Quote:
Originally Posted by Taylor95
That is a pretty good looking spoiler. Do the lateral fins make a noticeable difference?
Is that tape on the back or a light strip?
This is giving me ideas for a future Jeep project.
|
On the Insight the fins make a major difference to stability in crosswinds. The ability of fins to make this difference does, though, depend on the shape of the car. Fastbacks (and sedans) are particularly prone to crosswind wander as their lateral centre of pressure is often ahead of the centre of gravity. By moving area rearwards (as seen from the side) the centre of pressure is moved backwards, so that it coincides (or is even behind) the lateral centre of pressure.
On the Insight the presence of fins appears to lower drag - this is what my throttle-stop testing has shown. I think that this is because the trailing vortex development off the inclined rear pillars is altered - but that's just my guess. (That is, the fins alone - no spoiler).
The spoiler measurably increases pressures on the rear hatch (ie reduces lift) and does not increase drag. I was careful to make the spoiler so that the wake area is not increased over the standard car. (That is, the trailing edge of the spoiler is at the same height as the original trailing edge of the hatch.)
Lots of testing was done with different rear spoilers (including one that also operated pneumatically as an airbrake) and different rear fins - all just mocked-up from plywood, tape and plastic. The shape of the rear fins was found to be relatively unimportant but the shape of the spoiler was very important to getting best results.
The strip across the back is a full-width LED brake light.
I covered the development of the fins and spoiler in a series of videos on my YouTube channel - Part 7 is the summary: