cabin heat

[avidflyer]

Well winter is coming to Mn pretty soon, and I'm thinking about cabin heat for the newly rebuilt Kitfox 4 with 912. I've kind of always liked the idea of a muffler shroud, the muffler is always hot when the engine is at cruise rpm. But in cold weather, the engine may struggle to keep the coolant warm enough to draw a lot of heat off of it. Another option perhaps is run the oil through a cooler in the plane instead of coolant and a radiator. That may suffer the same lack of heat to spare in cooler temps. At least that is my take on it. I've done well with the muffler shroud approach, but have never used either of the other two approaches. I would like to hear from those who have experience with oil or coolant heat in a 912 powered setup. Muffler shroud as well for that matter. I've got to choose a method sooner then later. I don't have a lot of room around the muffler with the motor mount in the way, and that is part of what got me thinking about a different approach. Thanks all, JImChuk

[Dave S]

Jim,

Saw your other post and although we have an S7 with the 912ULS, and not a IV, thought I could mention a few things that might help with cabin heat. Overall I feel that the 7 is fairly comfortable in cold weather, although I don't venture out often if it is much below zero F (well, maybe once in a while!). Generally the cabin is comfortable in the winter and I normally fly without a coat or jacket if I decide I can endure the first 15 minutes till everything gets warmed up.

The big issue is cabin air leaks. With too much air infiltration there is simply no way to keep up with the heat loss. There are some physical differences between the IV and 7 I believe; but, if a person does what they can to minimize air leaks it's going to help. The two pneumonia holes on our 7 which made a difference are the wing roots by the back spar and the flaperon horn penetration on the turtledeck. One thing I haven't yet gotten done is some type of closure for the tail to block the air coming in through the tail access area in back - thinking some sort of flexible seal to go around the elevator push pull tube and close out at the tail access bulkhead would cure that - at least on our S7, the cabin seems to have reduced pressure compared to outside so air tends to be pulled in from any opening in the fuselage and cabin. I don't know what can be done with door seals on the IV but I suspect that is a fairly large contributor to air infiltration. During the build I made real sure everything was sealed up in the footwell/boot cowl area - but I am thinking the IV might be designed differently in that space.

Back a few years ago the original engine radiator developed some seepage and I replaced it with the new version aluminum radiator; and, at the same time switched from the previously recommended propylene glycol coolant (AKA Evans waterless) to 60% dexcool - that was done in the summer time and both changes together resulted in 20 degrees lower CHTs and lower oil temps. Winter observations since indicate that both oil and CHTs are lower year round which has resulted in a noticeable reduction in max cabin heat in the winter.

I have considered going back to the Evans coolant just to see if the rather dramatic reduction in overall operating temps is partially due to the coolant or just the very efficient radiator. I have also considered some sort of cowl flap mechanism for the radiator such as Highwing has fabricated but haven't done that either.

Masking off the oil cooler in cooler weather is a must - traditionally I cover half of it at 30 to 40 degrees F and cover it completely if below 30 f which keeps the oil temp around 180 F after the plane has been in cruise for a bit in the winter.

Hope that helps some - my sense of the airplane is that the biggest contributor to cool cabins in a kitfox is air infiltration and working with that can produce the biggest improvement.

[Bill U]

I did NOT build my IV but it has coolant run through two small radiators - each with a small fan on them - under the panel. Here in Phoenix it's the most useless thing on the plane. But I did try it out last December just to confirm it worked and there were no leaks. With 15 years in the Minneapolis area the last 33 here in Phoenix has been nice but this last summer has been trying - AND it's not over yet. 100 degrees today. I could take some pictures of the installation if you would like. But I do agree that with all the air leaks in a IV the heater fan and warm air are mostly for the mind.

Bill U.

[Av8r3400]

I use an "Earl's" cooler from Jegs performance that I sized to match two computer fans for airflow. This is my heater core.

I also have a coolant thermostat inline that I got from Highwing LLC before they closed up. It works great at stabilizing the coolant temps for heater operation. Now there is a product on the market called a Thermo-Bob that some folks are using. If you contact them just don't say it's going on an airplane or they will hang up on you!

