By now most have seen the lightweight detuned F2D combat wings that some of us are using for speed limit combat. They are indeed high performance and fun to fly. They also have a learning curve to them so here is a brief rundown on what I have learned about using the F2D formula for 80 mph N.W combat.
I first began experimenting with F2D equipment in our 80 mph event in the late 90's.
I had built several Stels F2D models and fitted them with Nelson .15's that were no longer popular for F2D. The most difficult thing about this combination was to get the engine to run slow enough for 80.
The early experiments showed great turning but light on the lines, especially when being wrapped up by an old .36 that weighed twice as much. If you could stay out of trouble, the combination was awesome.
I tend to try things, find the advantage and then get distracted and forget about it, I only built four of these and let it go.
(Fade to black)
I was never a big fan of 80 mph, so I only flew it now and then but the lure of a $1,000 speed limit contest in California brought me out to make a decent effort at the .15 formula.
I used Wakkerman's potent F2D wing with a Cyclon PC4 that would cruise easily at the 75 mph required at this contest. To my knowledge, no one was using the combination of F2D and .15's so it was a debut of sorts. It was noticed. I finally was eliminated by maneuvering before the start signal but left lots of wins to prove the potential and raised a few eyebrows amongst the "usual suspects" at Morgan Hills.
"Back at the home" I struggled with the shut-off and the light weight formula. I had been using the Thomas Mejzlik style line tension version without doing enough research to correct some of the problems. They worked OK for heavier wings but I was losing control in landings and upwind flying. Until Jeff developed the H&R. That was that, it works great as long as the wing is trimmed correctly.
I could refit the wakkerman to on the top controls, by pushing out the bellcrank pin, cutting off the line connectors and removing the belcrank and leadouts through the pushrod slot in the wing. To compensate for the lines on top of the wing I would tweak the wing slightly causing the outboard tip to be slightly up, and have a great flying wing at 80 mph.
There are a few things to know if setting up one of these little bottle rockets and if ignored they will cause you to likely go back to big old heavy, blubbering, lumbering .36 models.
One major thing about an F2D ship is, it was designed to go much faster than our event, and set up to fly on .015x 52 foot lines. This is important.
Airplane be done!
This combination will give you a fast-turning wing that will really outperform any of the big iron models.
You don't have to use an F2D engine!
I just happen to have a bunch, and the older slower ones are just right. Fuel is 10% but you can run any .15 on any fuel you want.
The F2D engine was fit to run on 10% nitro, I would go up to 15% but not more.
There are other good lightweight engines available that are more than capable. If you have an older 2D engine and it's slow, remove the 4 mm venturi and try it again, if still too slow go to 15% nitro but it will run hotter.
F2D engines can be hard to start so practice with them. Assume they are flooded when you land and you will have half of the problems in hand. Keep a "blow tube" handy in case of a real flood. The most effective way for me has been to learn the technique of starting the engine while holding it between my legs a la F2D style.
(More on using the F2D engine in another article.)
APC 6x3 to 7x3 will work fine for the 2D, if you have an older racing engine, then experiment. Mine are running around 28,000 rpm on the ground. I generally use a glass-carbon F2D prop but the right APC can be very effective.
Get used to the increased performance, it will likely take work and practice.
Do not become seduced to the tight turning and forget to detune the airplane. I have and still can overcontrol in a match, winding up in front of my opponent's prop instead of on his streamer.
A well tuned F2D ship will be stable flying level, turn like a crazy and then go back to being stable again. It sounds perfect and can be if you follow a few simple but hard learned details.
-- Kenny-B and the Bod Busters.
This page was upated Nov. 15, 2007