Sabremech Cowling Mod Testing (Ongoing)

[jamesm]

Huh  I thought  in the later model Mooney's Lopresti and company  fixed the cooling issues.  Of course there is the  popular  article on a M20C  with the guppy mouth original cooling air spill out the front. I can't seem keep my cylinders ( usually #2& #4 are my hottest) cool on take off.  but My CHT's temp  varies  on when the over temp some times it is in winter and won't do it in summer.  Seems to me when I measured my M20C with LASAR cowl  enclosure mod the cowl exit area  was much difference between inlet and outlet  area.

[Marauder]

Wouldn't that suggest that exit area needs to be larger ? 
A while back I posted a video Pipistrel Panthera,  where they discussed about engine cooling exit area being larger than air inlets and exiting the air on side  of the cowl rather than the bottom since that is high pressure area .  Maybe the it isn't as high pressure on a Mooney but I have noticed that some  Bonanza engine  cowling have side louvers   and wonder if that  isn't the case on the Bonanza's as well is to exit into a lower pressure area.
 
James '67C

On the F, at least my F, the combination of wide mouth, cowl flaps and the fixed center flap always kept my CHTs under 380°. In some cases, like on today’s flight, you may argue that it was pretty low.

I know some J owners adjust their cowl flaps a 1/2 inch open and later Mooneys actually allow you to electrically put the cowl flaps in a trailing position.

Getting this right is what David and Matt are doing now. A 40° increase in CHTs over a comparable operating environment is a lot of temp increase. They have however removed the fixed cowl flap. I suspect they will put it back on and see what they get.


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[Guitarmaster]

Newer planes have very small inlet area and large exit area. Like a 1:2.5 ratio. Look at the ovation, very small inlet area and large fixed exit area. My J spills air out the front when the cowl flaps are closed, why else would a leaking engine pull air and oil  forward And onto the windshield. 

That is windshield deice Byron. It was an option on the "J".

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[Guitarmaster]

Since MS deleted half my post, I will redo it here.... 

Attached are two flight with similar weather conditions roughly a year apart.

 

This is the old cowl.

[mention=7497]Sabremech[/mention] has been great to work with!  When I started this project, we knew this was a "semi-experimental" thing with the injected models.  I was happy to be the guinea pig as I love experimenting.   I can't wait to get the ram-air removed and continue helping in any way I can to make his design perfect.   

 

 

 

 

 

For whatever reason, MS doesn’t like this post and keeps deleting portions of it so I will repost for the third time....

 

Observations so far:

 

1. The temps are hotter. We removed the third cowl flap as an experiment so this is not totally unexpected. The plan is to add back the third cowl flap during annual in March. I believe there is some pressure building in the top section of the cowling thereby causing hotter temps and possibly some drag. Adding more exit air should solve this problem. It’s also my opinion that adding a third cowl flap to the “C” would be of benefit.

 

2. Speed is faster. 4% faster to be exact. I have a solid 6 knot gain in TAS. I now run 153 KTAS. I already had the LASAR closure. This fact alone makes the mod a huge success.

 

3. The ram air will be outta here. With only a 0.7” gain, it’s not worth it. In addition, with the removal of the Ram air, it allows a smooth pipe to go directly from the filter to the fuel servo hopefully reducing the restrictions in the system, maybe to the tune of .5” or better. In addition, I never really use the ram air since I don’t like the idea of unfiltered air entering the engine. Win-win.

 

4. The oil cooler relocation is fine. The oil temp is slightly warmer then before, but I suspect with more exit air, it will end up being cooler. In addition, it looks better!

 

David has been awesome to work with! He is very meticulous. It’s been great fun for me to be his guinea pig and see this come together. We tried some different things, some worked and some need a little tweaking. I am looking forward to working with David to perfect this mod!

 

 

 

 

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[Guitarmaster]

Looks good!  Has anyone flew any of the engine cooling certification profiles yet?  Load to max weight, climb to 10k at Vy and then correct for temp to verify engine and oil cooling? 

