Cowling mods

[slk23]

This covid-lockdown project has been going on for awhile; I hope to get the airplane flying again in the next couple months. 

The goals:

• Better ground cowling by reducing the distance between the cowling trailing edge and the prop from 4" to <1".
• Less airflow separation (drag) due to more gentle contours, especially at the lower trailing edge.
• Increase groundspeed (how fast it looks like it's going while parked).

2020-11-15_16-53-12_743.heic 2020-11-28_17-15-55_839.heic 2020-12-05_16-26-13_975.heic 2020-12-05_18-29-25_959.heic 2021-01-10_17-20-00_996.heic

[slk23]

Can anyone tell me how to make the attached photos display inline?

[Kent Ashton]

See   https://fileinfo.com/extension/heic    Change your phone settings to save them as JPEGs.  I can open your .HEIC pics on my Mac. 

You had a pretty large gap before.  Looks more than 4", but I doubt you are going to gain much with this mod except  "groundspeed"    I am not sure a 1" gap won't make your cooling worse.  I don't think the prop pulls much air through the cowl on the ground and in flight, you might be blocking some of the cowl exit area with the closer prop.  Hard to say without before-and-after-tests so don't take that as gospel. 

If you have a ground-cooling problem, maybe you just need to shut down when there is a delay and restart just before takeoff.  There is no reason to keep the engine idling for  XX minutes when you can just shut it down.  A restart is EZ unless you are hand-proping.  🙂

[slk23]

Amazon photos changed the file type. Will convert and repost. 

Thanks for the encouragement. I’m only a couple hundred hours in so what the heck 😕

Other canard drivers have reported improved ground cooling with a smaller gap. I’m hopeful.

An oil flow test showed significant airflow separation with the old cowling shape.  The new shape will definitely improve that; we’ll see if it leads to airspeed improvements.

And yes, I do hand prop like all self-respecting VariEze pilots. 

Edited September 10, 2021 by slk23

[Kent Ashton]

4 minutes ago, slk23 said:

And yes, I do hand prop like all self-respecting VariEze pilots. 

Good for you.  I tried that for a while on my O-320 Cozy III but finally gave up and installed a starter.  But surely you don't idle long enough on the ground for it to be a problem?  Just make those Airbus A-320s wait while you get out and restart.  🙂

[slk23]

[slk23]

Kent,

Yes, I do sometimes have to idle for quite awhile.  Why you are so skeptical?

This VariEze has a Lycoming O-235.  Weight and balance would not be pretty with a starter, as much as I'd like one.  But I've come to appreciate hand-propping because I am immediately made aware of leaking valves, etc.  It's also satisfying to develop the skills involved. 

More pix to follow.

[Jon Matcho]

2 hours ago, slk23 said:

Can anyone tell me how to make the attached photos display inline?

 

1 hour ago, Kent Ashton said:

See   https://fileinfo.com/extension/heic    Change your phone settings to save them as JPEGs.  I can open your .HEIC pics on my Mac. 

The HEIC file format is relatively new and is catching on, but not fast enough for the forum hosting service to keep up with it. It will happen eventually, but until then JPEGs work. 🙂

[slk23]

[slk23]

On 9/10/2021 at 12:39 PM, Kent Ashton said:

See   https://fileinfo.com/extension/heic    Change your phone settings to save them as JPEGs.  I can open your .HEIC pics on my Mac. 

You had a pretty large gap before.  Looks more than 4", but I doubt you are going to gain much with this mod except  "groundspeed"    I am not sure a 1" gap won't make your cooling worse.  I don't think the prop pulls much air through the cowl on the ground and in flight, you might be blocking some of the cowl exit area with the closer prop.  Hard to say without before-and-after-tests so don't take that as gospel. 

If you have a ground-cooling problem, maybe you just need to shut down when there is a delay and restart just before takeoff.  There is no reason to keep the engine idling for  XX minutes when you can just shut it down.  A restart is EZ unless you are hand-proping.  🙂

 

Follow up:  I'm not sure I gained top speed, but the airplane climbs better now, especially at higher cruise climb speeds.  That makes sense because with lower drag, more power is available for climb.

Ground cooling improved significantly, although the 1" gap between the prop and cowling trailing edge is probably costing me some top end speed (according to Klaus).  After I install in-cowling exhaust, which will help draw cooling air through the cowling, I'll try trimming the TE back another inch or two.

Edited November 2, 2023 by slk23

[A Bruce Hughes]

I am close to finishing replacement of a very heavy upper cowl with a lighter one made professionally.    During the painting (white, of course) I also have removed the common "stick-on" numbers and will use orange trim paint (already a trim on the prop) with the N-number.  I need to understand the FAA requirements on numbers.   

I want to slope the number on the winglet to get the letters/numbers large enough.  On the left winglet, the N will be low down with the rest slopping at a 45 degree angle upward and backward.   I think none will need to go as far back as tbe rudder.

Does that violate any FAA regulation ?

Thank you for comments.

Bruce Hughes

 

[Marc Zeitlin]

9 hours ago, A Bruce Hughes said:

... I need to understand the FAA requirements on numbers...

Does that violate any FAA regulation ?

See 14 CFR Parts 45.21 - 45.33.

All the registration marking requirements are there.

Of course, about 1/2 the planes I examine don't meet the FAR requirements, and other than for international flight, I've never heard of anyone getting their wrist slapped because of it, but those are the rules.