Any updates on the tunnel heat issue? Thoughts?

Folks,

Now that there are a number of RV-10s out there, what are your thoughts and solutions to the tunnel heat issue.

Thanks

I now have about 50 hours on the airplane and have no tunnel heat problems at all. I took the following steps during construction.

1. installed stainless steel aftermarket firewall heater box/valve. Sealed box well with red RTV and made sure no air was leaking past the valves while in closed position.

2. Installed koolmat on forward side of firewall. Heavy and expensive.

3. Insulated inside of tunnel. Can't remember the name of the material, but it was aircraft grade stick-on barrier with foil exterior. Wrapped hot air duct in tunnel with aluminum tape.

I have no idea if all or any of these precautions made any difference. However, my tunnel remains cool to the touch even while using lots of cabin heat to the front and rear seats. I did not install the "false floor" in the tunnel.

My person opinion (worth exactly $.02) is that the slightly longer exhaust pipes that are now standard may have helped the hot tunnel problem quite a bit.

What about a louver

I have another thought on this. I have no experience to go on yet, but the recent incident where an RV10 "exploded" after landing had me thinking if one should not have a small louver ( similar to those in the bottom cowl ) in the bottom aft section of the tunnel.

This may suck out any possible fuel vapours and heat built up.
What are the experienced guys thinking of this idea?

I know of at least one other -10 builder who is contemplating some kind of passive vent in the tunnel. Consideration is being given to issues such as insuring no access for insects, no carbon monoxide/exhaust entry, moisture, etc.

We insulated the tunnel floor after lifting the pump , filter ,etc. up about an inch. We also replaced the air vent boxes with SS and sealed them in. Other than that nothing. Our tunnel is covered with carpeting so we cannot touch it directly. I have noticed the Andair fuel valve handle getting a little warm, not hot just warm to the touch. Anyone else notice there handles getting warm?
Ron

Rear Heat

The tunnel heat in my opinion comes mostly from the rear scat heat tube. The only place that I have a warm tunnel is where I could not insulate the tube do to lack of room. I did insulate the floor board and firewall in the tunnel as well, but I think the real heat is when the rear heat is on. When it is off everything is cool. Be sure to insulate the scat and you should have no issues.

Tunnel heat

I put Koolmat on the firewall (engine side) and some on the floor of the tunnel. No other mods to the std kit. The tunnel gets quite warm, but I would not call it hot, even with both front and rear heaters in the off position. I do not consider it a problem.

cheers
Ron
RV-10, VH-XRM flying in Oz

Thanks for all the responses, but the sucking out of vapour still worries me. Or should I say the possibility of vapour building up, should one develop a fuel leak. So I see two possible problems - heat and vapour.

Jan....

...just about every airplane I've ever flown has fuel lines in the cockpit. They're just not visible usually and use the same AN fittings and hardware that we do. There's no way to route fuel lines outside the cockpit area without a fuel selector valve extension, like my Air Tractor has, to a belly mounted fuel selector and a false floor.

The sniff test usually works well....I had a Cessna Agtruck break the small 1/8th inch fuel pressure sending line in the engine compartment. The gauge went to zero and I could smell fuel, so I figured something broke and stopped spraying the field I was in and landed quickly. There was already fuel stain down the side of the airplane, fortunately no fire.

All we can do during building is to be very exacting and careful tightening all fuel and oil lines,

Best,

Tunnel Heat

I would not bother with louvers in the aft tunnel. You don't know what the differential pressure really is and you could end up sucking air in. The fuel lines aft of the pump are low pressure with little to no vibration. Install them carefully and check for leaks, then forget about them (except for the annual). Instances of these lines leaking is unheard of except for the accident aircraft and it had a non-standard engine. Don't know his fuel plumbing and if it is relevant to the rest of us.

You could always put forward-facing louvers at the forward end of the tunnel, and aft-facing louvers at the back, ensuring a continuous flow through the tunnel. Unfortunately, your airspeed will suffer from the added drag.

Thanks to everyone who has responded. Maybe it is a case of me wanting belts and braces. I agree that these lines should not leak if installed correctly.