New optional plans OP-58 - Lower cowl louvers for RV-6/7/9

[rvbuilder2002]

Originally Posted by DanH

Same here.

Scott, curiosity questions please. Assuming our intrepid owner is forced to fly with crappy baffling and too much timing advance...

(1) Why not just remove the core, make the 4 ply 9-oz layup, and cut the slots, skipping the metal louver?

That is an option that the installer could choose. Including the louvers give the installation a more purposeful / finished look (less of an after thought), and I think there is a very slight performance increase regarding flow volume (air doesn't like to exit an opening perpendicular to high speed dynamic flow) but I admit not a lot of effort was invested in proving that.

(2) Or, why not enlarge the standard exit? A simple 45 degree cut increases exit area by 41%. Costs nothing and can be done in 15 minutes.

Ease of installation and low impact on already painted cowls was a consideration. Along with other details and changes that could be involved with supporting the bottom of the cowl on "A" model installations

[airguy]

Originally Posted by DanH

Yes, you would need to modify and/or eliminate the A-model brackets. What do they support?

This is what I did - but I only ended up taking 1.5" off rather than the nearly 12" shown. I trimmed .5" at a time up to the 1.5" where the CHT's came under control for cruise, and then added the servo-louvers from Anti-Splat for hard climb scenarios to keep the oil temp happy.

[airguy]

Originally Posted by rvbuilder2002

Since in all instances where the owner was asking for help in improving cooling, I have never inspected an RV that didn't have at least some level of issue with the baffling / cowling installation, and most of the time it was more than just minor leakage (Even though they were sure that it was as good as it could be), so this shouldn't be considered a Van's endorsed method of resolving cooling issues.
This is for instances where the rest of the cowl/plenum system has been optimized but other factors make adding additional cooling flow path area, beneficial.

Scott - you're absolutely correct that, if done correctly, this is not needed. Reality and a large portion of your customer set seems to indicate that it is either very difficult to do correctly, or very difficult to motivate the builders to do it correctly. Either of those cases gives the same result - which is the cooling crutch. They are trading a few knots of drag for a few hours of modification and testing. It's not ideal but it is reality, and it's well for the kit provider to recognize trends amongst the customer set, even if it's distasteful. Not all builders are efficiency fanatics.

[engineerorange]

Now when will the engine baffle kit be modified to fix the #3 0-fin depth issue?

I really like this new approach by van's. It says a lot that #1 is willing to invest in getting better, whether actually better or just perceived as better.

[PilotjohnS]

If i convert to the new style RV9a front gear, do I really need the louvers, or will a careful baffling job be enough?

[greghughespdx]

Originally Posted by PilotjohnS

If i convert to the new style RV9a front gear, do I really need the louvers, or will a careful baffling job be enough?

We included the new louvers in the kit with the new gear. Personally, I’d try without them first and then add them if needed - but note that the new gear assembly is bulkier in physical size and as a result does tend to block the exit area a bit more than the original Wittman style gear. On our RV-9A demonstrator the teamfirst flew the new gear without louvers and then found it was necessary to add them for cooling purposes. The net result between the aircraft before the new gear and mount vs. after new gear/mount and louvers were installed was a slightly cooler-running engine compared to when the project started.

The fact of the matter is every airplane is a little different. My perspective is that it’s a good idea to optimize sealing and airflow first, see what the results are, and work from there. There a higher likelihood with the new gear you’ll need extra airflow. I’m sure others will want to just install them from the get go. Your airplane, your decision!

[ALagonia]

Originally Posted by greghughespdx

We included the new louvers in the kit with the new gear. Personally, I?d try without them first and then add them if needed - but note that the new gear assembly is bulkier in physical size and as a result does tend to block the exit area a bit more than the original Wittman style gear. On our RV-9A demonstrator the teamfirst flew the new gear without louvers and then found it was necessary to add them for cooling purposes. The net result between the aircraft before the new gear and mount vs. after new gear/mount and louvers were installed was a slightly cooler-running engine compared to when the project started.

The fact of the matter is every airplane is a little different. My perspective is that it?s a good idea to optimize sealing and airflow first, see what the results are, and work from there. There a higher likelihood with the new gear you?ll need extra airflow. I?m sure others will want to just install them from the get go. Your airplane, your decision!

Can you report on the effect on airspeed with the louvers installed?

[greghughespdx]

Originally Posted by ALagonia

Can you report on the effect on airspeed with the louvers installed?

Speed impact was negligible, essentially zero, when measured before and after the louvers were installed on the factory RV-9A.

[jump4way]

Is there a reason this kit would not work on the rv-8?

If using the 45 degree cut method, what is the speed penalty?

Thanks.

[greghughespdx]

Originally Posted by jump4way

Is there a reason this kit would not work on the rv-8?

Dimensionally the kit parts don?t fit in the space on the RV-8 cowl. You could of course fabricate something similar if you wanted to. The RV-8 is usually a well-cooled engine though. Have you already analyzed and optimized sealing of the existing cowl? What are you trying to address, oil temp or CHT or?