Last year I fabbed up an aluminum plate to completely cover my oil cooler (also an "Earl's" unit). This is nicer looking than the duct tape I was using and easier to clean up...

[avidflyer]

I ended up ordering an inline coolant thermostat for the 912 engine. Got one called the thermo-bob 1. It's made for the Rotax engine, and comes with a 180 degree thermostat. They have upgraded the bypass line to 1/2" ID now though, so that will be better to run though a heater core. $145 with free shipping. JImChuk
https://shop.watt-man.com/Thermo-Bob-1-Kit-for-Kawasaki-Concours-1986-2006-1-fittings-TB1.htm

[avidflyer]

I got the thermostat in the mail today. Looks real good. JImChuk

[Eric Page]

Does it even matter which model of Thermo-Bob a Kitfox owner buys, given that it's not being used it for its intended purpose anyway? For those of you who use one, how did you choose when they offer kits for 33 different applications?

How is this thing installed? It's not immediately obvious (to me, at least) where the heater core would go in this installation diagram (http://www.watt-man.com/uploads/IM_TB1_V3.pdf).

Thanks.

[DesertFox4]

California Power Systems carries one also.

Remote Oil Thermostat Complete kit: https://www.cps-parts.com/catalog/eppages/oil_15-05849.php.

Unit Only: https://www.cps-parts.com/catalog/eppages/rmtoiltherm.php


From C.P.S.
1. Q: Will this fit and work for Rotax 912 UL2 engine?
Yes, this will work on all 9 series Rotax engines.

2. Q: What are the thread sizes in this Remote Oil Thermostat? I'm guessing they're NPT, yes? T
Per the supplier: They are 1/2" NPT.

3. Q: What is the weight and dimensions of the thermostat?
It weighs a little over 1/2 lb. 4" L x 3" W x 2.5" H

[avidflyer]

California Power Systems carries one also.

Remote Oil Thermostat Complete kit: https://www.cps-parts.com/catalog/eppages/oil_15-05849.php.

Unit Only: https://www.cps-parts.com/catalog/eppages/rmtoiltherm.php


From C.P.S.
1. Q: Will this fit and work for Rotax 912 UL2 engine?
Yes, this will work on all 9 series Rotax engines.

2. Q: What are the thread sizes in this Remote Oil Thermostat? I'm guessing they're NPT, yes? T
Per the supplier: They are 1/2" NPT.

3. Q: What is the weight and dimensions of the thermostat?
It weighs a little over 1/2 lb. 4" L x 3" W x 2.5" H



You are showing an oil thermostat. I got the coolant thermostat from Thermo-bob JImChuk

[avidflyer]

Does it even matter which model of Thermo-Bob a Kitfox owner buys, given that it's not being used it for its intended purpose anyway? For those of you who use one, how did you choose when they offer kits for 33 different applications?

How is this thing installed? It's not immediately obvious (to me, at least) where the heater core would go in this installation diagram (http://www.watt-man.com/uploads/IM_TB1_V3.pdf).

Thanks.

The hose going to and from the Kitfox radiator are 1". The thermo-bob 1 is for 1" hose. Other thermo-bobs are for different size hoses. On the Kitfox, the thermo-bob with go in the line going to the radiator to keep the coolant from going thru the radiator until it's hot enough to open the thermostat. The bypass line goes through your heater core, and connects to the fitting in the return line from the radiator. JImChuk

[Eric Page]

Thanks, Jim. I see what you're saying, but there's one thing I don't understand. With that setup, once the thermostat opens, directing coolant to the engine's radiator, wouldn't there be zero flow in the bypass loop, so your heater would stop working? Or, does the thermostat never fully close the bypass?

[avidflyer]

I think the coolant would continue to flow through the heater core. Probably the radiator gives more resistence. JImChuk

[Av8r3400]

Thanks, Jim. I see what you're saying, but there's one thing I don't understand. With that setup, once the thermostat opens, directing coolant to the engine's radiator, wouldn't there be zero flow in the bypass loop, so your heater would stop working? Or, does the thermostat never fully close the bypass?

There is alway a slight amount of restriction through the thermostat. This will encourage flow through the heater core. I've never had an issue.

Honestly, if you're running the heat the thermostat usually doesn't open.