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Alternative cabin hot air source...

bjdecker

bjdecker

Well Known Member
Ambassador
...I'm not talking about the pilot or passenger :)

As I was pondering my #4 cylinder temperature/oil cooler temperature/plenum & cowling delta-p, I thought it might be interesting to route the exit air from the oil cooler to the cabin heat valve (instead of from the exhaust shroud).

I'm using a 3" duct to feed the oil cooler currently, and was going to change it to a 2" based on temp & performance data I have.

Has anyone else done this?

B
 
Nice article Bob.

BJ,
We had an unusually cold winter this past year and I was REALLY uncomfortable on two flights. That was with the standard kit setup for RV7A with IO-360-M1B. (There is a new one released this spring by Vetterman. I have the older style)

I added a second muff on Cyl 4, hooked in series with the original muff on Cyl 1 and fed the pair from a manifold on the back of the oil cooler. It did improve the heat but not as much as I expected. Possibly enough that I am done fooling with it. I can't imagine the oil cooler air by itself being nearly warm enough.
 
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Hmmm. It probably depends on which engine (jets or not) whether there will be enough oil heat in winter. Don't many people completely block off the oil cooler to keep the temperatures up in winter? If so, the colder it gets outside the less heat is available from the oil. 1200-1300F is always available from the exhaust pipes.

Disclosure - I have the AWI exhaust and they have welded studs on on the exhaust pipe under the heat muff. I am counting on them to provide enough heat from one muff down to at least zero F. I also have heated seats.

Maybe AWI would add them to your pipe for a nominal charge. They are resistance welded on with huge threads too.

I suppose if things get worse, I can get heated underwear like Dan H :D
 
Cabin heat

I purchased an RV-7A two years ago and read with interest all the folks complaining about not enough heat in the cockpit. I live in the Denver area and take my RV to AZ in the winter to have it with me in my other RV---Winnebago. Last year I flew it down to Coolidge, AZ on Dec. 23rd when Colorado was having some very cold weather. Crossing the Sangre De Cristo mountains and above some show showers, I flew for probably an hour between 16 and 17,500' with an OAT of -35 C. I was very comfortable in just a light jacket. The builder I purchased it from lived in Wisconsin and he has fabricated a plate to place over the opening in the upper rear baffle that goes to the exhaust heat muff, reducing the scat hose opening to only 5/8 ". I suspect that dramatically increases the temperature of the air going to the cabin because of reduced airflow through the heat muff.

Has anyone else done this?

My problem with cockpit temperatures is keeping it cool enough at lower altitudes in the summer, not warm enough in the Winter.

LL
 
I also live in Colorado, so I put some extra effort into the cabin heat. 1. I started off with heated air coming from the bottom of cylinder four (the curved section of the baffle). I welded a 1-1/2" aluminum tube to the curved section and ran a scat tube from there to the heat muff. 2. I changed my cabin side controlled valve to a firewall side controlled, so I could hook a scat tube on the inside of the cabin. 3. I ran a scat tube to the plastic valve and placed it even with the instrument panel, so it can be aimed toward the back cockpit or up at me. 4. I bought two wide mouth baby bottle nipples to cover the fresh air valves to stop unwanted cold air. 5. I sealed the spar braces on the side walls, RV-8A, but think the gear towers on the RV-8 should be looked at also for leaking air.

Even at 20 F or colder I can't hold my hand in front of the valve for more than five seconds. It is that hot and both cockpits are warm. At cruise settings the heat muff can only generate X number of BTUs. The warmer you raise its incoming air the higher the cabin temp will be. Bringing the hot air closer to the crew will also help them feel warmer.

BTW, on my current project I have converted my old cabin side valve to a firewall side by moving the actuator arm to the opposite side of the valve and then riveting a flange, so it goes through the firewall into the cabin. This is easy to do and can save you some money.

On my current project I spent some extra time fitting 1/16" inch rubber sheeting over all the openings (wing attachments, flap rod, rear spar, etc.).

Also, always fly in clothing that you could stay outside overnight comfortably. Hope this helps.

Jim
 
lllewis45 said:
I purchased an RV-7A two years ago and read with interest all the folks complaining about not enough heat in the cockpit. I live in the Denver area and take my RV to AZ in the winter to have it with me in my other RV---Winnebago. Last year I flew it down to Coolidge, AZ on Dec. 23rd when Colorado was having some very cold weather. Crossing the Sangre De Cristo mountains and above some show showers, I flew for probably an hour between 16 and 17,500' with an OAT of -35 C. I was very comfortable in just a light jacket. The builder I purchased it from lived in Wisconsin and he has fabricated a plate to place over the opening in the upper rear baffle that goes to the exhaust heat muff, reducing the scat hose opening to only 5/8 ". I suspect that dramatically increases the temperature of the air going to the cabin because of reduced airflow through the heat muff.

Has anyone else done this?

