Point well taken, Bill.  However, my cooling was more than adequate with the
old larger ducts, so unless I can get some benefit (like lower drag), I
don't see much point.  On the other hand, if I added a turbo producing more
waste heat then that would help there with the same size ducts. I'll
continue to see what I can do with it.

Ed


Subject: [FlyRotary] Re: Downsize inlet duct First Flight


> Ed, you might get even better cooling, although no change in drag, by
> keeping the opening large, but using the smoothing technique that you
tried
> on the smaller opening.
> Bill Schertz
> ----- Original Message -----
> From: "Ed Anderson" <eanderson@carolina.rr.com>
> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
> Sent: Wednesday, September 03, 2003 7:18 PM
> Subject: [FlyRotary] Downsize inlet duct First Flight
>
>
> > The modification (reduction) of my radiator inlet duct area from a total
> of
> > 48 square inches to 33 square inches is dedicated to Rusty (for obivious
> > reasons {:>))  Sorry, just couldn't help myself, Rusty,  - the devil
made
> me
> > do it.
> >
> > Ok folks, made the first flight today with my reduced/reshaped radiator
> > > inlet for the left evaporator core.  The right evaporator core was
left
> > > unmodified to  provide a safety net sufficient to do the pattern and
> land
> > if
> > > take off temps exceeded expectations.  Fortunately, that was not
> > necessary.
> > > OAT on first take off was a humid 85 degrees.  No temperature
increased
> > > noted during ground run up, so launched and made max rate of climb,
not
> > > seeing any abnormal temp increase I left the pattern and continue Max
> rate
> > > climb to 4500 MSL.  Max temp of coolant during climb was 210F (normal
> for
> > > max rate climb at these OAT temps is 205F), Max oil temp was 200F
> nominal
> > > for max power climb. Max temps were reached about 2/3 of the way
through
> > the
> > > climb.
> > >
> > > In level flight, my coolant temperatures normally run 5 degrees colder
> > than
> > > my oil temp.  Today my coolant and oil temps were the same.  So
average
> > > coolant temp was increased by 5 Degrees F.  Total radiator inlet duct
> area
> > > was decreased from 48 square inches to 33 square inches.  24 Square
> inches
> > > for the right inlet duct and 9 square inch inlet for the modified
right
> > > duct (See attached photo for comparision). Probably some drag benefit,
> but
> > did not try to investigate that
> > > aspect.
> > >
> > > I flew to an airfield 50 miles away to have my transponder recertified
> and
> > > when I launched out of it, the OAT (ground level) was 92F
> > >
> > > After level off I ran at different power settings to see the effect.
> > >
> > >  5800 rpm burning 11.9  GPH at 4500  MSL with OAT at 78F My oil and
> > coolant
> > > were both 190F.
> > >
> > > 5400 rpm burning 9.6 GPH at 4500 MSL with OAT 80F My Oil and coolant
> were
> > > both 185F
> > >
> > > 5200 (Around my normal cruise rpm)  burning 7.25 GPH at 4500 MSL with
> OAT
> > 80F My
> > > oil and coolant were both  180F
> > >
> > > In summary, the 33 % reduction in total  radiator inlet area appeared
to
> > > have increased coolant temps by an average of 5 Deg above the normal
> (the
> > > old duct).  It could be that both the remaining radiator and perhaps
the
> > oil
> > > cooler are rejecting any additonal load with no problem.
> > >
> > > It appears that smoothing out the path for the air from inlet to
> radiator
> > > surface has benefited the cooling situation.  It could be that
> additional
> > > heat may be rejected by the right (second in series) radiator as the
> > coolant
> > > it received from the left radiator was probably now a bit hotter. I
also
> > > observed that the plate of the PSRU covers an area 3 " in from top to
> > bottom
> > > of the rear of each radiator and the plate is only 2" from the rear of
> the
> > > fins at its closest, so that is obviously not helping flow, the Ross
> Bell
> > > housing did not, so a bell housing might improve flow conditions .
> > >
> > >  I strongly suspect I would probably  find that a similar  reduction
of
> > the
> > > right radiator inlet duct to 9 square inches  would see my coolant
(and
> > > probably oil) temps increase considerable more than another 5 F.
> >
> > OAT at  ground level was 94F when I landed, so not the hottest of days,
> but
> > not the
> > > type I normally prefer to fly in.
> > >
> > > >From what I have seen so far, I think it worth pursuing a reduction
> with
> > the
> > > right radiator duct.  I will probably not reduce it as much for the
> reason
> > > mentioned above. With some other things to take care of, probably
won't
> > get
> > > to it until later part of Sept at the earliest.  But, I have no
problem
> > > flying with current asymmetrical ducts, so will leave it as is for the
> > time
> > > being and collect some more data.
> > >
> > > It it appears that some cooling benefit is derived from providing a
> > smoother
> > > transition from duct to radiator (even if far from a perfect
> > implementation
> > > of the K&M approach) than my old duct provided.  The volume of the
duct
> > was reduced by at least 60%, so while hard to tell from photos the white
> > "filler" material actually fills most of the duct.
> > >
> > > Oh, yes, as an aside, its been 25 hours since I replaced the spark
plugs
> > and
> > > right on schedule - on the way back, I got the first SAG (Sparkplug
> > > Attention Getter)  indication.  So it appears 25 hours on 100LL about
> the
> > > average time for replacing plugs in my case.  I finally got a spark
plug
> > > cleaner, so need to clean a set (as the electrods do not appear worn)
> and
> > > see if getting the lead off the ceramic  cone helps any.
> > >
> > > Best Regards
> > >
> > > Ed Anderson
> >
> > Ed Anderson
> > RV-6A N494BW Rotary Powered
> > Matthews, NC
> > eanderson@carolina.rr.com
> >
>
>
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