Date
1 - 20 of 20
NACA Inlet question
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Joe Dubner
The attached photo is a Long-EZ NACA inlet. Has anyone seen a geometry like the parts I've circled? What is their purpose? Is there any basis in science for them? (I'm tempted to cut them off to get more air into the cowl.)
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DON JONES
Those little strakes are there to help contain the air flowing into the cowling. Oil flow tests have shown that without them air escapes the cowl inlet in the corners. Hope this helps. Don Jones Berkut FG
On Tuesday, August 3, 2021, 01:48:58 PM EDT, Joe Dubner via groups.io <jdubner@...> wrote:
The attached photo is a Long-EZ NACA inlet. Has anyone seen a geometry like the parts I've circled? What is their purpose? Is there any basis in science for them? (I'm tempted to cut them off to get more air into the cowl.) Attachments: Annotated NACA Inlet.jpg: https://canardzone.groups.io/g/members/attachment/335/0
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Roch LaRocca
I think it’s designed to prevent overflow and channel more air in. I actually have this on my aircraft and it seems to work great for me. I don’t ever have cooling issues so it must do something right.
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Rock L ERacer N382RB
On Aug 3, 2021, at 13:48, Joe Dubner via groups.io <jdubner@...> wrote:
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Todd Carrico
On Aug 3, 2021, at 12:48 PM, Joe Dubner via groups.io <jdubner@...> wrote: I remember Klaus talking about adding something like that, with good results. If you need more air into the inlet, VG’s close to beginning of the “ramp” seem to be the hot ticket. Tc
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Bob Holliston
Rock, one way to find out for sure is to do a before and after (you cut them off) comparison. You can always glue them back on.
On Tue, Aug 3, 2021 at 12:22 PM Todd Carrico <tcarrico.cozy@...> wrote:
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Joe Dubner
Thanks Don, Roch, and Todd. Three in the plus column; no negative (so far). Thanks too, Bob -- you make four.
I did try VGs ahead of the beginning of the ramp but when I designed and placed them in accordance with this Kitplanes article (https://www.kitplanes.com/vortex-generators-for-cooling/) they were honkin' huge and wound up being mounted on the speed brake. Totally unsatisfactory but they did improve airflow somewhat. I'd like to see a picture of others' VGs if they are effective. My oil flow tests show outflow at the inlet with air spilling over the little "strakes". Maybe it would be worse without them, maybe not. I'm tempted to take Bob H's advice and cut them off for comparison. Bob, you have an O360 Long-EZ with no particular cooling issues, right? Maybe we can talk.
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Michael Carra
Here’s an option for you… No to NACA…
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Do you want more air coming up through your cylinders? Think F-104 Starfighter. Use the sump blisters under the armpits and try this… See attached picture. Add ramps to the inside of the cowl to kick the air up between the cylinders. My engine has run at low temperatures for years. Thanks to Vern Simon… Michael Carra Long EZ N342MC Advanceservicesproductions.com
On Aug 3, 2021, at 13:48, Joe Dubner via groups.io <jdubner@...> wrote:
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Bob Holliston
Yes and yes. I had those corners on the NACA for awhile (mainly because I noticed Klaus did) and noticed no difference so I cut'em off. When I built a new lower cowl a couple years ago I incorporated dedicated tunnels (two into four) that blow on the cylinders. The cooling is better than with the ramps but the OT is now 190 instead of 180. Damnit, I wanted a FREE LUNCH! With the tunnels it is easier to tweak them than the ramps to even up CHT's Three of my cyls. are around 338 - 349, with one at 318 in cruise so I need to shrink the low one.... when I get the ambition. Also, with the ramps the CHT's were only about 15 F higher, so not that bad.
Thanks Don, Roch, and Todd. Three in the plus column; no negative (so far). Thanks too, Bob -- you make four. --
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Roch LaRocca
I think not! I love experimenting on my own plane but only to solve a problem…. Which I don’t have at the moment.
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I did add a camera to the back of the plane so I could see what I just missed. ….;) Rock
On Aug 3, 2021, at 17:43, Michael Carra via groups.io <mjc342@...> wrote:
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Joe Dubner
On Tue, Aug 3, 2021 at 02:59 PM, Bob Holliston wrote:
I had those corners on the NACA for awhile (mainly because IThat does it for me; I will cut them off on my next opportunity (too hot for anything these days). When I builtI'd like to see that. If you'll fly to Independence some time I'll buy lunch. Of course, if you fly to Aurora on a second Saturday, Gil would buy lunch <g>. (Inside joke -- you gotta know Gil Hutchison.) Damnit, I wanted a FREE LUNCH!See above. And flying to Hood River is an option for me -- sorta, kinda: I'm still in Phase I.
