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  #1  
Old 09-11-2021, 05:31 PM
Flyer2017 Flyer2017 is offline
 
Join Date: Mar 2017
Location: Providence, UT
Posts: 56
Default Comm antenna parallel to centerline?

I'm redoing my panel in our RV-9A and am installing an 8 ounce second bent whip comm antenna on the bottom of the fuselage in the back for a second comm radio. It will go just aft of the F-708 fuselage bulkhead on left side near the area where the side skin joins the bottom skin. The antenna comes with an .060 doubler and this location is closest to two ribs and will hopefully make the installation rigid. This spot was chosen because it puts it furthest away from an existing ADS-B antenna and a Nav antenna in the far back.

Because the fuselage tapers toward the back, if I install it parallel to the centerline, the end of the antenna will slightly stick out past the side of the plane. If I twist it slightly in toward the center it will more parallel the taper of the plane and not stick out. I don't think it will make a significant difference drag-wise either way since flights are more often subject to crosswinds and quartering tailwinds that disturb the airflow. If I move it toward the centerline, I lose the benefit of the stiffness provided by the rib joining the side and bottom skins.

Opinions? thanks
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  #2  
Old 09-11-2021, 05:51 PM
blaplante blaplante is offline
 
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more likely the airflow will be influenced by the propwash
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  #3  
Old 09-11-2021, 06:00 PM
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Sam Buchanan Sam Buchanan is offline
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The bugs on the leading edge of the wings will most likely have a larger effect than the antenna......

Not sure what you mean by the comment about crosswinds, etc (I'll start the popcorn ).
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  #4  
Old 09-11-2021, 07:21 PM
BobTurner BobTurner is online now
 
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Quote:
Originally Posted by Sam Buchanan View Post
Not sure what you mean by the comment about crosswinds, etc (I'll start the popcorn ).
Me neither. Although I have flown with a licensed pilot who held the plane in a slip well after lift-off, so that the plane would ‘fly straight’.
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  #5  
Old 09-12-2021, 06:12 AM
Desert Rat Desert Rat is offline
 
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crosswind will have nothing to do with any of this.

If it's sticking out past the tailcone laterally, I'd be more worried about it getting broken off by somebody catching it on their blue jeans than anything.
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  #6  
Old 09-12-2021, 07:33 AM
JDA_BTR JDA_BTR is offline
 
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You probably don't have to be so concerned with where the antenna is given a doubler is placed. You probably could move it inboard some without worry. Take a look at the RV14 plans where the antennas are placed for an example.
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  #7  
Old 09-13-2021, 08:11 AM
Flyer2017 Flyer2017 is offline
 
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Thanks to all for the replies. I moved the antenna in toward the center line. Makes it a little closer to the ADS-B antenna but only by a couple of inches. Much more protected. I'll get a ball to stick on it when on the ground.
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