Cowling options

[triple8s]

Food for thought about plentums. A friend built an experimental and came up with this. I couldn't find a photo of it but he also had a seal aft of the spinner. He has a site at n56ml.com.

[BigTex]

Back in the day, I built a cowling for my WAR P47D experimental so it's not that difficult.  Mine was done by blocking foam around the engine and carving it to shape.  Then laying fiberglass over the plug and let it cure.  Then it's a matter of cutting it off, finishing it out and then fitting it back to the engine.  But the real work is convincing the FAA to allow you to use it on your type certificated aircraft.  

 

The late great Tony Bingelis has two of the best books out there called "Sportplane Construction Techniques" and "Firewall Forward." Anyone wishing to tackle this type of work these two books are must have's.  They go into detail on creating the cowling as well as baffle theory and construction.  Actually, everyone on Mooneyspace should have these two books in their library.

[kmyfm20s]

We flew our plane a few days with a missing upper boot cowl fastener and that story David McGee told me about 250 KIAS and the upper cowling blowing off the airplane sounds real. There is far too much air inlet area for the exit area on a J model. The cowling inflates and expands. At 200 MPH IAS the spot where the missing cowl fastener was, was 1/4" off the boot cowl. There is some serious pressure in the upper cowl, which says to me there is far too much inlet area. Also a crank seal or a leaky front case blows the oil out the front of the cowl. I think all the flow through the spinner gap is reversed. There's a lot of cooling drag that is overlooked with the J cowl and a lot of drag can be eliminated with optimize inlet/exit areas.

Byron, I have a similar story when I was breaking in my cylinders. I was doing a speed run down low to see how the would do. I was watching the airspeed climb as soon as it hit 173kts TAS all of the sudden I got a massive vibration in the engine compartment. I first thought I lost a prop tip it was so bad and the cowl looked like it was going 2 inches in every direction, the vibration got better with lower airspeed. I landed at airport and looked at the exterior nothing was wrong with the prop, cow and no oil on the groundl. I took off the cowl and couldn't see anything immediately jump at me but then I noticed the back strip of silicone baffling was flipped backwards. I checked the underside of the top cowl and sure enough you could see where it was flapping against it. The pressure of the air had flip it backwards, that's a lot of force! Needless to say I went home changed my shorts and reinforced the baffling so it would not happen again.

[MB65E]

Wow, good to know. That's why there are plentums. Early "Dog houses" were good ideas, but I think owners remove them for better access/less work. A modern doghouse with the correct exit and inlet areas on the cowls would be nice.

Triple8s- tell your friend his airplane is beautiful. I spent hours on his sight a few years ago when I wanted to build somthing. Still do...

-Matt.

[Sabremech]

I'm planning on incorporating or using a plenum either a new design or reworking the original with modifications for maintenance. I do believe it's the best and most efficient way to control cooling airflow. I disassembled my airplane today and did some preliminary fitting of the James Aircraft nose section that I'm starting with. No doubt about the looks of the mod.

David

[jetdriven]

Flight testing in various configurations will lead you to the right inlet / exit area for a Mooney. It may be a lot smaller inlet than you think

[Sabremech]

Another picture to look at. Let the fun begin.

 

 

 David

[aerobat95]

Looks cool.  I would love to see an aftermarket cowl that wasnt 20K. 

[Shadrach]

Very interested David!

[Sabremech]

Just a quick question to the group. Would you like to see the oil cooler moved or leave it where it is? My first impression is to keep it simple and leave it alone.

 Any thoughts?

 

Thanks,

 David

[Oscar Avalle]

Leave it where it is now.

[N601RX]

If you decide to leave it where it is then offer an option to put a second landing light in the opening for the people who have already moved the oil cooler. The light weighs less than the oil cooler and the opening is already there and properly reinforced to support the oil cooler so from a certification standpoint it shouldn't be to much extra work.

[scottfromiowa]

Leave it where it is now.

+1

[Hector]

+1

+1

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[Shadrach]

+1

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+3

[cliffy]

Now this could turn out to be a great project. Very interesting and long over due for our Mooneys.