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Steve Rothert
For those of you who still remember how to do Calculus and Differential Equations (which excludes me), I refer you to a NACA report, from 1948, titled "An Experimental Investigation of the Design Variables for NACA Submerged Ducted Entrances" by Emmet Mossman and Lauros Randall. Figure 6 (see attached) shows "deflectors" as one of the variables.
My $.02 worth. Hope this helps. Steve
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Todd Carrico
Here’s an option for you… No to NACA… Thanks!
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Bill James
Good topic.
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Just passing through from left field.
“Almost any inlet will work if there is low pressure, or low enough pressure aft of the cooled element. And almost no inlet will work if there is high enough pressure or restriction aft of the cooled element. It is exactly
like pulling rather than pushing a rope.” Bill James
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Bulent Aliev
Hallelujah! I have been preaching it, but everyone is obsessed with NACA shapes, oil flows, VG’s etc. if you don’t have low pressure exit (pull), it ain’t going to work, Or just barely on the limits.
On Wed, Sep 1, 2021 at 4:09 PM Bill James <bill@...> wrote:
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David A Froble
Or, another example.
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The large doors on my barn/hangar face basically North. Many times I leave them open, even when it storms, and many storms come from the NW. Things don't get blown around, well, much. Why, there is no place for the air in the barn to go, so, more cannot get in.
On 9/1/2021 6:34 PM, Bulent Aliev wrote:
Hallelujah! I have been preaching it, but everyone is obsessed with NACA --
David Froble Tel: 724-529-0450 Dave Froble Enterprises, Inc. E-Mail: davef@... DFE Ultralights, Inc. 170 Grimplin Road Vanderbilt, PA 15486
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Bill James
More Fun,
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A forward facing opening is not always an inlet, and an aft facing opening is not always an exit. Bill James
On Sep 1, 2021, at 5:59 PM, David A Froble via groups.io <davef@...> wrote:
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Todd Carrico
On Wed, Sep 1, 2021 at 5:34 PM Bulent Aliev <bulent.enginegear@...> wrote:
The NACA paper I read was investigating the inlet to supply air to a jet engine... you know; a great big sucking thing that burns fuel like it's going out of style. Feeding a jet engine past the speed of sound or some such. I think it is a much different dynamic than cooling a radiator or an aircooled cylinder. If we could generate that much suck, the inlet shape is probably moot. Our Cozy III has exits in the top of the cowl over what I presume to be the hard to cool cylinders. We did not build this one, but I vaguely remember the builder talking about it being his solution. Judging from the amount of RTV on the baffles/engine, it looked like they put up a bg fight. IIRC, I read that one of the canard speed gurus said there wasn't much to gain from streamlining the top cowl. Maybe some property shaped exists that help pull the air to the trouble spots is something to add to this discussion. It is all about pressure differential.. tc
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Bulent Aliev
I had the cowling outlets as far as possible away from the prop hub, and outlet on top center of the cowling (low pressure area). Had way too much cooling. Had to reduce the NACA opening and block some of the oil cooler. Never had to pull back power due to overheating on climb out.
On Wed, Sep 1, 2021 at 5:22 PM Bill James <bill@...> wrote: More Fun, --
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Tim Hoversten
Also, a good rule of thumb is that the outlet area should be 1.5 times greater than inlet area - again, to help create a pressure differential that pulls the air out. Adding a lip on the cowl to disturb the air exiting, or using a cowl flap will also improve cooling, if needed.
Tim Hoversten
From: members@canardzone.groups.io <members@canardzone.groups.io>
On Behalf Of Bulent Aliev via groups.io
Sent: Wednesday, September 01, 2021 6:43 PM To: members@canardzone.groups.io Subject: Re: [Canard Zone] NACA Inlet question
CAUTION: This email originated from outside of EAA. Do not click links or open attachments unless you recognize the sender and know the content is safe. I had the cowling outlets as far as possible away from the prop hub, and outlet on top center of the cowling (low pressure area). Had way too much cooling. Had to reduce the NACA opening and block some of the oil cooler. Never had to pull back power due to overheating on climb out.
On Wed, Sep 1, 2021 at 5:22 PM Bill James <bill@...> wrote:
-- Bulent Aliev
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Terry Barr
Frank Costin used to say that a NACA duct only worked properly at one airspeed. --
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