My problem with cockpit temperatures is keeping it cool enough at lower altitudes in the summer, not warm enough in the Winter.

LL
Click to expand...

LL,

I was very specific about my setup because there are differences in what is available to builders depending on the engine.

So....one important aspect is whether the sump is a vertical intake (carbureted or injected) or horizontal intake (injected only). A second aspect is whether the craft is an A model or not (I see yours is an A). The exhaust designs and available spots for heater muffs are considerably different. It is my understanding that the heater muffs on the carbureted exhausts are much better than the puny unit on the horizontal injected exhaust for A models. Can you specify what is on your purchased craft?
 
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lllewis45 said:
I purchased an RV-7A two years ago and read with interest all the folks complaining about not enough heat in the cockpit. I live in the Denver area and take my RV to AZ in the winter to have it with me in my other RV---Winnebago. Last year I flew it down to Coolidge, AZ on Dec. 23rd when Colorado was having some very cold weather. Crossing the Sangre De Cristo mountains and above some show showers, I flew for probably an hour between 16 and 17,500' with an OAT of -35 C. I was very comfortable in just a light jacket. The builder I purchased it from lived in Wisconsin and he has fabricated a plate to place over the opening in the upper rear baffle that goes to the exhaust heat muff, reducing the scat hose opening to only 5/8 ". I suspect that dramatically increases the temperature of the air going to the cabin because of reduced airflow through the heat muff.

Has anyone else done this?

My problem with cockpit temperatures is keeping it cool enough at lower altitudes in the summer, not warm enough in the Winter.

LL
Click to expand...

But isn't it important to have a lot of air passing thru the muff heater to avoid overheating and failure? That is why the heater box has 2 positions, one directing the flow into the cabin, the other dumping overboard so you never stop the flow.

I am really interested in the articular about using engine oil for heat, really killing 2 birds with one stone, not only having safe cabin heat but also maintaining a constant oil temp for the engine. Muff heaters and CO have always made me nervous.

Other than possibly an oil line leak spraying hot oil into the cabin, does anyone see a down side to this idea?
 
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Mine works.

FWIW, I mounted my oil cooler on the firewall and fed air from the plenum to the top. I built a box on the bottom with a door, and an air valve to the cabin. When I want heat I open the air valve. If I want it hotter then I close the exit door. Then 100% of the air through the cooler must flow through the 2" cabin heat valve. I did this primarily to simplify construction and keep weight down; but I was also concerned about keeping CO gas out of the plane. I use the cabin heat any time I fly over 10k and it gets nice and warm.

Lance
 
Heater muff

Reply to rzbill and CDNRV7

Thanks for the comments. My concern for too much heat in the muff is one of the reasons I responded to this thread and asked if anyone else had done it. I think I will try enlarging the hole in in the plate to increase airflow and lower the cabin inlet temperature. The high altitude and cold OAT flight is the only time I've ever had to open the heat vent beyond about half way, even on Winter flights to Iowa, and you mid-westerners know what that can be like. ;-)

My engine installation is the Superior XP O-360 with standard exhaust and updraft carb.

I have inspected the muff/ exhaust pipe on the two Condition Inspections I have done, no issues.

Thx,

Bernie
 
Oil heat for the cabin

I use oil heat and it works great. But I have a turbo charger and it is recomended to cool the oil before it is returned to the engine so I run all the return oil through a large oil cooler before dumping it back into the engine. In the summer the hot air is dumped outside under fuselage. I had to custom make all the valves and covers which is time consuming but worth the time.
 
lllewis45 said:
Reply to rzbill and CDNRV7

Thanks for the comments. My concern for too much heat in the muff is one of the reasons I responded to this thread and asked if anyone else had done it. I think I will try enlarging the hole in in the plate to increase airflow and lower the cabin inlet temperature. The high altitude and cold OAT flight is the only time I've ever had to open the heat vent beyond about half way, even on Winter flights to Iowa, and you mid-westerners know what that can be like. ;-)

My engine installation is the Superior XP O-360 with standard exhaust and updraft carb.

I have inspected the muff/ exhaust pipe on the two Condition Inspections I have done, no issues.

Thx,

Bernie
Click to expand...

I would say that if only half open on an Iowa winter day keeps you warm you can afford to allow some more airflow. I know you have said that you seen no problems on inspections, but even a small crack in the pipe is serious. As I said before, maybe I'm being paranoid, but muff heaters make me nervous.....better safe than sorry. With the good reviews I have seen about using oil heat that is the way I will go.

Have fun
 
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not that this is a bad idea at all, but i'll chime in with my experience from a failed oil cooler line that got some hot oil into my cabin heat valve and subsequently on my legs/feet while i was flying


i don't want hot engine oil in my cockpit, it would take a lot of convincing to go with these ideas
 
Yeah, that was the only downside I could see from this, although a blown oil line would never be a good thing, hopefully you had someplace to land close by.
 