That will be coming with the modification to the exit air.

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[mike_elliott]

13 hours ago, Guitarmaster said:

Since MS deleted half my post, I will redo it here....

Attached are two flight with similar weather conditions roughly a year apart.

 

This is the old cowl.

This is the new

We are going to have some cooling to perfect.  To be fair, we kind of thought this was going to be the case since we removed the third cowl flap.  This will be an easy change.  David is also working on some other ideas to improve the exit air flow.  

Opinions and results thus far:

1) I have a solid 153 KTAS.  That's up 6 knots.  

2)  Jury is out on the oil cooler relocation.  It seems a slight bit warmer than before, but I believe that will change with an exit-air change.  It does look better though.

3)  The Ram-Air is going to be taken off the airplane.  At .7" it just isn't worth keeping.  In addition, with the Ram-air gone, there will be a smooth flow from the filter directly into the fuel servo.  That will eliminate the present 90 degree bend the air has to take.  I am hoping that will be good for .5".  

4)  I have a working theory that since the temps are warmer, there is not enough exit air and air is packing up on the top side creating some cooling drag.  Maybe with a higher negative pressure on the bottom of the cowl, the plane will be faster yet     

5) Finally, David @Sabremech has been great to work with!  When I started this project, we knew this was a "semi-experimental" thing with the injected models.  I was happy to be the guinea pig as I love experimenting.   I can't wait to get the ram-air removed and continue helping in any way I can to make his design perfect.   

 

 

 

I wouldnt be in a hurry to add the fixed cowl flap back. Why dont you simply set the cowl flaps open 1/4" or so in trail when closed and see what that does. Drag wise, you wont see a knot diff, and if anything, it may improve speed slightly by not creating a pressure plug under the cowl.

[Guitarmaster]

I wouldnt be in a hurry to add the fixed cowl flap back. Why dont you simply set the cowl flaps open 1/4" or so in trail when closed and see what that does. Drag wise, you wont see a knot diff, and if anything, it may improve speed slightly by not creating a pressure plug under the cowl.

That is the plan. Going to do my best to figure out the best opening and go from there.

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[rbridges]

11 hours ago, jetdriven said:

Newer planes have very small inlet area and large exit area. Like a 1:2.5 ratio. Look at the ovation, very small inlet area and large fixed exit area. My J spills air out the front when the cowl flaps are closed, why else would a leaking engine pull air and oil  forward And onto the windshield. 

Good point. I noticed that when my prop seal started leaking. 

[jamesm]

So does the relocation of the oil cooler help lower the drag if so how much ?

[Bob_Belville]

13 minutes ago, jamesm said:

So does the relocation of the oil cooler help lower the drag if so how much ?

0.1725%  

[jetdriven]

Maybe it’s more to make the oil cooler more effective. The old style location relies on ram air overcoming the higher pressure inside the cowl. I think someone pointed out that high power low airspeed operation the warm air inside the cowl actually comes forward through the oil cooler. A lousy design 

[bonal]

It was Paul Loewen that discovered this airflow issue which prompted his design and STC for the relocate to the back of the dog house

[MB65E]

The Fwd mounted oil cooler isn't exactly bad it's just the poor ducting in the cowl that's bad. I've thought about having a reverse naca duct on one of the cowl panels just for an oilcooling exit. However, the sq in required on the exit air is space prohibitive. I think the biggest duct one could route in the cowl would be about 3 in. It would be more efficient than taking engine cooling air to cool the oil. 

A remote oil cooler, with its own intake and exit air would be the most efficient. 

All for the next neatest experimental!! 

-Matt

[Guitarmaster]

There hasn't been much to update as of late, but I did want to share this.

