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Which heat box leaks the least?

IowaRV9Dreamer

IowaRV9Dreamer

Well Known Member
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.
 
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
 
Heat box

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.
 
Plane Innovations

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.
 
flapper on cabin heat box?

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
 
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.
 
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
 
metal to metal

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.
 
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
 
This language on the Plane Innovations site prompted my decision for their stainless boxes. There may be a little marketing spin in it, but it was good enough to convince me.

Phil



The all stainless steel heater bypass box was conceived while looking at aluminum hardware used for sealing the firewall on experimental aircraft. It didn't make much sense to try to seal a stainless steel firewall with aluminum hardware. It is well known in the metal working world that stainless steel melts at 2600 degrees and aluminum melts at 1200 degrees. What most pilots don't know is that windblown avgas burns about 1875 degrees. And so, work on the ALL STAINLESS STEEL heater bypass box began.

The all stainless box withstood the torturous flames for 10 minutes without failure. A good first test. Then the aluminum box was tested. In only 16 seconds the aluminum was a liquid puddle at the bottom of the simulated firewall. Only 16 seconds, you might not even know you have an engine fire in that time. This was an eye opener.

Once the all stainless steel heater bypass box was in production, the fun part began. Testing initially was a challenge because a simulated engine fire was required. But how hot does windblown avgas really burn? Our tests showed that windblown avgas burns at 1875 degrees. Now the test bed was in place.

Three models of the all stainless steel heater bypass boxes are offered. The engine side control lever comes with a backing plate that attaches to the cabin side of the firewall and has a 2 inch scat tube outlet so a tube can be attached in the cabin that directs air where wanted. The cabin side control unit is commonly used on RV7, RV8 and RV9 aircraft where the air is distributed in the cabin through a plenum. The RV-10 requires a special set of two that have offset levers to clear the upper nose gear mount.

All stainless steel construction offers a fireproof closure in case of an engine fire.

Designed with weight in mind, our stainless unit weighs 3.95 ounces and replaces the TG-10 aluminum box that weighs 3.28 ounces.

New flapper design offers better seal to keep out hot air when closed.

Direct replacement of the TG-10 aluminum unit. Easy replacement.
Click to expand...
 
Plane Innovations - Stainless

Dave,

My thought on it was if the firewall is stainless than the heat box ought to be stainless as well. That 2" inch hole would allow alot of flames into the cockpit. If a survey was taken on which box is currently being used on RV models once the stainless version came onto the market - I would be really surprised if the stainless model didn't come out on top.
 
Cold air in the summer!?

I had already purchased a hot/cold heater valve from Vans, but could not use it because I have mufflers on my vetterman exhaust, that need cooling air all the time (which can not be done with the hot/cold valve).

If you are concerned about heat in the summer, you could install a naca-vent in the cowl and put the scat tube on the vent in the summer and on the heat muff in the winter. That way you will have best of both worlds.

Regards, Tonny.
 
thanks.

thanks for the info I'm getting ready to locate heat and battery to the firewall now. Will certainly consider the Vans model heater.
 
Berge Valve

Twin inlets - thick solid stainless. No Leaks!

Made by Twin Cities RV Guru Tom B. No idea is he is still making them.

IMG_1325.JPG
 
cool valve Pete

Wow Pete - that things looks awesome. Never seen one like it. Very cool.

It may not work for me, as I need the valve to allow the hot air to flow even when the cabin valve is closed (so the mufflers won't overheat). It looks like when you close this one off, no air flows anywhere.
 
Question about a TG-10 Heater Box

Fully pulling the control cable on my heater leaves me with ~1/4" gap from fully "Open" on the air blocker door in the heater box....

Will air loads push it closed the rest of the way, or must I do a "dive under" on the panel and close it up that last bit?

Have sent the Mothership a query, but thought to consult the brain trust here as well...

Thanks,

Rob


IMG_20170628_143756.jpg
 
Yes definitely repair that.

Aggie78 said:
Fully pulling the control cable on my heater leaves me with ~1/4" gap from fully "Open" on the air blocker door in the heater box....

Will air loads push it closed the rest of the way, or must I do a "dive under" on the panel and close it up that last bit?

Have sent the Mothership a query, but thought to consult the brain trust here as well...

Thanks,

Rob
Click to expand...

Who knows what else you will find under there that is loose.

One suggestion - old pillows
 
Springs hold it closed

I put a compression spring on the shaft under knob to keep some tension on the control cable. Keeps the heat box flapper closed with no leaks.

Party on!
 
Arvey Fleur said:
I put a compression spring on the shaft under knob to keep some tension on the control cable. Keeps the heat box flapper closed with no leaks.

Party on!
Click to expand...

Could you explain or describe this in more detail please?
My first thought after reading was a spring on the flapper arm coaxing it to stay closed with the cable overcomming the spring to "open" it.
But your post clearly says "under the knob".
Thanks in advance
 
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