Long-EZ Lower intake Cowling

[cookedinlh]

Anyone know if parts like this are ever up for sale . . should a cowling from a/c A be able to fit a/c B or is that unrealistic . . . do I have to make a new one from scratch? The one I have has been modified beyond repairing it to original flow cross section. It  currently looks like this
 

Anyone?

Thanks

Cookedinlh

[A Bruce Hughes]

David

I am the LAST person that should give suggestions on glass work.   I am throwing my lower cowl away.

Anyway way can you put on some better pictures, NOT just one and NOT taken at an angle, please.

 

 

[Kent Ashton]

Lightspeed Engineering sells a NACA duct similar to yours but any refit into an existing fuselage is going to be a fair-sized job.    NACA intakes are not hard to build.   

https://lightspeed-aero.com/Services/NACAduct.htm

Not sure what you are trying to achieve.  A new cowl?

[Marc Zeitlin]

1 hour ago, cookedinlh said:

Anyone know if parts like this are ever up for sale . . should a cowling from a/c A be able to fit a/c B or is that unrealistic . . . do I have to make a new one from scratch? The one I have has been modified beyond repairing it to original flow cross section. It  currently looks like this

What do you think is wrong with what you have?

[cookedinlh]

The issue is engine temperature limits . . I'm limited to about 75% sustained throttle except for t/o roll before it starts to overtemp in cruise . .  it's just not getting enough air. Not sure why the builder ( not me) decided to go with that  version since it's very solid  somewhat overweight airframe and needs all the power it can muster for any more than mild performance w 2 pax and fuel

Will try getting a better photo when I'm back next week . .  thanks for all the quick response guys

Cookedinlh

[cookedinlh]

Here are a couple of other views . . . NACA yes I could not remember the name . . it makes for a nice slick flight and look but it dosen't "pass wind" very well

[Kent Ashton]

The intake looks pretty nominal to me.  It should work.  Maybe the leading edge is a little fatter than others.  However, that's only 1/3 of the story.  The baffles have to be tight and correctly oriented, and the flow has to have a suitable-sized exit.   More pics plz.  🙂  Top and bottom baffles, exit opening, diverters in the lower cowl.  Sometimes wrong timing or intake tube leaks will cause hot running, too.

IMO the best way to troubleshoot cooling is with piccolo tubes and a manometer--old style or digital.  A Lycoming requires 5+ inches of pressure differential to get adequate flow through the fins.  If you only get 3.5 or 4" it will overheat.    If you have 5+ inches then look for another problem.

https://www.canardzone.com/forums/topic/18661-kents-long-ez-project/?do=findComment&comment=61602

A couple of large angles (vortex generators) installed ahead of the NACA will often improve the flow but they are a Band-aid

 

Edited January 30, 2020 by Kent Ashton

[cookedinlh]

Thanks for that link and photos Kent . . that helps a lot . . the underlying concern in because I plan on putting a belly mounted (~1ft diam sphere IRST infrared Search and Track turret) right behind the AirBrake and that's going to obstruct the flow even more so I'm trying to anticipate if I can do anything to prevent further overheat issues.

Cookedinlh

[Kent Ashton]

13 minutes ago, cookedinlh said:

I plan on putting a belly mounted (~1ft diam sphere IRST infrared Search and Track turret) right behind the AirBrake and that's going to obstruct the flow even more so I'm trying to anticipate if I can

oooh, that will change everything.    For example, just leaving the landing brake extended will cause the engine to overheat pretty fast.  I am thinking you might mount it like a travel pod hanging from the wing or inset in the leading edge of the wing.  There is nothing but foam there so I would guess that would be pretty doable.  Or maybe just build it onto the nose if it is not too heavy.    I defer to the engineers.

What are you searching and tracking, if I may ask?

[cookedinlh]

Just for training FlightTest Engineers... needs the most stable mounting point on longitudinal centreline. Seems like the original scoup shape with some laminar flow fairing behind the turret might do it... or perhaps top mounted intakes but that maybe just complicating things more....it’s to become a single pilot a/c with instrumentation in back to allow for 2-3 hr Telemetry mission

[cookedinlh]

18 hours ago, A Bruce Hughes said:

David

I am the LAST person that should give suggestions on glass work.   I am throwing my lower cowl away.

Anyway way can you put on some better pictures, NOT just one and NOT taken at an angle, please.

 

 

Hi Bruce... did you say you still have an original style lower cowling with that scoop  shape?....where is it located?

cookedinlh

[Kent Ashton]

3 hours ago, cookedinlh said:

Seems like the original scoup shape with some laminar flow fairing behind the turret might do it

I doubt it.  It will be tough to get any kind of decent airflow around a big ball in front of the intake.   Downdraft or armpit intakes could work for you.   Like this except use an armpit scoop for the oil cooler and a small forward facing scoop anywhere for the carb.

https://www.canardzone.com/forums/topic/18661-kents-long-ez-project/?do=findComment&comment=57587

 

[Marc Zeitlin]

17 hours ago, cookedinlh said:

The issue is engine temperature limits . . I'm limited to about 75% sustained throttle except for t/o roll before it starts to overtemp in cruise . .  it's just not getting enough air.

There are many factors that can lead to high temps (you don't say what your CHT's or oil temps actually ARE, which would be useful for people trying to understand what you think a problem might be). What makes you think that the air intake is the cause of the high temperatures of whatever type you're seeing?

[Marc Zeitlin]

10 hours ago, cookedinlh said:

Thanks for that link and photos Kent . . that helps a lot . . the underlying concern in because I plan on putting a belly mounted (~1ft diam sphere IRST infrared Search and Track turret) right behind the AirBrake ...

Extremely bad idea, and almost guaranteed to screw up any cooling air into the engine.