Oil lines are on the outside.

In my setup the cooler itself would have to fail for oil to enter the cockpit, and I could easily close the the cabin air door if that we're to happen. However, if that did happen, a little oil in the cockpit would be the least of my worries!
 
I agree, losing oil for the engine would be a more pressing concern. In your setup how noisy is it and how much airflow comes into the cabin? I was thinking that opening up a hole basically in the firewall would transfer a lot of noise.....not true?
 
One of guys down here who flies "up North" frequently wrapped just his heat muff, not his exhaust, with exhaust wrap and insist that it will bake him out of the plane.

The only downside is he has to remove the wrap each year for his Condition Inspection.
 
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About that (carbon monoxyde), I have installed today my heater bypass box. I have the Van's model. I can't understand why we have to seal the firewall, wire hole and everything, and this box are full of gap everywhere !! Did I miss something, or it's normal ......?? :confused:
 
BillL said:
I have the AWI exhaust and they have welded studs on on the exhaust pipe under the heat muff. I am counting on them to provide enough heat from one muff down to at least zero F. I also have heated seats.

Maybe AWI would add them to your pipe for a nominal charge. They are resistance welded on with huge threads too.
Click to expand...

I have had the AWI 4-into-1 exhaust for 6 years and it will throw out a lot of heat. I wish Larry V. put studs on his pipes, but the original 4 into 2 from Larry that was on my -8 had a heat muff that was off-center so I don't know where you'd know to put the studs. I bought the AWI product because I was living in Northern Illinois and flying a lot in the winter and wanted the extra cabin heat.

Here's a link to a thread about using stainless steel wool or stainless steel scrubbing pads to pack into the heat muff. http://www.vansairforce.com/community/showthread.php?t=106026&highlight=steel+wool
Here is a source for the pads http://www.amazon.com/gp/offer-listing/B002CQTXBC/ref=dp_olp_new?ie=UTF8&condition=new
 
Closterman said:
About that (carbon monoxyde), I have installed today my heater bypass box. I have the Van's model. I can't understand why we have to seal the firewall, wire hole and everything, and this box are full of gap everywhere !! Did I miss something, or it's normal ......?? :confused:
Click to expand...

The standard air supply for the heater is either the back of R/S baffle or up front in clean(er) air. The bypass simply keeps air flowing through the heat muff to keep that section of exhaust pipe from over heating. If you have gaps in the heater valve then you should seal them up, along with all the firewall cracks. You seal the firewall so it will retain fire incase of engine fire. See DanH posts on his FWF materials work. He has exposed many materials and practices that could have negative effects on the occupants in case of engine fire. You should be familiar with that. The standard Vans heater valve uses an aluminum flapper, many have replaced that with a stainless flapper version (like the 10 uses) . Don't use pro seal for a firestop material.
 
Anyone ever thought of wrapping and exhaust header with a copper tube filled with coolant a small circulation pump and a heater core inside the cabin? With a small 12v fan these can pump out btu's a ball valve can isolate the core for summer operation.
 
BillL said:
I suppose if things get worse, I can get heated underwear like Dan H :D
Click to expand...

It's hard to beat an electric motorcycle vest. Wore it for years flying open cockpit stuff. In the RV I put it on Patti, and she seems happy. Been meaning to buy another one, but so far I've not felt a need. I just wear a cold weather pullover riding suit. I guess my Yankee cousins would pick a snowmobile suit.

Anyway, it's fine down to zero OAT over jeans and a sweater, with ordinary nomex gloves. Very comfortable walking on a cold ramp, and meets the winter survival requirement if forced down.

No firewall penetrations for heater boxes, no scat hoses or heat muffs in the engine bay, no CO risk. We're in the era of the all-electric airplane, yes?
 
Motorcycle vest

DanH said:
It's hard to beat an electric motorcycle vest. Wore it for years flying open cockpit stuff. In the RV I put it on Patti, and she seems happy. Been meaning to buy another one, but so far I've not felt a need. I just wear a cold weather pullover riding suit. I guess my Yankee cousins would pick a snowmobile suit.

Anyway, it's fine down to zero OAT over jeans and a sweater, with ordinary nomex gloves. Very comfortable walking on a cold ramp, and meets the winter survival requirement if forced down.

No firewall penetrations for heater boxes, no scat hoses or heat muffs in the engine bay, no CO risk. We're in the era of the all-electric airplane, yes?
Click to expand...

Dan. Do you recommend plugging into the 12v system in the plane or the self contained battery vests?. I have no heat in my plane, live in the North East and would like to fly this winter.
 
Heated vests like Dan says.

Heated motorcycle jacket liners are the way to go. Just plug them into a properly rated outlet. They really only draw about 3-5 amps when on full power, and I assure you they won't be on full power. I use them in the Stearman and have flown it down to 35F and was toasty warm and was on about 1/3 power. They are very light and go right over your shirt.

Vic
 
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