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Ed, here's a link to Brandie's Elapor Soup Recipe...
http://www.rcgroups.com/forums/showp...&postcount=256 |
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I'm going to post some EZ COG/trim info here because it will help you with the first flight.
Update: 6/3/07 Added some COG measurement and manual pictures. ********************************** Update :5/10/08 I now have a high speed 60" wing that is difficult to perform power off test glides. Without a heavy head wind I simply can't throw it fast enough and it noses in because of lack or lift. I have to launch this pylon racer type plane with the motor on. Still the hand toss, where practical is a good final check to make sure the plane will be stable in the air, especially for new flyers. I wondered about that no unpowered glide tests when first looking at the EZ instruction book. Every other plane I have (except 60" composite wing) I do unpowered glide tests. I started thinking, was it a mistake in the instructions? Is elaptor foam made out of some special formula? Anyway, it's all clear to do unpowered test glides in my book. I'd make sure the COG is right on the money, this is most important. Don't try to trim out a bad COG with the elevator and think you got it right. Be a master of the hand launch before firing up that motor. Nose heavy During the "motor off" test glide if the plane is too nose heavy your COG balance point will move forward. There will be enough lift to carry the plane when first thrown then as the speed decreases the lift decreases and the plane nose drops and speed starts to build again. If you are on low/ground level test glide you will nose in the dirt before the plane recovers (unless you hit a little up elevator so you can bring it in without crashing). In the same situation if you happened to be higher in the air the plane would continue to dive until it picked up speed again, generate lift and start to climb nose up. Then as speed decreased, back into a dive. What you have now is a hard to control roller coaster situation which in the case of a new flyer will cause you to crash, especially when landing. Tail heavy During the test glide if your plane is too tail heavy it will go into a stall and the stick controls will have little control and act wacky. My too tail heavy planes simply flip over backwards or veer off left or right flip over and cart wheel. Very ugly. . If you get your tail heavy plane in the air they fly but bounce and jump on very tiny pieces of air. The controls are very wacky and can have sudden unexpected results when flying. Landing is very hard because the controls are dicey and overly sensitive. The new flyers will over control a tail heavy plane and crash because of unexpected behavior. BTW many sailplane pilots move the COG as far back as they can and still be able to control the plane. This makes it easy to watch the plane because it will jump even when it hits the slightest lift. I do this with the EZ as I move the COG back slightly (from 78mm to about 77.5 to 80mm). Makes it a better thermal hunter. Flying COG check Not very scientific but works ok to check COG. The plane is trimmed neutral. The COG is on the spar (EZ is measured 78 mm from the leading edge next to the fuse). On a no wind day chop the throttle at 200 ft altitude and put the EZ in a shallow dive, then take your hand "off" the stick. If the plane comes out of a dive and then goes up, you are nose heavy. If the EZ stays in a shallow dive then you are tail heavy. BTW after the tail heavy dive test remember to grab the stick and pull back so you don't crash. If you come out of the shallow dive slowly and return to level flight you got it right. Hope this helps. Where possible and based on the model design, hand launch and test glide your models before cranking up the motor. 6/12/07 Updates: Added some helpful links lift, drag, cog, etc. http://adamone.rchomepage.com/index4.htm http://www.mh-aerotools.de/airfoils/...tributions.htm http://www.gylesaero.com/_frames/f_liftcalc.shtml
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