REFLECTOR: Early model Velocity RG Engine Cooling

Tue Nov 20 16:07:37 CST 2012

Dave, 
My experience has only been with Ezees and Long Ezees, and recently helped a friend for several years with a Lancair IVPT. I can't afford one of those and think I prefer the simpler and far more economical Velocity.
Does your top NACA extend into the roof of cabin? Do you have any pics you can send? Also you confused me on the exhaust, your statement; "keeps the entire exhaust inside the cowl and exits aft of the prop", aft of prop? or just aft of prop extension? Can you send pics of this as well. You also stated and someone else as well that the right scoop was used for induction air. Also mentioned earlier was the "Cold side of cylinder air". Both of my inlets appeared to be used for engine cooling only with a ram air scoop on bottom, (that stuck down an out into airstream) for induction but I am converting to a smaller NACA. I was also working on smooth streamlined fitting main gear doors and am trying to design a smaller wing mounted door to completely close wheel well opening. As far as everything else, Clean, Slick, Light, and smooth flow has been high priority second only to safety. 

David Smith dwsmithaircraft at yahoo.com  

Message: 1
Date: Tue, 20 Nov 2012 14:05:44 -0600
From: Dave T Nelson <dtnelson at us.ibm.com>
To: reflector at tvbf.org
Subject: Re: REFLECTOR: Early model Velocity RG Engine Cooling (Now -
    which    performance mods)?
Message-ID:
    <OF95BA38FA.629A9548-ON86257ABC.006C88FB-86257ABC.006E6440 at us.ibm.com>
Content-Type: text/plain; charset="us-ascii"

I've got a STD-RG, Lycoming IO-360 and an MT prop.  I started off with
armpit scoops feeding into a tops-down plenum, along with a single nose
mounted oil cooler.  Intake air was off a second scoop mounted on the right
wing.

My situation was that I built my plane while sharing my shop with a good
buddy who built a really nice Cozy 3 place.  We got them both flying at
about the same time, and spent many happy years racing (and bragging).  I
still say his plane was the slow ugly one.

Anyway, the main thing(s) you do to make these airplanes go fast are all
about weight and aerodynamics.  Power increases don't get the same bang for
the buck.  I focused mostly on drag reduction... really clean gear doors,
clean canard/fuselage interface, minimum cooling drag, and clean exhaust
system.  The last two are the most important.

The armpit scoops are a bit of an aerodynamic disaster... they are all too
big.  If you tuft or do an oil study on them, you'll find that the bulk of
the air is getting pushed back out of the scoop because of the inherent
flow resistance of the  tubes taking the air to the top of the plenum, the
flow through the plenum & engine, and the output behind the prop.  An oil
study will likely also show nearly dead air at the output (right behind the
prop).  The total square inches of inlet are too great, and so is the total
square inches of outlet.

Many of my initial mods were in trying to clean up the cooling and intake
air..  I made several different styles of cooling air intakes, each smaller
than the last.  Nothing worked particularly well.  Eventually, after
developing significant cooling issues (which turned out to be an engine
issue, not an aerodynamic problem), I went to the rooftop NACAs.  As I
said... they work fabulously.  I take my induction air off the right NACA.
There are no external protrusions on my plane.

The exhaust changes were probably the most speed gain.  I've gone from the
original rear exiting 2 in 1's that exit through tubes attached to the
lower cowl, to the "straight out the bottom" types you see on many XLs
today (which were by far the worst performers - a real disaster), to what I
have today - a one-of design of my own that keeps the entire exhaust inside
the cowl and exits aft of the prop.  That was a big gain!

OK, performance... I see around 185 knots true +/- at around 25 squared...
middling altitudes... at around 10 - 11 gallons / hour ... cold air, down
low, with a light plane is better still.  It's not as fast as I'd like, but
I'm not done trying.  The next effort will be a complete cowl redesign to
get rid of those awful turns where the cowl angles in just aft of the last
cylinder.  All the attached air detaches at that point...

Hope this helps.  What numbers to you see?

Dave

Dave T. Nelson
T/L 553-4327, Voice 507-253-4327, Fax 507-253-3648
Program Director, ISC ECAT NPI & Test Engineering

----- Message from "Richard J. Gentil" <richard at naples-air-center.com> on
Tue, 20 Nov 2012 10:38:47 -0500 -----

      To: Velocity Aircraft Owners and Builders list                
          <reflector at tvbf.org>                                      

Subject: Re: REFLECTOR: Early model Velocity RG Engine Cooling    
          (David Smith)                                            

Dave N,

Which go fast mod have you done and what speeds are you getting? (Please
mention the engine and prop combo you are running.)

