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Blade antenna ? sloping edge ? is it the leading edge or the trailing edge?

Kalibr

Well Known Member
I feel a bit silly as this must be obvious for most. But I am wondering whether the blade antenna should be mounted with the straight edge leading and the sloping edge trailing or the other way around... My aerodynamic gut feel thinks the sloping edge should be trailing to help reduce turbulence and, hence, drag. But it seems that the common way to mount it is the sloping edge leading and the straight edge trailing. Thanks!
 
Depends on whether you like the Mooney look or not. :D

I have mine with the sloped edge in the front, straight in the rear. The electronic signals received probably don't care which way the antenna is mounted.
 
Thickness

Is the thickest part in the middle or towards one way. If the thickest part is not in the middle, i would think the thickest part needs to go forward. JMHO
 
Is the thickest part in the middle or towards one way. If the thickest part is not in the middle, i would think the thickest part needs to go forward. JMHO

The straight edge is very slightly thicker (if you look really carefully). It?s another reason I thought it should go in front.

I think mounting this thing optimally would be worth at least 2 mph, if not knots.

The Mooney looks fast. Plus, the Cessna reverted back to the sloping leading edge ? obviously to keep with the reputation of being slow.
 
I looked at pics the vendor posted showing the antenna installed; the ones I saw show the sloping side forward.
 
Yeh, but it doesn’t make sense from my understanding of the aerodynamics. It’s like all the car roof mounted carriers look mounted backwards to me — the narrow gently sloping end is in front with the blunt thick end in the back.

I measured the thickness — the straight edge is about 25% thicker than the sloping edge.
 
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This is experimental aviation. Go get your bicycle and an extra wheel mounted with the axle vertical over the handlebars. Then put one blade antenna with the slope forward on one side, and the slope aft on the other. Go ride, collect data at different speeds, and see which one moves aft - that’s the one with highest drag! Report back.

Yes, this technique has been used before by a couple of bicycle mechanics in Ohio over a century ago...;)
 
OK, if you're going to be anal about low drag, do what I did: I drilled a temporary pilot hole on the bottom of fuselage where the blade antenna would go. On the inside, I hooked up a length of skinny Tygon tube to a syringe containing Champion spark plug anti-sieze. I used clay to seal the Tygon to the fuselage. I took off and, in cruise configuration, squirted some of the black anti-sieze out the bottom. It left a nice trail in line with the airflow which, on my plane, was angled 7 degrees from centerline. That's how I mounted my Delta-Pop transponder antenna and that's why I was seeing 226 MPH today on 140 HP, burning 5.1 GPH. <evil grin>

Oh yes, I installed the slanted edge of the antenna facing the front like God intended :D
 
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Thanks all! I?ve mounted the antenna ? straight edge forward.

I like Paul?s experiment suggestion. Since i don?t have any antenna?s left, i might replicate the shape out of plywood or something and will do the experiment.

226 moh on 5.1 gph!? In level flight? TAS? On Earth? What airplane is that?
 
Clever!

OK, if you're going to be anal about low drag, do what I did: I drilled a temporary pilot hole on the bottom of fuselage where the blade antenna would go. On the inside, I hooked up a length of skinny Tygon tube to a syringe containing Champion spark plug anti-sieze. I used clay to seal the Tygon to the fuselage. I took off and, in cruise configuration, squirted some of the black anti-sieze out the bottom. It left a nice trail in line with the airflow which, on my plane, was angled 7 degrees from centerline. That's how I mounted my Delta-Pop transponder antenna ...
I would never have guessed that it's 7 degrees - impressive experiment!

Cleaning the bugs off after a flight a day or so ago, i am always amazed at the influence the prop has on the bug spat patterns. They don't make much sense to me, but I'm sure it's all the result of sound physics.
 
Smokin!

226 moh on 5.1 gph!? In level flight? TAS? On Earth? What airplane is that?
LOL! It's a Lancair 235 with a 140HP O-290-D2 motor and fixed pitch prop. To be completely honest, though, that was my peak ground speed and I was in a slight descent with a 20 Kt. tailwind. ;) My ASI was indicating 160 Kts, so I was smokin'. The fuel flow was accurate, though. I had just cleaned my plugs and was able to get slightly lean of peak. Yes, I had a big grin on my face. You can see the blade antenna is located where the fuselage is narrowing down so that explains the 7 degree angle.

Video Evidence
 
I've seen a lot of antenna installs, can't recall ever seeing one mounted backwards (straight edge fwd). :)
 
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