Lower Engine Cowling

[Bobdog]

Rob, I'll let you guys continue the thread. I've decided to keep the cowl original, and just not fly on the hot days!
Bob

[Robert Lees]

Re: Lower Engine Cowling

Bob: I resurrected the thread because of my opposite problem. If you still want to delete it, feel free. Rob

My suggestion would be to:

1: Make sure your temperature gauge is calibrated.

2: Add a lip to the cowl if it's still too hot.

I have the opposite problem.

My original BC12D bottom cowl had a lip (it came from Texas), and the whole thing was used as a pattern for my new lower cowl (photo here). Note the cooling louvres..these were on the original too. I later added the lip at the trailing edge, as per the original.

Now my engine runs too cool (the oil filler neck gets filled with emulsified goo, and the oil temp hardly makes it above 140.

So I closed up the opening under the prop with a blanking plate, and that raised the oil temp by only 10 degrees.

I'm thinking that by laying the new cowl on the old on (the way that my metalworkers made it) in effect made the whole lower opening MUCH bigger, so inducing too much additional airflow.

I might try lessening the lip angle, to further reduce the "suction" effect.

{for reference, all my cowl work is at http://www.Documents/Taylorcraft.org...uild-Cowls.htm}

[Winston L.]

Re: Lower Engine Cowling

Bob: I resurrected the thread because of my opposite problem. If you still want to delete it, feel free. Rob

My suggestion would be to:

1: Make sure your temperature gauge is calibrated.

2: Add a lip to the cowl if it's still too hot.

I have the opposite problem.

My original BC12D bottom cowl had a lip (it came from Texas), and the whole thing was used as a pattern for my new lower cowl (photo here). Note the cooling louvres..these were on the original too. I later added the lip at the trailing edge, as per the original.

Now my engine runs too cool (the oil filler neck gets filled with emulsified goo, and the oil temp hardly makes it above 140.

So I closed up the opening under the prop with a blanking plate, and that raised the oil temp by only 10 degrees.

I'm thinking that by laying the new cowl on the old on (the way that my metalworkers made it) in effect made the whole lower opening MUCH bigger, so inducing too much additional airflow.

I might try lessening the lip angle, to further reduce the "suction" effect.

{for reference, all my cowl work is at http://www.Documents/Taylorcraft.org...uild-Cowls.htm}

The Texas cowlings were made on the original wood Taylorcraft form block.

I found that if it doesn't have the compound curve it puts everything out of place including the opening. What problems did you have with the "Texas" cowling?

[Robert Lees]

Re: Lower Engine Cowling

No problem at all..the aircraft was exported from Justin, Texas, to the UK in the late 1980's. It had the proper compound curve too...hence it cost me close to $1000 to have it replicated here in the UK.

Worth every penny, as we would say here in England.

Rob

[VictorBravo]

Re: Lower Engine Cowling

Rob, I'll let you guys continue the thread. I've decided to keep the cowl original, and just not fly on the hot days!
Bob

Not fly on the hot days... in Gila Bend, Arizona... shit you're funnier than me!

[Robert Lees]

Re: Lower Engine Cowling

I'll let you guys continue the thread

Thanks, Mate...

I flew today in 25 degrees Celcius (what's that in old money? 77F?)

Even with the opening under the cowl closed off, oil temp still under 155F.

[Bobdog]

Re: Lower Engine Cowling

Rob, 77 degrees here is a nippy winter day! I'm talking 85 to 105 degrees...Then there's the summer days.....

Although your new cowl is slightly larger than the old one, the opening should still be about the same, if you still have the center Dzus fastener. The original hole distance between the two bottom dzus fasteners (aft end) was 30 5/8 inch center to center. That determines how much cowl "hangs" down below the firwall. Maybe the lip really IS adding a lot of suction to the cowl. How were your temps before you added the lip?

[VictorBravo]

Re: Lower Engine Cowling

I'd like to hear about the temp numbers versus the clwo opening myself. I've been fighting that same battle but trying to get the temps cooler.

Rob, and anyone else who wants to chime in, I'd like to know what the vertical distance is between the bottom of the firewall and the inside of the bottom cowl (without the lip, meaning if the lower cowl simply extended straight back without a lip what would the opening be).

Then I'd want to know the vertical displacement of the lip from the imaginary line continuation of the lower cowl.

On my airplane (pre-war) the lip does not make any difference in the size of the opening at the narrowest part, because the lip (or no lip) is behind that gap. So a lip may make a slight amount of additional suction behind the gap, but it does nothing to increase the actual size of the gap, and that's why I believe the lip is of marginal effectiveness. I have a movable lip on mine, and it unfortunately makes very very little difference.

[VictorBravo]

Re: Lower Engine Cowling

Rob did you boil your oil temp bulb in water to calbrate your indicator? With the opening covered at that temp you SHOULD be getting some higher oil temp than 155F. did you do some of those race car ceramic and moly coatings inside your engine to reduce heat transfer? Do you have fins welded onto the oil tank? Little mice with palm fronds fanning the oil tank???

[Winston L.]

Re: Lower Engine Cowling

No problem at all..the aircraft was exported from Justin, Texas, to the UK in the late 1980's. It had the proper compound curve too...hence it cost me close to $1000 to have it replicated here in the UK.

Worth every penny, as we would say here in England.

Rob

I misunderstood I thought you bought a cowling from Taylorcraft in Texas.

[Len Petterson]

Re: Lower Engine Cowling

My lower cowling has 2 rows with 3 luawers in it my oiltemp is 180 on a hot summer day and never over 130F on mild winter day. With restictorplats on the grill. 1 * 1" hole a side and 1 * 3 1/8" hole a side, it oes up to 180F on a mild winter day. The carp heat and cabine heat do not well without a pc of tubing bettween the plates and the airintakes. Fogot a foam plug in the bottom one time got to 240 in a hurry! It know has a red flagg on it! Engine is a A 65.
Len