This thread has been quiet for awhile, so I thought I'd share how I addressed my two major faults with this plane.
1) Canopy Hold Down
This mechanism is hokey at best. Four tabs have to be perfectly aligned and are engaged by four cones mounted on a CF rod. You release the mechanism by pulling on a cable that is attached to the rod. To hold the canopies down a weak spring engages the tabs. If one tab is misaligned it can cause the canopies to be loosely engaged.
On a friend's L-39 the cable pulled off the rod and there was no way too open it. It took over an hour and slight damage to the canopy to get it open. Consequently it couldn't fly that day.
On my L-39 apparently the tabs weren't full engaged and the rear canopy came off in flight. It took three months to get a replacement and by then flying season was over.
To address this situation I removed the cable, got a CF tube with a 2 mm. ID and epoxied it over the 2 mm. rod that contains the cones. The rod is now extended to the front access panel. I pull on the rod to release the mechanism, and more importantly now I can gently push it rearward to insure that all tabs are securely engaged.
2) Leaps Off Runway due to Negative Wing Incidence
It doesn't speak very well of Jet Legend to get wrong something so basic. In looking at numerous YouTube videos you can notice that some JL/BVM L-39's sit with a nose down attitude and tend to leap off the runway on take off. Others, along with competitive models (CARF, Fei Boa, Skymaster, etc.), sit more level and take off smoothly. My guess is that when JL came out with the Gen2 version the nose gear is mounted deeper into the fuse than on Gen1, and JL didn't want to spend the money for a new slightly longer nose strut.
I put in a stiffer nose spring and slightly more TO flap which helped slightly. I toyed with the idea of weaker main springs, however I was concerned that it would bottom out too easily if I bounced a landing. Finally I decided that a longer nose strut was required to remedy the situation. I wasn't able to find a suitable longer strut so I decided to extend the one I have.
I started with a 5/8" OD, 1/4" ID 3/4" long aluminum spacer. I removed the steering arm from the top of the strut, drilled and tapped the spacer to mount the steering arm there, then drilled and tapped set screws to attach it to the steering pin. Then I got a longer steering pin to attach it to the top of the strut.
The nose retract had to be mounted 1/2" rearward to accommodate the gear door. Then the opening behind the door had to be extended 1/2" and a new cover made.
Now the plane sits with zero wing incidence with no fuel onboard. I expect that it will have a slightly positive incidence with a full load of fuel. Now I'll have to wait until spring to see how well it takes off.
