"Marginal cooling" is actually a point on a curve. So that supports your
concept of it being fuzzy, undefined. If you find yourself watching the
temperature and changing decisions based on it, you are approaching
marginal. If you have outside air temps you have to avoid, you are
clearly marginal.
There is no reason to tolerate anything approaching marginal. Ask
yourself: "Is it truly necessary that I have temp this high?" Simple
solutions can yield much better safety margin. It does not necessarily
have to include larger radiators. There are lot's of decisions made
during construction that negatively affect performance. Type of rad,
position of rad. Little air flow diverters are very effective.

If you guys just measure your temps as I described earlier, then all of
the successes could be copied.

Headed to beach, so I may not respond to posts for a few days. Seeking
razor clams..mmmmmmmm.

As always, enjoyed the discussion Ed.


-al wick
Cozy IV powered by Turbo Subaru 3.0R with variable valve lift and cam
timing.
Artificial intelligence in cockpit, N9032U 240+ hours from Portland,
Oregon
Glass panel design, Subaru install, Prop construct, Risk assessment info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html





On Tue, 15 May 2007 21:04:16 -0400 "Ed Anderson"
<eanderson@carolina.rr.com> writes:

No question, Al, that a cooling system failure can ruin your day,
particularly if it detracts you from "Fly the Airplane" mantra. But,
I also
agree its a tough sell, but I believe it is a tough sell because of
whether
you or I, or Joe or Bill  mean the same thing by a marginal system.
Perhaps
we could come to a meaningful definition but one eludes me at the
moment.  I
mean consider the nature of the beast, we KNOW of some
configurations which
have repeatedly shown they perform their function - now, you might
think
that would mean everyone would adopt them - but, who am I trying to
kid -
certainly not you, Al?  There is always going to be somebody (most
folks in
this activity?) who are going to want to skin that grape another
(better?)
way.

 I guess the real underlying question in my mind is how do you
define a
marginal system. I have flown my system for 10 years now in all
sorts of
Summer heat, long waits while taxing, etc.  I (obviously) personally
don't
view the system as marginal but actually finely tuned to my
installation. So
while we can all perhaps agree you shouldn't fly with a marginal
cooling
system - I'm not as certain we could all agree on the definition of
one
{:>).

 I gather (hopefully correctly) that you feel any temperature
excursion
beyond some point temperature point X in some regime of flight would
 mean a
marginal system.   So the next question becomes what temperature
point X and
why?   There should be some meaningful reason we choose temp X. Like
beyond
X  Water boils, coolant boils, metal cracks, spark plugs shatter?

For instance, I fly with no thermostat, for whatever adverse effect
that
might have on engine efficiency, it does one thing a system with a
thermostat can not do.  My system begins removing heat from the
engine the
second the engine is started, with a thermostat no (significant)
heat is
removed until the coolant reaches the thermostat opening temperature
and
only then does the cooling start becoming effective in removing
heat. I have
never had problems with ground operations on hot days.  The system
cools
fine - until I pour the fuel to it on take off and then the
temperatures
start a slow rise - fortunately so does airspeed and airflow through
the
cores.  Once 120IAS is reached my "marginal" period is over and
cooling (if
anything) is excessive at my normal cruise power settings.

 Yes, hotter coolant does mean more theoretically efficient cooling
- but,
I don't think that increase efficiency can make up for the fact my
system
has been removing heat from the system from start up.  Now some
folks would
probably think that without a thermostat the system is marginal - I

obviously am not one of them{:>), but, again, my point is how to we
define
the parameters and how do we populate those parameter with
meaningful
values.

I suspect the generic  parameters would have a degree of commonality
for
just about all liquid cooled engines - but the values for a Subaru
would
undoubtedly be different from a Rotary or from perhaps a Chevy V8.
Just a
gut feel there, but again how do we decide.  Exhaust valve temps
might be a
suitable parameter for some engines but would of course be
meaningless for
the rotary.

 My point is I think it would be difficult to get agreement on the
parameters from which to evaluate a marginal system much less agree
on the
parameter values that will categorize a marginal system.  The
extremes are
easier to define
If the engine seizes from over-heating, if the coolant boils out of
the
system, the fiberglass cowl catches fire, etc, we could probably
all
agreed that the cooling system was "marginal".  But, if none of that
(or
similar things)  happens - what makes it marginal?  1 Degree F over
some set
limit?  10F over?  You get my point.


