REFLECTOR: Performance

Peter Braswell peter.braswell at gmail.com
Wed May 8 12:23:41 CDT 2013


Geoff:

RE: C/S vs F/P prop - yes I agree.  I debated and debated and debated ...
 In the end I figured that even a little TO margin (full gross / all family
members aboard) the little extra umph (hopefully) at take off will be worth
the many extra 1000's of dollars (gulp!) :)

Good going on the NACA scoops for cooling as far as I've heard .... I think
that any pusher is going to be cooling challenged.  Add to that a
relatively new engine and you have to be real careful on climb out.  My
Glastar had a newly overhauled engine and I too had to be careful with
steep climb outs on a hot day.

Best,
Peter

------------------------------------------------------------------------
*"It's a Jungle Up There": www.zuluworks.com*
------------------------------------------------------------------------


On Wed, May 8, 2013 at 1:02 PM, Geoff Gerhardt <geoff.gerhardt at gmail.com>wrote:

> Peter,
>
> I have the dual NACA ducts on top, down draft cooling.  Generally speaking
> my cooling is ok.  I do have to watch on climb out that I lower to 75%
> power as I climb from ~2000-6000' as my CHT"s can creep up to 410F if I
> hold full power on climb.  If I hold 75% power on climb, though, they max
> at about 400F in climb then settle down to 380F or less in cruise.  Past
> about 5-6000', tho, I can go WOT as at that altitude the lower MAP doesn't
> allow me to generate enough power to overheat.
>
> I don't think the CS prop will give more speed (if you have a cruise prop
> like mine), it will just allow you to still hop off the runway quicker and
> have a better rate of climb.
>
> Geoff
>
> On Wed, May 8, 2013 at 11:35 AM, Peter Braswell <peter.braswell at gmail.com>wrote:
>
>> Hi Geoff,
>> I'm still building, so I'm afraid I can't contribute much to helping you
>> find more speed, but I was wondering what you're doing for engine cooling.
>>  Do you have the newer style NACA ducts for engine cooling or do you have
>> the older scoop?  I understand that can make a significant difference.
>>
>> I was also wondering about the prop.  I opting for a V/P MT three blade
>> hoping to be able to milk a little more top end.  Is your prop considered a
>> climb, cruise or climb / cruise prop?
>>
>>  -Peter
>> ------------------------------------------------------------------------
>> *"It's a Jungle Up There": www.zuluworks.com*
>> ------------------------------------------------------------------------
>>
>>
>> On Wed, May 8, 2013 at 10:38 AM, Geoff Gerhardt <geoff.gerhardt at gmail.com
>> > wrote:
>>
>>> Folks,
>>>
>>> I'm getting pretty consistent performance out of my 173RG over the last
>>> 8-9 months since initial flight testing.  My question to you guys is, are
>>> the performance numbers I'm seeing typical, or should I be seeing better
>>> performance?  Normally, on a cross country, I'll fly b/w ~8-12,000', ~60deg
>>> LOP which typically has me going 150kias at 8-8.5gph.  Full power, 160kias
>>> is about my max speed.
>>>
>>> I have a fixed-pitch Catto prop (66x74, design target 200mph @ 2800RPM).
>>>  When I'm doing 160kts, my prop is spinning at ~2800RPM.  That tells me
>>> that I have the power to spin the prop, but may have air frame drag that's
>>> keeping me from seeing the 200mph predicted by Catto at 2800RPM.
>>>
>>> I have a standard 200hp, Lyc IO-360, Lightspeed EI on one side, Mag on
>>> the other.  Timing as per spec for both EI and Mag.  About 90hrs on the
>>> engine (rebuilt).  Compression/oil consumption is normal.  Very stable
>>> performance from the engine.
>>>
>>> My plane is fully finished and pretty tight.  Main/nose gear doors are
>>> not hanging out and are reasonably well tucked in when the gear is raised.
>>>  Main wing angles of incidence are spot on, no rudder trimming was
>>> necessary to center the ball - she flies nice and straight.
>>>
>>> The factory predicts I should be able to cruise at 175kias - that's just
>>> not possible with my current setup.  Can others with Std Velocities relate
>>> the performance you are seeing?  Is this as good as it gets, or does anyone
>>> have suggestions for things to check to see if I can eek out a bit more
>>> speed?
>>>
>>> Thanks.
>>>
>>> Geoff
>>>
>>>
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>>
>
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