First of all, I'd like to say thank you all for your inputs on the prop size to start with.
The total dry weight turned out to be 28 oz, I was actually surprised when I found out. I thought the final weight would be around 35-37oz.
Given that I have a very light ship, I decided to go with 9 inch prop diameter, even though the wing area is quiet large for the 25 engine size.
I tried two props, 9x5 and 9x4.
And here's the details of my every flights:
1st flight (Maiden):OS LA-S 25
APC 9x5
12,500-ish launch RPM
Avg 4.9 sec lap times
0.015 60ft lines
2nd flight:OS LA-S 25
APC 9x4
13,400-ish launch RPM
Avg 5.1 sec lap times
0.015 60ft lines
3rd flight:OS LA-S 25
APC 9x4
12,400-ish launch RPM
Avg 5.45 sec lap times
0.015 60ft lines
4th flight:OS LA-S 25
APC 9x4
12,900-ish launch RPM
Avg 5.30 sec lap times
0.015 60ft lines
At the end of the day, I felt that my 4th flight was the best one (in terms of engine setup). Please advise if it still sounds too lean or not.
However, even though I like how the engine ran on the 4th flight during upright level, wingover, and inside loops, it showed some oddities when I was trying to go a full lap of inverted flight. The RPM seemed to drop and it flew slower yet the tension was decreasing. The moment I flipped the ship back to upright level, the power was restored. And after couple of upright level laps, I could do another inside loops easily.
I suspect this had something to do with the fuel tank height and the long lines I had.
It seems I need to move the fuel tank a bit higher and change the in-line filter so I can shorten the fuel lines.
Does it sound like a plan?
Looking forward to hearing more feedback from you guys!
Best,
Kafin