eertan's blog archive for October, 2012 - RC Groups
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Archive for October, 2012
Posted by eertan | Oct 15, 2012 @ 08:35 PM | 2,169 Views
This is a method I used to reinforce the wing spar on my Sky Surfer (aka Bixler), but it can be used for any tube spar. I know this is an overkill but it is cool.

What you need?
1- corn starch
2- water
3- syringe
4- hot glue
5- epoxy

The catch?
A non-newtonian liquid acts as a liquid when there is no force acting on it. If there is a force, the liquid phase changes into solid phase. The stiffness is proportional to the force applied. See these videos if you want to see how a non-Newtonian liquid behaves. Youtube-Video

In summary:
Fill the CF tube with a non-Newtonian liquid. During a normal flight (e.g. gliding) the net force acting on the wing spar is mediocre or zero, so the wing spar will behave as usual e.g. a liquid filled hallow tube. In extreme cases, i.e. wind gusts, aerobatics, crash etc. the liquid inside the CF tube will solidify and make the CF tube stiff, the stiffness will depend on how extreme the situation is, after the extreme case is over the material inside the tube will liquify again. So the stiffness of the spar is modified realtime.

How to do it?
The CF tube of Sky Surfer will take about 6-7ml (1/4 fl ounce) of liquid so you do not need too much material, to be on the safe side make a bit more than what you will need. 6-7ml of water based liquid will weigh about 6-7 grams approximately.

Add starch slowly into 1/2 ounce of water while stirring SLOWLY. At some point the stirring easiness will depend on how FAST you are stirring it. If you can not...Continue Reading