Aerodynamic Streamlining Template: Part-C

[aerohead]

I photo-bucketed two new drag tables for ellipsoids and assorted geometric bodies tested in ground proximity at the same ground clearance.
They are with the streamline bodies above at #515 permalink.
Sorry about the double entry for the ellipsoids.I suck at computer!

[freebeard]

Maybe it's time to take all the prior files I've saved and put them in a folder called "old".

I'd like to update the figure in the middle of Permalink 514.

Can anyone populate an Excel spreadsheet with the sgtlethargic/3-Wheeler profile in section and the squircle in cross-section?

( x - a )^4 + ( y - b )^4 = r^4

[some_other_dave]

Originally Posted by freebeard

My problem is that in my head, Y is up-down and Z is nominally front-to-back. So I'm not sure I'm interpreting all this correctly. T=Z?

No, T has no direct representation on the graph. It is merely a quantity that gets varied to generate X and Y points.

-soD

[freebeard]

Ouch. The only thing I thought I got, and it was wrong. So T varies with (in this case) the color of the line?

How are Z and Y points ordered in the Zth dimension? Lathing? The formula in Excel only returns a 2D result?

[some_other_dave]

I believe we're both referring to the formulae in this post: http://ecomodder.com/forum/showthrea...tml#post362869

The colors of the line are generated by different "m" numbers. The "t" is just a number that gets varied to generate a single teardrop shape. It is the parameter that gets varied in the parametric equations.

You are always going to run "t" from 0 to ~6.283. (That's 3.14159... * 2.) Plugging each "t" in turn into the two equations provided produces the X and the Y coordinates for that particular curve. Look at the table from the spreadsheet, the first column is "t" in increments of 0.1, and the next two are the X and the Y calculated from that particular "t".

-soD

[ChazInMT]

Ya Know, I was looking through this again today wondering again why this isn't a sticky.

[freebeard]

Me too. But I was confused because it wasn't a Sticky. Maybe it got demoted, like Pluto is no longer a planet.

[MetroMPG]

Can anyone confirm offhand if the new "faster" template is the one currently in use in the overlay tool? Does that also need updating -- because we have quite a few members using the tool.

[aerohead]

Originally Posted by MetroMPG

Can anyone confirm offhand if the new "faster" template is the one currently in use in the overlay tool? Does that also need updating -- because we have quite a few members using the tool.

Darin,It's the original profile.
It appears to work with really 'slow' rooflines,as in vans,whereas the more recent contour would aggravate the situation.
Members probably ought to appraise both 'n see if one didn't better lend itself to a project compared to the other.

[ChazInMT]

I have analyzed Phils Gen II template and there are some niggling issues I think are worth mentioning in case they need to be corrected.

I'm afraid what may have happened is that in the course of scanning the new images in, they got their aspect ratios messed up, and what we're left with is a fatter/shorter version of the previous template.

With the new Car Template Dwg, It seems to have an aft body ratio of 1.7 d when before Phil was indicating 1.78d for this same ratio. If you look at this drawing I made using essentially the same shape as Phils teardrop, but shifting forward the breakover point to make the aft body 1.78, there is a bit of a difference.









Big Version Here to look at.



What the new template does in essence is shift the alignment point on top of the template back 5% from where it was before with respect to the 1.78 aft body ratio.

Here are the 2 different teardrops, one with 1.71, the other 1.78. The difference in this picture is not discernible.



In the Bigger version Here you can sort of see a difference.

And here You can see it when zoomed in.



If this is the intention to go with a 1.71 aft body ratio then who the heck am I, as a plebian compared to Phil, but to say anything other than "Let's Roll".

If this is not the intention, than I think I can easily generate a new very precise drawing to fill in where Phil is using a drawing board and pencil.

Here's the New (My longer version) template on the old "Car" to see the change.



Bigger Version of Same

Here is my analysis of the teardrop GenII drawing.



I hope this makes sense what I'm trying to point out, the difference seems to be right on the edge of significant since the new template as drawn deviates from the old by 5%. From all that Phil has said to this point, it seemed he wanted to simply tweak the shape making faster in the first 30% and flatter in the aft 70%.