Do you guys have some reason for using Cd numbers less than 0.3 for a lakester? Back in the fifties, Don Francisco said in a Hot Rod Magazine article that lakester numbers range up to 0.9- and over the years, I've found no reason to dispute it.
Hard telling what they are without either wind tunnel numbers or knowing what your true RWHP is for a given speed along with the actual frontal area, but I agree that under .3 for the car as a whole is not realistic and I just assigned that to the body itself..
I'd think a tank as it comes off of a plane should be near .1 or below all alone, but that is before we start messing with them and then adding suspension and inlet tracts and exhaust and wheels and tires. The spread sheet I use....
... lets you separate the tires from the body and I assigned a Cd of about .5 for the tires and assigned .25 for the body and parts hanging off of it. It looks like I was maybe a little small on the tire frontal area. I felt they did a good job on the body and got the axles, and tie rods and stuff pretty much in line with each other so felt .25 wasn't totally unrealistic for the body by itself. Guessed at the frontal area also. Came up with about 770 rear wheel Hp so probably at least 900 crank HP and it sounds like the car might not of made that much.
I'm going to lengths with my lakester to keep all of the stuff from the body to the tires/wheels enclosed in a fairly good aero shape and getting the tires/wheels at least 12 inches from the body so that the body should stay pretty clean in the air vs. having the tires/wheels up against it. Both approaches have achieved records though.
Was wondering when someone would notice that. We use Cd=0.6 for our lakester. Derived the number from prior runs. Formula 1 cars are around 0.75!
Is there a picture of the car online? I'd like to see it. If you use the .6 Cd and know RWHP numbers does it then run the mph that would be expected from those numbers. .6 doesn't really surprise me for some lakesters if you consider the tires and wheels in that but it still seems a little high. Finding tire/wheel Cd numbers is hard. I've seen anywhere from .2 to .6 and I usually use about .5 if I'm guessing. The tires/wheels probably account for 60%-70% of the drag on a lakester if the body is clean and the parts between the body and the tires/wheels aren't terrible.
If I assigned a .6 for the car as a whole and upped the total frontal area to 13 sq. feet (9 for the body and 4 for the 4 tires) then I came up with 1189 RWHP and I doubt they had that, but maybe???
Door slammers can easily have a lower Cd than a lakester, but we can make our frontal area less than them
. Formula 1 cars and dragsters are terrible, but do what they do for a reason,
Sum
