The flying monkeys got me...

Helis and fixed wing

AMA 957918
IRCHA 4345
AMA Intro Pilot Instructor

Saturday, December 31, 2011

Cornell Rewinged

The other day was crazy windy. We flew only a couple flights, and they were a lot of work against a heavy cross wind with 10 mph winds and 20 mph gusts Stupid fun flying. So it was a great time to take my Eflite PT-10 Cornell up! Kenny Chandler, the only other flying fool, asked me why I hated the Cornell... then as I headed out to the flightline crabbed his camera and said he just had to film this!  (Here's your sign... but I was being bold!). Touchy cross wind takeoff in a plane that begs to roll the upwind wing, flying 45 degrees to the wind to run down the center line, kiting around turns near the tree line. There's always a nice burble on windy days along the tree line at the south end, and I flew into it. She rolled the wing nearest the tree line down hard, I compensated, she did it again, I over compensated... a nice pilot induced oscillation, tip stall, POWER, stall, crashes onto her wing. But it was a WILD ride!

Yesterday I redid the wing, and today the cote. Getting the cote right was tough as I learned how to use the heat gun (LOVE the heat gun for cote, but there is a very very thin line between shrink and melt...). I decided to redo the cote on the vertical stab... that was a pain in the ass and I redid it 3-4 times. The left side still isn't right, and I was too tired to take any pics... the wing came out pretty good though!


Pre-repair with the cote removed, underside right wing. The wing is broken clean through aft, a couple ribs and the leading edge spar, held together here by the top cote. I carefully peeled the S of U.S. off and would replace it later. 



Repaired the ribs and spars. The wheel box was shattered, though you can't tell from the pre pic. I had to remove the sheet balsa, reconstruct the box with the existing parts, build a new roof under it and then re-sheet the balsa. In rebuilding the cracked spars I used the technique below to add supporting wood behind existing structure.


I use popsicle stick wood, Dremel sand some arcs to reduce weight.



The wheel box is re-sheeted.



And the underside cote is done nice, clean and snug, using my newly developing heat gun skills. I did the underside easily, but the topside took a couple tries. I also put the S back on and made new periods.



But it too came out near perfect.



The dihedral is spot on, no new twists that I can see. The new wheel box is sturdy.



She looks great, though I wish the left side of the vert stab cote looked better... next time.

No pics, but I decided to change the motor. I had a HURC 2836-09 driving a 10x8 Master Airscrew powered by 3S 3300. I think this was a marginal power setup. I decided to change to a HURC Power Up 450 motor Kenny Chandler had given me. for a few more kv and 50 more watts of power without any more weight up front (remember she has the metal motor mount, so front end weight is an issue). I think she will fly a tad better, and can even handle a 4S if I want to. Hoping to fly her tomorrow!

UPDATE (1/1/12): Went back this morning and redid the left side of the vert stab, and it came out wonderfully. I also took a moment to strengthen the structure of the frame, which you can see through the cote in the pic of the right side.





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