No reason why it can't work and work well. Good luck to you!

[triple8s]

Moving the cooler would probably raise the cost by almost a grand by the time you buy new hoses and mounting material, build/ modify the baffling to provide for air to the scat hose or mount to the rear of t he engine baffling. One thing to think about though, when the oil cooler is mounted on the lower cowling this means ever time the cowling is removed the oil cooler/ hoss are disturbed, which increases chance for damage, also if the cooler remains on the cowling then there is another place for air to be disturbed hence more drag. With all the talk about how much pressure is built up in the cowl and how much too large the openings are I'd think it would be much more efficient to have the cooler relocated, although it will add more cost.

[Sabremech]

I'm currently not planning on moving the oil cooler. The main reason will be to keep the STC as simple as possible. The second reason will be cost as I'm well aware of the value of the older Mooney's and this can't be a $10-15k mod.

Thanks,

David

[Hank]

Go, Sabre! Now that I'm moving back into the Land of the Air Conditioner, I suspect that additional engine cooling will be desirable for takeoff and climb. last week I had almost 2000 fpm before turning crosswind at 500 agl, but it won't get that cold down here very often. In summer [longer here, too, as well as warmer], the limiting factor is almost always oil temp. Better airflow through the cowl should help reduce that some, which will let me climb faster.

 

Thanks in advance for your hard work, from a hopeful future customer!

[jetdriven]

David just don't let mission creep take over or else you will have a fiberglass cowl so close to an E cowling in performance that you only have cool looking inlets to sell it on. The J cowl is a really optimized cowling and the Lo presti is an optimized version of that.

[Sabremech]

Hi Byron, there's going to be some compromise here. I don't see trying to copy the Lo Presti for ultimate performance and price myself out of being able to sell any product. Would I like to see some performance gain? Absolutely. What or if that happens won't be seen until I put my airplane in R&D and test fly it. I'm not looking at doing a fiberglass cowling mod if I can help it. My goal is for it to be aluminum and rivet on at factory seams for a nice finish and no exotic resins for flammability requirements or that nagging cracking like I'm having with the ARI enclosure.

For me, it's about updating the look of my airplane first and if I get a performance gain, awesome. It's fun so far figuring out little issues with each step.

Thanks,

David

[Sabremech]

Question for C & G owners. I'm looking at a minimal modification to the carb air box and thought of moving the air inlet and filter to the oil cooler opening. The old square air filter inlet would be removed and aluminum put in to smooth out the lower center cowl.

Any thoughts on this idea?

Thanks,

David

[Andy95W]

Very interesting idea. Not sure if I will be interested for my '64 C, but I had a few questions.

Where will the oil cooler go? LASAR has the mod to move the oil cooler on the E, how will you do it on the C/G?

What gain do you see for moving the air intake?

One suggestion is to screw on the cover where the existing air filter goes and not rivet it on. Never know when you'll need an access panel.

[Hector]

Question for C & G owners. I'm looking at a minimal modification to the carb air box and thought of moving the air inlet and filter to the oil cooler opening. The old square air filter inlet would be removed and aluminum put in to smooth out the lower center cowl.

Any thoughts on this idea?

Thanks,

David

Was never a fan of the square box for an air inlet. It just does not look very good. If you can get rid of it then why not? It will look better and I have to think there is probably some aerodynamic benefit there. I guess you would need to relocate the oil cooler if you move the air inlet there. Also wonder if there will any losses associated with a curved path to the carb air inlet.

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[Sabremech]

I don't believe air loss is an issue. I've seen several mods where the air filter was moved up to just inside the left hand air inlet opening to the cylinders. I've thought of that option as well, but in trying to keep as much of the original cowling and baffling intact, have kind of ruled that out. I don't want to change too much as the price goes up the project becomes that much more complicated. I'm thinking the air box is going to get modified and turned toward the oil cooler opening if I go that direction with my mods.

I really wanted to see what the general consensus would be having the air inlet there before I proceeded to far that direction.

Thank you,

David