[Marc Zeitlin]

4 hours ago, cookedinlh said:

Just for training FlightTest Engineers... needs the most stable mounting point on longitudinal centreline. Seems like the original scoup shape with some laminar flow fairing behind the turret might do it... or perhaps top mounted intakes but that maybe just complicating things more....it’s to become a single pilot a/c with instrumentation in back to allow for 2-3 hr Telemetry mission

So if you need to install something on the centerline of the airplane underneath, then you're going to need to get rid of the NACA scoop entirely and go to armpit scoops under the strakes. Otherwise, you'll melt your engine, as Kent indicated.

[A Bruce Hughes]

David:

Marc and several others are expert; I am not.

I have a NACA duct which is close to identical to those that I have seen on a lot of other Longezes.

That means that it odes NOT have such a curved shape as your picture.   I have 45 hours on it and I have NEVER had a temperature problem, either for the oil or the cylinders.   I have not even smoothed out the airflow inside the engine space so there is a lot of turbulence on both sides; I just have not had the time to get that last bit of smoothing done.    I do need to balance the temps a bit  #4 is the hot one and most people have that problem, I think. #3 is next, #2 is cool and #1 is the coolest.

The oil cooler does restrict the air flow a little close to #3 cylinder.   It sits on the lower cowl and is bolted to it.  It does hang from a small aluminum bracket floxed to the back of the main spar. Air flows in the NACA duct, makes a right and climbing turn, goes through the cooler and exits on the underside of the lower cowl.    I think most builders do it that way.

You will not succeed trying to put a ball in front of the NACA duct.      I have heard of people trying to use the armpit or downdraft for many years.   Most of them had a lot of trouble, I think.    My neighbor DID have such a FLIR ball but he was using the original RAF "P-51" type scoop (he flew for the army in an experimental project that almost nobody has heard about.

Bruce

 

[cookedinlh]

All great comments guys thanks for pitching in so readily. Yes the NACA was expected to be a problem with this FLIR mount and we'll likely have to find a (different) better solution for cooling and breather air. Going to have to do some flow analysis likely and design a new intake. Does anyone know the target intake airflow that's needed for a cool running engine at max cruise?

Richard Schubert did a nice simple calcs and came up with at max pressure of 0.786 lbs/Sq Inch at 150mph . . . but how many cuft/sec of air is needed for carb and cooling if you want the cylinder heads to remain as Lycoming says  65% below of rated and <400F oil 165F-220F

Cookedinlh

[A Bruce Hughes]

David, TERRY Schubert's name is Terry Schubert.

His publication of 136 issues of the CSA newsletter did more to help us than any one person besides

B. Rutan.   He had to manage to write, print, and mail close to 1000 copies 4 times a year at an incredibly low price.   So let's get the name right.

[cookedinlh]

Woah  . . .  sorry Bruce . .  that was a direct (Copy Paste) from a post by "Richard Schubert" . . . must be another Long EZ builder . . here's the whole quote (Italics).

======================Cookedinlh===============================================================

Richard Schubert said:

Well, dynamic pressure is equal to 1/2 * the density of the fluid * the velocity squared.

Lets say 150 mph(thats indicated) 150*5280/3600= 220fps

Density of air = 0.002377 lbs/cuft (approx.:) )

so (0.002337)(220)(220)= 113lbs/sqft of pressure

divide by 144 for sqin =0.786 lbs/sqin

atmospheric pressure = 29.92 in mercury or 14.7lbs/sqin

2.03 in mercury/1psi

0.786*2.03= 1.6" max theoretical pressure gain

YMMV

"Just finished a fluids course and I couldn't resist":D
Thats a lot of numbers. On my IO360, 1.2 is about what I see on the manifold gauge when I switch from the filter to the direct ram air. Numbers aside the difference between the two on a sea level take off is worth every bit of the little drag of the scoop. the difference starts at about 150 mph and makes about a 500 ft./ min increase in climb rate. As to the drag issue, the air has to get to the engine somehow. even if it comes in with the cooling air into the cowling it is still creating drag. if some of the air goes for engine intake then that is air not used for cooling. the total of intake and cooling drag is the same weather it is in one scoop or two. why would you not take advantage of the higher pressure air and pipe it directly to the intake.

COWL AND WINGLET MODS:  Finally got to check my cowl mods.  The two exit scoops look very promising.  You will notice that I have a fairly tight opening around the prop hub; I did this because I do not believe there is good exit flow around the hub of a pusher based on oil flow I have seen inside the cowl and other indications.  Originally (2nd pic) , I believed I would get good exit flow from large openings around the exhaust pipes at the edges of the cowl but that did not seem to pan out.

The new exits allow air to blast out of the cylinders and return to freestream by the most direct route with the minimum turns and turbulence, I think. (pics 3,4).  In addition I think I've added a few sq. inches of exit area.

Before, I was only getting about 4 to 4.5" of water differential across the cylinders.  I am now seeing about 6" and 330 deg. at moderate cruise speeds.  I will have to wait for a hot day for a full test.   Manometer setup, pic 5.  I added an adjustable door on the oil cooler.  At current temps--about 55F--I have the door cracked a bit to get 180 degree oil temp.  This oil cooler duct system is not the easiest to install but it seems to work well.  (pic 6)

 

 

[A Bruce Hughes]

Well, I have to apologize (again).    I had not heard of Richard Schubert.    He certainly gave a good email discussion on drag.    I have had to apologize a few times before due to my dumb comments.

So, anyway, we have TWO very knowledgeable Schuberts.   

[cookedinlh]

No Apology necessary . .  honest mistake . . .never heard of Terry  . .  but will look him up now too. Thanks for the reference

Cookedinlh