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From: "Thomas y Reina Jakits" <rijakits@cwpanama.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-1155599@logan.com>
Subject: Re: [FlyRotary] Re: Remove Turbo
Date: Thu, 15 Jun 2006 23:21:03 -0500
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Hi Steve, Ed and all,

I may be wrong:

Isn't there some selfstreamlining effect when an intake starts to spill air
because of backpressure?
What if you start to block off your cooling exit with louvers/flaps/etc. to
the point where you reduce cooling air flow speed.
Theory:
If you don't push it through the system it won't produce drag.
Excess cooling air, doesn't even enter the system as it spills past the
intake (aerodynamic diffusion??)

Steve said, you can only do so much with flaps/louvers.
Well I guess you can make them big enough to close off enough air to keep
flow down...

TJ


----- Original Message ----- 
From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Thursday, June 15, 2006 11:02 AM
Subject: [FlyRotary] Re: Remove Turbo


> Steve's comments are on the money, Thomas.  Yes, you can certainly design
a
> cooling duct system optimized for cooling in a climb.  However, as Steve
> indicated you will then pay with additional drag/weight,etc for each of
> those many hours at cruise airspeeds.  Many (most?) of us try to design
for
> optimum cooling at cruise (minimum drag) and accept the fact that for a
few
> minutes during/after takeoff we may incur a cooling deficient.  My limits
> are 200F oil and 220 Coolant, so long as my full power climbout does not
> cause either of those limits to be exceeded, I feel comfortable.
>
>  Now, once I have reach 120 MPH IAS I start to get into the sufficient
> cooling capacity region and all temps start back down.  At cruise my
cooling
> temps are normally around 160-170F for both oil and cooling - which could
> indicate that I still have a bit too much cooling capacity (and therefore
> cooling drag). Ideally at cruise, I would like to see oil and coolant at
> 180-185F.   However,  since I don't wish to exceed my establish limits in
> climbout, I accept that I probably have more cooling drag at cruise than I
> need to have.
>
> If I were flying a Bush plane in and out of hills and valleys carrying
heavy
> loads and at relative slow speeds, then I would opt to optimize the
cooling
> system for takeoff and climbout.  If I were flying a canard type I would
opt
> to optimize the cooling system for cruise.  With an Rv I'm someplace in
the
> middle {:>).
>
> Like most of areas when discussing aircraft, cooling is another one of
those
> "compromise things"
>
> Ed
>
> Ed Anderson
> Rv-6A N494BW Rotary Powered
> Matthews, NC
> eanderson@carolina.rr.com
> ----- Original Message ----- 
> From: "Steve Brooks" <prvt_pilot@yahoo.com>
> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
> Sent: Thursday, June 15, 2006 9:51 AM
> Subject: [FlyRotary] Re: Remove Turbo
>
>
> > Thomas,
> > You could design a cooling system for extended climb, but you would be
> > adding
> > significant drag to the aircraft.  There is only so much you can do with
> > cowl
> > flaps.
> >
> > I believe that most builders (and also most certified aircraft) design
> > cooling
> > for cruise, and tolerate temperatures climbing somewhat in climb.  There
> > do
> > have to be tolerable limits, however.
> >
> > I'm afraid that if I built my cooling system to maintain temps on an
> > extended
> > climb, at full power, on a 95 degree day, I would have much cruise speed
> > when
> > I leveled off.
> >
> > I've seen several discussion on this group, where people leveled off for
a
> > while, or reduce power and go to a cruise climb, in order to let thing
> > cool
> > back down.
> >
> > On my aircraft, the oil temperatures are fine, but coolant is marginal
on
> > hot
> > days.  On a 95 degree day, I could only get to about 2000 feet AGL
before
> > my
> > coolant temperature was at redline.  Leveling off and reducing power,
> > cools
> > it down, and then I can increase power and continue climbing at a cruise
> > speed.
> >
> > I have some more gains that I can make on mine cooling system by making
> > improvements in air flow.  Currently I have some dead space below the
> > radiators which I'm sure allows some air to roll back out.  I also have
a
> > couple of spots that are allowing air to leak through, which I need to
fix
> > as
> > well.
> >
> > Steve
> >
> > On Wednesday 14 June 2006 09:30 pm, Thomas y Reina Jakits wrote:
> >> ""
> >>
> >> > While it doesn't make sense to try to have sufficient cooling for
> >> > climb,
> >> > I think that I can still make some air flow improvements and get a
> >> > little
> >> > better cooling.
> >> >
> >> > Steve ""
> >>
> >> Steve, what makes you think/believe that!?
> >> I always assumed that one would design/plan for the worst case
scenario:
> >> Slow/steep/pro-longed max power climb....
> >>
> >> You always can close the flaps/louvers (streamline/reduce drag) when
you
> >> change into a less severe regime.
> >> But what good is a 250hp engine if you can't use it for more than 2
> >> min....
> >> I would at least want a 5 min limit for T/O-power. As Rotaries go, they
> >> will hold up fine with max power for cruise/racing/etc. fine too - but
if
> >> you can't cool it.....
> >>
> >> What if you are in line on really hot day? You might not even get 2 min
> >> of
> >> max power.
> >> I would rather err on the wild side of cooling - you always can cut
down
> >> and close off, once you know your ride...
> >>
> >> TJ
> >>
> >>
> >> --
> >> Homepage:  http://www.flyrotary.com/
> >> Archive and UnSub:   http://mail.lancaironline.net/lists/flyrotary/
> >
> > --
> > Homepage:  http://www.flyrotary.com/
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> >
>
>
>
> --
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