Thanks,

Richard

Sent from my iPhone 5
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Message: 2
Date: Tue, 20 Nov 2012 15:53:41 -0500
From: "Richard J. Gentil" <richard at naples-air-center.com>
To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
Subject: Re: REFLECTOR: Early model Velocity RG Engine Cooling (Now -
    which    performance mods)?
Message-ID:
    <312BF841-6BEE-4FEF-8939-00A874F148B1 at naples-air-center.com>
Content-Type: text/plain; charset="us-ascii"

Dave,

My plane is heavy and still in primer. It is a Standard RG with Elite doors. IO-390-X, with an MT. 

With radar power down low I cannot get anything faster then 170kts true. When I am at 7500 feet at 23 squared is around 157kts with just me in it burning 7.5 to 9 gallons depending how far lop I want to go. 

I did fly through a little light rain and saw no change in TAS so I am assuming I do not have any laminar flow with just a rattle can primer paint job. 

Richard

Sent from my iPhone 5
combo you are running.)
I have an OLD SCHOOL Std FG that was setup for a water cooled engine with the NACA scoops on the bottom. I am changing to a Lyc. 4 cyl. with possible updraft cooling. However, I may install NACA scoops on the top of the airframe as well and use the bottom scoops for ram air to the carb. Any thoughts from the group?

On Nov 20, 2012, at 12:52 PM, Willem Huisman wrote:

> Larry,
> 
> Armpitscoops with plenum and Franklin is what I have, and very,very
> low CHT as well.
> My previous Velocity had armpits with Lycoming and baffles, always had
> to battle high CHT.
> 
> In both cases however CHT temp probes are on same side where cool air
> is. You need to add around 50 degrees thet claim to derive to real
> CHT.
> 
> Still however, Armpit with plenum seems the best way keeping CHT low.
> I? planned top Naca , but Scott Baker convinced me to keep as is, and
> he was correct.
> 
> Wim Huisman
> N59WH
> 
> >> Date: Tue, 20 Nov 2012 12:12:40 -0600
>> From: "Laurence Coen" <lwcoen at hotmail.com>
>> To: "David Smith" <dwsmithaircraft at yahoo.com>, "Velocity Aircraft
>>? Owners and Builders list" <reflector at tvbf.org>
>> Subject: Re: REFLECTOR: Early model Velocity RG Engine Cooling
>> Message-ID: <SNT117-DS853B8BAC61073A417C89AD3550 at phx.gbl>
>> Content-Type: text/plain; charset="iso-8859-1"
>> 
>> David,
>> 
>> I have the armpit scoops and they work very well.? I have a Franklin engine with a downdraft plenum that is connected to the air inlets with 4" scat tubing.? This time of year I have trouble keeping my CHT above 200 F.? I made a modification to the scoops by adding an internal venturi to the scoops to enhance pressure recovery.? I think it worked pretty well since I blew a scat tube off one side of the plenum during 200 Knt flutter testing.? I make sure I get the clamps real tight now.? To get top NACA scoops to work, most find that they have to put vortex generators ahead of them.? IMHO the only reason for going with NACA's is they look cool period.
>> 
>> Larry Coen
>> N136LC
>> 
>> P.S.:? As a way to solve all your problems, you could buy my plane and go flying right away. :>)
>> 
>> 
>> From: David Smith
>> Sent: Tuesday, November 20, 2012 8:15 AM
>> To: reflector at tvbf.org
>> Subject: REFLECTOR: Early model Velocity RG Engine Cooling
>> 
>> 
>> I have bought and am rebuilding a damaged Standard Velocity RG. It appears it has gone through a couple of air inlet mods with the latest being under strakes at wing to fuselage corners. I am at the stage where I would like to incorporate the best cooling to drag design before paint. The baffling that came with the aircraft is all wrong for the flow in the cowl. I have looked and thought about differences between up-flow and down-flow cooling with down-flow being simplest with baffling, but with low air inlets being simplest at modification. Any suggestion or a point in where to go for info will be appreciated.
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