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Northernliving

Well Known Member
I’ve been lurking here for a number of years – on and off, considering an RV. I’ve always wanted to build and have looked at the Murphy Rebel, the Sportsman and the Velocity. I visited the Velocity factory this past spring, but I’ve always come back to the RV – in particular, the -8. Bob Ellis from the UK was kind enough to meet me in Ireland south of Dublin at a small grass strip on the coast in Newcastle this past spring to let me see and ride in his recently completed RV-8 G-JBTR . Mike Draper joined me a few weeks ago south of Boston in Plymouth and let me work on and fly in his newly completed RV-8. Well, I’m sold. I have some work to do around the house getting ready for this project, but I’d like to get started next spring. I’ll probably do a slow build just because – well, because I want to build it all. So, I’m planning now and doing a little dreaming. I’ve looked at a number of threads on cabin heat, or lack thereof – especially in the rear seat. During my stint at looking at canards, one thing that I noted is that many used oil heat for the cabin. So I’m wondering if anyone has tried in in an RV. Seems simple enough, and you could probably put one in the rear. Here is a diagram with the necessary valves, etc. Any thoughts or comments on this? Sure would keep my bride warm and happy in the rear. I’m float rated, and I would also like to put this on a set of amphibs, but that’s another thread!

Brian

http://nickugolini.com/Website/Oil Heat/EZ_Heating_System Article.pdf
 
RV8 Cabin Heat

Hi Brian
Planning to fly northen Europe ,Groendland Canada Alaska and Aleutian with an RV8A I am extremly interrested by your installation .
Any pictures availables ?:)
Hotel Juliet
 
One of the issues I've read about with this installation is a lack of heat in the winter. The oil will be running 180F or so (maybe lower) in the winter vs a much hotter exhaust mounted muff, so the air coming out of an oil/air heater just won't be as warm as what you get from a traditional heat muff.
 
Using engine oil as a source of heat is a very limited option. My hangar-mate's 8A uses this technique as its primary source of heat, effectively ducting air through the oil cooler and either dumping it overboard or routing the warmed air to the cabin, as necessary. For flight in cold weather this system does not produce nearly enough heat. Keep in mind we're in Canada, so cold weather is cold - we consider temperatures around freezing to be "cool" while "cold" doesn't start until at least -10C.

My hangar-mate's experience leads me to believe that, first and foremost, getting a seal on the canopy is the first step in being able to achieve any degree of comfort in this aircraft. Snoop around here and you'll see somebody came up with a great idea for an inflatable canopy skirt seal - definitely worth looking into.

Once you've got the canopy sealed you can start working on similar sealing to prevent airflow coming in from the aft baggage/tail area and from fuselage penetrations at the wing root. Without addressing the air leakage points one is just throwing away any available heat.

There's also another good post or two about piping hot air to the back seat through SCAT ducting - definitely worth a look. The concept of installing two heat muffs to provide additional heat is also one worth considering.

When all else fails, check out the posts here on electrically heated garments - socks, leggings, vests, gloves... My aircraft has limited heat from the engine so I installed heated seat cushions and I wouldn't be without them. They get plugged in as soon as the temperatures drop below freezing and don't get unplugged until the next spring! I would highly recommend heated seats, irrespective of the means used to heat the cabin. They simply feel terrific, and as an added benefit they help warm the tempurfoam seat cushions to make them softer - otherwise they're like a brick when cold.
 
Seems to me that in a rear-engine plane like the canards, this could be an effective and feasible approach since you can much more easily restrict the amount of cooling air the whole engine gets... and thus improve on the amount of heat you could extract from the oil for the purpose of cabin heat.

The problem with the RVs is that with the engine up front and generous-sized fixed openings in the cowl for ram air cooling at 160+ knots in really cold winter temps, there is so much cold air blowing over the whole engine that the oil cooler rarely comes into play at all since the vernatherm is always letting the oil bypass the cooler, and most of us have to use plates, shutters, or other various contraptions to block airflow over the oil cooler in order to allow the oil temps to get up high enough since there is always a small amount of residual oil flow thru the cooler even with the vernatherm fully retracted.

In my O-320 RV-6, I even blocked off both the front and rear of the oil cooler with aluminum plates and still could barely get the oil temps over 150 on cold winter days.

In my friend's RV-8 with a fire-breathing IO-360 that normally has trouble with high oil temps in the summertime.... on cold winter days however the airflow over the cooler must be blocked off or it will never even reach the full 180 degrees also.

I would think that trying to use engine oil as cabin heat in an RV, in very cold winter climates, that you'd never be able to get enough heat out of it to do much good, plus you'd also risk running your engine oil temps too low as well.
 
Thanks for the reply guys -has me thinking. I didn't realize that the engine would be running so cool as-is. Do stock engines have a veritherm to regulate oil to the cooler?

If I read the author's notes correctly, there is an engine veritherm set at 185F that controls the oil flow to the "normal" cooling circuit, so no oil leaves the engine unless it's 185F or more. Then there is a second veritherm in front of the primary oil cooler set at 190F. As long as the oil temp is above 185F and below 190F the hot oil bypasses the stock cooler and is pumped into the cabin oil "heater" that recycles cabin air (apposed to outside air). So, the cabin will get first dibs on extra heat from the engine that is normally passed to the cooler mounted in the engine compartment. The stock cooler would only be used if the oil temp is over 190F. Given what you have said about engine temperature, this may still not be enough.

