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  #1  
Old 06-23-2019, 12:41 PM
lr172 lr172 is online now
 
Join Date: Oct 2013
Location: Schaumburg, IL
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Default Do I need Louvers

I am wondering if anyone has successfully gone without louvers on the 10 or if they are really required to keep temps in line. I suspect that they will add some drag and would like to avoid that penalty if possible. My issue is break in heat and a lack of desire to experiment with this during break in. However, getting rid of the louvers latter will require a bunch of glass work.

Anyone leave them out with success? Anyone know what the drag/speed penalty is for these louvers? I am curious if the louvers are a crutch for poor baffle sealing or truly a necessary component for airflow.

I could make a cowl flap, but trying to accelerate the build process to get in the air before the cold weather.

Thanks for the input.

Larry
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  #2  
Old 06-23-2019, 05:43 PM
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Bill Boyd Bill Boyd is offline
 
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Location: Landing field "12VA"
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I have an Anti-Splat cowl flap and am seriously considering starting out with no louvers to see how it goes - or perhaps a modified set of louvers without as many slots - for the reasons you list (drag).
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Hop-Along Aerodrome (12VA)
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RV-10 - N130YD reserved - under construction

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  #3  
Old 06-23-2019, 05:58 PM
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aturner aturner is offline
 
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Location: Clarion, Pennsylvania
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Larry, after flying my -10 for a year and seeing cylinder head temps consistently on the cool side, I removed the louvers and covered the slots with an aluminum blanking plate. Results over the past four years are acceptable......the worst case situation is a quick fuel stop on a hot day, and in a case like that, with a heat soaked engine and high OAT I need to cruise climb or step climb. Cool weather and a cold engine, no problem with a high performance climb. I would not advise going without louvers if one flies a lot in hot weather, but for those of us that do most of our flying in cooler weather, it works out. I wish I had not cut my cowl, it will be a lot of work to fill those slots.

Cowl flaps would be even better, and are on my long term project list.

Andy
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  #4  
Old 06-23-2019, 06:01 PM
Kyle Boatright Kyle Boatright is offline
 
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Location: Atlanta, GA
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I asked the same question some time back to Scott McDaniels. He indicated that the factory prototypes showed a need for additional cooling and louvers were the solution.
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  #5  
Old 06-23-2019, 08:59 PM
lr172 lr172 is online now
 
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Quote:
Originally Posted by aturner View Post
Larry, after flying my -10 for a year and seeing cylinder head temps consistently on the cool side, I removed the louvers and covered the slots with an aluminum blanking plate. Results over the past four years are acceptable......the worst case situation is a quick fuel stop on a hot day, and in a case like that, with a heat soaked engine and high OAT I need to cruise climb or step climb. Cool weather and a cold engine, no problem with a high performance climb. I would not advise going without louvers if one flies a lot in hot weather, but for those of us that do most of our flying in cooler weather, it works out. I wish I had not cut my cowl, it will be a lot of work to fill those slots.

Cowl flaps would be even better, and are on my long term project list.

Andy
Thanks for the input. Did you notice a speed increase when you covered them up? Trying to quantify the drag penalty.

Larry
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  #6  
Old 06-23-2019, 09:00 PM
lr172 lr172 is online now
 
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Quote:
Originally Posted by Kyle Boatright View Post
I asked the same question some time back to Scott McDaniels. He indicated that the factory prototypes showed a need for additional cooling and louvers were the solution.
This is what I was afraid of. Assuming they did a good job on the baffling (likely, I think), that is probably the confirmation I was looking for.

Thanks,

Larry
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  #7  
Old 06-23-2019, 09:01 PM
lr172 lr172 is online now
 
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Quote:
Originally Posted by Bill Boyd View Post
I have an Anti-Splat cowl flap and am seriously considering starting out with no louvers to see how it goes - or perhaps a modified set of louvers without as many slots - for the reasons you list (drag).
Have you compared the area of the cowl flap vs. the louvers? I would expect the cowl flow to eliminate the need for louvers.

Larry
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  #8  
Old 06-23-2019, 09:38 PM
AviatorJ AviatorJ is offline
 
Join Date: Feb 2015
Location: Oklahoma City
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I have cowl flaps in lieu of louvers.... Iíve been working on baffle and cowl improvements and recently got my temps where full power take offs are manageable on a 95 degree day.

Still working on a few things and if I canít to where I can do a solid 120 knot full power climb and keep all CHTs below 400 then I might try some louvers as well.
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  #9  
Old 06-23-2019, 11:10 PM
bob888 bob888 is offline
 
Join Date: Jul 2012
Location: Fresno, CA
Posts: 249
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No Louvers & no cowlflaps. I fly in San Joaquin valley CA with CHTs all well below 400 even in climb with OAT >100 F. Standard Vans construction with VERY careful attention to sealing all possible air leaks. I do have to cruise climb a bit faster in hot weather (120 to 130 kt) to keep oil temps under 220
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  #10  
Old 06-24-2019, 12:51 AM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
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One comment that will do little to answer the original question but will help understand the issues involved.....

There is no one absolute configuration that will work perfectly on every RV-10 (or other models for that matter). Every engine has a different personality. It is not uncommon for two exact matching airplanes (with the exact same level of workmanship regarding baffle installation, etc.), to have differences in temperatures.

I have experience with removing an engine, having it overhauled, and reinstalling it exactly the same as it was before, and having totally different CHT and oil temperatures.

The louvers were added to the RV-10 based on the limited testing that could be done with a couple of prototypes. In service experience seems to have shown that on most RV-10's having louvers installed will be preferable to not having them.

In the recent flight testing done with the louver installation for the new nose gear on the RV-6,7,9, all of the speed test data indicated that after adding the louvers, if there was a speed penalty, it was so small that it was lost in the data noise. I can't say for sure why, because in theory it should cause some drag. Possibly this type of flow path (one where the flow is not exiting parallel to the external flow) is throttled somewhat at high speed, but at lower speed in a climb it increases the mass flow enough for a cooling improvement (we didn't take the time to instrument and see what the differences were at different airspeeds). The goal was to improve cooling in a climb and that is what they did. Some amount of speed loss was expected but there was none. This could be because the louvers were offsetting a loss in flow caused by the new (more restrictive) nose gear.
FWIW, I recently installed the louvers on my personal RV-6A, which does not have the new nose gear installed, and in the limited testing I have done so far the cruise speed seems to be unchanged.
As a comparison, these louvers are slightly larger in total area than what is supplied in the RV-10 kit.
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