Drag Coefficients

[gasblender37]

I am looking for drag coefficients for the different bodies used in the modified roadster classes.
Thanks,
Skip

[Stan Back]

I'd guess that between 1923 and 1938 Ford (the most-popular make used) didn't do too many aero tests on their sub-sub-sonic roadster bodies -- which usually went down the road with a big top up.

And, as for use in Modified Roadsters, their aero probably depended on the shape of the builder's body fashioned from the firewall forward.  Hardly any two are alike.

If someone gave you a clue on their body, it probably wouldn't apply to someone else's same-year body -- and not be reliable to use for comparisons to other years only.

You've also gotta look at Streamliners -- where there are hardly any restrictions -- and notice that almost all of them are also unique.  (I'm not much help here, am I?)

[Milwaukee Midget]

I think the closest shape to a 30's style roadster that there has been any aerodynamic testing on would be the Lotus 7 @ about 0.7.

Anything you chose is not likely to be much better, and it will definitely have a larger frontal area, but for estimates, I think that number would likely get you close.

[jimmy six]

Even thou you may not like the look of them, get pictures of RO Yales Contrivance modifieds. You'll be chasing him anyway. To me they a bu-- ugly but I'm not in modified. One thing to consider is how the air leaves the design not only the hole it punches in the air...Good Luck..

[Dynoroom]

Al I can say is............


F R O N T A L

[wobblywalrus]

Somewhere on this website there was this list by Dr Mayf, or Prof Mayf, that lists all sorts of drag coefficients.  Maybe someone remembers how to get it.  I forgot. 

[4-barrel Mike]

Somewhere on this website there was this list by Dr Mayf, or Prof Mayf, that lists all sorts of drag coefficients.  Maybe someone remembers how to get it.  I forgot. 

Close! http://www.mayfco.com/tbls.htm 

Mike

[Jim Phelps]

Besides frontal area, the grille shell is important.  It is the most prominent front end feature.  In the applications I've seen, the grille area is blocked so it acts somewhat like a flat plate.  You want the minimum size and a round transition from front surface to side to promote flow attachment along the sides and top.  Some of the roadster grilles seem to have rounder edges than others.

[saltracer1]

in modified roadster (the class he asked about) I believe you can make any kind of nose you like, forward of the firewall. "streamlining ahead of and including the cowl (4.I.1) is permitted" 2014 rulebook

[Stan Back]

Back to square one -- he's looking for the drag coefficients on the various Roadster BODIES.

[jimmy six]

For Fords a 23 shoul be better than a 26/27 and on up......Contrivance is a 23

[Jim Phelps]

in modified roadster (the class he asked about) I believe you can make any kind of nose you like, forward of the firewall. "streamlining ahead of and including the cowl (4.I.1) is permitted" 2014 rulebook

In the words of Rick Perry: "Oops".  In the future I'll read the OP's post and rules book more closely. Thanks.

[Seldom Seen Slim]

In re:  reading the rulebook more closely:  Now you have a better idea of why I always suggest buying at least three copies of the rulebook -- station one by your easy chair, one in the shop/garage, and one on the back of the toilet.  Whenever you're sitting down or working on the race vehicle -- read, read, and then read some more.

[SPARKY]

I picked up my copy at the GG event and ordered 2 more when I sent in my test and tune entry the other day

yep the rule book controls our lives almost!!!!!!!!!

[Jack Gifford]

Re: the link in Reply#6. Does anybody know the legitimacy of drag coefficients in that table? The intro says they were derived by a "computer program"- whatever that means? It isn't clear to me what data they were based on.