Knowing that winter was quickly approaching northeastern Ohio, a few weeks ago the DOG Aviation procurement department purchased a Reiff preheating system specifically configured for the Rotax 912 engine. The Reiff preheating system is designed to keep the engine and oil tank warm … improving cold weather starts and reducing engine warm up times.
As mentioned in the last post, Thursday’s test flight after working on
the carburetors was kept short … but it also served the purpose of warming up
the engine. Only two warm days remain before a forecasted instant 50 degree
drop in temperature grips northeast Ohio, so decided after Thursday afternoon’s
test flight was completed, the time had come to begin installing the Rieff
preheating system for the Rotax 912 engine while the engine was warm and air temperatures
at the hangar were still in a range that the epoxy could be kept warm enough to
cure. The main reason about being concerned about the temperature stems from
the slow cure epoxy used to install a couple of components in the Rieff
preheating system onto the Rotax engine. The epoxy used requires near 70 degree
temperatures to cure correctly and even at that, the cure time is 24 to 48
hours … that will be hard to accomplish in an unheated hangar when nighttime
lows are 20 degrees and highs for the day around the mid 30’s. So I needed to
sacrifice two wonderful 70 degree flying days to let the epoxy cure.
Rieff offers three preheating system kits specifically designed for the
Rotax 912 engine. They are available in different wattages … 150, 250 and 350
watts. Because the winters in northeast Ohio are not as severe as some
locations in the US, the DOG Aviation procurement department chose the 150 watt
version based on the info from Rieff about the heating capabilities of the 150
watt system. The Rieff WEB site states “PERFORMANCE (standard 150 watt system)
- RV-12 aircraft in a hangar with two
tennis balls plugging the air inlets, towel stuffed in oil cooler inlet, and
blanket over the cowl Ambient temp 20-23F …. After 12 hours of heating time oil
temp was 96F (temp rise of about 75F above ambient) Temp measured by Dynon
engine monitor”. Based on that information, I feel the 150 watt system should work nicely here in
northeastern Ohio. If it is much colder than 20
degrees, I think I would likely prefer staying at the house reading a good book.
The 150 watt Reiff preheating system for the Rotax 912 engine chosen for the DOG Aviation RV-12 consists
of two heating elements, a thermostat, a pack of epoxy, wire ties and wires
with premade connectors. One of the heating elements is for the oil tank and
the other heating element is for the engine case. The heating element for the
oil tank is a long 50 watt “HotBand” stainless band clamp which has an orange
colored heating element affixed onto the band. The second heating element is a 100 watt "HotStrip" and attaches onto the bottom of the engine casing with the epoxy. The thermostat is attached onto the oil tank and it too
requires being affixed using epoxy.
The 150 watt Rieff preheating system for the Rotax 912 engine. The kit
consists of a “HotBand” 50 watt heater for the oil tank, an associated thermostat, a
“HotStrip” 100 watt heating pad for the engine casing, associated wires with
preinstalled connectors and a package of slow curing epoxy.
Instillation is fairly straight forward, the “HotBand” clamp is
installed around the oil tank and snugged down, but not over tightened … over
tightening will damage the heating element. The areas on the engine and oil
tank that will have epoxy applied are to be scuffed with a ScotchBrite pad and
cleaned with solvent to remove oils. The smooth side of the “HotStrip” also
receives a scuffing with a ScotchBrite pad and cleaning with solvent.
My right hand is pointing to the 50 watt Rieff “HotBand” that is snugged
up around the oil tank. My left hand is pointing to the thermostat that was slathered
with epoxy and affixed to the oil tank using masking tape to hold its position
while the epoxy cures.
Next, a socket is used to roll over the plastic epoxy package to mix the two part
epoxy components together. The epoxy is then slathered onto the bottom of the 100 watt “HotStrip”
and it is affixed onto the bottom of the engine casing on the right side adjacent
to the #1 cylinder. I used a piece of wood wedged between the oil cooler and
the “HotStrip” to keep the strip seated firmly onto the engine casing. I later
discovered this area presented more of a challenge than I thought it would in
that, the engine casing is at an angle and much to my surprise the
“HotStrip” slid away from where I had originally placed it. It is OK but now it
looks much messier because there are smears of epoxy all over the bottom of the
engine. If I had it to do over, I think I would have used a piece of duct tape
to prevent movement in addition to the wood or a foam block to keep upward
pressure on the “HotStrip” while the epoxy cures.
Using a piece of wood to keep upward pressure on the “HotStrip” to keep
it pressed up onto the engine casing. The unexpected result of this is that the
“HotStrip” moved a little. Fortunately, the 100 watt “HotStrip” slid towards
the case screws and not the other way where it would likely have fallen off the
bottom of the engine due to the slope in the engine case at this location.
While the epoxy cures on the engine, the remaining epoxy in the package
is to be placed in a freezer overnight because it will be used again the next
day. The following day, the remaining epoxy is used to overlap the edges of the
“HotStrip” this will prevent it from falling away from the surface of the
engine should it loosen up from the epoxy on the bottom of it.
To offset the cooler night time temperatures, a piece of plastic covered
with a moving blanket was placed over the engine. Two halogen shop lights were
used to create heat … one placed under the oil tank area and the other placed
under the engine near where the epoxy was applied to the “HotStrip”. The
halogen lamps generate quite a bit of heat so, until the temperatures make the
big plummet forecasted, the two lamps should allow the epoxy to stay warm
enough during the evening hours so it cures nicely. Only have 36 hours for this
to pan out after that ... winter will arrive in northeastern Ohio in one big blast.
A piece of plastic and moving blanket are being used to trap heat from
two halogen lights so hopefully the epoxy can cure correctly on the thermostat
affixed to the side of the oil tank and the “HotStrip” affixed onto the bottom
of the engine casing.
The day after the above photo was taken, a quick trip was made to the hangar to
check on the progress … the epoxy appeared to be curing nicely so the remaining epoxy was applied to the edges of the "HotStrip" per the instructions and left to cure. Have not completed
the wiring because decided to stay hunkered down at the house. We were in
the 70’s on Friday and on Saturday plummeted to lows in the 20’s with daytime highs
in the 30’s with snow. After 35 years out in California the first winter cold
and snow usually keeps me in the house until I get acclimated to the cold ... (which truthfully never happens). I still
need to finish up on the Rieff preheating system ... the wiring connectors still
need to be installed and dressed out with wire ties. Sounds like a good project
when we get back into the 40’s.