I went flying today and here's what I learned about engines, wind, and nitro.
The plane:
Harbinger. 625 sqs about 53 oz. T&L ST .51 swinging a Bolly 13 X 4.25 prop release RPM 10,600 to 10,700 Lap times about 5.4 to 5.5 seconds.
I usually fly using 15% nitro because the airplane doesn't slow down in the square eight. The wind was pretty much straight line at about 10 to 12 mph.
Using the 15% nitro Sig fuel the airplane would show signs of winding up and would struggle a bit in the overhead eight.
I brought along some 25% Sig fuel and filled it up. It started and without touching the needle to ran about 11,100 rpms. I richened the needle to about 10,600 to 10,700 and released the plane.
The engine ran in a very deep but powerful 4 stroke. Line tension was very good and lap times were about 5.4 to 5.5 seconds. I tried some loops and the tendancy to wind up was all but gone! The engine didn't even break at the tops of the loops. Tried some square loops and the same thing. I was delighted! I tried some overhead eights and the engine pulled the plane very well in the inside loops with a little bit of a break at the top of the circle, but in the outside portion, it broke hard and just powered it's way throught the wind! Next up was a vertical eight. Nice break at the outside portion with great line tension everywhere. I do have my tank positioned to give a little leaner run inverted than upright. Not much but just a little.
Tomorrow I'm goning to try it again to see if I can duplicate the runs. As far as today goes, I learned that the extra nitro gave the power boost yet almost acting as a limiter to wind up in the wind.
Has anybody else experienced this and could somebody explain what went on.
Thanks.