info for builders of RCM&E's March 2013 free plan
in the shops 8th Feb!
in the shops 8th March
Colin Budds rediscovers his love of autogyros
|Richard Harris||28/01/2017 16:44:32|
1884 forum posts
Please ignore my last reply as I read your post wrong! my time is limited on the net at the moment so it was a little bit rushed.
Your Panther will climb under power, if you think its too much and your CG is correct just add a little extra shim under each blade. You will be surprised at just how little you will need to bring down the nose, maybe even a piece the thickness of a piece of paper.
|don cardy||12/02/2017 17:44:46|
10 forum posts
EUREKA - with brief details.
As promised earlier I increased the down-thrust to 11 degrees so that the prop thrust-line passed exactly through the vertical CG position. After one aborted take-off (made difficult by all the worm-casts on our take-off and landing square) I achieved lift-off. Panther flew like a pylon racer, very fast and neutrally stable. If the nose dropped a quick nudge of "up" would put it right and vice versa. It sure made me concentrate and I managed a safe landing at the second attempt. Phew!
Back to the drawing board to do what we are told not to do and change three things at once. I reduced the down-thrust (to about 8 degrees), the negative incidence of the blades (by 1 degree using less shimming), and the gimbal neutral pitch (by 1 degree).. I was again back to Panther tending to hang on its prop, but because there was a 6mph breeze it was more difficult to land this time and Panther collapsed on its tail from about 5 ft up and needed a little remedial work.
Back again to the drawing board for a through review of what had gone before and of the advice received via postings. It was clear that the "hanging on the prop" problem had only occurred after I had changed the motor and the battery after the major crash reported earlier. The motor was 34 gms lighter and the battery 54 gms lighter than before. Had my recent check of the horizontal CG position been right? NO IT HADN'T - how embarrassing! I found that 125 gms of lead positioned between the under-carriage and the fuselage and secured by the fixing bolts would put this right. I left the blade incidence where it was and increased the gimbal neutral pitch back to 5 degrees. At last Panther flew like a dream - patience was rewarded! There were problems taking-off because of the worm-casts making it necessary to using a bit more throttle than usual but landings were no problem at all.
Back to the drawing board - hopefully for the last time! To eliminate the lead I had to move the motor and battery forward by at least 2.5 cms and probably reduce the inherent weight of the tail sections. A major re-fit was needed so the whole frame was stripped back and the motor mounted on the 2.5 cm extensions I had used previously but then discarded when I extended the battery compartment by 2.5 cm after the big crash. The battery would be capable of being moved well forward into the motor bay. A hole was cut into the rudder to lighten it and eight holes in the tailplane. The fin would use an open framework instead of being sheeted and the stern post be one piece instead of being cut at the tailplane. The fuselage was also lightened (see pic). These changes took at least 20 gms off Panther's back end. Finally, to cope with the worm-casts, the spats would have to come off to make room for larger wheels and the tail-skid be replaced by a small wheel to give the rudder more ground-clearance. After all these changes and then re-covering the CG came out dead-on with an all-up-weight of 4 lb 11 oz.
I'm looking forward now to an improvement in the weather and am confident enough to give the pilot a ride!
Edited By don cardy on 12/02/2017 17:49:01
144 forum posts
Ah, so the fundamental problem was a rearward cg. Glad you got it sorted. I flew my Panther last wek for the first time this year. It's always a somewhat tense affair because of the constant fear of disorientation. We had next to no wind so I was envying you our prerotator. However after a steady J shaped take-off run it lifted off smoothly and I enjoyed a short but reasonably comfortable flight and a slow, safe landing. As always, very rewarding.
Good luck with the next phase of the flight trials.
|don cardy||12/02/2017 20:26:35|
10 forum posts
Yes I've been pleased to benefit from the prerotator. Am about to start making another with a 6 mm main shaft. I've had no problem with disorientation because the spats seem to help so much - but now I've removed them who knows? Just for the record the balance point, both horizontally and vertically, is exactly where it's shown on the plan. I've put a spike through the pylon in order to check this very carefully. This means that my present down-thrust setting gives a thrust-line passing about 15 mm below the CG. Am checking with Rich whether the note on his diagram about the thrust-line needing to be through or above the CG is correct.
|Richard Harris||17/02/2017 18:42:27|
1884 forum posts
I have just replied to your PM, hope all your modifications work out ok. I will be test flying a new one this coming weekend that I have built for a friend. Photos and video will hopefully be taken if all goes well , but for now a 'before' photo. Not my choice of colours may I add
Edited By Richard Harris on 17/02/2017 18:54:23
|Richard Harris||19/02/2017 21:44:02|
1884 forum posts
Maiden was undertaken yesterday with 3 more flights today, the newly finished pea green Panther was passed on to its new owner today.
I managed to take a few snaps and a video off my phone yesterday. The flight in the video is its 3rd and was the final trimming flight of the day, trims ending up pretty much the same as my last two which is always reassuring.
|Daniel Johnson 1||20/02/2017 22:13:00|
|1 forum posts|
Nice build and flight Rich. I really like the colour.
Please login to post a reply.
Love Model Aircraft? Sign up to our emails for the latest news and special offers!