exams and a new rc-plane again

Hi everyone,

Yea, I know I haven’t updated in a while, so I’m doing this right now.
Aside the work for my assignment I’m, as always, learning for some upcoming exams, if nothing fails, these are my last ones!

As my last rc-plane got damaged during the last launch I’m working on a new one. Basically the same flying-plank concept, but this time with higher wingspan and thus higher aspect ratio. Another novelty will be a small electric motor (brushless outrunner) with a folding prop, to assist the time in between thermals.
Maxi Dancer Planke3 wing-cores
The design of the wings is different as well, this time I cut a styro-foam core (with Joern’s help 😉 ) which I’ll cover with 1mm obeche veneer. First I tried using the rest of the styro and 36kg in water bottles to press the veneer to the core, while the epoxy was curing, but this didn’t work well in the strongly curved areas around the leading edge.
pressing the wing
For some time I thought about using a vacuum system for the pressing, so this time I decided to finally build such a system. All I need is a airtight bag, to put the wing and veneer in and a vacuum-pump to evacuate the bag.
For the bag I got me some 0.09mm PVC foil which I then sealed with a hot wire on a wooden bar, pressing it to a flat surface.
hot wire sealing
To create the vacuum, I used a cheap aquarium-air-pump, reversing the tubes on the inside, measuring the pressure-difference with a small tube, hung on the wall of my kitchen with the open bottom end in a bottle of water. The height the water rises when a vacuum is created on the other end is proportional to the pressure-difference, with 1m corresponding to roughly 0,1 athmospheres. This showed a sufficient pressure-difference of about 0,3 athmospheres while the pump was still rather quiet.
vacuum pump pressure gauge
On the last two pictures you can see how nicely this works. But these were just preliminary tests, without the epoxy. The real test will be tonight!
without vacuum with vacuum

I’ll post some further update once I see how the final test worked.
Cheers, everybody!

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