Nose Cowl Inlet Discoveries

 I'm still trying to solve my high cylinder head temperature problem.  Cylinder cooling depends on the size of the inlet openings, to get good inlet pressure.  Then the baffles have to assure the air coming in goes through the cooling fins, with no leaks.  The rate of airflow across the cylinders depends on the outlet size to create a pressure drop from above the cylinders to below them.

I started with the assumption that the Taylorcraft nose cowl openings were obviously larger than the old cowl so it should work fine.  I've worn myself out looking for leaks and playing with the outlet opening and skirt.  I've made some improvements but never solved the problem.

The other day I had the bright idea that maybe the grills on the Taylorcraft cowl were blocking the airflow.  After all the Taylorcraft used a 65 HP motor and mine's 85 HP.  I decided to remove them and see if it improves the flow, when the airport reopens in November.  This required removing the nose cowl to get them out.

While I was removing the nose cowl I decided to position the old nose cowl so I could visually compare them (I don't throw things away until I'm sure I won't ever want them).  I think the current term is OMG.  Houston, we have a problem.  The useful area of the Taylorcraft openings is clearly smaller than the old cowl inlets.

Time to lay this out in CAD to learn some truth.

I used the prop opening to align the 2 cowls in TurboCAD.

The Yellow line is the old Inlet.  The one thing you see is that it is positioned to focus air on the cylinder head.

The Magenta line is the top of the front baffle.  The best airflow is above that line.  Most of the Taylorcraft inlet is below that line.

Yes the grill is blocking airflow to my cylinders.

Here are the numbers:

Old  Inlet                                  T'craft Inlet

33.9 sq in                                  58.6 sq in without Grill  (much bigger)

                                                  39.2 sq in with Grill       ( not much bigger)

Above Line

26.1 sq in                                   23.6 sq in without Grill (10% smaller)

                                                   15.5 sq in with Grill      (41% smaller) OUCH!!!

I've removed the grills and redone the skirt without the lip.

They're ahead of schedule on the runway so I may wait to recover the fuselage until after the runway is done so I can see if this is the answer.

They have the base gravel down and this runway really looks good.

The first picture is looking SW and the second looking NE.

Very flat, slightly downhill to the NE

July 19 Added Lip to Cowl Skirt - July 22 Last Flight From Gordonsville's Old Runway

 

My last experiment, for now, was to add a small curved lip to the bottom of the shallow cowl skirt and reinstall it in place of the steep one.  By the time I got done, on a very hot, humid evening, it was too late to go flying.  I hammered the curve using a plastic hammer and dolly while holding the skirt so it was curved, like when it is installed.  I only did about 20" in the middle where the skirt is perpendicular to the airflow under the cowl.

It came out nice but made the temps hotter so I was back on the ground in 15 minutes.

They're rebuilding our runway, last paved around 1955, to get rid of the cracks, widen it from 40 feet to 50 feet, get rid of the hump near the north end and the dip near the south end.

Looking southwest from the displaced threshold for runway 23.  There's a low spot near the south end.  From here the runway goes downhill, behind me to the northeast

This view is from the north end looking back uphill to the displaced threshold

Another nice warm evening flying.  This was the first change I made which made the temperatures worse, so I learned something from it.

This view is from the end of runway 5 looking back to the northeast.  You can see the dip near this end.  The runway will be flat but still run downhill when they are done.  This end can't be lowered because it's at the property line and the adjoining land owner won't give permission to cut into their property.  The crack will be gone and you'll be able to see if someone or something is on the runway when you start your roll to the south.  Their plan is to reopen it in November, about Thanksgiving (120 days).

While it's closed I plane to recover the fuselage and tail which I covered with cotton it 1994, 28 years ago.  Time goes by quick

July 15 - Nice Evening Flight

 

I didn't have time to mess with the cowl so I enjoyed a nice warm evening flight.  Straight ahead under the right brace wire is Orange airport about 3 miles out.

The white building is the Rigid factory south of Orange.  They had very sexy calendars at one time.  I expect they're not allowed anymore.

The ever present tail.

July 13 - Reinstalled Steeper Cowl Outlet Baffle

I removed the shallow outlet skirt and reinstalled the steeper one.

It made on change but I had a nice warm evening flight for about 1/2 hour. 

The setting sun was lighting up the clouds east of us nicely.

It was pretty when the sun finally hid behind the clouds over the Blue Ridge, to the west.

I have one more experiment to try before they close the runway.

July 11 - More Baffle Changes and A Nice Evening Flight

 I keep looking for some reason that I'm getting high Cylinder Head and Oil Temperatures. My belief is that there are 3 most likely causes.  The first is that I have a leak somewhere from the high pressure above the cylinders to the lower pressure below.  The second is a poorly designed outlet. The last is that somehow changing to the Taylorcraft nose bowl is causing low inlet pressure.  The last doesn't seem very likely since there were a lot of Taylorcrafts made using this nose bowl.  I decided to remove the nose bowl and reinstall a baffle I had made to force more flow below the crank case for better oil cooling.

When I removed the nose bowl it looked like my front seals weren't rubbing as tightly against the nose bowl as well as I would like, especially on the left cylinders, there was a gap between the 2 pieces of felt.

I remade these to cover the gap and to allow more felt to lay against the nose bowl for a better seal.

On the right side I moved the felt away from the baffle a little so there would be more of it lying against the nose bowl on this side as well.

The main plan was to reinstall the baffle below the crank shaft so more air would flow under the crank case to cool the oil better.

I had originally made this baffle so the felt sealed against the case, forcing all the air down. I decided to remove some of the felt to allow a little air to go over the nose of the crankcase.

The baffle is back under the crankshaft.

There is now a small gap to allow some air to move by it on the right (arrow) and left sides of the case.

Another beautiful warm evening for flying.

An algae clogged lake south of the airport.

Looking north the airport is to the right of the water tower and left of the left brace wire.

Looking south the airport is in front of the wing strut.

It was a nice flight but my efforts had no affect on the temperatures.  I haven't given up but I'm running out of time before they tear up the runway to rebuild it.

Sailplane Ride At Harris Hill, New York

 I'm a couple weeks behind reporting what I've been doing with the Fly Baby.  But before I get caught up, yesterday my Grandson, Duncan and I went for Sailplane rides at Harris Hill Soaring.  While we waited for our turn, our tickets got us into the National Soaring Museum. Both were great fun.

Duncan and his pilot ready to go in a 1984 Schleicher ASK-21, N363KS.

Takeoff

Adjusting the rudder pedals so I could fly once we released.  A good plan but once the canopy was closed I couldn't get my knees under the panel.  I flew the stick and he flew the rudder, it worked.

My ride is a 2008 Schleicher ASK-21, N621HH. Very nice feel and easy to control.

Takeoff!

Heading down the runway and liftoff.

Towing out over the drop-off.  The field is on top of the hill about 750 feet above the valley.

Steep Sides of the valley and river below.

Just before release at 4200 feet MSL, Good countdown communications with the tow pilot.

A couple more pic's before taking the stick.

Returning to land.  We had a cross wind so landed from the grassy end and taxied back to the paved launch area.

Landing

The end of a nice 17 minute flight as one of the helpers gently lets the wingtip down.  It seemed much longer and was great fun.