Steve Ashby

Steve Ashby

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Over the years, I have acquired two Commant 139 blade antennas for eventual use on my 8A. Last week at OSH I was looking at the sea of RVs and noticed that none had blade com antennas. Almost everyone is using a bent whip.

Now I know that the blade antennas are meant for fast(er) movers and that the drag reduction for ships in our speed range would be minimal, but is there any reason I should not use those antennas? It is just an asthetic thing? Do they look that bad? I do not think it is a clearance issue. The blades will only stick down 14" from the bottom of the fuselage.

Help me out here. What am I missing?
 
I started out with em on my 7. Got em off Ebay for cheap. They just looked weird on my RV so I swapped em out with DeltaPop bent whips and never looked back.
 
Main reason for blade antennas is protection and performance. On a rod type antenna the radiating element can be shorted to ground by carbon exhaust deposits, oil or ice. On a blade antenna the radiating element is shielded by the plastic blade housing that keeps the radiating element from getting shorted to ground and also from corroding. Unlike rod type antennas that can act as a static wick, blade antennas are less susceptible to static noise. If using exposed radiating elements it is advisable to keep them clean to optimize antenna performance.

Pepe
 
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I think you see more bent whips because they are pretty much the cheapest option - if you have the blades, you like the looks, and you have the clearance...why not?
 
Ironflight said:
I think you see more bent whips because they are pretty much the cheapest option - if you have the blades, you like the looks, and you have the clearance...why not?
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Exactly. If they're paid for, use 'em. :)

Blades have less drag but more expensive. They only really make sense when drag is critical (sailplanes, racers) or speeds are high (jets). Whips are simple, cheap and effective, all good RV qualities.

TODR
 
Cost

The funny thing is, they are considerably cheaper. I picked up the blade antennas, in good condition, for about $35 apiece (at different times) from Wentworth at OSH and SNF. New (and even used) bent whips were considerably more.

Thanks for the advice guys!
 
Steve Ashby said:
The funny thing is, they are considerably cheaper. I picked up the blade antennas, in good condition, for about $35 apiece (at different times) from Wentworth at OSH and SNF. New (and even used) bent whips were considerably more.

Thanks for the advice guys!
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I did the same thing for about the same cost. One on top, one on bottom. I think they look cool.

The only minor downside is the occasional tech counselor who suggests I mount them backwards and use them for a wire cutter like on a helicopter :D.
 
I found a pic of what mine looked like with the blades.

Ignore the dork in the cockpit!

2z4047m.jpg
 
you ain't missin' nuttin!

I think you might be one of the guys paying attention to the old NACA drag video, where Fester Bestertester demonstrates the round section having 10 times the drag of a streamlined shape!!!!
I guess the bent whip reduces that a bit by making the shape oval to the airstream, but you have a far superior product in my eyes!
 
The main reason they are used on RV's is because they chaper, are a HUGE step up from the embedded wingtip antennas that people use, and in all reality the drag difference between the blades and rods at RV speeds is negligible (sure, it exists but we're not a turboprop or jet speeds). Static is not an issue on RV's, neither is ice or carbon buildup...though on higher performance faster planes I agree on that front.

If you want to buy used, be carefull with antennas. Sometimes they are bad internally. Also, the new price on the blades vs. the rods is MUCH more expensive (like double or triple or more).

In the end, this is one of those things with homebuilts where indeed everyone before me is right, but the return on the investment is pretty much moot (but for used ones and that carry their own danger). Like everything, we as builders strive to find the point on the chart where quality and price intersect...and in this case it's the plain old bent whips. There are better ones and there are worse ones, but for RV's the CI-122 or similar is the best overall.

Just my 2 cents as usual!

Cheers,
Stein
 
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