4 blade Idle/Braking (4 blade prop/Zen 120/Webra 145-Greve pipe)

[Bob Pastorello]

Yep - to spin the 4 blader well, I had to get the Mintor 1.70 on it's Bolly
pipe.  And the weight of airframe plays a big part in how well the 4 blader
works in verticals.  I'm liking the downline advantages so much that it's a
good trade off for my heavier plane.
    With the Viper, at 10lbs, vertical is NOT a problem, 4 blader or not.
Next best is the 17 x 12 Std, followed by the 17 x 13N.  Both work well, but
if you have clearance problems....not so good.
    You may consider a three-blade.  I have used the Bolly 16.5 x 12 3
blader, and it WORKS -very well - albeit somewhat noisier in the air than
APC.

Bob Pastorello, Oklahoma
NSRCA 199, AMA 46373
rcaerobob at cox.net
www.rcaerobats.net


----- Original Message ----- 
From: "White, Chris" <chris at ssd.fsi.com>
To: <discussion at nsrca.org>
Sent: Friday, December 05, 2003 7:58 AM
Subject: RE:4 blade Idle/Braking (4 blade prop/Zen 120/Webra 145-Greve pipe)


> I finally tried a 4blade prop on my Zen 120/Webra 145/Greve combo
> (10.2lbs)..... Talk about slowing downlines and more constant speed
> maneuvering, the only downside I can see is it really cuts into the
vertical
> performance.  Thanks to all who advised me to try this, alot of windmill
> braking on the 4 blade, I could really see it when changing from the APC
> 16-14 to the 4bl 15-12:)  I need to try a 2 blade 17-10 or 12, but the Zen
> has a ground clearance concern.
>
> Chris
>
> -----Original Message-----
> From: discussion-request at nsrca.org
> [mailto:discussion-request at nsrca.org]On Behalf Of Dean Pappas
> Sent: Thursday, December 04, 2003 3:46 PM
> To: discussion at nsrca.org
> Subject: RE: Idle/Braking (was Re: Winter / Focus / Fuel/Electric.)
>
>
> Hi Doug,
> Sure ... the braking gets better at lower and lower RPM until the combo of
> RPM and airspeed stalls the prop airfoils, which are flying "inverted" at
> that point.
> The braking versus RPM curve at a given airspeed will have a hump.
> Regards,
> Dean
>
> -----Original Message-----
> From: Doug Cronkhite [mailto:seefo at san.rr.com]
> Sent: Thursday, December 04, 2003 4:39 PM
> To: discussion at nsrca.org
> Subject: Re: Idle/Braking (was Re: Winter / Focus / Fuel/Electric.)
>
>
> > I gather that you are saying as far as you can tell, the slower the
idle,
> > the better the braking? If so,  we are in agreement. The training manual
> is
> > wrong.
>
> This is correct to a point. As rpm goes lower and lower.. the drag starts
> to go down.
>
> I know just the guy to ask this stuff about too.. he's an aerodynamicist
> with gulfstream.. and also a Team JR guy.
>
> -Doug
>
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