Thanks Bob !
A generally good article, BUT ..... i don't have 10,000 hours on
Citation jets, however, I have owned a few aircraft that definitely
DID have a 'step' -- a few moments of inattention could cost you
15 mph cruise on our old Aeronca Sedan !
With the Rebel, we have found that it does take a certain amount
of power to get the advantage of reflex - my 150 hp. Rebel gives me
about 118 mph at 2,450 rpm with 2 notches reflex. Dropping down
to 2,350 costs me about 4 or 5 mph, but saves one gallon/hour !
Our 80 hp. Rebel would not pull reflex at all if heavily loaded on
a hot day - the nose went up, it slowed a bit, and just 'sagged' ....
if you were light, and used the 'step' technique of trimming out
a couple of hundred feet high, then gently pushing down to
cruise altitude, it would give an extra 6 or 7 mph. My thought was
that once you had overcome some inertia, and unloaded the engine
by increasing the speed slightly, some of the extra rpm stuck
without as much work .... could be imagination, but it cruised
at 97 mph every time I did it !
Our O-235-C2C Rebel could only pull one notch of reflex, sometimes,
and was still several mph slower than the 912. The other Rebel,
with a newer O-235-L2C (118 real hp !!) could easily pull 2 notches,
and gave 110 mph cruise consistently....
Jesse - I would give it a try - and use 2,450 rpm .... see if that
helps a bit. 96 KT seems a bit slow - what prop do you have ?
Mine is a Sensenich metal, 74 x 56 ... maybe a bit too coarse,
but not enough hassle to change at the moment ... maybe one
day I'll try dropping back to 55 or so ...
C of G position can have an effect too - mine is forward, about 8.5".
You are right that cleanup can really help - there's 10 mph to
be had just in the gear fairings, - maybe 3+ mph in the gap at the
top of the legs alone, ... and seal the gap in the middle of the flapperons !
You wouldn't believe the vortex that comes out of there !!
It's easy to put a strip of aluminum on top, wrap it under, cutting
the center into a finger to bend up & rivet to the top. This avoids
making a 'pocket' there, and clears the hinge. There are lots more !
Steve Sloan even has snap on fairings over his float attach lugs ...
and tapered balsa trailing edges on the stab struts ...
All his cleanups gave him 135 mph cruise on 125 hp !!!
Being glider pilots, we used wide electrical tape to seal air leaks
on the wing root fairings, and other spots.... not for everyone ! ;-)
--
......bobp
bobp@prosumers.ca
bobp@pattersys.com
http://www.Pattersys.com
http://www.amway.ca/BobPatterson
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On April 8, 2011 03:39:08 pm Bob Palmer wrote:
AVweb has a article that has a good understanding of induced drag in
this situation. It is a good description of the mechanics involved in
cruise airspeed set up. (Paragraph heading"Myth #1 --- Getting It "On
The Step"" <
http://www.avweb.com/news/airman/184274-1.html>. )
Although, it seems to me that she isn't aware of how it came to be
referred to as "on the step". My understanding is that the term
represents an easily understood example of induced drag where the floats
are designed by the use of a step to take advantage of the lift
properties of water and at a certain point allow for a significant
reduction in induced drag by reducing surface friction. (where the water
seperates aft of the step or being "on the step"). Something similar is
"being behind the power curve".
Bob.
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