prop repitching

[NSRCA]

Hi guys,

Just a note on this to be careful that you don't drop a blade doing it -
it's easy to end up with a each blade tracking differently, which
effectively throws the prop out of balance.  The basic technique Dave
mentions is the same as we use to repitch the Bollys (although we use a
quench bath, kevlar gloves and bolt the prop to an aluminum bracket/table
jig).  When you're done measure on a flat surface the distance from each tip
to the surface - it must be exactly the same.

I've never tried this on an injection molded prop (APC, Clubman, MA) and it
won't work for a hollow prop, but on the epoxy composite props it works
great.

Wayne Powell
Bolly Props North America
http://www.BollyProps.com
1-877-WEFLYRC

> -----Original Message-----
> From: discussion-request at nsrca.org
> [mailto:discussion-request at nsrca.org]On Behalf Of David Lockhart
> Sent: May 15, 2003 8:11 PM
> To: discussion at nsrca.org
> Subject: Re: RE: Mintor
>
>
> Wojtek,
>
> What you need is -
> APC prop
> Heat gun (2 is even better)
> 2 dry thick wash cloths
> 1 wet thick wash cloth
> Prather Pitch gauge
> 2 pair large channel lock pliers
>
> I heat the prop blade close to the hub, and then hold onto the prop at
> the hub with one pair of pliers (using a dry wash cloth to protect the
> prop) and then grasp the blade outside of the heated zone with the
> other pair of pliers (and wash cloth).  If the blade has been heated
> all the way through, a lot of pressure is not require to twist the
> blade.  Recheck the pitch after twisting, and if it is correct, wrap
> the wet (cold) wash cloth to cool the blade.
>
> I've changed the pitch on an APC by as much as 3 pitches with no
> adverse effects.  When repitched as described above, the pitch remains
> stable and I have several props with 500 flights on them and some are
> 10+ years old at this point.  I don't remember exactly when, but I
> believe Pappas published a description of re-pitching APCs in his
> column in Flying Models several years ago.
>
> Dave Lockhart
>
>
> ----- Original Message -----
> From: "Tomanek, Wojtek" <tomanekw at saic-abingdon.com>
> Date: Wednesday, May 14, 2003 7:30 am
> Subject: RE: Mintor
>
> > Dave
> >
> > How do you depitch a prop??
> >
> > Wojtek
> >
> >
> > -----Original Message-----
> > From: 	David Lockhart [DaveL322 at comcast.net]
> > Sent:	Tuesday, May 13, 2003 8:22 PM
> > To:	discussion at nsrca.org
> > Subject:	Re: Mintor
> >
> > Given all other parameters are similar (airfoil, aspect ratios,
> > etc),
> > the 3 blade is never more efficient than an equivalent 2 blade.
> > More
> > little wings are not as efficient as fewer big wings.  I'm sure
> > one of
> > the regular contributors to this list could provide more details
> > in
> > better form than I.
> >
> > So far as the 18-10 - a 170 isn't needed.  Any of the current 140s
> > on a
> > pipe should turn the APC 18-10 at 8000 - give or take.
> >
> > For the 3 blader - I've been running an APC 15.75-13 depitched to
> > 11.25
> > for about a year now (some may remember seeing it on my plane at
> > the
> > 2002 NATs, but you probably didn't hear it!! <G>).  RPM on the
> > ground
> > is typically 7,700 (slightly rich)- OS140 EFI, Asano pipe and
> > header,
> > 20% S+W fuel.  An APC 18-10 turns about 300 more (slightly rich)
> > and is
> > definitely louder - but still quiet compared to many of the setups
> > currently used.
> >
> > I don't remember the exact numbers, but I think the stock 15.75-13
> > was
> > about 500-600 RPM more load (than the 15.75-11).
> >
> > Regards,
> >
> > Dave Lockhart
> >
> > ----- Original Message -----
> > From: wgalligan <wgalligan at cnbcom.net>
> > Date: Tuesday, May 13, 2003 4:43 pm
> > Subject: Re: Mintor
> >
> > > On the prop thing on the 3M 1.70. Bigger engines dont like to
> > spin
> > > as fast and usually are designed to develop more torque in a
> > > certian range.  SO if this is true wouldnt you want to prop this
> > > engine to be more usefull in the 4000-7800 rpm range?  I'm sure
> > > this engine will be capable of turning an 18x10 prop but then
> > the
> > > tip speed will go sonic.  What 3 bladers out there do you
> > > experienced guys think would work best in loading the engine and
> > > giving the best performance?  How does one determine dia. and
> > > pitch to load this size of engine? I think taking advantage of
> > > this engines midrange transition and torque will be key in
> > making
> > > it perform.  Much like the 4c guys enjoy now.
> > >
> > > While on the subject of 3 blade props...  where does the
> > efficency
> > > of a 3 blade come in (rpm) or drop off?
> > >
> > > Cant wait to get mine bench run and flying.
> > > Wayne
> > >
> > > > Hi Ihncheol,
> > > >
> > > > The rpms/props may look similar, but the 170 was noticeably
> > more
> > > powerful in
> > > > the air.  The 140 runs VERY smooth and has good power.  The
> > 170
> > > shakes a
> > > > little more at idle, but has more power.  With a 20 oz tank I
> > > can fly 2
> > > > masters patterns and a little more (170).  The engine will
> > give
> > > a burp when
> > > > the tank is about out.  The 8100 rpm for the 170 might not
> > make
> > > it the rpm
> > > > king on the ground, but it seemed very powerful in the air.
> > > >
> > > >
> > > >
> > > > As for how rich the engines are running?  I don't know.  I use the
> > > > "pinch-the-fuel-line" technique for finding the peak, then I
> > > back it off a
> > > > few clicks, then I fly it.  If it sags on uplines, I land and
> > > richen it 1
> > > > click and try again.  After doing using method, the ground
> > > running was in
> > > > the 8100 range.  I would not characterize them as running
> > rich.
> > > If they
> > > > are, the twin plugs is helping to hide the signs of it which
> > > would usually
> > > > show up in transition.  I played around with it this weekend
> > and
> > > went from a
> > > > "rich" midrange to what I thought was about right.  If it
> > gives
> > > a loud pop
> > > > with pushing from inverted flight while adding power, the
> > > midrange is too
> > > > lean.
> > > >
> > > >
> > > >
> > > > Jim
> > > >
> > > >
> > > >
> > > > -----Original Message-----
> > > > From: Ihncheol Park [PatternFlyer at msn.com]
> > > > Sent: Monday, May 12, 2003 9:15 AM
> > > > To: discussion at nsrca.org
> > > > Subject: RE: MINTOR
> > > >
> > > >
> > > >
> > > > Jim,
> > > >
> > > > I have a few questions,
> > > >
> > > > 140 turns APC 16.5 x 12W @ 8350
> > > >
> > > > 170 turns APC 17 x 12 @ 8100
> > > >
> > > > both with 15% Cool power?
> > > >
> > > >
> > > >
> > > > How rich are the engines running?
> > > >
> > > > I am not sure how the two props are loading when use on a same
> > > engine, but
> > > > the output figures sound like 140 is running better.
> > > >
> > > >
> > > >
> > > > How about fuel consumption of both engines?
> > > >
> > > >
> > > >
> > > > Thanks,
> > > >
> > > >
> > > >
> > > > Ihncheol Park
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > >
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> > >
> > >
> >
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> >
> >
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