This plane is an original design of mine based loosely in appearance on the "Extra" series of aerobatic sport-planes. It took about two weeks to design and build. The size of the model was dictated by the length of some carbon fiber tubular stock that I had and wanted to use for the wing spars without splicing or cutting. I previously used this same material cut shorter for the spars of the 70% X-250.

After making a rough profile sketch of the plane the actual design began using Autodesk 3D Studio.  The wing was designed first. After beginning the construction of the wing, the fuselage was designed and scaled to the right proportion to match it.  I wanted this model to be specifically for electric power so several design elements were put into it to accommodate the unique requirements of electric flight.  Among these is its crash survivability features. We hear 'experts' say "build it to fly, not to crash." But unfortunately reality demands some attention to 'crashability'.  They wouldn't put ejection seats in full-scale fighter planes if they didn't think these would crash now and then.  This plane is also designed to allow a wide range of batteries and motors to be selected with plenty of room.

I reduced the throws to about 75% versus the original 125% and shifted things about some. The CG was a little better but not by much. The second flight was a little easier than the first but the nasty snap tendency was still there. Being still very tail heavy it was over sensitive to all control inputs.  I bobbled it a little on the second landing and  ended up cartwheeling it about two revolutions. A thorough examination revealed no damage (whew)!

I got to further test the crash worthiness on the fourth flight. I had tried a big 10x5 propeller and the flight behavior was very strange ( I later discovered that a damaged rudder servo was jamming.)  After fighting it a couple times around, it ended up snap stalling and doing a power dive straight into the ground from about 40-50 feet up. Several pieces scattered and we feared the worst.  When I got to the wreckage I was amazed to find only a broken propeller, a crack in the motor mount, and the landing gear mounting was worst with a fracture. My modular break apart construction proved itself as all the pieces that flew about were still intact. The wing and battery sled had cleanly sheared their nylon screws and jettisoned as designed. The battery sled would probably have been OK except that I had replaced the nylon screws holding the landing gear earlier in the day with steel ones. This was something I would rather not have tested in such a severe manner but I was tickled with the good results.

Finally a good flight!
That evening I repaired the minor damage and there was hardly a blemish. I discovered that the motor and gear shaft were both bent and had to replace them. I made up a new battery configuration to concentrate the weight more forward, and also move some of the R/C gear more forward. Now the balance point came to about 30 percent back. In making up the new battery pack I decided to push the envelope a little more and so added another cell for a total of eleven!  It had adequate power before but I just wanted "a little extra". Two flights the next day were excellent! It was very stable and all the snap tendency seemed to be gone.  I did some loops, rolls, flew around a bit, and did a few diving 'strafe runs'. This thing really speeds up nicely.  Landings were a breeze; it would glide in nice and smooth at almost the perfect approach angle. It started to rain so we had to leave in a hurry and it was cold out anyway.  I can't wait to fly it again!

2/13/01
About 10 more flights have been made now. I've tried an 8x7 APC sport prop, and wheel pants. The plane is VERY fast with this setup, est 50mph+ level flight but its heavier this way at about 29.5 oz . It handles the wind very well. Several flights were made in 15+ mph winds. I've also tried lightening it. I got the weight down to 27.5 oz and the resultant handling was very sweet. I think I like lighter rather than faster so I'm going to further reduce the weight to 26 oz by using a lighter ESC and prop and dropping back to 10 cells.

5/29/01 New Motor Tests!
I have installed a Permax 450 turbo motor with a 2:1 gearbox. This is running on 10 Sanyo 800AR cells and turning the 8x7 APC prop. The performance increase is dramatic. Even with the much higher wing load of almost 22oz/sqft it still handles very stabile. But the climb angle is almost double what it was with the 400 motor.

Unfortunately I couldn't find a suitable 2:1 gearbox on the market for this motor so I had to make my own. Here's the installed unit fitting nicely into the nose of the plane:

	See the bones
	Crash survival modular  construction
	How to make your own Carbon fiber landing gear