this?

I'm just having a difficult time visualizing it.

[drmiller100]

Originally Posted by kach22i

Could you post an image or to which illustrates this?

I'm just having a difficult time visualizing it.

uh oh.
i was wrong on this one.

i was thinking planes had the tail extended, but it looks like most of the small planes just carry the taper straight on back.

Piper Pa-18 Super Cub - Alaska Bush Plane - Popular Mechanics

[ERTW]

Yes, 40 years of experience and knowledge are bottled up in the template. You can deviate significantly and get 8/10 results...few people have to knowledge to guide your design, and those that do won't do it for free. It's very high level and specialized knowledge - hence expensive. More kudos to Phil for releasing the template.

There are many ways to skin a rabbit (respect to my cat). The thing that drmiller said about moving the peak back is what Morelli did 10 years ago. At 0.25 there is "lots" of creative license. Aero is counter-intuitive and not easily grasped. OEM's super computers aren't adequate to cite an exact Cx - much less a casual glance at a picture. They still mete it out for hundreds of hours in the wind tunnel. Starting with an ideal body is easy. Starting with a real car is complex and no one can tell you what will work or not. I don't feel so dumb because top researchers can't either

It's either: study mech eng for a few years, make a bunch of prototypes and test over the years, or pay someone for their knowlege and skill if you want it now. Or accept whatever results you get.

George, like nasa said, aero is 3D. We don't know their full design intent OR their results. It's pointless to speculate. I also think you didn't line up the template properly with the lift body. My .02

[kach22i]

Originally Posted by ERTW

I also think you didn't line up the template properly with the lift body. My .02

Guilty as charged, but in my own defense the deviations were rather symmetrical which was something I was trying to point out.

Proper alignment:
Automobile 2 - Odds and Ends pictures by kach22i - Photobucket


Compare to first overlay:
Automobile 2 - Odds and Ends pictures by kach22i - Photobucket

[ERTW]

I didn't have a chance to consider that lift body this morning. I'm sitting here, having an espresso, and I can't take my eyes off it. I'm VERY intrigued by it. I'm trying to visualise airflow and I believe I know what they're doing. There may be a slight thickening of the boundary layer on the back side, and I believe they're using the streamlines that wrap around the body to fill in the wake, and make the fin effective (and the fin controls vortices). My mind is blown, and I have to fire up the ole CFD. Must do more research! Stay tuned

[ERTW]

lifting bodies are new to me. There's a pdf in post #2.

Lifting Body Design - The Rocketry Forum

the flat is on top, and it flies at a large angle of attack. I'll explore any tech transfer to ground vehicles (specifically my malibu

[aerohead]

Originally Posted by kach22i

Guilty as charged, but in my own defense the deviations were rather symmetrical which was something I was trying to point out.

Proper alignment:
Automobile 2 - Odds and Ends pictures by kach22i - Photobucket


Compare to first overlay:
Automobile 2 - Odds and Ends pictures by kach22i - Photobucket

For the 'Template' to function,nothing can be altered except where the truncation is made.The shape IS the premise for its performance.And the shape is chosen with great care in mind.
The curvelinear contour of the aft-body behind the position of max. body camber cannot be altered(*) in any way or you assassinate the boundary layer,the flow will separate and you're inviting a low base pressure and strong vacuum in the wake turbulence.
(*)The exception would be to 'relax' the contour,extending the rear even further back,but you must understand that the extra length is adding wetted area and the drag will begin to climb again do to the additional surface friction.
The same will happen with streamline sections.The drag minimum will occur at a length/width ratio of 3.92:1.Any shorter,or any longer and drag goes up.

[cfg83]

aerohead -

Here is a normal 1980's Trans-Am with a spoiler that appears to closely match your template :



Now, if we were to turn the Trans-Am into a "Limo Trans-Am", I would like to know how to apply the template. Assuming I elongate the Trans-Am from the point of max camber, would I (B) keep it in the same place? :



Or (C) be allowed to slide it to meet the spoiler? :



CarloSW2