The 2-Part Aero-Body Concept

[kach22i]

1A. .....dashed line,from cowl to nose,in between fender blisters is basically straight.

1B. I'll arc that plane, generous radius at the top.

2A. .....11.5% of canopy length.

2B. I'm at about 20%, but will try to get a little more length.

3A. Also,to minimize interference drag where the canopy and body actually join,a fillet which is 4-8% of canopy length (chord ) is best.

3B. I'm sure that if I were working in clay that I'd already have something like that built in there. I'll probably use some colored caulk on the next model.

Canopy/blister is 15 inches long if I extend a straight line, would like to get 16 inches. 1/10 of 15 inches is 1.5 inches, and half that or 5% is 3/4" R at this scale of 2"=1'-0".

I don't see myself adding more than half of the minimum recommended radius, on the model, this comes out to 3/8" R. or just over 1/4" (reaching glazing sill height).

Radius on other corners or plane changes will be about half of recommended radius as well. I'll explain in more detail later, these will be based on using the Monopan honeycomb material and their factory details.

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4A. I like the leading edge plan view radii and plan taper at rear.Her heartbeat is strengthening![/QUOTE]

4B. Thanks, and I do realize that the greater these radii are the better they will be for aero, but I'm also attempting to keep the overhangs to a minimum.

EDIT:
Just a nice image which I didn't know where to put...........
http://forums.pelicanparts.com/off-t...tures-703.html

[kach22i]

I'm through with this model, it will become another dust collector.

Finished sanding the removable targa top, not going to fret over getting a perfect fit, or even a close fit for that matter.

The next model will be better in every way. Less learning and experimentation though. I'm not a fan of finished models, I like study models which serve a design purpose and not a presentation or marketing purpose. However I would love to do one of those one day or have one printed out on one of those fancy 3D printers.

Here is the roof, not exactly quite the right shape, but I learned what I would and would not do next time.

Industrial Design - Transportation pictures by kach22i - Photobucket

[kach22i]

I stumbled upon a car in the same color as my model which reminded me of where I left off on this design. An interesting comparison of the rear?

Industrial Design - Transportation pictures by kach22i - Photobucket

[kach22i]

Originally Posted by kach22i

If I were to pick a race car to model after (or be inspired by) I would like to know the Cd, hopefully without the massive rear wing and a few of the other aero down force creations which I would not need on the street.

Banned Mooncraft GT300 to become road car
By Sam // January 13, 2012
Banned Mooncraft GT300 to become road car | Racecar Engineering

UPDATE: 05/07/12

I find that my current set of sketches follow the Mooncraft pretty closely, intentional or not. I'm also taking great liberties with the template by breaking it down into parts and pieces. This is my current level of thinking, and it's directing me into a more complex solution, one where I can foresee my next model being built out of clay. I'll have to try that waxy professional clay, never used it before.

Industrial Design - Transportation pictures by kach22i - Photobucket

[kach22i]

Another liberal use of the aero-template.

Industrial Design - Transportation pictures by kach22i - Photobucket

[NeilBlanchard]

The last image in the previous post (#54) is the most accurate one.

[kach22i]

Originally Posted by NeilBlanchard

The last image in the previous post (#54) is the most accurate one.

Thanks Neil, but would you be able to recommend a good source for the type of template scaling I'm currently exploring?

Seems like there are minor references here and there to Hugo (wheel fairings, attachments, mirrors and so forth), but nothing "whole scale" or even including the canopy.

[NeilBlanchard]

The "ideal template" is precisely for the whole car. A car pushing it's way through still air needs to be considered for the car in total. Once the front of the car has started to move air in all directions, any subsequent portions of the car that come along have to be considered in the context of air that is already moving in one direction or another.

So, no one piece of the car is standing alone, and the template has to be for the whole car; not individual pieces of it. Hucho is a good place to look at how specific areas work in relation to the whole.

I'm a little unclear on your question -- is my answer making sense?

[kach22i]

Originally Posted by NeilBlanchard

Once the front of the car has started to move air in all directions.....

I'm a little unclear on your question -- is my answer making sense?

1. RE: The first part of the partial quote above;
Yes and no, you actually took on another topic which has frustrated many when using the template, the front part of the car and the wild stuff which can happen even before we get to the all important tail end (everything past the zero mark or high point of roof). Good answer, I'll try to save it.

2. RE: The second part of the partial quote above;
Let me try to clear up uncertainty about question, I am trying to get a feel for how the air moves, and suspect that for the most part, the air don't give a squat about the scale of the template being used.

It is as you pointed out above Neil, the air is just as subject to the stuff happening up front as it is at the tail. Which in most regards goes counter to the traditional template debate where almost everyone agrees that only the rear part really counts.

3. My Theory; I think there is a point where the mass of air being pushed and moved will just move as a mass, and not trickle and flow over every surface like water would. Where exactly this limit of detail verses mass is set is a mystery to me.

I think I can teardrop each wheel bump and the canopy to good affect, but it will have more actual surface area than a large single simple form resembling the template.

There might be a happy medium or compromise in real life where both approaches can meet at an optimum setting. This is the question, where is that point? I'll sketch something up, a picture is worth a thousand words and all that.

EDIT:
I screwed up the top sketch, the tail does not go up, just imagine it fits the template in plan and elevation.
Industrial Design - Transportation pictures by kach22i - Photobucket


It's logical to say for instance; if I install rear view mirrors or budding out headlights that I should attempt to teardrop them somehow, right?

Therefore every little item right down to tear dropping the aerial antenna in section should be addressed, right?

A minimal aerodynamic skin over a four wheel go-kart of a car would different than the template, right?

It's the "how and why" that I'm pondering right now.

[Sven7]

To expand on Niel's comments-

Just as cars and planes differ in design because of ground effect, you will have consider the rest of the car when designing the wheel bumps, as the greenhouse alters the airflow and you cannot count on canned shapes to solve it for you. Jaray and Sason used the "2 part body" you drew for a reason- it's easier to manage and simpler to produce.





Do yourself a favor and radically simplify the design. Even the "Goddess" was designed around the simplicity principle.



Though it did end up drawing on Kamm's work. (Your last picture in post 52 reminded me of the DS's greenhouse)



Essentially, the more things sticking out from your car, the harder it is going to be to tune them for efficiency. If you really wanted to do that I would suggest making a third scale model and tuft testing it at high speed (I believe you'd have to do 40mph for 1/2 scale and 80mph for 1/4, so something in between those). You'd spend at least a couple hundred dollars if you wanted it to be clay (Check out Russ Simpson in Warren).

Anyway, yeah. Simplify this thing, and teardrop it in plan view too.