Mintor

[David Lockhart]

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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> > # discussion-request at nsrca.org
> > # and put leave discussion on the first line of the body.
> > #
> > 
> > 
> 
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