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                           Allegro-List Digest Archive
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                     Total Messages Posted Sat 07/15/06: 1
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Today's Message Index:
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     1. 07:53 PM - Initial Setting of Prop Pitch  (Hugh McKay III)
 
 
 
________________________________  Message 1  _____________________________________


Time: 07:53:57 PM PST US
From: "Hugh McKay III" <hgmckay@bellsouth.net>
Subject: Allegro-List: Initial Setting of Prop Pitch

Gentlemen: I will soon be attaching the prop to my Allegro 2000 (built from
the Kit) for the first time. Since I have never done this before I need some
advice and guidance. Here is what I have:

Plane  Allegro 2000
Engine  Rotax 912UL
Gear Box Ratio  2.2727/1
Prop  WoodComp (3 blade),
Type  Klassic 160/3/R
Diameter  1600 mm/ 63 inches
Max prop rpm  2700 rpm

The WoodComp instruction booklet (second page) gives a general description
of setting the prop pitch. I have a Warp Drive Propeller protractor to set
the pitch in degrees. I need to know what would be the optimum degree of
pitch for good cruise speed. There are various opinions (11, 13 15.5, I
understand Bob Griffin operates his Allegro at prop pitch of 20.5)
concerning this, so I would appreciate input from those of you with
experience in this area.

The WoodComp instructions also state that during the test run the rpm (I
assume this is the engine rpm) at full throttle must be 6% less than maximum
engine allowed rpm (i.e. 5452 rpm if max allowed rpm is 5800). This would
give a propeller rpm of 2399. This is well below the max of 2700 rpm. At the
max engine rpm of 5800 the prop rpm would be 2552 rpm, still well below the
max prop rpm of 2700. Since the carbs on the Rotax engine are spring loaded
and set at the factory at full opening (full throttle), I assume this
setting gives the 5800 max rpm. Am I correct? If so, how do I set the
throttle to never exceed the 5452 rpm (6% less than max rpm) or is this
number just a conservative number to assure never exceeding the engine rpm,
and propeller rpm? I can set the throttle stop on the Allegro at the max
throttle opening easy enough, but dont know how to get the 5452 rpm
setting. I am somewhat confused on all of this.

If some one has the time I would appreciate a step-by-step procedure on how
to do this for the Allegro and, Rotax Engine.

Hugh McKay