Springs, Rubber Bands and Hi Starts

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This is something I have been curious about for a while, sorry about the un sharp Pics

Rules regarding 2 M RES etc, and the availability of different size rubber, and stretching the hi start to a max of 4 KG so that the airframes survive.

Rubber with a higher spring constant K does not need be stretched as far as one with a lower value to exert the same force on a spring scale.

Doubling 2 pieces of rubber may not give you a higher launch, of course there are other variables

It is Potential energy in the Mechanism which effectively does the launch, of course the mass of the plane, winds air currents aloft, pilot ability also add to this.

All things being equal though I believe a longer stretched rubber band will give a better launch then a shorter stretched one. :)

Even If the overall length is made equal with more line,


My two hi star rubbers


the 3 set of 2 bands (Hi Start B) stretches to 60 cm to yield 3 kg on the scale


the 5 x 1 piece rubber (Hi Start A)  stretches to around 210 cm to the same 3 KG


The difference is 150 cm. So goes to say the rubber 3 x 2 needs an extra 150 cm of line to have the same length at 3 kg when anchored at the same location

Now, of course there will be stretch in the line etc,

Next step I added some fishing line and when I stretched it to 3 kg it cut thru the single rubber band Hi start A


Back to Square One


Haven’t proven anything yet, but surely when the rubber that is stretched out longer is released it will go farther then the one that isn’t stretched so far.

Hence unequal Hi Start rubber while still fun, is not the same.

Latest update, Launched these Hi Starts, 1 x4  (Histart B Modded) and 2 x 3  (Histart A)  from the  end of a pen, both stretched to yield 2 kg on the Scale.

the 1 x 4 went 28 ft or so, and the other only about 1/2 the distance , aimed for similar Trajectories as well