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tunnel heat

Mine doesn't seem hot. My exhaust pipes (stock Vetterman delivered in 2009) are really long, so that may be the reason why. I think (but am not sure) that these are longer than on the older exhausts.

Our tunnel has fabric from Flightline covering it. The only metal we can touch is the Andair fuel valve. The handle is quite warm but certainly not hot. What is the standard for hot? What should we be checking for? We have the Sounddown insulation in the tunnel floor, it's about one inch thick. I moved our fuel system components up about an inch from their standard location to accomodate the insulation.
Tunnel Heat

I have a center console and mine does get warm. My throttle quad is mounted in the center console and was very warm to the touch so I am sure everything else in the tunnel is warm. This weekend I removed the forward fresh air scat tube from the left heater muff and plumbed it directly into the tunnel. This appeared to help. I still have aft heat and when the day comes that I need heat in Florida/cross country I will tee it and hook back up the forward heat.

Pat, those mufflers NEED airflow thru them or you are going to burn them up. The fix is to put a "Y" into the scat tube off of the back baffling behind Cylinder 5, and run the output to both the right hand muffler and the firewall tunnel area.

the tunnel heat issue is resolved easily by:
1) putting some sort of insulation between the heat valves and firewall. Best would be a piece of silicone baffle material - this largely prevents the heat blowing on the valves from conducting to the cabin side (tunnel) and therefore heating up the tunnel

and 2) swapping to the stainless heat valves which have much better sealing than the stock aluminum versions.

If you elect to stay with the stock aluminum heat valves you can get probably fix most of the issue with generous application of red RTV in strategic locations on the valves. First, air gets under the hinged side of the flapper because of the play in the hinges. Make a little RTV air dam so the air isn't blowing directly on the hinged edge of the flapper. You might also consider a light coating so the flapper seals better when shut. You can see the issue by simply hooking up the blower port on a shop vac to the engine side heat valve air port and watching what happens.

Tunnel Heat

Thanks Vic,

Do you then just let the heat muff exhaust inside the cowling. I had considered that however that would put the heat muff exhaust just forward of the oil cooler.

Heat Muff Removal?

If you remove the air supply to the heat muff and remove the shroud will the muffler part still suffer heat damage?
We really don't need heat here 9 month out of the year and keeping the air in the plenum on the top would do more good than running it through
the heat muff.
Just curious.
Just run the scat tube out the bottom of the cowling instead of connecting it up to the heat boxes on the firewall. Bob's suggestions are right on the mark for those who are still building. It's a little tough to get in there and change the boxes after the engine is installed and everything is plumbed.
For those of you who don't think you need the heat because you live in hot climates, I would hint that you might not be getting the most out of your RV-10 in flight. In the summer time, the performance of the 10 allows you to climb to 10k'-15k' quite rapidly. It typically gets you out of the summer time haze and into smoother, more comfortable air. And then sometimes you will want that heat, even in the summertime, especially if there is a high overcast blocking the sun.

I pulled the heat shrouds on my -10 in the spring and put them back on in the fall. In the summer I route the fresh air scat tube to better cool the fuel pump. The "mufflers" are fine.

I have two heat muffs, one for the front and one for the rear, but having them boh hooked up and open will drive you out of the plane 30f temps. I now have plumbed one heat shroud for both front and rear and have flown in 10f temps in light jackets.

I agree with Vic and for those building a -10 an O2 system is a must. The airspace between 12k and 18k is smoother, and a "road less traveled"

Hope this helps.
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I had considered both adding a scat tube to the heat shroud and directing out the bottom of the cowl and option b to remove the shroud.

Thanks guys.

We replaced our air boxes with S.S. while building. Our control quadrant does not get warm , just the fuel handle.
Thanks for the help.
Insulate the floor of the tunnel, the firewall in the tunnel and insulate the scat tube that is in the tunnel. My fuel selector is even cold. The only warm spot is where I could not insulate the scat that come over the spar if the heat is on. Keep the heat in the scat and the exhaust heat out at the floor and all is well.
Tunnel Heat

Perfect timing to discuss too much heat in the center tunnel area. My fuel selector doesn't get too hot but the sheet metal is very warm. My concern is that it could damage the wires I have routed there. It appears that the solution would be to cover the floor of the tunnel with a heat refletive material. My concern is damage to the wires.
Randy Means

The floor of my tunnel is insulated however the standard heat boxes are mounted to the firewall with no insulation between them and the firewall.

Tunnel Heat

I have cool mat insulation on the firewall and the floor of the tunnel. My tunnel does get very warm to hot (my wife can't place her leg against it, but I have no trouble.) Seems to be very much affected by outside air temperature (ie more noticeable in the summer at low altitude - certainly more comfortable with cooler OAT).

My standard aluminium heat vents are mounted directly to the firewall- I will try insulating them and see what happens.

VH-XRM flying in Oz

Don't underestimate dealing with the gaps created by slop in the valve hinges. Building up a small air dam will go a long ways toward dealing with that. It's actually hot air from the opposite side feed that gets under the flap.

Between some sort of insulator between the valves and firewall and some RTV to deal with the above you'll solve most of the problem. Since you've got to take the valves off to install the insulation, consider just upgrading to stainless steel at the same time. The flapper and hinge are much better and don't have sealing issues.

Yep, same manufacturer (EMP.AV). Planeinnovations is their "store website" IIRC, but good to know there's another place like Avery's to buy them from.
Insulate between boxes?

Bob -

You said to insulate between the SS boxes and the firewall. I just ordered the SS boxes and will be replacing my aluminum ones. Do you mean to place a "gasket" of some type of material between the control boxes and the firewall? I guess you are saying the heat transfer there is conductive and can be significant. What would you recommend for a insulating material? Correct me if I'm wrong in my understanding.

Yes, you got it. A piece of silicone gasket material (the red stuff used for baffling sometimes) will work great. It does stop the conductive heating.

I bought my ss ones from Plane Innovations...

they are built very well and come with a small tube of high temp sealant. I insulated firewall and tunnel floor with ceramic insulation from ACS. We'll see how it works out this fall. The wires can stand much more heat than we can. Tried a bic lighter on some tefzel and standard pvc coated wiring. Made a believer out of me.
My current plan is to hook up only one side of the flap valve to only one heat muff and split the heat front and rear. It sounds to me like there is no need for both heat muffs and two heat sources. Everyone I have sopken with seems to indicate that the heat will drive you out of the plane. That is how my current aircraft is and it is more than enough heat. Use the second flap to vent cool air down the tunnel during the summer and off during the winter by having it directly connected to fresh air. I can understand how Van's demo plane would be cold, they have no insulation whatsoever, but most of us are insulating the cabin where it will not only retain the heat, but keep it cooler in the summer. If I find it is not warm enough in the winter I can always hook up the second muff.
In addition, I have layered the floor and the firewall with 1/8" ceramic insulation covered with 1/2" black insulation using the 3M ceramic cement. I tested this with a 1500 degree flame for 5 minutes and could still touch the insulation side. My firewall will have Koolmat on the engine side.
It is my belief that the type of temps that do not allow a person to touch the metal, are far to high for fuel lines, and just plane don't make good sense. If the fuel selector is hot, just think how hot the valve and the aluminum tubing is!
You are right in that there is more than enough heat out of ONE of the RV-10 heat muffs to heat the entire cabin. You should be fine. Just make sure you supply air over the remaining heat muff and duct it overboard.

I was intending on removing one of the heat muffs to avoid having to do this. I have not looked at how they are attached yet, but I will do that this evening.