Maybe...personally I think it was the NITRO Working!
Jim of course has nitro straight from the Hoover Dam. I, on the other hand, was indeed running YS 20/20 in my RO-Jett 61 (with no compression changes, for the "head gasket patrol") and that really woke up the engine compared to the 15% Powermaster RC Sport fuel I used in the past. It was only in the 70's, the density altitude ranged from 1950 to 2200 feet over the weekend, and I made almost no compensation for the conditions when flying.
For people interested, comparing to similar temp at sea level, I changed from a 12.5-3.75 Eather Flat-back (green dye) to a 4.1" version of the same thing, with the tips around 4.25, went to YS 20/20, and moved the "up" line out one notch on my Ted handle. Launch revs went from about 10,100 to 97-9800 and my lap times slowed to about 5.45-5.5 from about 5.25. I got slightly better mileage, maybe running 30 seconds longer than I would normally. That suggests that I could have gone up some more on the nitro. I asked Jim to bring along some 45% "Wildcat" for mixing purposes but it flew so well as it was I never tried that.
The YS 20/20 ran very well in flight. It ran a lot like the way the RC sport fuel works, with more tendency to boost and even more so, brake on downlines. YS 20/20 and the RC Sport fuel tends to cause the engine to put on the brakes much more in places like the wingover and the descending leg of the hourglass compared to the RO-Jett fuel, which runs at a more constant speed and is not significantly affected by the back-driving. This cause one of my rather large mistakes on both official flights (and all the practice flights), specifically, pulling out high on the hourglass. The engine backs off just about the time I start the corner, so it decellerates, which makes the corner tighter than intended and the overall pullout height at 8-10 feet instead of 5 or so. I can overcome that with a lot of practice but that's why I run the RO-Jett fuel when I can. In the normal case this is a non-issue, but I have the same problem when running the Sport fuel (because they don't make 15% RO-Jett - yet...).
Next time I need 20%, I will definitely try adding about 3% castor to make it close to the RO-Jett fuel.
I flew with much less compensation for altitude than I had in the past, almost none in fact. It actually felt pretty sprightly and I didn't notice a huge difference. That (and Jim's experience) shows that getting the engine/motor working makes far more difference than fiddling with aerodynamics. Mine does not have vortex generators, by the way - I would just knock them all off every time putting it in the car.
I had considered switching to an alternate head button with .005 or .010 less head clearance, but didn't try it. Based on previous experience, it was more-or-less impossible to get over the top compression with any of the series of head buttons I have (from nominal, to "squish band hits the [iston") in any normal range of nitro. Note that this is NOT adding or subtracting head gaskets, these buttons were made with the shoulders and plug depth in different spots to maintain the same geometry at different compression ratios.
If I flew there in the heat of summer, I would have to do something different, because I could see getting in the 35% nitro range with my current system.
Brett
Topic: Results of Southwest Regional Control Line Championships. (Read 5951 times)