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sealing the heat box flapper

KayS

Well Known Member
G'morning Together,

i have the standard vans exhaust muffler routed to the triangular TG-10 heat box on the firewall. i followed the advice of some threads here and sealed all kinds of openings at the canopy/cabin/fuse but the heating in my 7 is still only marginal. yesterday with OAT in the 20's my smartphone stopped working due to temperature. i'm tired to dress like somebody heading for an arctic expedition everytime i fly during winter.

besides preventing cold air from entering the cabin, the warm air from the muffler should freely run into the cockpit. looking at my heat box i figured that there are gaps (1/16 - 1/8) between the edges of the flapper and the heat box housing when the flapper is in the open postion (warm air in). i'm sure because of the gaps a lot of hot air does leak into the lower engine area.

anybody did seal these gaps? have an hard time to figure out how to do that. any pictures are very appreciated.

Cheers
Kay
 
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Do you have good hot air flow into the cabin?

I have the same TG-10, and the same heating problem in my RV-8. My problem is that the air coming in is not very hot. When I remove my exhaust next I will add some stainless steel wool in the "heat muff" to increase (hopefully) the temperature of the air that comes into the cabin. I had not considered leaks in the TG-10 itself.

I'm guessing that the air pressure in the heat system will be a lot higher than cabin air pressure or the "low pressure" side of the engine. I think if the temperature of the heated air is high enough, that a small amount of "wasted" hot air should not make a big difference. Sealing it will help - not clear how much of your heating problem is the TG-10 seal, or the temperature of the air.
 
Size of cold air intake to heat muff?

Another thing to consider is the size of the cold air intake on the baffle. If you have a 2" hole in the baffle to the 2" duct tube to the heat muff the ratio of cold air to heat from the muff may result in lower temperature air coming into the cockpit. When I was building it was passed on to me that the baffle hole should only be 1" in diameter. This has been satisfactory for me. You could try taping over part of the baffle hole to try different size openings to see if it improves your cabin heat.
 
I'd like to ask again... anybody sealed the flapper door in the heat box?

I have not sealed the flapper in either my 4 or my 7. Have not found a need. In my 7 the door on my SS heat box seals ok.

Here is what I have done for winter flying. I use 2 heat muffs in series, one on each side, on my O-360 powered 7. They are plumbed in reverse flow...meaning the inlet is at the back and the outlet at the front so the outlet (with the restricted baffle holes) is at the hottest part of the pipe. I also wrap the heat muffs with 2" wide header wrap (Amazon) to keep the heat in. In our Canadian winters I fly down to -10C (14F) with no problems keeping warm. Any colder and I wait for a warmer day. I also installed seat heaters from Flyboys in the seat bottoms to warm and soften the memory foam, which is like sitting on a block of ice when they get cold. Not enough room around the cowl for me to install that turbo muff.

In my purchased 4 I found the heat lacking from a single muff. I installed a second muff and connected it to the cabin air inlet for winter flying. The 2 muffs improved the heat, but did not provide as much as my 7 with the series configuration.

I have seen that some fly with battery powered heated clothing to stay warm.
FWIW
 
I'd like to ask again... anybody sealed the flapper door in the heat box?

I proseal the heater flapper flange at the firewall connection because it was in the instruction. I haven't flown my RV8 or will fly it anytime soon in the kind of cold weather where you are. I also notice the heat muff end caps in the firewall forward kit do not seal very well, and hot air may leak pass these locations too.
 
I'd like to ask again... anybody sealed the flapper door in the heat box?

Yes. It's easy. First, open the door until it's edge is at the top of the scat tube. That's as far as it needs to go. It is fully open and further does nothing to change heat. You can see how much room you have to make a 3 sided picture frame from thin stringer or sheet you bend yourself. Rivet them to the box. Do a nice job and the door back will sit flat on these seals.
On the other side, just below the scat tube, bend the existing lip down so it seals that gap. Proseal if you wish. I did not.

I have pics but no access to them until the weekend.
 
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Here's the images I promised
 

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