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  #11  
Old 09-15-2017, 05:44 PM
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N363RV N363RV is offline
 
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Location: Arlington, tx
Posts: 200
Default Probably not.

Quote:
Originally Posted by Bob Martin View Post
Thanks for the report.
Nice pictures too.
Any thoughts on installing two, one on each side?
If one is good, two might be better?
Hi Bob! Probably not. I'm having good enough results that I don't feel I need it. In addition to that I'm not convinced you get more airflow with 2 holes as opposed to 1. Dan Horton has covered the issue of airflow thru the cowling in some other post. You might search on "shrinking exit" or something like that.


I think that there are diminishing returns for 2 cowling doors as opposed to one with a standard vans inlet size... and even less for a sam james.
As I understand it, if you want more flow you gotta have big holes on both ends. I'm sure somebody will raise their hand and tell you all about. :-)
I think these guys with io540s could probably use more flow...sometimes. I just have a plain vanilla O360. A stock vans cowling.

Brantel went with 2 of them. I think he likes 2 but i don't know if he tried it with one or not. I really like the product, but it is a little expensive for me to sling out the bucks for 2 right out of the shoot. Now that I have tried it I am satisfied.

What really sealed it for me was the last test I did. My wife and I took off with a bunch of water in the cargo hold to simulate our bags on a normal trip. It was 96F around 3pm. We flew for about 20 minutes and landed. Filled up on Fuel. So with full Fuel, the two of us, and our simulated bags we took off. We were heat soaked as you would expect. Field elevation is about 700'. We climbed out between 500 and 800 feet per minute up to 10,500. I didn't take any pictures on this flight... but IIRC, the oil was about 205 and highs CHT was 410. The good news is that after we leveled off it cooled right off. Then I shut the door. Funny as the oil temp dropped a little more after I shut the door.

Hopefully this link works... it is an album of pictures I took. There aren't very many and it certainly is not scientific. It was mostly meant for me to look at so I would not lie to myself about the results. I was alone in all the photos you see in this album, but I usually conducted continuous climbs of between 800 1100 feet per minute. Enjoy. Let me know if the link doesn't work.

When you clickon the pictures, there is a little info button on the right side. Click this then go thru the pictures and you can sorta see the time line as I took them.

https://photos.google.com/share/AF1Q...paakFjWkNvdlFB
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Last edited by N363RV : 09-15-2017 at 05:46 PM.
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  #12  
Old 09-16-2017, 06:10 AM
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Bob Martin Bob Martin is offline
 
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Location: Richmond, Virginia
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Default Great

John,
Thanks for the informative post!!
The link to pictures worked great, very nice.
I am a student of "Dans"...shrinking exit thoughts as well as many other fiberglass lessons.
Thanks for the reminder of Brantel's dual set-up.
Can I assume you chose the left side location because it was directly under the oil cooler?
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  #13  
Old 09-16-2017, 08:50 AM
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DanH DanH is offline
 
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Quote:
Originally Posted by N363RV View Post
I think that there are diminishing returns for 2 cowling doors as opposed to one with a standard vans inlet size... and even less for a sam james.
As I understand it, if you want more flow you gotta have big holes on both ends. I'm sure somebody will raise their hand and tell you all about. :-)
Yeah, just might...

Forget about the size of the holes for a moment. Think about pressure instead. Mass flow through the fins is driven by differential pressure. To get more mass flow, you either raise the pressure in the upper cowl, or reduce the pressure in the lower cowl.

Here are measured static pressures from two different airplanes:



Airplane Blue and Airplane Red exhibit approximately the same differential pressure, so assuming they are equipped with the same baffle wraps and oil cooler, they will have the same mass flow, i.e. equal cooling. Either can increase deltaP (and thus mass flow and thus cooling) by further reducing lower cowl pressure. Neither is currently at zero, so adding more exit area would do it. Obviously Blue can effect a greater change.

So two points.

One, an aircraft with better pressure recovery can vary mass flow a lot with variable exit area, while poor pressure recovery limits the effectiveness of additional exit area.

Two, all that's necessary to determine if an additional cowl door would be beneficial is a simple pressure measurement. One leg of a manometer connects to a piccolo tube in the lower cowl, and the other connects to airframe static. If that deltaP is already quite low with one door open, a second door won't have much effect. If there is pressure remaining, a second door will increase mass flow.
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  #14  
Old 09-16-2017, 08:14 PM
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N363RV N363RV is offline
 
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Location: Arlington, tx
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Default Yes

Quote:
Originally Posted by Bob Martin View Post
John,
Thanks for the informative post!!
The link to pictures worked great, very nice.
I am a student of "Dans"...shrinking exit thoughts as well as many other fiberglass lessons.
Thanks for the reminder of Brantel's dual set-up.
Can I assume you chose the left side location because it was directly under the oil cooler?
Yes. I put it on that side because my oil cooler is on the back of the baffling on that side.
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  #15  
Old 09-19-2017, 09:25 AM
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airguy airguy is offline
 
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Default

I had similar results after installing one on my 9A, definitely helps the oil temps on hard climbs, especially when it's warm outside.
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Last edited by airguy : 09-19-2017 at 09:32 AM.
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