Helicopter Flies

[1234]

Hi coaches, me and my partner have a moderate ffm heli built but we are unable to fly over 2 minutes we’ve tried .125 width and .115 width from 8 in to 12 in length but it’s always around 1:30 best 1:59. We usually stretch it to 4-5x its length because whenever we try to stretch it longer 80% of the time the rubber band breaks. We use the winding calculator and wind to 85% of max wind and a launch torque of 0.9-1 torque. Stretch length, launch torque and winds are constant so I’m wondering if there is anything we’re doing wrong? Is there anything we might be able to change?

[1234]

The helicopter is exactly 4 grams. The weight of the rubber band varies. Is a lighter band more helpful?

[coachchuckaahs]

Please give more info on your winding technique, especially number of winds, number of unwinds to launch torque, and max torque achieved. Also report rubber parameters such as mass of the rubber, linear density, etc.

It would also help to record and report rubber density in g/in. this characterizes the torque curve for a particular piece of rubber, and can vary 15% or more in a batch. You are seeing this by seeing some loops lighter than others while the loop length is the same.

When you stretch and it breaks, is it breaking at the knot or elsewhere? It should not be breaking just from stretching, unless you are really pulling it hard. You should be able to stretch to a "wall" between 6x and 8x. If the knots are coming apart, review info on the NFFS site about knot tying.

Also, report on your turns remaining. That will give some indication as to whether you need denser or less dense rubber, or more or less mass.

It is most likely that your winding can improve, and that your rubber needs to be higher density (wider). But without further info it is difficult to tell.

Congrats on getting to 2 minutes. That is a great accomplishment so far, but makes you hungry for more!

Coach Chuck