misterv47

Big_g,

Thanks so much for your reply. It is beyond helpful to know that my weight is in the same realm as your Tipo.

I agree with you that power, or lack thereof, may be the problem. Here at Denver altitude there is about a 15% reduction in IC engine performance across the board.

I did some driveway testing to understand where I'm at with a few of my engines:

Jett 46 w/JettStream muffler:
Pitch: 7
RPM: 14600
Static thrust: 6.5 lbs
Computed Horsepower: 1.7

Rossi 60 w/Novarossi Tuned Pipe #50400:
Pitch: 8
RPM: 13000
Static thrust: 7.25 lbs
Computed Horsepower: 1.9

OS 75 AX w/JettStream muffler
Pitch: 8
RPM: 13450
Static thrust: 8.25 lbs
Computed Horsepower: 2.3

Notice that even with the piped Rossi 60 I am nowhere close to the RPM's that you have. The "computed horsepower" is based on a web site I found, and takes pitch, RPM, and static thrust as inputs.

I find it very odd that Jett 46 produces so much more power (as evidenced by thrust/RPM) for its displacement than the Rossi 60.

Anyway, my plan is to shave about 4 ounces off the current weight and try to get to 8.5 pounds or so, then I think I'll try to fly it again.

Thanks so much for you response, and please let me know if you have any other ideas.