I've read through almost all the posts that I could find on this site (and others) about RV8 heat and I seem to remember someone saying that John Huft's "Nuisance" had oil heat. I could have been mistaken. Also, I think I read that Mike Stewart cut through his web spar (not the spar) to so he could run the scat duct through it. I prefer the oil option as long as there is enough extra heat.
 
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Most stock Lycomings do have a vernatherm. However, the way the oil cooling circuit is designed in the back accessory case of the engine, the oil follows along 2 paths in parallel. One path is thru the oil cooler fittings, the second path is a bypass around those fittings. When the vernatherm reaches full extension at 180 degrees, it blocks off the bypass path like a needle-and-seat style of valve and forces all the oil to flow thru the cooler fittings. When the oil is cool and the vernatherm is retracted then the lion's share of the oil flows around the bypass, but some amount is always going thru the cooler's path too.
 
Canadian JOY,

Thanks for all the tips on sealing - spot on.

Here is the link to Mike Stewart's S8 with rear heat through the spar web. This might be the best way to go. It also seems that pulling air FROM the cabin through the heat muffs is desirable. (not sure it's possible, though). Perhaps some fresh air mixing box is in order.

http://www.mstewart.net/super8/rearheat/index.htm
 
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Hotel Juliet,

No pics yet! Perhaps in a year or two. Just doing some planning. My bride loves her heat the winter and cold, and as I used to say in the south, "when mama's happy, everyone is happy."
 
I wired Powerlet sockets into the front and rear cockpit walls. When flying at the higher altitudes or on cold days, my passenger and I can wear Powerlet heated clothing (the same as worn by many motorcycle riders). We stay nice and toasty. The Powerlet sockets wire up just like any other cigarette lighter 10 VDC adapter. Nothing to it.
 
Powerlets also work for battery-minders ...

I installed a female Powerlet socket just inside the oil filler door, wired directly to the battery terminals (less than 1' away.). I then found a pre-made short adapter from the standard two-prong battery maintainer plug to Powerlet male plug. Anytime my battery is a little low, or we get extended cold weather, I plug the battery maintainer in thru the oil door. Very handy; easy to rig up.
 
Canadian RV cabin heat

Hi Brian
I put about 30 hours on my Canadian RV7-A last winter during flight testing. Early on, I needed long underwear, wool sweater, toque and gloves to function, even then it was not comfortable when temps dropped below freezing. (I flew as low as minus 20 Celsuis OAT). I have one heat muff supplied by Van's, but it is not that effective because I have no muffler on my Lycoming with forward facing fuel injection. Here is what I did to warm things up:
-Improved canopy seal as mentioned by another responder
-Installed aileron push rod boots from Classic Aero to stop the icy blast
-Installed interior panels from Classic Aero
-Installed additional insulation on forward side panels aft of rudder pedals
-After engine break-in, I ran higher EGT at cruise power settings
-Reduced air inlet to heat muff by 50% for lower volume, higher temp
-Improved seal on cold air vents with RTV to stop leakage

The plane is now reasonable to fly with OAT of minus 15 C, but not cozy warm like other planes I fly. (experimental and factory built)

Drawing heat from the oil cooler would not work with my Lycoming M1A engine because I block 3/4 of the oil cooler in winter to keep my oil temp above 180 degrees. I leave 1/3 of the oil cooler blocked in summer

In my opinion, RV's need some form of cabin heat to take advantage of their high altitude cruising capability, however exhaust heat is marginal unless you have a muffler, or are willing to weld a bunch of nuts and bolts to your exhaust header to increase the surface area underneath the muff. Also, exhaust heat is the primary cause of carbon monoxide poisoning.

I am planning an RV4 build, and will forego the exhaust heat muff in favor of electric seat heat from Classic Aero, and an electric cabin heater from DC Thermal. New avionics and lighting systems are so efficient, a standard 60 amp alternator has capacity to provide cabin heat so long as you keep an eye on the amperage following engine start-up.


Jay
RV-7A
C-FXPT
 
2nd cooler

Canadian_JOY said:
Using engine oil as a source of heat is a very limited option. My hangar-mate's 8A uses this technique as its primary source of heat, effectively ducting air through the oil cooler and either dumping it overboard or routing the warmed air to the cabin, as necessary. For flight in cold weather this system does not produce nearly enough heat.
Click to expand...

This and other comments appear to be directed at a system design which uses the engine oil cooler for a heat source. The schematic referenced indicates a second oil cooler in the cabin. All available oil temperature would be directed to the cabin heater first, and excess temperature would be dumped at the engine cooler second. Regardless of outside temperature, there would always be some oil temperature available for cabin heat. Additionally, the air routed thru the cabin heat source would be recirculating cabin air, not fresh intake air. I don't know whether this system would provide adequate heat on a cold day, but it seems like it would provide better heat than a system which used the engine cooler as a heat source.

I can think of a variety of reasons not to use this system, but I'm not yet convinced that the system shown in the schematic wouldn't provide adequate heat. It doesn't seem like you would need 185 degrees at the cooler, particularly with recirculated air, to provide an adequate heat source.

While I don?t see myself using this system, this is an interesting conversation.
 
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