Which body & fender package is more aerodynamic at say 60 mph? A 1928-29 Coupe or a 1930-31 Coupe, ...and specifically why (i.e.: what part(s) makes it dirty or cleaner between the two)?
I would guess that the drag coefficient is roughly the same on the two, but the early body might be slipperier due to smaller frontal cross section. Either one has more drag than a brick, especially with fenders attached.
I've wondered the same thing. The 29 fenders come down further than a 30. I would think that the 29 fenders have a higher low pressure area created from the fender travelling down the road. The shorter 30 fenders would have more air underneath them so there would be less of a low pressure above the fender. Maybe it's not as much a question of drag, but the whole front end "lifting" and losing steering control at high speed (~160km/h).
The 30-31's are less sharp in their radii, being broader but creating less pressure differential. The cowl area is improved from the step feature in the 28-29. Brick is apropos as the windshield pushes like no tomorrow above 70mph.
brent.... are you allowed to do any "work" to the fenders? maybe extending the front like later fenders would help to get the air around them and keep from the "scoop" effect? whats the rules on the top? chopped? slant window cowl? roadster with a hard top?(one existed in the past, red and white i believe?) what about tires? getting the tires as close to the fenders would help cut down on the air actually hitting the inside of the fender and getting them out toward the outside as far as possible with wheel discs i would think would help push the air around the fenders how about some strategically shaped "oil-water-gas" cans on the running board to direct air around the rear fenders? and make sure your door handles arent sagging good luck with it brent Zach
I've wondered about this all my life, keeps me awake most night's.. Just one of life's mysteries.. You need a Lambo
One way of getting some numbers is readily available...problems would include equalizing tires, drag in gear train, and the probable aerodynamic changes caused by hight of fender to wheel from spring sag... Seems like a year at your place should give you access to a number of coupes...so equalize the above factors as much as possible and do some coast-down tests. Runnemup to a standard speed...shift into neutral...measure time and distance of coast-down. Not perfect due to the number of possible variables, but cheaper than building a wind tunnel...
Building the wind tunnel?? Chicken coop with end walls and chickens out, surplus 3310 motor and propeller, wire throttle to "combat emergency" setting, chain the car to your bathroom scales. A snap. The coast down is a legit engineering test too, basically just time or distance for dead stick coast from X MPH to Y MPH. Obviously it measures all drag together, so main need is to get tire and geartrain drag as equal as possible. I think it gives a reasonable test of what amounts to negative horsepower...
One of many sites giving high and low tech approaches...you will get results under "coastdown test" and "coast down test" http://www.hpv-klub.dk/artikler/coastdowntest/default.asp
Note from that the two schools...level test is basically a coast to stop, hill test adds in influence of gravity...
Yes he did ...with a borrowed engine. --and in 2006 and 2007 he did ??? Not to take anything away from Pete because he already has a car built --and I currently don't-- but for some reason in my mind, a 28-29 Coupe seems like a better choice. One doesn't know whether he started with a 30-31 because he already had one, ...or whether he felt there was an advantage. I don't know why I think the '28-29 would be the choice but maybe it is because you seem to see more '28-29 roadsters over '30-31 roadsters. If the roof-line is similar between the two coupe bodies (other than the width) then the nod would seem to go '28-29. I might further say that Pete's record has no "immediate worries" from my camp as I am planning on Maxton since that is on my side of the world. Might even do a roadster in lieu of the coupe So confusing. Already have a ****nal of V4F and V4 banger bullets to run. Just tired of traveling 400+ miles to go run with A.A.R.A . Kinda ready for a new chapter and a different challenge I suppose. Again, thanks everyone for the help! I appreciate your thoughts!!
The pictures I had were from 2004, that 98 was his best speed that year. His record then was around 94 mph. According to this years record book in 2006 he moved it to 107.778 I don't recall even seeing the car this year. My gut feeling is in agreement with you that the 28/29 seems like it should be slipperier. I have a 28 roadster, my dad has a 30. my roadster definitly feels narrower than his. I've never made measurement to back up that feeling though. I do also remember setting a 30 front fender on my car back when I built it and seeing that it fit wider than the 28.
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