As most of you know, we are using my plane as the "test bed" for the injected models.  Of course, the nature of experimentation involves theories and testing.   One of the things we did was to remove the third cowl flap.  David wanted to see if it made any difference in CHTs.  Well, it did; to the tune of about 35 degrees warmer.  This was not a huge surprise.  

I have a friend that races airplanes so I picked his brain about cooling and drag.  He suggested I put some "indicating fluid" on the cowl and fly it.  This would give a good visual indication of the high. low and stagnant pressure areas.  He assured me I would be surprised by the results.  
I did exactly that.  The results were enlightening!

I haven't had good luck inserting pictures in the middle of the post, but I'll try again.

Here is the key for interpreting the pictures:  thin streaks = fast moving, low pressure air.  Sloppy (runny) streaks are slower moving air with higher pressure.  No streaks or pooled = stagnant air.   

The first picture is right before flight

The next picture is just after landing.  Cruise was 140KIAS.  Notice the thin, well defined streaks on the lower part.  Fast moving, low pressure air as opposed to the sloppy lines toward the top front.


Next, the plane had been sitting for about 30 minutes in the following picture, but it really shows where the high and low pressure areas are on the front of the cowl.  The original location of the oil cooler appears to sit right in the middle of where the high and low pressure area separate.   It also shows the drag being produced where the cheek cowl meets the rest of the cowling.  In addition, the Ram-air is barely catching the high-pressure area.


By far the most intriguing and telling of the pictures are from below the cowl.  Notice the relatively fast moving air between the cowl flaps.  This was where the removed third cowl flap used to reside and will again.  Now look at the cowl flaps.  There is very little fluid on either one.  Granted, I only dabbed fluid on the left and center, but still they are almost completely clean indicating stagnant/separated air.   Without fast-moving air over the cowl flaps, there is no ability to draw a vacuum.  This explains the paltry 10 degree difference between the cowl flaps open and closed.  


David has some good ideas as to what he is going to put into action using the above information.  I am excited for the results!!  

P.S.  I am secretly hoping to be able to remove the movable cowl flaps altogether in the future....

P.P.S.  I feel truly blessed to be part of this process.   The tinkering has been a blast, but most of all, I am thankful for the friendship that has developed from this endeavor!  (of course I haven't received David's bill yet  )

[Guest]

8 minutes ago, Guitarmaster said:

There hasn't been much to update as of late, but I did want to share this.

As most of you know, we are using my plane as the "test bed" for the injected models.  Of course, the nature of experimentation involves theories and testing.   One of the things we did was to remove the third cowl flap.  David wanted to see if it made any difference in CHTs.  Well, it did; to the tune of about 35 degrees warmer.  This was not a huge surprise.  

I have a friend that races airplanes so I picked his brain about cooling and drag.  He suggested I put some "indicating fluid" on the cowl and fly it.  This would give a good visual indication of the high. low and stagnant pressure areas.  He assured me I would be surprised by the results.  
I did exactly that.  The results were enlightening!

I haven't had good luck inserting pictures in the middle of the post, but I'll try again.

Here is the key for interpreting the pictures:  thin streaks = fast moving, low pressure air.  Sloppy (runny) streaks are slower moving air with higher pressure.  No streaks or pooled = stagnant air.   

The first picture is right before flight

The next picture is just after landing.  Cruise was 140KIAS.  Notice the thin, well defined streaks on the lower part.  Fast moving, low pressure air as opposed to the sloppy lines toward the top front.


Next, the plane had been sitting for about 30 minutes in the following picture, but it really shows where the high and low pressure areas are on the front of the cowl.  The original location of the oil cooler appears to sit right in the middle of where the high and low pressure area separate.   It also shows the drag being produced where the cheek cowl meets the rest of the cowling.  In addition, the Ram-air is barely catching the high-pressure area.


