Quote:
Originally Posted by Fat Charlie
Given the general size and shape of the interior of a generic car, the template seems to be a very predictable way of cleaning up the rear end. On any particular car you can get better results, but offering a template is much more constructive than shrugging and telling modders they're on their own and should simply design and test their own prototypes.
While citing a T-100 built to the template is nice, more relevant here is JulianEdgar's false horror at the Insight not meeting the template- and then his addition of a spoiler to his own Insight. Which seems to have brought it closer to the template...
What would be more valuable would be an explanation of how he arrived at that spoiler. What shorter or longer versions didn't do as well? Higher? Lower? How about a good profile pic to put against the template? Simply attacking the Holy Template while seeming to apply it isn't a good method, especially if your position is one of data and testing. Presumably the testing that went into that (beautifully done) spoiler had one experimental version that met the template, or perhaps the final version does. Either one of those facts would have been a much more constructive argument than the ones we got. |
Fat Charlie,
Excellent points. I agree "the template" a great starting point. Not an end all be all for every shape every time. If someone actually built the full 3d hemisphere vehicle I surmise it would be rather low drag.
The point of the T100 is that it is Aerohead's truck. Which Julian chose to put in his book. Before the internet discussions became contentious there was some level of mutual respect or the two would not have agreed for this to occur.
It is no secret that there are many low drag cars that do not meet the template. There are also many that do. Balancing drag, lift/downforce, cargo volume, etcetera must come into play in a design.
Julian goes into a few details in his book on the wing, but the point of the wing/spoiler (as explained by him in his book) is to increase downforce and straight line stability, while increasing drag only a little. This appeared to be his same goal with his full belly pan and diffuser, which as tested slowed his car down on hill decent velocity which he equates to drag, but decreased the ride height which he equates to downforce.
The question in my mind is why the insight needs all these modifications to increase downforce? Is there something about its basic shape that is causing lift? Would it have been better for the designers to pick a different shape, perhaps with higher drag but less lift? Studying various diagrams, local minima for drag typically do not align with local minima for lift. A choice must be made between the two.
One of the reasons I chose to use the AST-2 diagram to plan my modifications is that it is "safe" in that it is not at the bitter edge of the air "letting go" before I want it to. I can put a load in the truck/suv, drop the rear, make all the angles steeper, and it still works. Does that mean I could have made it more aggressive initially? Probably... but what them when I load it?
I do not understand all the drama about a suggested shape that is being offered free of charge on the internet. Not behind a paywall for $$$. Not mandated for new car design. Suggested. For free.