Thread: Discussion Pioneer Glider
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Old Jun 07, 2012, 06:11 AM
cambridgekiwi is offline
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New Zealand, Waikato, Cambridge
Joined Mar 2009
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Not sure how you guys are getting on - however I do have a suggestion and some observations. I fly LOTS of flying wings off the slopes, and plank style slopers have REALLY TIGHT tolerances on the CG position, often a difference of 1mm (0.039") will mean the difference between good stable flight and being either nose or tail heavy. If you can get the model up and slope soar it with a CG close to where it should be, you can test (and hopefully recover from) bad CG related issues.
Right at the beginning of this thread, the first guy suffered from a classic "tuck under", this is caused all to often by a CG that is REAR of the correct position - hence his bringing the CG forward from 40 to 35mm is not a bad one! Flying wings need very little elevator movement - often up or down of 2-3mm is ample - start with more available on dual rates so you can switch down if you have too much.
Test glides are good, but often they don't get the model close to the flying speed where you will really notice CG issues.
Best test for CG on a wing, get the model up and flying off the slope, get some height (if you can) then put the model into a dive (gradual at first) to pick up some speed - watch for tuck under, this will be an indicator of Rearward CG - land and correct with a small external weight taped on to the body - try again until the model dives straight. If the model pulls out of the dive quickly with speed, there is too much nose weight - land, add some weight behind the CG and don't forget to take out a click or two of the reflex in the elevator surfaces.
For reflex in the ailerons, I doubt you would need more than a mm of up, the German guys' reflex in the video looks excessive - could possibly be to counter for a downward thrust angle maybe? Good luck, would like to see how you get on, I too have watched and followed Marskes designs for some time...

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