There is still a lot of work that needs to be done once a plane comes back from the paintshop. Most frustrating is that after the big “wow” of putting it together, the next steps are barely visible and yet there’s a risk of really messing things up. Probably the scariest thing is cutting out the control surfaces on the wings. If that goes wrong (not a straight line, wrong place), you at least have a very visible mistake and even risk ruining all the work and having to start again.
A crucial step for cutting the control surfaceds is always made during the building of the wings, where we drill small holes in the abachi between the two spars that mark the division between the control surface and the wing. These holes need to be kept open during all subsequent steps, so that you can find them back! With these holes you know that you’ll be cutting in the right place.
For the actual cutting we use two different methods. The first is an adapted Dremel with a 0.8mm mill bit, that’s pulled along an aluminium ruler which is in turn stuck to the wings with bits of double sided tape. I used this method for the Urupema wings. The second is a nifty little gadget with a small motor running on a 2S LiPO battery, running on an aluminium “track” (see picture below), which Andi and I used for the Orlik wings. Both methods require a steady hand and double-checking before you cut. Fortunately Andi is an expert in this and perfectly cut our control surfaces. Using wooden templates we also cut out the openings for the servos.
Following this there’s a lot of work cleaning out the foam. Then we sand back the upper part of the wing so that the gap between control surface and wing is around 2 to 3mm wide. Then we sand the part where the control surface goes under the main wing back so that you have a sharp edge. Finally, we apply 49gr glass inside the main wing so that it’s protected against humidity and slightly reinforced.
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