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Author Topic: FF Newb builds an Ikara Butterfly...  (Read 3687 times)
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Jimmy JFlyer
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« Reply #75 on: January 01, 2014, 09:40:41 AM »

Really??? Wow, so then the loop, unwound, is actually as long as, if not longer than the plane eh?

I looked at the Minislick maiden flight vid by Alan and see the whole flight the rubber is still quite wound even at landing. I was wondering how it would be with the huge length of rubber hanging from it but it probably does not get unwound that far. Looking at what you are saying, it all makes perfect sense.

Thanks for another lesson and taking the time to teach a newb John!  Wink

Jimmy
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OZPAF
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« Reply #76 on: January 01, 2014, 04:40:48 PM »

Yes thats correct Jimmy. I usually start with a loop length around 1.5x the distance between the prop hook and the rear hook. Indoor models quite often have more.
Its not only done for more turns - it enables the motor to have a smoother power delivery through a larger % of the run time. Thats only a very basic answer however - better rubber minds than mine would give a better answer.
Its one of the attractions of rubber models - matching power and torque to the model and the use.
No problems - its a pleasure to be able to help.
John
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herreraa
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« Reply #77 on: June 02, 2018, 03:08:28 PM »

Dear All,
I have just build mine yesterday . Unfortunatelly, does not fly.
It is made on foam.
weight :2.65gr
rubber ( smallest i can buy, i do not have a cutter): 1/6 x 1/32 (1.58mm x 0.9 mm), loop pf aout 7.5in (about 19mm)
turns:600 or 700
CG : is about plans

Problem: At high torque fly nose down , later goes ok for a couple of turns then goes tail heavy then looses lift ad fall to the grown.

I have tried everything:
- move wings forward
-move wing angle of attack
-reduce length of tail to move make it glide better nose heavy but nothig work.
-use a single string not a loop of 1/16


can you please share weight of the tail of your models?

Any additional advice?

I will try to make a video.

Thanks

Alex
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Re: FF Newb builds an Ikara Butterfly...
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OZPAF
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« Reply #78 on: June 03, 2018, 09:46:17 PM »

I suspect that the rubber motor is bending your motor stick under full power. This would cause the tail to increase it's angle of attack and kill the climb.

How does it fly on lower motor winds?

Try adding a bit of balsa - 0.8 or so along the top of the motor stick to stiffen it in bending.

Try sourcing some smaller rubber form indoor suppliers or perhaps SAMS in England.

Good luck.

John
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herreraa
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« Reply #79 on: June 04, 2018, 08:57:16 AM »

John,
Many thanks for the response . The planes goes very good and even climb in middle turns but as soon as i get low turns gets tail heavy , stalls and fall to the floor.
I will follow your advice to see if helps but it will add weight and get a smaller rubber.
Do you happen to know the size of the rubber that came with the ikara butterfly kit?

Thanks again,

Alex
 
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OZPAF
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« Reply #80 on: June 04, 2018, 08:43:18 PM »

I would hold off doing that for a moment Alex as what you describe sounds more like a balance / thrust problem.

Check the balance point - with the rubber motor first. Also check the thrust line - make sure you do not have any up thrust.

If both of these seem ok - then take the motor off and the prop, and balance the model at the right place without them. Now check the model on the glide and trim for a slow but not stalling glide(onto a bed or something soft). Only change the wing incidence or the tail - leave the balance point where it is on the plan. Add the prop but not the motor, rebalance the model at it's cg and check again the glide again. You may need to make a minor adjustment.

Fit your motor and rebalance, Try on low turns - 50 -100 and you should get a slow circle or 2. Increase the turns in small steps and add down thrust if it power stalls - don't change the incidence settings of the wing or tail.

These small rubber models can be very tricky to trim and the heavier they are - the harder it gets. Have a search through HPA for info on mini sticks - there are much better indoor rubber heads than me on this Forum.

Good luck.

John
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herreraa
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« Reply #81 on: June 05, 2018, 09:19:51 AM »

Many Thanks I will try it.
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