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Author Topic: The Art of Rubber for Indoor Scale?  (Read 1869 times)
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Jack Plane
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« Reply #25 on: November 22, 2015, 06:02:14 PM »

Jon, 1/8" seems rather feeble for the span and weight you've got there - but I've never flown indoors! I have found that models seem to fly when very underpowered, but act all anæmic and land with acres of turns left on the motor. If the motor weight is 6% of airframe weight and the model's going to land with unused turns, I wouldn't think it would be up for long - but it depends rather on the prop and how draggy the model is.

Stephen - You're quite right.  I test flew the 18" Chipmunk (with a standard Ikara 6" plastic prop) for the first time today and deliberately stuck with the 1/8" (0.125) as it was indoors in a not very big hall and I'm terribly inexperienced - so I contented myself with cautious 'powered-glides' with up to 500 turns on a 1.5 length single loop.  Power was indeed too low, wouldn't ROG or climb beyond a 6ft launch height, but certainly sufficient for my initial aim of sorting out basic trims etc.  Fortunately Flitehook were about, so I bought some lengths of 0.150, 0.165 and 0.185 (effectively 3/8") to experiment with.  Hopefully we'll get some calm dry days soon enough, so I can do this outdoors.  Needless to say, I expect to have to readjust trims to account for the progressively higher torques.

Jon

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DHnut
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« Reply #26 on: November 22, 2015, 08:49:03 PM »

Jon,
      I have a KK Chimunk and it flies fine on about 4 strands of .135" tan and weighs 51 gms with rubber. the prop is an Ikara 6". The side thrust is 3 deg and downthrust is also 3 deg. The challenge has been to tame the tight left hand turn due to torque. reduction in rubber size has helped and trimming is ongoing. The starboard wing has washout (1/8") and the port wing is flat. I also use a tab at this stage. Little flying lately due to the wind that results from El Nino. Also your turns a very low and with and I suggest a short motor to start with so that there is high torque for a short period that can be assessed before a disaster.
  Ricky       
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Jack Plane
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« Reply #27 on: November 23, 2015, 04:15:56 AM »

Thanks Ricky - very useful to hear.

Before adding tabs, side-thrust or extra nose-weight my test-glides were stable and straight.  I'd built-in 1/16" washout on both wings, but the left (inside) wing came out with a tad more than the right wing once shrunk and doped.  This doesn't help the tendency to roll left under torque but I'd hoped increased side-thrust and the up-tab on the right wing would deal with this.

My aim has always been to optimise the weight and power for this Chippie for indoor flying, therefore a final flying weight under 35g and limited loop-length - thus the limited assessment time you correctly predict!  Shocked

Now I've gained understanding and a little practical experience of these multiple factors, I can be methodical in my remedies:  eliminate all inside wing washout if I can (strip and recover the outer third of the wing?), widen outside wing tab so I can better regulate its effectiveness, make up two more loops of rubber at 25% and 50% thicker but still of indoor length (and still much weedier than your own thickness needed for outdoors/airframe weight), rebalance, test in field on very calm day.

Jon

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« Reply #28 on: August 01, 2018, 08:31:20 AM »

Ref Pete's bunching querey at #6 - bunching tends to happen when the person winding "comes in" too fast.  Usual advice is put on half the intended number of turns then start to come in so that you finish winding on or about the final turn.  Bill referred to Dave Hipperson's views on this as above.  'Nuff said.

As a beginner in the indoor scene, I would watch Doc Martin (MIAMA) (RIP) slowly walk his winds in carefully and methodically, and he could pack the longest motor into the shortest fuse! Just before the end he would stop and "milk" his knots forward. This is how I do it just because I was easily influenced by older guys with more experience. I never saw him with a bunch, although I am sure it happened only as an exception! I use this technique and rarely get a bunch. Winding a motor is just as vital as anything you do with a model. One does everything as he does anything!
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