Second, I think anyone who puts Evans in a marginal cooling system
clearly
doesn't understand the thermodynamics of the situation (in my
opinion).
With a lesser Cp (considerably less  than water and even an
water/anti-freeze mixture) you will remove even less heat from the
engine
per unit mass of coolant flow and ensure you will eventually cause
even the
high boiling temp Evans solution to overheat.

  Yes, you can heat Evans to a higher temp before it boils - but all
that
means is your engine and everything else is at that temp as well.  I
do
believe there is one way you could remove more heat with Evans but
that is
only if you increased the flow rate of the coolant. That stuff was
originally used for racing and racers care more about winning than
longevity
of the engine - so it does have its uses, I just don't believe
aircraft
engines is one of them    And even if I am wrong about the other
aspects of
Evans, its higher operating temperature  may be withstood by  some
engines
but the rotary is not one of them (again in my opinion).

I always enjoy the pertinent points you bring up, Al.  They
certainly force
us (me for sure)  to re-examine our premises and perhaps even change
them.
I guess we could say any marginal system, be it cooling, fuel,
ignition,
controls, structural is  operating on the "edge" and it could only
take a
factor or two different to suddenly make the system very, very
marginal.
So it comes down to the inescapable fact that those of use who 1.
Fly, 2.
Fly experimental aircraft, 3. Fly with Alternative engines are
probably
closer to the margin in a larger number of areas than we would care
to dwell
upon - sanity might be one of them {:>).

Best Regards

Ed







----- Original Message ----- From: "al p wick" <alwick@juno.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Tuesday, May 15, 2007 7:01 PM
Subject: [FlyRotary] Re: Marginal Cooling contributes to Crash.


