Motorcycle helmet - duckbill or no duckbill?

[V8Pinto]

The "duckbill" on most of today's motorcycle helmets (assuming this is for venting?) has always bugged me.  I have heard that it is not an aero penalty but it sure looks like it.  I was looking through a few of the A2 videos and the AGV helmet with a more forward facing rider (rider looking forward vs. down at the tank) seemed to be the smoothest shape.  The AGV does not have a "duckbill" but does have a swept rear shape like the bicyclists use, though not as pronounced and thankfully without the spandex.

A traditional style helmet with a more round shape would seem to me to be the worst aero shape.  The AGV looks best, and the duckbills - ? 

Which style would work best with street style bodywork e.g. not a streamliner or fishtail bodywork. 

[V8Pinto]

Duckbill vs. AGV

[John Noonan]

Shane

Two different tests and two different results.....are you coming to El Mo next month?

[V8Pinto]

Noonan,

Yeah I noticed the AGV rider also has a hump on his neck.  Wish I knew which helmet to buy

I am skipping El Mirage next month to go to the Shootout which is the same weekend.  I will be running at El Mirage in November for sure.  I need to send you my mailing address for that newspaper.

[stobl]

Noonan,

Yeah I noticed the AGV rider also has a hump on his neck.  Wish I knew which helmet to buy

Think of the duckbill like a spoiler.  It helps to break the flow on the back of the helmet.  I use one on daily motorcycle riding and at 80+ it's definitely noticable vs my old round helmet.  The old style (at least on my bike) would try to pull itself up, off my head at speed.  with the duckbill, it no longer does that.  (This is in a "standard" bike riding position which has the air coming straight as my face, which amplifies the effect of the lift). 

As for the hump, that's a back protector.  It also does the nice job of providing a transition from the empty space behind your helmet to your back, helping the air transition off your noggin

[Cereal KLR]

We still use a spine protector with the hump. I don`t believe it was ever meant to be used as protection, but rather to do just what you see in the picture, aid the airflow.