Am hoping that the good brethren can provide some insight here. Whenever cool weather and higher humidity set in, I find it a major challenge to get good needle settings and decent power out of my 1/2A engines. I'm beginning to think that as Fall comes on, I ought to shelve my little critters and fly the bigger guns.

What do you all think - operator malfunction or just a reality I need to face?

Dave Mo...

Operator malfunction...but no barb from me.

I've got a jewel of a 1/2A plane (flapped Keil Kraft Radian) built by a British chap. He wanted a surrogate flier and sent it my way. While I could bench run the low hours Medallion .051 with high compression glowhead, any time it got in the air it absolutely floundered. I mixed a bunch of different blends from 15% Vitamin N up to the latest ~23%-25% brew. If it ran a tank out, it flat raced out the lean run at the end of the tank. Needling for just off lean was almost impossible. I changed fuel lines, flushed the tank and NVA and bench ran it some more.

I talked the runs over with FredV4 last weekend., and he asked "any chance you have too much compression?" Hmmm.

This morning I added two glowhead shims, and ground ran another couple of short tanks, each time I wound the needle valve in 1/8 turn. After three tanks, I checked tach at 16,700 and lined up the camera...and ripped off four solid flights. I ran the needle in maybe another 1/2 turn or so. The engine needed a prime to start now. The worst part is knowing I was scared to fly it for the last four years because I couldn't trust the powerplant. The best part is I can really play with the plane now! Yes, I have video to prove it.

I will mix up some 30%N for the next outing. Don't be afraid to make changes to your engine...add a few shims, change your nitro ratio, change your oil. But adding/removing shims is easy and fast, so it can be done at the field.

There were only 278 Medallion .051s ever made, and they were sold to free flight guys for nostalgia events. Are you sure what you have? And if so, it is a collectors item. Look at the piston and see if it has a copper colored ring ground into it.  🤠

Mr. Dave,

I wanted to back up what I said earlier. This was some time ago. I couldn't trust the engine to try anything.
https://youtu.be/pvEUoF8VFJE?feature=shared

Here it is this last Saturday with two extra head gaskets (three total-the only change) under a Cox high compression glowhead. There are several others from Saturday if you care to look/listen. It is as if it were a completely different engine!
https://youtu.be/y97zhUvS6Dw?feature=shared