Re: Re: Good starting Penny plane prop pitch?

From: Nick Ray <lasray_at_gmail.com>
Date: Sat, 17 Dec 2011 10:11:54 -0500

I think what Joshua is talking about is when the prop blade deforms so
badly that under camber in a give blade element becomes over camber. In my
experience when soft balsa flaring props are set at two high a blade angle
a phenomena can occur where the blade element looks like a ~ (tilde) when
viewed from the side at the beginning of the flight.

Nick

On Fri, Dec 16, 2011 at 5:59 PM, Leo Pilachowski <leop_at_lyradev.com> wrote:

> **
>
>
> Okay, I'll bite. What is this "pitch reversal" for a flaring prop with too
> much static pitch?
>
> LP
>
>
> --- In Indoor_Construction_at_yahoogroups.com, jwfinn_at_... wrote:
> >
> > Mike, I form mine on a 4-5" cylinder using p/d 1.8-2.0. They seem to
> work best in that range. Lower and you risk blade tuck with a flaring prop,
> higher and you run into pitch reversal with flaring blades. All of the
> blade area is kept forward of the spar to maximize flare, and I use carbon
> spars to maintain impact resistance while still having it floppy enough to
> flare under the torque of a thick motor. Make sure your wing spars and
> motorstick are good and strong though, as those take a lot of punishment
> and need to be rigid so the model won't twist up and dive when it hits
> something.
> >
> > Flying F1D in low ceilings requires either heavy flaring, a good VP, or
> VD. I've never used a flaring prop on F1D and would think it to be pretty
> difficult, albeit easier to build. VD is pretty critical in construction,
> but has fewer itsy bitsy parts than VP, IMO.
> >
> > A good F1D can bounce off the ceiling, walls, etc just fine if you have
> strong wing spars and posts. One that won't survive hitting the ceiling
> also isn't likely to survive steering. Definitely build a quarter motor
> dummy, though, as you gain a lot of information from quarter motor testing
> and can make many test flights in a fairly short flying session. You also
> waste less rubber when the quarter motors break. Whatever you do, don't let
> them break on the plane. It always involves carnage.
> >
> > Good flying,
> > Joshua
> >
> >
> > --- In Indoor_Construction_at_yahoogroups.com, "mkirda_at_" <mkirda@> wrote:
> > >
> > > So I am starting with a Cesar Banks Novice Penny plane.
> > >
> > > I will initially be flying only in 20-40 feet range, so I am looking
> for recommendations for prop pitches.
> > >
> > > If I use the Propeller forming block Excel workbook, I enter in 12
> inch diameter, 2" block thickness. Not sure what I should look at for
> desired P/D ratio. Maybe 2.0 or 2.2?
> > > Will be using some leftover pink foam, so I could do more than one
> rather easily - Just not sure what I should try first.
> > >
> > > I should probably already ask about F1D for the same flying spaces
> too, with simple non-VP props...
> > >
> > > Thanks in advance!
> > >
> > > Regards.
> > > Mike Kirda
> > >
> >
>
>
>
Received on Sat Dec 17 2011 - 07:11:56 CET