New Vent!

Isn't there a lot of drag in a long, narrow tail boom that will restrict
the amount of air flowing to the tail? Also, how big of an exhaust
outlet can you put back there?

Also, I don't think the Boersmans graph shows pressure on the top of the
fuselage, where these outlets are located.



On 12/7/2010 8:40 AM, jcarlyle wrote:
Paul,

The non-technical write-up at DG on the Mandl air extractor
experiments backs up your position ( http://www.dg-flugzeugbau.de/mandl-absaugung-e.html
). But graph 7a in Prof. Boermans' paper ( http://frotor.fs.cvut.cz/doc/37.pdf
) suggests that the tail position is on a par with the pressure in
back of the wing.

-John

On Dec 7, 11:24 am, wrote:
An interesting gadget. However, wouldn't it be more logical to vent

nearer the rear of the fuselage, say in the lower tail?

Absolutely not... and this one of the major contributing factors to
why most glider's vent do not work. That's where designers have been
sticking them ever since Wil Shuman put one on his Libelle.

-Paul

Greg,

I think the major effect on air exiting at the tail would be the total
area of tail vent. My LS8 tail has a lot of vent area (can't measure
it right now, but it's got to be 4 times the area of the inlet at the
nose). Even at that size, the interior diameter of the tail cone at
its narrowest has a much bigger area.

As for Boermans' graph, it's the total pressure around a "rotationally
symmetric body". I really have no idea from this graph what the
pressure is on the top or bottom of the fuselage, but somewhere (can't
find it now when I want it) I've seen a 3D colored pressure
distribution on a sailplane fuselage that clearly showed the pressure.
Unfortunately, I can't say where it showed the least pressure
appearing.

-John

On Dec 7, 11:52 am, Greg Arnold wrote:
Isn't there a lot of drag in a long, narrow tail boom that will restrict
the amount of air flowing to the tail? Also, how big of an exhaust
outlet can you put back there?

Also, I don't think the Boersmans graph shows pressure on the top of the
fuselage, where these outlets are located.