I saw on someone's plane (Mr Mills?) what looked like a fairing on a belly mount antenna. Perhaps Mr Mills (to remain a good boy to get his special tie downs) would add his insight.
So I could fair in my pitot tube, transponder and comm antennas and gain two knots for each!
Ron,
Larry Vetterman told me at Mitchell, SD (start of AVC) that if I swapped my two TED ball and stick antennas (for the XPNDR and the Monroy) that I'd gain 1 knot per antenna. I put a CI-105 in place of the XPNDR TED, and moved the Monroy to the glareshield (Pete Howell's idea). At the same time I pulled my belly whip for the APRS and put a jpole in the tip, leaving just one belly whip (comm 1).
I did not have time or weather to do a before and after of each mod, but in the next race (following the mods) I ran my first 250+ average time (previous best was 243). That does not mean I gained 7+ knots from the mods, because wind was on our side that day, and everyone ran fast that day. So I don't have science backing me up this time, but I feel did gain some from the mods. Many mods are incremental (almost immeasurable, but when added up...), and I think these are among them.
On the bent whip fairing, that was Mike Thompson's plane you saw. Here are blown up crops of two pics I have of his plane. Not good, but something to stir the pot.
It makes sense that a fairing here might help (surely we can fair it at less than 9 times the thickness of the rod!) Hmmmm...new winter mod?
That was great. I really enjoy that kind of demonstration. I find drag and airflow even more difficult to understand than the wiring. I am apparently pretty slow.
Nope, you're normal...this stuff is black magic...or just PFM...or both!
I think that guy was my Aerodynamics porfessor at SJSU!
It's not, but he talked like my guy, who was a Skunkworks aerodynamicist during the development of the SR-71...really shmart feller...and the hardest college class I took!
One guy I know chopped the nice fiberglass aerodynamic tips off his rocket and gained a substantial amount of speed. Nice slick looking tips looked fast and efficient. The cut off tips and block hershey bar shape looked lumpy and slow... just the opposite was true speed wise. Wierd, but great to learn about.
I have a set of flat tips reducing the wingspan to 21 feet. It is faster than the stock tips also. I have a set of streamlined 3" tips that are faster than the flat tips.
Bob Axsom
I have flat tips too, and testing showed 2-3 knots gained over my stock tips. Some science to back up this one...multiple 4-way GPS runs at 4000' (low as I could get over the high desert, it may be more at Sea Level). The flat tips seem to get the gain from span reduction rather than aerodynamic shape magic. Sharp corners on them seem to work better as well, due to a lower Oswald Factor (gotta ask Paul Lips to explain that...but I followed his advice on it!).
With already clipped wings, they are some stubby lil' things! Flies well though...4-5 knot stall increase, but very flyable.
I still hope to borrow Bob's streamlined tip mold and test that shape out too!
I usually remove my NAV antenna elements for racing but the difference in speed is so small I can't measure it. I still take them off for races.
Bob Axsom
So does Tom Martin...must be a good idea, given his speeds!!
Cheers,
Bob
