Which heat box leaks the least?

[IowaRV9Dreamer]

I want to get a cabin heat box (maybe two) for the RV-9A. I've heard that some of them leak hot air into the cabin in the closed position. Is this true?

I'd love to hear which box leaks the least (or which ones leak a lot). As far as I know there are models from Vans, Spruce, Plane Innovations (steel) and Robbins. I don't know which one(s) to get... I think I'll need two: One with inside control for the bottom center of the firewall and another somewhere else.

Thanks for any replies, especially from people flying.

[Greg Arehart]

Dave,

I have two of the Vans versions and don't notice any heat leaks when closed. However, it only takes a slight opening to yield a LOT of heat. I mounted one each on the pilot & copilot side of the firewall (I do not have the single heat distributor in the center that is standard in the plans). I suspect that if one leaked, it would be a fairly simple fix to add a bit of RTV as a seal.

My experience, anyway.

greg

[JimWoo50]

and are you happy with it?

[flyboy1963]

Dave,
I have the 2 muffs feeding a 'box' on the firewall. When doors are closed, the hot air dumps out the bottom of the cowl. I don't like the design, ( didn't build it personally). It heats the firewall all the time, right on the other side of the fuel lines and pump, and you have 2 nice big holes through which fire, fumes etc. can enter the cabin. This is less of an issue when the flap in the box is wide open, (which is rare)
My armchair engineering suggests;
Use all stainless hardware, and build with a mind to shield from spraying oil, fuel, flames etc. Since the pressure from the muffs, and the heated engine air from the lower cowl is free to enter the cabin.
Look at someone that's done the hot/cold air mixer, more plumbing, but in many ways superior & potentially safer IMHO.

[Bob Martin]

I live in Central Virginia.
We need 2 heat muffs to supply enough warm air while flying without the sun shining into the cockpit. I have replaced Vans Aluminum units with the very nice SS units from Plane Innovations. I don't notice any leaking of air.
I highly recommend the SS units.

[IowaRV9Dreamer]

Thanks Bob - do you recall if the Plane Innovations box has any sort of flapper (rubber, etc.) or is it metal against metal in the closed position?

I'm going to install 2 boxes, and want to get ones that don't leak. My beechcraft leaks heat in the summer and it will just about fry you.

Thanks for any info,

dave

[Jamie]

For what it's worth, some people tape over the baffle heat hole in the summers. This prevents hot air from dumping onto the firewall and also (theoretically) increases cooling air going through the cylinders.

For what that's worth, I haven't done it in three summers of Georgia flying and I have no problems with the Van's heat box leaking hot air.

[IowaRV9Dreamer]

Thanks Jamie -I have to do exactly that in the Beech. One time in summer flight I reached down and touched the heater box. Won't do that again! I

I guess I'm just too senstive about this and just need to pick a box and go with it.

dave

[Bob Martin]

The fit is metal to metal......and you could bend the parts until you get a near perfect fit. From what I remember, it is a nice fit to begin with.
Not sure how close the tolerances are but you could put a mold release on the flap and a thin coat of RTV on the base and create a very tight seal if you wanted to.....I haven't tried it.

I'm pretty sure you should NOT block off the air going to the heat muff. The muff will over heat on the exhaust with out the airflow going thru it.
You could tape off the inside of the firewall seasonally if you wanted I guess.
or remove the heat muff from the exhaust seasonally.

[Greg Arehart]

JimWoo,

I have the TG-10 model. And it seems to work just fine so I'm happy with it. If I had it to do over and had plenty of money, I would probably go with SS rather than the Al (have to purchase from another vendor since Van only offers the TG-10 style in Al), just for the safety reasons.

greg