NACA Scoop

[EZRider]

Is the NACA Scoop notched into the bottom of the fuselage and firewall or does it just lay on top?

[GlennBob]

Don,

The NACA scoop is indeed " notched " into the bottom of the fuselage.  The bottom of the fuselage is the level " plane " from whence the scoop takes it's air.  This scoop protrudes through the firewall.  Some guys choose to use a " P - 51 " type scoop instead.  This scoop protrudes down and forward into the slipstream.  

Best to peruse some photos if you can.

Glennbob

[flyingwaldo]

The last couple CSA newsletters detailed one fellow that has found much better results with a modified scoop instead of the NACA and another that is trying it.  This may change your mind about the NACA.

[EZRider]

I am still trying to decide on the NACA scoop or down draft cooling.  Which is best and which is easiest?

[Waiter]

From my experience on building, the NACA was far easier than my downdraft.  Prefab scoop, prefab cowls,  AND - known track record. It cooled my O-320 for years with no problems.

DOWNDRAFT - everything needs to be built, including the cowl, there are no prefab parts.

There are many different versions and designs. There are thousands of these working, (almost every spam can uses downdraft)

For my money (and time) I think the downdraft offers a lower drag solution than the updraft.

Waiter

[EZRider]

I want to quit modifing and start flying after 18 years.  I think I will go with the NACA scoop and getter done!
Thanks for everyones input

[Drew]

Just one more opinion.  I have both updrafted (according to plans using a NACA scoop) and downdrafted a Longez.

The mods to the cowl for downdraft were not a big deal.  The baffle job for downdraft was muuuuuccccccchhhhh easier and cleaner than the updraft.  I had lots of problems cooling my O235 in a updraft configuration.  I had no problems with an O320 in a downdraft config.

For updraft---all the stuff you have to baffle around  (pipes, alternator, starter, breather (for some))----as well as getting a good seal with the lower cowl-------all go away with downdraft cooling.

Good luck bending lots of metal and trying to seal off your updraft.

BTW, I still run updraft on my Cozy with good results---I just hate all the stuff the aft baffle has to get around.

[EZRider]

Well Drew, you got me thinking about it again........

[Drew]

You can see my baffles on my website---and see how simple it is.  I copied my inlets from George Shell.  You can do a search for him and see some detailed photos of his baffles.  Mine are somewhat different---but it all does the same thing.  Unlike George, I had a  door in the left pressure plenum so that I could check the oil.  With my pressure plenums up from the strake and away from the fuselage, I had no probs.  Others have had good results with small Naca scoops on the top.

I still had my bottom Naca.  I walled it off and installed a bunch of round circle thingys to attach scat to.  Oil cooling came thru one of these (completely separate from engine cooling.  I also had a rectangular slip joint on this wall that gave me ram air to the carb.

[Waiter]

Drew;

Good points.  

Making pleniums and baffling for DOWN is much simpler than UP.

Modifying a prefab cowl is fairly simple.

Downdraft may be easier and faster than updraft.

Waiter