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Old 10-08-2017, 01:19 PM   #1
MartinG
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Default Reduce Drag on our Christen Eagle

We are looking for aerodynamic clean up mods (for sale or homemade molds for rent/sale) ie: Wing root fairings, I strut fairings, tail plane fairings, 200hp cowling mods. Other?

Thanks for replys.


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Old 10-08-2017, 01:47 PM   #2
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Cameron has some pretty sweet fairings for the Eagle. Check his build thread, it's a great read. I think the fairings are available for sale from him.


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Old 10-08-2017, 02:08 PM   #3
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Default Reduce Drag on our Christen Eagle

Just curious as to why? Any biplane has a significant amount of inherent drag (flying wires, 2 wings...). I think a majority of the mods are cosmetic rather than functional. I have the original wing root fairings that I provided Benny Davis to make a mold from. He now sells them. They are sweet and slick looking
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Old 10-08-2017, 02:24 PM   #4
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Default Reduce Drag on our Christen Eagle

I don't think any of the mods that I did made any appreciable decrease in drag.

But I do share Martins desire to clean up the Eagle. A cleaner airplane is easier to maintain energy during acro....plus, it's just faster and I like going faster. I've got some ideas that I'm going to try out. I think there is some opportunity in the cowling, particularly with the cooling air exit and sealing the upper plenum from the bottom better.

There are some good articles in the last two issues of Kitplanes on drag reduction. I've also been reading Kent Passer's "Speed with Economy."

This all might be a bunch of work for nothing, but it's still interesting.

And Mark is correct, a biplane inherently has a lot of drag. The Eagle is pretty fast in stock form for what it is.
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Old 10-08-2017, 03:16 PM   #5
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Default Mods

Cameron is correct that drag reduction results in speed which can significantly improve aerobatic performance.
Most of the Pitts mods translate to the Eagle.
The pressure recovery wheel pants are a big item, at least 4-5 mph increase in cruise at Pitts S1 speeds.
Improve gear to fuselage fairing.
Improve the canopy to turtledeck transition-a BIG project. But you could include a removeable carbon turtledeck as part of this.
Cowling and baffling is where the greatest potential is. The Eagle cowl is just awful. Look at the pictures of the Iron Eagle airplanes to get ideas. An optimum plenum would allow a 30% reduction in inlet and outlet cooling area.
Then there is the engine and prop. 4 into 1 exhaust, ram air induction, cold air sump, 10-1 pistons.
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Old 10-09-2017, 12:45 AM   #6
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Jim, nothing money won't cure! ��
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Old 10-09-2017, 09:39 AM   #7
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Default Sealing canopy and ruddergaps

Thank You for Your interesting replies. The question why clean up and reduce drag has been answered very well.
Befor flying the Christen Eagle I used to fly gliders ( DG 800 ) most of the time. The best measure to increse performance was to seal the canopy and the gap of the ailarons .
Do You have expiriance with these measures and if, how doese the Egle react ?

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Old 10-09-2017, 11:18 AM   #8
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The a Eagle responds very well to sealing the aileron and tail surface gaps. Better control response and better feel. No speed increase though.
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Old 10-10-2017, 10:36 AM   #9
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Thanks Cameron
I saw Your drawings on your block.
So to start with I ordered
Frost King T94H Clear Plastic Weather-Seal Tape 2-Inch by 25-Feet, Cleafrost tape 2 inch

to seal the ailarons

Next step will be the canopy - here there is relevant of almost 4mm
and I am not shure on how to fill it



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Old 10-10-2017, 12:29 PM   #10
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Here's another option, Scotch Book Tape 845, it feels a little less sticky than the Frost one, and hopefully, should be easier to remove/reapply when the time comes

link
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Old 10-10-2017, 02:54 PM   #11
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I've often heard the airflow through the cowl is a major source of drag, both the inlet and the exit. My Pitts has a rounded transition on the bottom of the firewall for smooth airflow as it exits the cowl. It is probably about a 4 inch radius. Looking at photos of the bottom of the Eagle firewall and it looks like a sharp corner and this would cause some loss as the airflow accelerates out the bottom of the cowl.

