Ducktail spoiler
I can't see drilling an original trunk for a less than perfect reproduction spoiler. Is there anyway to mount without drilling the holes? Is there enough surface area between the fiberglass and the trunk lid for 3M trim adhesive? I realize that you'll still have dimples...
Nice story but I agree with your incredulity. Unless the spoiler somehow disrupts a major spot of aerodynamic turbulence, top end speed would only be hurt by an effective spoiler. You're exchanging drag for downforce.
So...a really effective spoiler might improve top speed by improving stability enough to affect driver confidence...or perhaps it could allow the driver to get on the throttle sooner from the previous corner? Unlikely though.
There's really nothing on the backside of the spoilers to mount them, the spoilers are hollow and even the fiberglass ones are basically just a single layer of fiberglass. If you're handy with fiberglass you could probably add some kind of additional bracing or mounting tabs on the backside of the spoiler. But as is there's nothing under there to attach them with trim adhesive or 3m tape. The only exception is the CNS spoiler, it has straps on the bottom for mounting it because it doesn't have the screw pockets. But that was is intended to be mounted with a couple of lag bolts. No kidding. That's what came with it. There still wouldn't be enough surface area for tape or adhesive.
As for the story, I wish I could remember where I saw it. I probably still have the info somewhere, but I could spend hours looking and not find it. It was completely anecdotal, like I said the entire thing came down to- they ran it at the track and got a 10mph increase in top speed on the straights. Which could mean
anything as far as why they managed to do that, could just be the "dumbo" effect, driver thought the spoiler would work better and he drove faster. Just installed some "matched tires" there days of thunder, haul ***.
Now, I kinda think that's probably not the case either. In general you're right, spoilers add downforce which adds drag, slowing the car on the top end but improving traction. Problem is, these cars are not aerodynamically well designed. So it's VERY likely the slipstream could be improved by a small spoiler like the DC ducktail. All you need for evidence is the Superbird's and Daytona's. First Nascar to hit 200mph, rear wing so big you could flip it over and use it for an ultralight aircraft. How the heck did that giant spoiler make the car faster? The original body was so aerodynamically unstable that the giant wing represented a significant improvement.