>I know it's a tough sell. Hard to believe you have significant risk
when
> you are normally able to just throttle back, wait a while, and
temps
> start to drop. Tons of times I heard the same response in my
> occupation...."If he just reacts to xxx, then the problem goes
away".
> Marginal systems place you closer to the boil over temp. It only
takes a
> 20F rise in ambient temp to affect marginal system. It takes 80F
rise to
> affect robust system. If you heat soak a marginal system, that
places you
> right on the edge of boil over. Add a bubble of air to marginal
system,
> you are screwed. As your temps rise, your piloting skills drop off
due to
> anxiety. I've gotten a number of reports from guys who landed gear
up
> even though their warning horn was blasting away...just because
they were
> worried about the engine behavior.
>
> The incident I referred to was the guy that took off with
marginal
> cooling. Landed at Whyoming airport, changed to Evans, then took
off and
> bit it. Underlying root cause was marginal cooling. He never would
have
> changed to Evans if he had started out with robust system.
>
> Our day to day problem solving skills set us up for failure. We
are so
> used to making marginal decisions, that we find it difficult to
see the
> significance of robust design. Easy to fly for years with marginal
> system, then all of a sudden the other contributing factors stack
against
> you.......
> High ambient temp, high altitude, heat soaked engine.
Fortunately,
> statistically it will only nail a few guys. A few for marginal
cooling, a
> few for marginal fuel delivery. One common cause....sys designed
too
> close to failure point.
>
> Certainly agree, spray bar a good solution.
>
> -al wick
> Cozy IV powered by Turbo Subaru 3.0R with variable valve lift and
cam
> timing.
> Artificial intelligence in cockpit, N9032U 240+ hours from
Portland,
> Oregon
> Glass panel design, Subaru install, Prop construct, Risk
assessment info:
> http://www.maddyhome.com/canardpages/pages/alwick/index.html
>
>
> On Tue, 15 May 2007 15:10:12 -0400 "Ed Anderson"
> <eanderson@carolina.rr.com> writes:
>> Hi Al,
>>
>> I would be interested in these other factors you mention
referring
>> to the
>> crash.  I have years of flying under cooling deficit conditions
>> right after
>> take off  as do others as you mention - without any problem.
Every
>> study I
>> have read on cooling indicates the designer strives for an
optimum
>> cooling
>> system- for an operating regime - (frequently for the cruise
regime)
>> and
>> then uses whatever, cowl flaps, exhaust augmentation, spray
bars,
>> to cool
>> it under less than ideal conditions-  like immediately after
take
>> off.  I
>> understand even the P51 faced that problem on taxi and take off
on
>> hot days.
>>
>> You can certainly design your system to not have a "take off"
>> cooling
>> deficit but, you are now starting to talk bigger radiators (may
have
>> space
>> constraints), more weight, cooling drag, etc. for some airframes
and
>> flight
>> regimes a bit more would not be significant, but for other
airframes
>> and
>> speeds these factors become more significant.
>>
>> Perhaps we need to be as bit more specific as to what degree of
>> "overheating" we are referring to.  My limit on oil temp is 200F,
my
>> limit
>> on coolant is 220F and those only for the short duration of
launch
>> and up to
>> 120 MPH IAS at which time my system is on the good side of
cooling.
>> 10 years
>> of flying with that limitation has not yet revealed any problem
so
>> far as I
>> can tell. Now with a rotary,  if your temps are going 240F on
oil
>> and
>> similar on coolant then I personally would feel that is too high
and
>>
>> something should be done.
>>
>> A crash to which the overheating was apparently one of a set of
>> factor is
>> certainly something that I would be interested in.  How bad was
the
>>
>> overheating and how did it contribute to the crash?  I (and I
>> believe all of
>> us) would be interested in the details of the crash you mention
that
>> was
>> contributed to by marginal cooling - for lessons learned.  A
spray
>> bar does
>> indeed provide a considerable margin, Tracy flew with one for a
bit
>> (mainly
>> for racing I believe), I've never experimented with one since I
>> don't go
>> racing and once airborne and 120 IAS and my system is happy.
>> However, it
>> might be interesting to see exactly how much benefit such a
simple
>> system
>> would provide.
>>
>>   Gotta put that on my long list of  "to do" things.  Another
thing
>> I have
>> been thinking more about is that my GM cores which have served
well
>> are
>> approaching the 10 year point.  They are really not designed for
>> water flow
>> as we know, so  I would not be surprised that a custom made set
of
>> radiator
>> cores might lower my coolant temps by 5-10F by simply providing
>> improved
>> coolant flow.
>>
>> As always, appreciate your input and perspective, Al.  Any risk
we
>> can
>> eliminate or reduce is worth examining and taking action on.
Again,
>> would
>> be interested in the details of the accident if you have them.
>>
>> Best Regards
>>
>> Ed
>>
>>
>>
>>
>>
>>
>>
>> ----- Original Message ----- >> From: "al p wick" <alwick@juno.com>
>> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
>> Sent: Tuesday, May 15, 2007 12:08 PM
>> Subject: [FlyRotary] Re: First Flight - Renesis in RV-7A
