Cabin Heat – Forward airflow

The elevator torque tube, not being concentric in operation, means a large opening in the fuselage up front and cold feet.  Here's my solution.  It seems so simple.                                                    

First seal the entire canopy with soft, open cell foam from the hardware store. The canopy has no problem closing and it’s air tight.  Next, get the cabin air flowing forward.

This is a fuzzy shot of the torque tub opening.  I have fared the hole back so air tends to flow out, not catching and blowing in.  The canard then gets a small set of fairings to divert air away from this hole. 

A small NACA duct under the wing feeds air to the oil cooler and 60 percent of that air goes into this plenum and  is piped through the firewall with a butterfly valve controlled by the GIB via push-pull cable.

Scat tube takes the hot air to the front opening of the hell hole.

A piece of 1 inch foam board forms the seat back which has a U channel cut so that heat comes up and into the cabin behind the head of the GIB.  Heat could possibly be fed into the hell hole and allowed to find it’s way forward at a lower level. but I’m not sure heating up the landing gear is a good idea.  This picture also shows a second seat back specially built for the little lady, who seems to be shaped differently than a man. The principle is the same. Fiberglass reinforces the foam where necessary.

The key is in the  fairings under the canard.  I made a set out of aluminum and duct taped them on to experiment.  They are about 4 inches long and keep air from slamming into the  elevator tube.  Even before fairing the hole I had warm air around my feet.  No cold draft at all. Now I’ve made them officially out of fiberglass.

Nose wheel Fender

With only 11 hours on the finished airplane I’ve had to refinish the varnish on the prop once already.  Granted, I’ve done a lot of taxiing, but the nose wheel is famous for kicking tiny pebbles up into the prop.  So while the fiberglass is going, we build this.

Proper spacing is corrugated cardboard covered with duct tape and glassed over.  The fender has to go all the way around until it almost touches the ground.  Then all of this has to fit in the wheel well when the gear retracts.  And it CAN NOT bind on it’s way down!

Exhaust Augmentation

  

I don’t understand how Long EZ pilots keep temps down while idling.  There is very little air flow for cooling before take off.  A few have used exhaust augmentation and it seems like the solution.

Mine consists of  an aluminum heat barrier around the exhaust pipe. It is 20 inch wide flashing rolled into a cylinder and riveted.  Foam spacers keep the pipe concentric. What diameter?  Double the diameter of the pipe seems right.  That makes it slightly larger than the intake diameter, which is ram air.  These cylinders get glassed to the lower cowl and spacers removed.                                                                        Lastly I will glass over the aluminum and fare it into the lower cowling.                                                          Theoretically, the main opening should now be sealed off!  I’m going to have to experiment with that.

Downdraft Cooling Plenum Finished.

The finished product. The cowling slides right on, the dipstick is air tight and so is the plenum. 

To access the spark plugs requires removing the plenum lid, a ten minute job.

The difficult part of down draft cooling

It would have been easier to form the plenum lid from foam and cover it, I think.  My way required going back too many times to strengthen edges and create the mating surfaces.  Note the ridge on this opening.  When the top cowling lowers into place it must meet this face.  Hopefully sealing can be accomplished with a bit of weather-stripping.

The real difficult part is getting the cowling on over the dipstick in such  a way that it is air tight.  The thing is just IN THE WAY!!  Finally, I shortened the dipstick tube 1 1/4 inches.  Now I can fiberglass right to it and it is down out of the flow of air.  Again, the upper cowl will have to join these surfaces in a tight fitting manner… somehow.  I’m sure somebody knows a better way to  get air from the cowl intake to the plenum.

Down Draft Cooling Construction 12/15/2009

Our experimental downdraft cooling system worked so now we’ll make it official.  Starting with the intake plenum, the left and right intakes need to be framed up. Note the fiberglass frame.  The outer edge is vertical but the inner is angled so the upper cowl will find its way ‘home’ when we set it in place.

The dip stick is always in the way.  The big improvement is to seal it off so no pressure is lost to the lower side.

Frame on the right side.  These will be riveted in place and silicone sealed.

Next we replace the sheet aluminum lid with fiberglass.  The shape was too complex for a single sheet.  I started by lining the surface with duct tape and building a flox corner, kind of reverse engineering.  After it hardens I’ll sand it flush with the edge to give us a surface to attach the lid.

Here’s an idea from the old days of covering with Ceconite.   It is tacked down around the edges and heat shrunk to remove wrinkles.  Next, two plies of fiberglass are wetted out right on top.

Incidentally, I’ve heard that the plenum lid is necessary because using only the upper cowl as a lid creates internal pressures in flight that would be worrisome at least. 

When this hardens, it is removed, Ceconite and all.  The Ceconite is natural peel ply.  It rips right off.

                                                     

Disassembly

       Isn’t ironic?  It was the last snow of spring when we assembled the plane at Saratoga.  Now we disassemble with the first snow of winter.  I guess it’s good timing.                                                                                                                                                                                                                                                                                                                             Last Spring                                        My thanks to David and Billy Underwood for helping.  It was cold and windy but the job is done.  Now for the long list of modifications and repairs.  We need wheel pants, finish the down draft cooling system, add interior lights, arrange to carry a passenger, etc.   Sure beats driving to Saratoga.