Today's Message Index:
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1. 05:59 AM - Re: Re: Kitfox 2 (Malcolm Brubaker)
2. 08:37 AM - airspeed (Ed Gray)
3. 10:12 AM - Re: airspeed (Michael Gibbs)
4. 07:07 PM - Re: Kitfox 2 (mikeperkins)
Message 1
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i agree with walter analog tack are very un reliable.=0A-- prop tweking
is almost an art in its self.=0Amal=0A=0AMalcolm & Jeanne Brubaker =0AMich
igan Sport Pilot Repair =0ALSRM-A, PPC, WS=0AGreat Sails - Sailmaker =0Afor
Ultralight & Light Sport=0A(989)513-3022=0A =0A=0A________________________
________=0A From: dave <dave@cfisher.com>=0ATo: kitfox-list@matronics.com
=0ASent: Wednesday, November 23, 2011 8:48 PM=0ASubject: Kitfox-List: Re: K
=0A=0AWalter,- how do you know that you are actually- turning 6100 rpm
?=0A=0AOnly tach I would trust is a tiny tach- ==analog ones are not
dependable.=0AI have a 2 here- --- 75- cruise -- not faired- but op
timized prop. this is on- 21"- tires=0A=0Amy- mod 4- 58=0A=0A2 crui
se- is- 90 to 92 on- kingfox- tires- 21"=0A=0A--------=0ARealtime
Kitfox movies to separate- the internet- chatter from the truth=0Ahttp
://www.youtube.com/user/kitfoxflyer=0AHundreds of Kitfox Movies =0AMost vie
wed Kitfox on youtube=0AMost popular on youtube=0AHighest rated on youtube
=0A=0A=0A=0A=0ARead this topic online here:=0A=0Ahttp://forums.matronics.co
===============
Message 2
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Walter, my Model II , 582, GSC cruises at 77 or 78 at 5500. All struts and
gear are faired and I have the radiator scoop. My tail feathers are
enlarged to Mod. 4 Speedster dimensions but no wheel pants. Try the
fairings and radiator scoop and you will see 10-15 mph increase. Its not
meant to be fast, but why not clean up some of the drag. I also have the
leading edge cuff from Kitfox, I think that cleans the wing up some.
Ed Gray k2 582 Dallas do not archive
Message 3
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When I added a radiator scoop to my model IV-1200 I didn't notice that much difference
in speed but maybe messing with it some would have yielded better results.
The big payoff items seemed to be strut fairings and wheel pants. The strut
fairings were built-in during construction but the wheel pants were added
after it was flying for a while and they made a dramatic difference.
Mike G.
Kitfox IV-1200 Speedster
Phoenix, AZ
Message 4
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The wisest counsel that could be offered is to suggest that before you start tweaking your prop pitch, watch the EAA webinar Is Your Two Stroke Engine About to Fail?. The link for it is: http://www.eaavideo.org/video.aspx?v=626943072001
The webinar explains just how easy it is to overload the engine with incorrect
pitching and how unreliable an engine immediately becomes when it is overloaded.
It is also possible to underload an engine, also with detrimental effects.
Before changing anything in the engine or prop, its important to know just what
your EGTs are in all phases of flight slow cruise, fast cruise, descent, cruise-climb,
and Vx climb. An accurate EGT is your best friend when it comes to
knowing how reliable your engine will be, as is an accurate tach.
I have a Kitfox Model I that I finished in 1994. Its 532 with B gearbox and a three-blade
66" GSC prop has run for 375 hours with minimal maintenance. Pistons,
cylinders, and rings are currently all nominal. I replaced the rings at 100
hours because they were stuck tight, probably from using synthetic oil which
I no longer use.
Full-throttle static RPM in 60-degree temps varies from 5800 to 6100 (one variable
in static RPM readings is the windspeed towards the prop). Full-throttle climb
at Vx is between 6500 and 6700. For cruise, I set the RPM at 5800 - 6000,
which gives me about 72 MPH TAS. My airframe has the optional lift-strut fairings,
but that is all.
I know that I could coarsen-up the prop pitch, but Im also aware that the engine
would soon become overloaded. Ive set the combination of the carb needles and
the prop pitch to make the EGTs read about 1100 in cruise, 900s at full-power
in climb.
It is important to have two things before repitching your prop: an accurate tach
and an accurate dual EGT.
The EGT probes need to be located at the correct distance from the piston skirts,
which I believe is 4. If you are unsure about the accuracy of the EGT in any
way, Id strongly advise getting a new one you have to be able to trust it
absolutely.
Tachometer calibration is also important. Some EAA chapters and A/P mechanics have
remote-reading tachometers (based on a photocell that remotely senses the
frequency of the blade-passings), and borrowing one can help you discover if your
tach is reading correctly.
Im stressing the value of accurate EGT and tach because Im aware of how often they
are inaccurate and also how their inaccuracy can cause an owner to make his
engine less reliable rather than more reliable.
Watch the webinar - it's very valuable.
Mike Perkins
EAA TC/FA
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=359142#359142
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