By far the most intriguing and telling of the pictures are from below the cowl.  Notice the relatively fast moving air between the cowl flaps.  This was where the removed third cowl flap used to reside and will again.  Now look at the cowl flaps.  There is very little fluid on either one.  Granted, I only dabbed fluid on the left and center, but still they are almost completely clean indicating stagnant/separated air.   Without fast-moving air over the cowl flaps, there is no ability to draw a vacuum.  This explains the paltry 10 degree difference between the cowl flaps open and closed.  


David has some good ideas as to what he is going to put into action using the above information.  I am excited for the results!!  

P.S.  I am secretly hoping to be able to remove the movable cowl flaps altogether in the future....

P.P.S.  I feel truly blessed to be part of this process.   The tinkering has been a blast, but most of all, I am thankful for the friendship that has developed from this endeavor!  (of course I haven't received David's bill yet  )

One of the Comanche gurus used a similar process in his testing.  He mixed coloured powder with new oil then dabbed it on to see what the air flow was doing.

http://www.hdneubert.com/Reno_Presentation.pdf

Clarence

[Dream to fly]

If I understand this correctly the fast air is the thin oil streaks?  So if instead of cowl flaps one was to install louvered vents where the cowl flaps are wouldn't that help in creating a vacuum in the engine compartment sucking the hot air out?  Also could the ram air be relocated to a high pressure point to actually cause it to work properly?

[MIm20c]

33 minutes ago, Guitarmaster said:

David has some good ideas as to what he is going to put into action using the above information.  I am excited for the results!!  

I would start with copying the removable ovation exhaust shrouds. They have a half canopy shape to them that probably produce a lot of vacuum.  Enough to keep 310 horses cool. 

[Guitarmaster]

10 minutes ago, Dream to fly said:

If I understand this correctly the fast air is the thin oil streaks?  So if instead of cowl flaps one was to install louvered vents where the cowl flaps are wouldn't that help in creating a vacuum in the engine compartment sucking the hot air out?  Also could the ram air be relocated to a high pressure point to actually cause it to work properly?

Yes, the thin streaks is the fast air.  No streaks is stagnant air; which is what is occurring over the cowl flaps.  You can see just a little bit of oil streak toward the outside.

Since I have lots of time to think while cruising across the country at five miles up, I considered the possibility VGs in front of the cowl flaps or possibly sealing the gap at the hinge. 

 

[Guitarmaster]

1 minute ago, MIm20c said:

I would start with copying the removable ovation exhaust shrouds. They have a half canopy shape to them that probably produce a lot of vacuum.  Enough to keep 310 horses cool. 

That is one of the ideas being entertained.

 

[Guitarmaster]

54 minutes ago, M20Doc said:

One of the Comanche gurus used a similar process in his testing.  He mixed coloured powder with new oil then dabbed it on to see what the air flow was doing.

http://www.hdneubert.com/Reno_Presentation.pdf

Clarence

A very interesting article for sure.  I was amazed when I first learned how much drag ( in the 1958 MIT video) a round shape produced!  

[Guest]

8 hours ago, Guitarmaster said:

A very interesting article for sure.  I was amazed when I first learned how much drag ( in the 1958 MIT video) a round shape produced!  

The series “Fluid dynamics of drag” on YouTube is very interesting.

Clarence

[Sabremech]

Here’s a picture or two of Matt’s new induction system as well as Bob’s. I’m modding Matt’s by removing the ram air and building Bob’s baffling using Matt’s airplane to fit the parts. 

 

[Guest]

57 minutes ago, Sabremech said:

Here’s a picture or two of Matt’s new induction system as well as Bob’s. I’m modding Matt’s by removing the ram air and building Bob’s baffling using Matt’s airplane to fit the parts. 

 

Van’s aircraft make Mooney parts now?

Clarence

[Sabremech]

15 minutes ago, M20Doc said:

Van’s aircraft make Mooney parts now?

Clarence

Yep and the FAA likes me using their parts in my mod. 

[cctsurf]

2 hours ago, Sabremech said:

Yep and the FAA likes me using their parts in my mod. 

That's obviously not how you're doing the carbureted models...