Jul 08 2020

Ram Heat Part 2 (Heating design)

Over the years I have tired EVERY way imaginable to heat the plane. I could tell you many stories of flying in cold weather. It is really a horrible environment to fly in. Gloves, hat, jacket, sweat pants or a snowmobile suite. It is so cold at altitude. ITS CRAZY that ytou can buy a cheap car with better heat than our planes.

Over the years:
I tried improving the plans exhaust heat system with additional contact area on the exhaust pipes and a fan. Worthless
I tied an electric heater. Drew 40 amps. Worthless
I tired a high pressure, recirculation air system. Fair

Engine oil pressure->external vernatherm->heater->engine return It uses a fan to blow air through the core.

This system worked ok. I had to duct the hot air to the pilot. I could keep the plane comfortable to about 20 def F OAT. At 15 deg F, OAT the plane was drown right cold due to the air leaks. Also I did NOT like the thought of high pressure oil in the cabin and the potential of a uncontrolled oil leak.

When I rebuilt my LongEZ, The driving factor for cutting off the nose was that, well I HATED IT, and the decision to incorporate a ram air opening and couple it with a heater using an oil pump to move the oil. I call it Low Pressure RAM Air heat. Using a ram air opening, i raise the cabin pressure to eliminate air leaks and additionally provides method of heating the incoming air without a fan. Simple and safe.

The air inlet on the nose of my EZ supplies both the heater and cold air supply vents for the dash. You can see some of the nose build process in my blog.

The LP RAM Heat concepts works exceptionally well. I can fly in any weather with no air leaks and in the coldest weather with jeans and light shirt. No air leaks, no fogging of the canopy. The coldest I have flown in is 0 deg F and I was still getting 110 deg F out of the heater. What I love is flying on a chilly day, like 45 def F. Turn on the system and supply just enough heat to be comfortable since the heat out put is adjustable. I love flying in cold weather now.

Note: Generally I measured a delta T across the cooler around 100+ def F. The temp of the oil supply from the engine at the heater is typically at 145 deg F.

I’ll be detailing the installation of RAM heat in my Cozy next.

Jul 08 2020

Ram Heat Part 1 (The discovery)

Ram Heat? What is it??

The discovery which started the process of Ram Heat began while flying home from Jacksonville, FL. It was raining, and naturally, I was getting little drips of water coming into the plane from leaks. The ones coming down the dash was especially annoying. Normally I just had air leaks, but in the rain its water leaks.

While watching the access door, to my amazement, I saw the water bubbling up from a tiny crack. Why? What as happening?

Eventually I connected an ASI to the static system of the plane an measure a -55 mph of air pressure in the cabin. If I opened the belly light, (which works exactly like a cow flap) I could increase the NEGATIVE cabin pressure all the way down to -120 mph!

YIKES, this the reason I have air and water leaks in the cabin. Its because the cabin is constantly at a negative pressure relative to the outside air.

Which leads to the question… Where does the negative pressure come from? I tired closing off and tapping ever opening I could in the plane with the exception of the GU torque tubes openings and the canopy. Up for a test flight, and guess what..? Still -50 mph pressure.

HUM, the problem must be the GU torque tube openings which are HUGE.

Back to the shop and I fabricated a set of offset GU torque tubes (you and see them and how to make a set at the website). I believe it is the first set ever made. Installed them, took the plane up for testing and the plane had not changed. Still -50 mph.

NOTE: I have come to believe that the cause of the low pressure is the 150 mph air flowing across the transverse opening in the plane, like turtle back or the front of the canopy. Just like blowing air across a soda straw. It creates a vacuum.

Solution 1. Because I was mainly interested in stopping the flow of rain water into the plane at that time (I used to travel a lot of rainy IFR), I knew I had to raise the cabin pressure. If the pressure is higher that static, then air would be pushed out of cabin and water could not enter.

I made an alternate air inlet door on the ram air duct of the engine (it was easy and convenient to do). In the rain, I would open the door, to allow air to be pushed into the cabin from the air inlet. It worked ver well to raise the cabin pressure cabin which completely stopped the entry of water. I could actually feel the air reversing from the eyeball vents. The major problem for this design is that it was VERY LOUD (from the engine breathing pulses) and I could only use it in the rain.

Conrolling cabin air pressure is essential in the plane. if your vent blows air into the cabin, you have a negative cabin pressure. Negative pressure means air and water leaks because your sucking it into the plane. The only realy way to stop air leaks is to raise the cabin pressure to positive.