Hi Tom,

I prefer the "shark fin" blade, and not just because I sell them and they
are more expensive.

I'm not an expert, but I do remember my Fluid Dynamics classes at Purdue
University in which they stated that 2 of the worst shapes in regard to drag
are the sphere and the round rod - which is exactly what the rod style
antennas are. However, the shark fin antenna has a lot more surface area -
so it is not clear that the shark fine is dramatically better - but it is
probably a little better.

I also think the shark fin antennas look cool (as you mentioned below).

I imagine the shark fin antennas are more robust and would handle trailer
bangs better, but I wonder whether they would chip or be damaged by a hit to
the trailer.

I'm amazed by the low price you found below from Aircraft Spruce on the rod
style antenna. I wonder why the Comant brand I buy is so much more
expensive? The Comant antennas are very nice but they have gone up in price
dramatically over the last year or so - much more than the drop in the US
dollar would account for. I wonder if the low cost units that "meet the
same specifications" are approved for use in certificated aircraft. If they
are then I should sell them. So far, I've been very hesitant to sell what I
would consider "low cost copies" of aircraft parts. I would never want a
customer to come back to me and tell me I'm selling items that should not be
used in certificated aircraft.

Good Soaring,

Paul Remde
Cumulus Soaring, Inc.
http://www.cumulus-soaring.com


"5Z" wrote in message
...
Any aerodynamic thoughts on the two available choices?

My ASH-26E came with the stub mounted just behind the wheel. Every
now and then it catches on the trailer, so I just straighten it, no
big deal.

An ASW-24B in our club is about to get a transponder and the factory
recommends the installation to be part way up around the fuselage
above the rear gear door hinge - looks like just behind the oxygen
bottle.

The blade looks cool, but is it really any better aerodynamically than
a $20 (http://www.aircraftspruce.com/catalo...ransponder.php)
stub?

-Tom