Very Bumpy Afternoon - No CHT Improvement

 

It was a warm sunny afternoon.  See those fluffy little clouds in front of the flying wire.  They are a good indication of turbulence, if you pay attention to them while you're on the ground.  It was rougher than a cob.  I gave up after about 1/2 hour.  

Just after take off, at maybe 20 feet, I got slammed from the left so hard I moved above the right edge of the runway and the gasoline sloshed so hard it was forced out of the cap on the tank.  I've never had that happen before.  The wind was only about 5 knots, all day, and from a little to the left of the runway.  Who knows.

The arrow points at our house near Lake Louisa.  At least I did get to fly.  At 2,000 feet the hawks were hanging out in the thermals.

The cylinder head temperature was not improved at all.  I could not establish steady flight but there was no obvious change.  After I landed I installed a temporary seal for the leaks by the carb heat box.  We'll see if it helps next flight, and I'll keep looking for air leaks to plug up.

Putting the elevator trim tab back on worked perfect.  It just gets rid of a slightly annoying back pressure required on the stick.  Now there is just the slightest touch of back pressure required.  I'll fly with it as is for a while before I consider any adjustment to it.  I'll also think about a longer term solution to trim adjustment.

Larger Cowl Outlet - For Lower Cylinder Head Temperature

 This is my 4th change to the outlet opening and I've run out of room to make it bigger.  If this doesn't fix the problem I have an air leak somewhere reducing the pressure drop across the cylinders.  I think I've found a leak around the carb heat box, but I'm not touching it until I fly with this change.

The original opening was 61.4 sq. in. minus the outlet for the cabin heat box for when heat is off, of 3.1 sq. in. gave a net area of 58.3 sq. in.  The holes for the exhaust pipes were only about 1/4" bigger than the pipes so they really didn't add any outlet area.  They do now.

The other day I drew a pattern of the opening for the cowl outlet on my C-140, also powered by a C-85.  It measured 120 sq. in.  It does not have a skirt but extends below the fuselage about 2".

This final version has a net area, in the center opening, of 130.9 sq. in. plus 28.5 sq. in. around the exhaust pipes for a total of 159.4 sq. inches, enough already.  Literally, if it were any bigger the cowl would be split into 2 pieces.

I followed the same procedure as last time.  I drew a guide line on the cowl, then made a cardstock pattern of the skirt.  Unriveted the old skirt and made up the skirt, using the ends of the old skirt to get the mounting holes at each end to match the holes in the cowl.  The new shirt was fitted to the cowl, on the plane.  The new holes were only drilled to 3/32" so I would have more freedom to get the final 1/8" holes aligned, if needed.  I brought all that back to the attic to trim the cowl to fit the new skirt and then rivet it all together.  The plane under the cowl is my 1926 WACO NINE project.

I made new stiffeners for the 2 narrow webs of cowling beside the exhaust holes.  I have enough opening area without the couple inches lost to them and they do stiffen it all up.

Ready to go back on the plane.

Each time I've changed it I like it better.

There is a lot of opening area.  Now I just need the weather to calm down.  Spring is here.

Flying on a Warm Sunny Afternoon

 

We had another beautiful March afternoon, blue skies, light winds down the runway.  I finally left the airport traffic pattern.  Our house is about 10 miles away.  The pictures are looking back, west, toward the airport, arrow.  The first row of mountains is on the west side of the airport.

Nice afternoon, happy pilot.  I flew for almost an hour.  

When I got back there was a slight rattle back in the fuel gauge float.  I haven't been able to get the fuel out completely so I weighed it after some more soldering.  I'll re-weigh it in a couple weeks to see if it is taking on fuel.

Hopefully today will be as nice.

Fuel Gauge Problem Solved

 

I replaced the wire with a straightened piece of the 0.063" wire I have for the trailing edge on the WACO NINE wings.  I weighed it and it now weighs 19.3 grams vs the 31 grams it weighed when I started, big change.  It turns out gas had leaked into the float and came out when I unsoldered the wire.

It made a tiny pinging/rattling sound when you shook it.  I thought it sounded like a little bead of solder rattling in it, turns out it was a little gasoline.

When I first brought it home and tried floating it in auto gas it sunk, bummer.  Now it floats about 1/2 out of the gas, awesome.

The gas I used had been out side in 23 degree F weather overnight and was very cold.  In the short time while I took some pictures, the lower pressure of the cooling air in the float sucked some gas in, the rattling sound was back.

A careful inspection of the soldering on the new wire showed I had the tiniest leak at each end where the solder was not well bonded to the wire.

Since cooling it sucked in the gas, I used the heat gun, at 250 degrees F, to heat it and push the gas back out, it worked.  I put it in the freezer for about 5 minutes before heating it to have the most air to push it out,

I thought that worked so well that maybe could I show the leak was there by freezing it then bubble testing it in water just below boiling, nope.  I even tried adding dish soap to the water so it could maybe blow a bubble after pulling it out of the hot water, nope.

After a couple tries at fixing the leaks and using the cold gasoline I was able to fix them, no more leaks.

I used my 1500 watt soldering iron to heat the wire without overheating the float.  It's not pretty but it's sealed.

Tomorrow is forecast to be in the low 70's and sunny so I hope to try it out in flight.

One Hour of Flying On A Nice Warm March Afternoon

 Yesterday afternoon we had a gentile warm (61 degrees) breeze from the southwest, straight down the runway.  Who could ask for more in early March.  

The CHT problem isn't solved.  It was running about 405 degrees F.  During climb out it reached 455 degrees F at 1,000 feet.  After about 45 minutes the oil temp had stabilized at 190 degrees F, OK, but corresponds to the CHT.

I had planned to leave the pattern and climb to about 3,000 feet.  It was beautifully clear but fairly bumpy.  Roger reported it was worse at 3,000 feet so I just stayed in the pattern.  I got to fly for an hour.

I think I need a lighter wire for the fuel gauge.  The float just barely holds it up.  It doesn't take much of a bump to sink it.  I replaced the old wire years ago so I don't know how thick the old wire was.  This wire is 0.092" diameter.  I think a piece of 0.063" piano wire should work fine and make a significant reduction in weight.  My math says I'll lighten it by .29 ounces or about 8 grams.  The float and wires weigh about 31 grams so it should help.  I have a coil of 0.063" piano wire but I'd rather work with a straight piece of wire.

Spring and warm air are on the way.