For the second day of testing at Barcelona, Williams bolted on the back of its FW38 a radical rear wing which featured a double-decker configuration and extra winglets.
Felipe Massa, in charge of testing duties on Wednesday, put the strange design to the task but insisted its primary use was to diagnose aero flux in order to better understand the balance of the current car.
"For sure this wing is not making the car quicker!" Massa said.
"This wing is there for us to understand some things about the balance of the car, in view of some things we're hoping to have to make the car better, to develop the car. But I think it was interesting for us to try it."
Indeed, under current regulations the wing would be deemed illegal, but teams are allowed to test irregular designs during in-season testing.
Williams, which also tried a few added modifications on its front aero appendix, through the radical aero designs, is evaluating its development direction for this year and for 2017.
"It was a day totally devoted to the aero tests we were doing for the future. Hopefully not for a too distant future, hopefully for earlier than we had even hoped for.
"We understood a lot of things that are important to help us develop the current car quicker, to make it better, especially in the type of corners we know we're losing out to compared to the other teams.
"No doubt it was an important day for the engineers and also for me, to be able to give very precise feedback of what I was feeling from inside the cockpit, both in low and high-speed corners. These two days were certainly aimed more at the engineers' work than to ours, of course.
Both Felipe Massa and Valtteri Bottas have struggled this season with the performance level of the FW38 in slow-speed corners, so yesterday's work will hopefully help the team improve in this area.
"The feeling was good, yes, but we tried a lot of things, a lot. Some of them didn't work, but the general feeling was very positive and we found things that were important to lead us in the direction we think we should be heading into to develop this car."
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