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leading edges....... SQUARE??

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leading edges....... SQUARE??

Old 01-29-2023, 09:37 AM
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donnyman
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Default leading edges....... SQUARE??

I have been stumped by the use of square leading edges, no matter where they are used it is my thought it is not the thing to put on a flying machine.

If you know otherwise now is the time to say so or forever hold your peace!

Yes I have used them with success, but don't know WHY???
Old 01-29-2023, 10:33 AM
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speedracerntrixie
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Can you provide an example? I’ve never built a model with square leading edges but many with square trailing edges.
Old 01-29-2023, 11:13 AM
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The model I flew with square Horizontal and vertical leading edges was the Goldberg eaglet, I saw a stunt plane (full scale) with square horizontal stab also don't remember what it was. Squared trailing edges did not seem to make any difference.

I offer the flying stop sign sign, my friend rounded the edges and it didn't fly well at all.

Last edited by donnyman; 01-29-2023 at 11:46 AM.
Old 01-29-2023, 01:39 PM
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Flat foamys are this way. At that low of a Rn, it can actually be beneficial. It promotes clean separation for snaps and high Alpha. If the Eaglet had square LE's on the tail, someone didn't use the sanding block lol.
Old 01-30-2023, 03:59 PM
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Originally Posted by Lownverted View Post
Flat foamys are this way. At that low of a Rn, it can actually be beneficial. It promotes clean separation for snaps and high Alpha. If the Eaglet had square LE's on the tail, someone didn't use the sanding block lol.
That flat foamy is one thing,Granted the sanding block was ignored but the eaglet was a total success. now the ones I built with rounded edges were failures as far as I am concerned
Old 01-30-2023, 05:34 PM
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Iíve not built anything but flat foamies with square leading edges. Iíve built plenty with squared off trailing edges including wings. In fact my latest design has very thick trailing edges on all surfaces. It tends to soften the controls around center and introduces drag where you want it. In these two photos, you can clearly see the thick/square trailing edges.





Old 02-16-2023, 12:09 PM
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Trailing edges do not cause turbulent airflow over control surfaces but leading edges ..................... ?
Old 02-16-2023, 05:55 PM
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Originally Posted by donnyman View Post
Trailing edges do not cause turbulent airflow over control surfaces but leading edges ..................... ?
Are you certain the square leading edges create turbulence?
Old 02-16-2023, 06:00 PM
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my post does end with a question mark!
Old 02-17-2023, 06:00 AM
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I was curious so I did a Google search of cars with a blunt front end being tested in a wind tunnel. Although the noses are blunt, it appears to not affect the airflow much.
Old 02-17-2023, 06:53 AM
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Not only cars... Boats use rounded bulbous noses. the idea is to induce a smooth transitional laminar flow over the surface at the speed for which the vehicle will travel.
The car isn't as blunt as it could be it has a downward slope to the front inducing air to flow over as apposed to bunching up.

Consider the ww1 se5 biplane it had a huge flat nose but was a mean flying machine. (inquiring minds wanna no)

Last edited by donnyman; 02-17-2023 at 07:28 AM.
Old 02-17-2023, 09:20 AM
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Reminds me of the first time saw an F-16 in the flesh. The wing LE was about 1/4Ē squared off. The wing tip if an F-15 not only has about 6 degrees washout but is undercambered. Point is, sometimes aerodynamics donít make sense to us layman.
Old 02-17-2023, 09:42 AM
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trying to down load pics........ wont work. how does this file look to you?
Attached Files
File Type: pdf
Flying Stop Sign Article.pdf (1.09 MB, 12 views)

Last edited by donnyman; 02-17-2023 at 09:56 AM.
Old 02-17-2023, 02:21 PM
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I remember getting that issue back in the day. My hypothesis is that it works better with square leading edge due to the relatively high AOA in which it flies.
Old 02-17-2023, 05:02 PM
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The air forms its own pocket in front of a blunt face so the free stream air doesn't follow the square shape anyway. This is true of a car front and no doubt a wing section. Generally cars are "bluff" bodies and not very relevant to airplanes anyway. This is especially true since they run along a surface (the ground).
Of course any crisp edge on the front of a form may trigger the boundary layer to go from laminar to turbulent which, due to its higher energy, will not separate as soon. This can reduce the overall drag due to the smaller wake area produced.
Old 02-17-2023, 05:36 PM
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Originally Posted by speedracerntrixie View Post
I remember getting that issue back in the day. My hypothesis is that it works better with square leading edge due to the relatively high AOA in which it flies.
maybe I missed it but I have seen many of these stop signs fly and not one appeared to have a high angle of attack and were highly maneuverable

Allanflowers I appreciate your response but ............ To me what you said sounds like pure nonsense. (I intend no offensiveness) It is likely what you say is far over my head.
Old 02-17-2023, 06:31 PM
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Originally Posted by donnyman View Post
maybe I missed it but I have seen many of these stop signs fly and not one appeared to have a high angle of attack and were highly maneuverable

Allanflowers I appreciate your response but ............ To me what you said sounds like pure nonsense. (I intend no offensiveness) It is likely what you say is far over my head.
IMO, with models anything over 4 or 5 degrees is considered a high angle.

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