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Thread: Thermostat or radiator shutters

  1. #1
    Senior Member cap01's Avatar
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    Default Thermostat or radiator shutters

    after a couple of years of flying in a cold cockpit I finally tried the duct tape on the radiator and finally some heat . Now for a more permanent fix , thermostat or shutters . Not too sure about a thermostat without some kind of bypass but also not sure of how affective shutters would be on the back side of the radiator . Maybe some of the guys up in the real cold country would have some thoughts on this ? Thanks
    chuck
    kitfox IV 1050
    912ul warpdrive
    flying B , yelm, wa

  2. #2
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    Default Re: Thermostat or radiator shutters

    we used a in line thermostate from" highwing llc" it works well summer or winter. we can have some 95' days in the summer and the temps are fine.
    on those real cold days around 40' the water temp is around 190'

  3. #3
    Senior Member Dorsal's Avatar
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    Default Re: Thermostat or radiator shutters

    Two concerns I have about the inline thermostats is;

    - Restricting flow and increased pressure. They are certainly used in other Rotax applications so perhaps not an issue though some models use a by-pass.
    - Restricting flow to the cabin heater as I think the heater T is down stream from the likely location of the thermostat. This might keep the coolant temps up but not provide more cabin heat.

    For these reasons I went with AL tape on half the radiator, seems to work OK but I liked the idea of the coolant thermostat better. I use a thermostat on the oil and it works great. If others know why my concerns above are silly please chime in
    Dorsal ~~^~~
    Series 7 - Tri-Gear
    912 ULS Warp Drive

  4. #4
    Senior Member Dave S's Avatar
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    Default Re: Thermostat or radiator shutters

    I theory, like the idea of a coolant thermostat, primarily for the sake of maintaining a constant healthy temperature for the engine.

    In practice, I have not installed one simply out of wanting to keep the system as simple as possible.

    I.C. (internal Combustion) engines operate most efficiently with as high an operating temperature as the materials the engine is made of and the oil will tolerate. An inline thermostat serves that purpose; and, provides the side benefit of a more effective heater. (same idea with oil thermostats...keep the temp up to a decent operating level)

    My first concern with any kind of liquid or air restriction device like a thermostat or radiator shutter in my airplane is failure mode operation. A liquid thermostat has two failure modes...stuck open or stuck shut...(or something in between). The first is not an operational problem; however, stuck shut means the engine has to be shut down in time to prevent damage or it will shut itself down due to overheating...either way...no power. Having said that, I can't say how common that kind of a failure is with Rotax in line thermostats...I know I have had stuck shut thermostats in cars and you are all done pretty quick.

    I have thought about a shutter designed so failure mode would blow the vanes open....although, control systems on certified aircraft (throttle, ICO, Carb Heat, cowl flaps) have no fail safe mode...they count entirely on the system not failing...so maybe failure mode concerns are over-rated.

    I am pretty cautious about things like this.....my luck is best explained in terms of a contest I was in once....with 200 door prizes......There were 201 entrants including myself.....and I don't need to even say who didn't get a door prize........

    I am leaning towards some kind of shutter system on the back side of the radiator as a more fool proof system; but, the fact that all is running well and the cabin is comfortable....oh well.

    Dave S
    KF7 Trigear
    912ULS Warp Drive

  5. #5
    Senior Member HighWing's Avatar
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    Default Re: Thermostat or radiator shutters

    There is one other option for you guys with the in cowl radiator fed by the NACA duct. The 5 Outback with Series 7 FWF, I helped finish, has a "Door" on the NACA Duct opening that consists of the cowl skin cut along the curved sides and aft but with the short forward edge uncut to act as a hinge. A fiberglass "joggle" provides a seat for the door. and foam stiffeners were bonded to the door for rigidity. To avoid having to unhook the control cable when removing the cowl, we designed a mechanism that reversed the pull on the cable at the cowl firewall interface to a push motion. Fail safe was a spring set-up that would open the door in the case of cable failure. Pulling on the cable in the cockpit pushed the door closed through the nesting push fittings. Three photos attached.
    Lowell
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    farmboy's Avatar
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    Default Re: Thermostat or radiator shutters

    I had my first flight today after installing a oil Thermostat,oil temp held at 158 degrees outside temp was 11 degrees farenheit. Before installation I was running 128 degrees.

    Do I understand this correct that the 912 needs a bypass inline when a coolant thermostat is installed? I have a cabin heater so I want full heat and do not want too much pressure in system when thermostat is closed. Sorry if this has been discussed before but just want to do things right. Thanks for the help!

    Series VI 912s

  7. #7
    Senior Member HighWing's Avatar
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    Default Re: Thermostat or radiator shutters

    A quick note on the HighWing LLC inline thermostat.

    The thermostat was designed after a similar thermostat that was shown at some of the European airshows several years ago.

    There is an internal bleed or vent just like in your Porsche or Corvette.

    The system pressure is determined by coolant temps and the pressure cap on the Spider Tank.

    They have been in use for four years.

    Any feedback has been similar to jamesmil's

    I have one on my new Model IV and since most of my hours have been in Phase One, constant monitoring shows very consistent temp rises - much quicker than bare naked - then holds the minimum during flight.

    Respectfully,
    Lowell

  8. #8
    Senior Member cap01's Avatar
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    Default Re: Thermostat or radiator shutters

    lowell , what thermostat do they use and what temp do they regulate to ?
    chuck
    kitfox IV 1050
    912ul warpdrive
    flying B , yelm, wa

  9. #9
    Senior Member cap01's Avatar
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    Default Re: Thermostat or radiator shutters

    farmboy , dont you think thats still a little cool for oil temp ? i also have the thermostat in the oil system but also have to cover the oil cooler in in the winter . i run the temp 190-200 f . the radiator cover is a slide arrangement with holes so i can vary the amount of air passing thru the cooler , ground adjustable . we dont normally get outside air temps in the as cold as you do in the winter either .
    chuck
    kitfox IV 1050
    912ul warpdrive
    flying B , yelm, wa

  10. #10
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    Default Re: Thermostat or radiator shutters

    I use a oil thermostat from Bullyhawk. It keeps the oil at 200 degrees and definitly helps warm the engine faster. In the real cool weather 32 F or 0 C...I still put duck tape over the oil cooler just to help out. At those low temps the oil will only reach up to 180. I do not have a water thermostat. I also put duck tape on the water radiator. If you look close at the photo you can see the tape. I leave two cooling veins open on both rads. So yesterday I went up it was -5 C or 28F and the oil was at 205 and the head temp was 210.
    Question...I do NOT have a heated hanger or pre engine heat. Before start up I hand prop about 50 blades, then crank without mags on for 3 or 4 seconds(I now have indicated oil presure). Turn on mags, fuel pump, pull choke and it fires almost immediately.
    With the oil this cold will this method hurt my engine?
    I have 70 psi presure before it starts. I have head temp in about 4 minutes and my gauge starts at 120 degrees. The oil temp moves the gauge in 7 minutes also at 120 degrees. This is at a 2000 rpm idle.
    Your thoughts....?
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