Interesting thread on drag reduction on Pitts S-1. New cowl and plenum for engine cooling gave him 10 MPH inrease:
http://www.biplaneforum.com/showthread.php?t=1583

Don't forget weight reduction!

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Old 10-10-2017, 04:18 PM   #12
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I'm using "Gorilla Tape", clear because that is what was available locally. Works well and comes off but it does stick rather tightly.
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Old 10-19-2017, 03:58 PM   #13
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the Wolf Cowl is supposed to be pretty phenomenal, not only less drag but way better cooling...right Chris?
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Old 10-19-2017, 04:42 PM   #14
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Quote:
Originally Posted by Gmovies View Post
I've often heard the airflow through the cowl is a major source of drag, both the inlet and the exit. My Pitts has a rounded transition on the bottom of the firewall for smooth airflow as it exits the cowl. It is probably about a 4 inch radius. Looking at photos of the bottom of the Eagle firewall and it looks like a sharp corner and this would cause some loss as the airflow accelerates out the bottom of the cowl.

Interesting thread on drag reduction on Pitts S-1. New cowl and plenum for engine cooling gave him 10 MPH inrease:
http://www.biplaneforum.com/showthread.php?t=1583

Don't forget weight reduction!

Paul Klusman
Cleaning up the cowling air exit and also adding baffling just behind the flywheel are a couple of the things I'm going to try. I'm hoping that I'll be able to block off the cowl cheek exits after this. If I get real curious, I may try to put a cover over the upper plenum instead of using the conventional baffle sealing.
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Old 10-19-2017, 04:49 PM   #15
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Quote:
Originally Posted by plschulten View Post
the Wolf Cowl is supposed to be pretty phenomenal, not only less drag but way better cooling...right Chris?
Haha yep......
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Old 10-21-2017, 02:50 AM   #16
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Strap a 540 on it........MUCH FASTER!
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Old 10-21-2017, 04:39 AM   #17
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Quote:
Originally Posted by Cameron View Post
Cleaning up the cowling air exit and also adding baffling just behind the flywheel are a couple of the things I'm going to try. I'm hoping that I'll be able to block off the cowl cheek exits after this. If I get real curious, I may try to put a cover over the upper plenum instead of using the conventional baffle sealing.
If you're successful blocking the cowl cheek exits you could add some kind of fairings to transition the sides of the cowl smoothly into the fuselage sides. That step just aft of the cowl is horrible for drag, though I can see how it helps pull air through the cowl for cooling with the openings like that.
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Old 10-21-2017, 12:02 PM   #18
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I've thought about smoothing that transition too...but one step at a time.

I tried blocking the cheeks off a couple months ago. I can block them about halfway off without much change at all. Blocking off the other half does make the temps go up. I saw oil temp near 240, and cylinder head temps around 390. I was so focused on engine temps that I forgot to do a top speed run to see if there were any gains.

But, I think Randy may have the best speed increase solution.
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Old 10-21-2017, 01:15 PM   #19
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Quote:
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I've thought about smoothing that transition too...but one step at a time.

I tried blocking the cheeks off a couple months ago. I can block them about halfway off without much change at all. Blocking off the other half does make the temps go up. I saw oil temp near 240, and cylinder head temps around 390. I was so focused on engine temps that I forgot to do a top speed run to see if there were any gains.

But, I think Randy may have the best speed increase solution.
That is encouraging you can nearly block off the cheeks. I'll bet some improvement at the inlets and exit at the bottom might allow the cheeks to close off completely.

A 540 on a plane this size is lots of fun I can tell you that, but man it hurts every time you fill up at the pump!
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Old 10-23-2017, 01:28 PM   #20
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That is encouraging you can nearly block off the cheeks. I'll bet some improvement at the inlets and exit at the bottom might allow the cheeks to close off completely.

A 540 on a plane this size is lots of fun I can tell you that, but man it hurts every time you fill up at the pump!
I don't try to think about the extra gallons since I have all the extra "grins" its kinda worth the bang for buck! :}



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