REFLECTOR: Second flight

Mon Aug 20 13:03:58 CDT 2012

Also, with the new design we noticed a much quicker acceleration of the
engine. Craig told me that the theory behind the aggressive twist was to
scoop more air and to let the air accelerate our of the way faster allowing
more air to be trap and pushed away at the same time. The practical reality
is that in fact these prop accelerates the engine very fast compared with
the standard one. By the way, in previous message said 145kkts at 2450rpm,
but we generally get closer to 150KTAS at the rpm. 

If you can take off fine and have a hard time getting speed, you must have a
standard pitch for climb prop. The new design pitch for a cruising angle
will make you feel are in a totally different airplane, but realize you
would lose some of the take off and climb performance.

Ruben

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From: Dennis Martin [mailto:dennis.doc at gmail.com] 
Sent: Monday, August 20, 2012 12:32 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Second flight

Thanks for the details on your Catto, Ruben. Take offs are no problem,
butI'm having trouble getting enough speed at full throttle. I'll get back
after talking with Craig - maybe that new design prop is what I need.

Dennis

On Mon, Aug 20, 2012 at 10:05 AM, Ruben Creus <ruben at vainneg.com> wrote:

Geoff, 

Mine is a SE-FG with and IO-360. The numbers you are giving here sound
pretty much a similar experience I have. In the last couple of years I have
been back and forth with Catto, I have used 3 different props. Cruise, and
Climb props ranging my static from 1,900 to 2,200rpm, and take of distance
from 1,500ft to 2,500ft., climb rate from 300-500ft./m  to 700-1000ft.m and
cruising from 130KTAS to 150KTAS.

The conclusion is that there has to be a compromise, when you use a fix
prop. You can get climb in sacrifice of speed or speed in sacrifice of
climb, but the good news is that last year Catto came our with a new prop
design. It looks much fatter than normal from the bottom than the top, and
also the blade is kind of twisted more aggressively than a normal prop. With
this design, the range of sacrifice between climb or cruise seems to have
been reduced a lot. 

I got one of these new designed props and it improve my take of distance and
climb rate without scarify almost any cruising, maybe a couple of knots. My
take off roll out can rage between 1,600 to 2,200 depending on temperature
and weight. In a cold day by myself I can be in the air pretty quick, in the
summer and with full weight, I always count a minim safe distance of 2,500
and if there are trees around, I aim for a minimum of 3,000ft runways. Climb
again it depends a lot on temperature and weight. In the  winter at full
weight and climb at 700ft/ with no problem, in the summer and full weight
300ft/m with DA of 4000' is the max I can get making planning for take off
and important thing, but when I am up in the air at flat level I easily get
the 145Ktas cruising speed at 2450rpm. I guess with a retract you would get
at least 10 to 15 more than that.

Do you know what type of prop do you have? The old one, or the new design?

Ruben G. Creus

* +1.571.215.0025 <tel:%2B1.571.215.0025> 

*  <mailto:ruben at vainneg.com> ruben at vainneg.com

  _____  

From: Geoff Gerhardt [mailto:geoff.gerhardt at gmail.com] 
Sent: Monday, August 20, 2012 7:50 AM
To: Velocity Aircraft Owners and Builders list
Subject: REFLECTOR: Second flight

Guys,

I spent Sunday morning fixing a few issues that were identified in the first
flight, then took her out for a second flight this afternoon.  I think I'm
going to have to send my prop back to Craig to have it re-pitched, but I'd
like to hear your input.  There's a link below to a post on my website that
shows the flight video as well as a CloudAhoy analysis (if you're not
familiar with CloudAhoy, its a very cool app for recording a flight).  With
just me on board and only ~20gal of fuel, I need ~2200' of runway to lift
off (DA 2000'), then I have to stay low to build up some speed to start my
climb.  Once I can get to 90-100kts, I can climb ok, but I feel a bit unsure
about flying into any 3000' runways with only 800' of wiggle room,
particularly if there's any trees past the runway.  My prop is currently
66x74.  Have a look at the video and CloudAloft and let me know how this
compares to your experience with a fixed-pitch prop.

Here's a link to the post on my website that describes the second flight and
videos.

http://thegerhardts.com/velocity/?p=513 

Geoff

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-- 
All the best,
Dennis

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