| Hi Neil
I've listened over the years to the debate over thermostats. What makes sense to me is reducing the intake as much as possible and using cowl flaps to increase the delta P across the face of the core/s and so to minimise cooling drag. And I'm with you, I have never known a thermostat to fail and it seems its a great way to stabilise and quickly establish operating temps. I took the one out of our Renesis 4 port and hope we'll be OK with our setup and add the cowl flaps as needed after testing.
I have always found Paul L very helpful though some of the figures for radiator area and intake area are quite large (600cu inch) compared with a number of flying examples that are cooling well. My research: (I believe the numbers are accurate) Ian Beadle RV6 - 374cu inch water cooler (similar to your setup me thinks) He reduce his intake size significantly while still cooling. It was all about diffuser shape. Dave Leonard RV6 - 422cu inch water cooler (again similar under setup as yours) Tracy's 3 rotor RV8 - 540cu inch fed by a 5 1/4" (22in2) intake. I have tried to model of this setup. 2/3 of Tracy's would be 360cu inch cooler with an inlet area of 15in2. Ours is 540ch inch cooler with a 18in2 intake. Hoping our diffuser is somewhat as efficient as Tracy's.
Hey I'm not flying so my wisdom could be vapor.
Cheers
Steve Izett Perth Oz
Thermostats are a touchy subject apparently. Most say to definitely not put
one in, but in 50 years plus of driving everything from cars to heavy machinery,
I have yet to have one fail. Now I find myself in the same position as
yourself with a rotary that is too cool. there must be only the two of us
in the world. Yes I also have too much cooling drag but am now restricting
the air inlet to try and get the cooling right for my summer temps, and reduce
the cooling drag. Today I cut the inlet back to 80 square inches or 18% / 20% of
total exchanger area. It appears that I may have to restrict further yet!
I ran it on the ground at 4000 Rpm expecting it to overheat, stationery, but the
water only got to 180 degrees and the oil to 165 degrees( 100 degrees
OAT). My cowl flaps only make about 8 degrees difference. Did not
fly as it is possible that my computer A may have died. Ran everything on
computer B. My aim is to get the cooling right for the 115 degrees that is
possible in summer here by restricting the air to the heat exchangers, possibly
take off the cowl flaps and put a thermostat in the line next to the water pump
for winter temps. I may also have a second setting for the inlet
restriction to restrict the air more for winter as well, for is only 5 screws to
change the position of the air inlet. My aim is this. To get normal
cooling as close as possible to perfect without the need for a thermostat, then
put one in to accelerate the motors initial heating up from cold and to
maintain that temp at altitude without the need for cowl flaps, even though I
already have them. Neil.
Sent: Wednesday, December 18, 2013 2:45 PM
Subject: [FlyRotary] Cooling Water Temp
Today I got a chance to sneak out to the
airport and play.
The RV-8 cowl was off due to changing the oil, so I gave it a pretty good
inspection, reassembled it and started it up.
I was planning to do a tethered trial at take off power, but the weather
was clear and cold with low overcast and no wind, so I taxied about while
waiting for the engine to warm up.
It never warmed up. The oil temp came up to about 156F, but the water temp
came up to 128F while idling or slow taxiing. I did 4 aborted take off, the
water temp rose to about 138F.
I have heard that this is not warm enough for full power. I did accelerate
to 4850 RPM (2200+ prop RPM) before I let off the brakes and concentrated on
rolling down the runway, lifting the tail and throttling back @ about 45 MPH.
I don't have a thermostat in it right now, the one try with a thermostat
ended in an overheat shut down before damage. maybe I didn't have all the air
pockets burped out. So I might have removed it prematurely.
What does the group say about warm up before take off, and about using a
thermostat?
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