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Peck Polymers Peanut Druine Turbulent by jgood. Viewed 1536 times.
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jgood | 22-May-09 10:09 | In the air. She flew 'ok'. Max flight time was about 15 seconds. |
jgood | 22-May-09 10:13 | This was with about 500 turns (there were quite a few left on the aircraft once it landed) of the 0.08 inch rubber (5 inches longer than the hook to peg length). I don't think it's properly balanced yet. I think I need help with that! It seems to glide OK without power, but I feel there was not enough thrust from the prop. I'll try and get some video of it next time, so one of you experts can analyse it. |
jgood | 22-May-09 10:16 | BTW, the nose looks a little odd, since I taped a little stone to the front as balancing weight. There is definitely 'wobble' on the prop - is that typical of a rubber powered motor? |
John Cooper | 22-May-09 10:24 | James: 15sec is pretty good for starting out. It seems like the 0.08 rubber is not quite enough, but you could first try putting in more turns (600 - 700). From the photo it seems that the port wing is dropping- ideally a free flight model will not bank at all, in order to get maximum lift. You could try putting a little flap, angled down at 45 degress on the edge of the port wing. |
John Cooper | 22-May-09 11:35 | Wobble in the prop is fairly normal because the knots in the rubber tend to be asymmetrical However, it is a good idea to have a balanced prop. Also, if the whole nose block is wobbling, this would not be good. |
hjlittman | 22-May-09 11:44 | After excessive weight, the chief cause of poor performance in rubber powered models is loose nose blocks. Make sure that your nose block is tight on the nose even if you have made a shimming adjustment to the thrust line. There should be no wobble visible in the prop and the motor should unwind smoothly. Check that the prop shaft is not bent and that the thrust button is not loose in the nose block. If the thrust button is loose in the nose block glue it down being careful not to get any glue in the shaft hole. There is some argument on this, but I always balance my props. Spin it on the shaft and see if it always stops one blade down. Add weight to the light blade (paint,glue, thin lead tape) or sand the heavy one, if the weight difference is not too great, until it always comes to rest level when spun freely. You'll find that the motor run is smoother with a balanced prop. Some people go so far as to balance their props on the edge of a razor blade. Wind the motor and let it run down while holding the model. It should be smooth and quiet until near the end of the motor run when the motor is contacting the sides of the fuselage. The motor should not bunch up and contact the frame in the nose, right behind the nose block. A small S-hook or D-loop with a sleeve of electrical insulation, between the motor and the prop shaft can cure this besides making the motor easier to wind. Another cure is to bind a loop at the front of the motor by wrapping a small rubber band (dental band) around it. Sometimes a rubber motor can bind at the rear peg. This can be cured by putting a piece of thin-wall aluminum tubing over the motor peg to act as a rocker bearing. I like to bind this into the loop at the back of the motor with a dental band. Another way to deal with this is to get a small (1/4 inch) plastic drapery ring (sewing crafts shop) and put the motor loop through it when you make up the motor. Bind it in place with a dental band. It both acts as a rocker bearing and makes it easier to load the motor with a pusher stick by giving you a bigger target to put the motor peg through. A well lubricated motor that is free of binds at both ends, a balanced prop and a tight nose block to control the thrust line, will give your rubber powered model much better performance. It should be so smooth and quiet that observers should wonder if it's electric powered. Hope this helps. |
jgood | 22-May-09 14:32 | Thank you chaps! I'll give all of that a go, and let you know. We seem to be getting lots of storms here at the moment, so maybe I'll get out in a calm before the storm this weekend. |
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