wind noise / replacement screens

I'm 6' and in a relaxed riding position (arms bent), there is a lot of
turbulenced leading to a lot of wind noise. When I straighten my back
(so sit more upright) the difference in noise is significant - with
earplugs in it's really quiet.

When I bought the bike (Sprint ST 955) I ordered it with the touring
screen - but it didn't look right so changed it back to the origininal
within a week or two.

I am trying to work out what is happening with the airflow that creates
the turbulence - if sitting more upright reduces the noise then I guess
my head is moving clear of the turbulence. So I would not expect a
higher screen to be the answer - but ICBW.

 

Sound about right, but The Boy Carley is the man to answer this one.

 

If sitting normally gives turbulence around the head, then sitting up
moves the turbulence to closer to your chest so you are less aware of
it.

A higher screen will move the turbulence up and over your head when
sitting normally, but obviously if you sit more upright with a high
screen then you'll experience the turbulence again.

Or something.

 

Seems like a lower screen would be the answer then.

Or something.

What're double bubble screens supposed to do?

 

My guess is that they are supposed to create two bubbles

Looking at the design of them it looks like one bubble is low and wide,
for the rider's body, and the other taller and narrower, for the helmet.

I get a lot of wind noise/turbulence on my ST1100 (though a laminar lip
helps a *lot*), but on my 675, which has a double bubble, the airflow
is incredibly smooth and quiet. On the 675 my head is way up over the
top of the screen (I don't do that crouchy thing), and yet I don't get
any neck strain etc.

 

Indeed. We had them on both Thunderaces. The smaller bubble would
deflect air heading for the helmet, while there was plenty of air on
the shoulders to help support the upper body. Worked a treat.

 

You rang?

The tests we've done show the windscreen effect on noise comes from
the wake from the lip of the screen hitting the helmet. That wake will
be slightly above the screen height, depending on the angle of the
screen. To reduce the effect, you either want a high screen which
lifts the wake above your helmet, or at least above visor level, or a
low one which drops the wake below the helmet.

My bill is in the post.

 

The K4 thou was appalling with the standard screen. Since fitting an
Airblade double-bubble I haven't really noticed whether it's good or not
which, given how noticeable the wind was before, probably means it's
done the trick.

 

So it's just trial and error for Joe Public then? Based on the different
dimensions of the human form, differing postures, differing bikes....

 

Probably. I know that the Rizla Suzuki K3s that were raced in BSB were
also fitted with DB screens, cos I bought one from them for mine.
Certainly seemed to do the biz.