>>
>>
>> >I know a lot of you guys are flying with conditions similar to
what
>> Ed
>> > describes. It gets hot during climb, but cools off during
cruise.
>> It
>> > seems manageable. I encourage you to not tolerate such a
design.
>> This is
>> > a root cause for crashes. You have marginal system, normally
>> easily
>> > managed, but suddenly other factors come into play.  We had
crash
>> last
>> > year with marginal cooling as one of the root causes.
>> >
>> > One simple solution that provides extra safety margin is to
just
>> add a
>> > spray bar in front of radiator. It just takes a tiny mist of
water
>> to
>> > dramatically improve cooling. Strongly encourage spray bar at
a
>> minimum.
>> > Great solution for initial testing.
>> >
>> > Even then, I would seek improvements that eliminate need for
spray
>> bar.
>> > There are simple improvements out there. There are guys flying
>> exact same
>> > hp as you, yet they have 10 to 20% better cooling efficiency.
Find
>> out
>> > what they are doing right.
>> >
>> > If you had everyone flying record their temp as they climb out
>> from sea
>> > level to 12k ft, you would find a couple guys with better
>> efficiency than
>> > the others. You'd have to record outside air temp. Coolant,
oil
>> temp at
>> > start and end of climb. Everyone would have to climb at same
rate,
>> say 80
>> > mph, then 90mph. Compare area of radiators. With some facts
like
>> this you
>> > could end up with some genuine breakthroughs. Speculations do
not
>> lead to
>> > breakthroughs.
>> >
>> >
>> > -al wick
>> > Cozy IV powered by Turbo Subaru 3.0R with variable valve lift
and
>> cam
>> > timing.
>> > Artificial intelligence in cockpit, N9032U 240+ hours from
>> Portland,
>> > Oregon
>> > Glass panel design, Subaru install, Prop construct, Risk
>> assessment info:
>> > http://www.maddyhome.com/canardpages/pages/alwick/index.html
>> >
>> >
>> > On Tue, 15 May 2007 07:47:09 -0400 "Ed Anderson"
>> > <eanderson@carolina.rr.com> writes:
>> >> Congratulations, Dennis.  A great day for sure!  A lot of
work
>> and $$
>> >> coming
>> >> to successful launch.  Unless you make the cooling system
>> capacity
>> >> considerably greater than you need at cruise, you will always
run
>> a
>> >> cooling
>> >> deficit during climb - high power, low airspeed.  So long as
it
>> >> doesn't
>> >> exceed your limits and cools off once sufficient airspeed is
>> reach,
>> >> you
>> >> should be fine
>> >>
>> >> Ed
>> >> ----- Original Message ----- >> >> From: "Dennis Haverlah" <clouduster@austin.rr.com>
>> >> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
>> >> Sent: Monday, May 14, 2007 10:23 PM
>> >> Subject: [FlyRotary] First Flight - Renesis in RV-7A
>> >>
>> >>
>> >> >I made my first flight this evening!!  All systems worked
fine
>> -
>> >> cooling
>> >> >was marginal in climb but we had a good inversion and the
>> outside
>> >> air
>> >> >temperature was quite warm.  Several neighbors videoed the
>> flight
>> >> and I
>> >> >heard several comments about how quiet the rotary plane was
when
>> we
>> >> played
>> >> >the video.  We had a 180 hp RV-7A flying chase and on the
video
>> it
>> >> was much
>> >> >louder!!  Only flew about 10 minutes but made an acceptable
>> landing
>> >>
>> >> >considering there were about 50 people watching.  I'll post
>> some
>> >> picures of
>> >> >the plane later tonight.
>> >> >
>> >> > Dennis Haverlah
>> >> > RV-7A, Renesis, James Cowl
>> >> > Radiators under engine
>> >> > Catto 76 in dia- 8 in pitch
>> >> > EC-2, Em-2, RD1-C
>> >> >
>> >> > --
>> >> > Homepage:  http://www.flyrotary.com/
>> >> > Archive and UnSub:
>> >> > http://mail.lancaironline.net:81/lists/flyrotary/List.html
>> >>
>> >>
>> >> --
>> >> Homepage:  http://www.flyrotary.com/
>> >> Archive and UnSub:
>> >> http://mail.lancaironline.net:81/lists/flyrotary/List.html
>> >>
>> >>
>> >
>> >
>> > -al wick
>> > Cozy IV powered by Turbo Subaru 3.0R with variable valve lift
and
>> cam
>> > timing.
>> > Artificial intelligence in cockpit, N9032U 240+ hours from
>> Portland,
>> > Oregon
>> > Glass panel design, Subaru install, Prop construct, Risk
>> assessment info:
>> > http://www.maddyhome.com/canardpages/pages/alwick/index.html
>> >
>> > --
>> > Homepage:  http://www.flyrotary.com/
>> > Archive and UnSub:
>> > http://mail.lancaironline.net:81/lists/flyrotary/List.html
>>
>>
>> --
>> Homepage:  http://www.flyrotary.com/
>> Archive and UnSub:
>> http://mail.lancaironline.net:81/lists/flyrotary/List.html
>>
>>
>
>
> -al wick
> Cozy IV powered by Turbo Subaru 3.0R with variable valve lift and
cam
> timing.
> Artificial intelligence in cockpit, N9032U 240+ hours from
Portland,
> Oregon
> Glass panel design, Subaru install, Prop construct, Risk
assessment info:
> http://
>
> --
> Homepage:  http://www.flyrotary.com/
> Archive and UnSub:
> http://mail.lancaironline.net:81/lists/flyrotary/List.html


--
Homepage:  http://www.flyrotary.com/
Archive and UnSub:
http://mail.lancaironline.net:81/lists/flyrotary/List.html

-al wick
Cozy IV powered by Turbo Subaru 3.0R with variable valve lift and cam
timing.
Artificial intelligence in cockpit, N9032U 240+ hours from Portland,
Oregon
Glass panel design, Subaru install, Prop construct, Risk assessment info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html

--
Homepage:  http://www.flyrotary.com/
Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html