REFLECTOR: Fwd: My Velocity setup

[Jim Agnew]

If you look at a lot of the new small blimps you will find a fan inside the
engine cowling attached between the engine prop hub and the prop extension. 
The fan is a flat many blade device that looks like the turbo fan on the front
of many of the large jet engines.  Obviously blimps don't have a lot of ram
pressure and spend a lot of time almost stopped.  This installation was on
Lycoming engines.

Jim

--- Jim Sower <canarder at frontiernet.net> wrote:

> Probably. I've seen such a setup on a Long-EZ and the guy swears by it.
> 
> 
> ouglas Holub wrote:
> 
> > Would it help to suck air through the NACA ducts if I put a fan on the 
> > prop extender just before it exits the cowl?
> > Doug Holub
> >
> >     ----- Original Message -----
> >     *From:* Al Gietzen <mailto:ALVentures at cox.net>
> >     *To:* 'Velocity Aircraft Owners and Builders list'
> >     <mailto:reflector at tvbf.org>
> >     *Sent:* Friday, December 03, 2004 10:54 AM
> >     *Subject:* RE: REFLECTOR: Fwd: My Velocity setup
> >
> >     My idea behind this is to scavange some of the flow that comes
> >     through the bottom radiator, across the bottom of the pan, and out
> >     the "suction slot". at about 18" from the center of prop rotation,
> >     it should also add to the suction the prop places on the cowl
> >     opennings. Well.. at least that is my idea, we'll see if it works
> >     out. I am hoping that I can get away without an oil cooler with
> >     that setup. No worries though, I have a backup to put an inline
> >     cooler on the #2 NACA scoop if I need it.
> >
> >     Keep in mind that the reduced pressure (“suction”) generated by
> >     the prop dissipates rapidly (exponentially) as you move away from
> >     the prop, so even a foot is a long way - and at cruise it is
> >     almost non-existent; you have to rely on dynamic pressure and
> >     whatever gradients are produced by the flow. Remember, the air is
> >     standing still, the airplane is moving. Some air is getting
> >     pushed/pulled downward by the airfoils, some is being pushed back
> >     by the prop, the rest is getting out of the way as best it can.
> >
> >     Al
> >
> >    
> ------------------------------------------------------------------------
> >     __
> >
> 
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=====
James F. Agnew
Jim_Agnew_2 at Yahoo.Com
Tampa, FL
Velocity 173 Elite Aircraft Completed & Flying