Saturday, May 29, 2010

The Rudder and Schmetterling Aviation






I started the rudder by preparing and prepping all parts as the number of parts is very low and it was easy to read ahead and see what I was supposed to do to finish this quickly. Now that I have the primer I want to reduce the amount of time spent to clean the spray gun and that is by collecting as many pieces for a spraying session as possible.
So, I match drilled, deburred edges and holes as far as possible until it was time to rivet - oh, wait! There was this one really awkward step in building the rudder. And that was to trial fit the clecoed rudder spar to the already finished rudder (you'll need to have finished the hinges - remember?).
There was no hint in the manual how in the world I was supposed to fiddle those handful of washers into the different places they were supposed to go into with just my own two hands! With a lot of patience (did I mention that I'm not good at that?) and calm hands and some sort of nihilism I finally put them all where they were supposed to go and ..... it just matched perfectly! It revealed that the travel stop for the rudder which is built into the lower hinge assembly was not even on both sides and the rudder horn did not rest on a large area on that stop on one side. This would cause some wear on the aluminum part later and as I had the upside down (and the downside up), I could easily trim this little thing to make it a flat fit. I quickly reprimed it to cover up the blank aluminum and that was that.
After all this time spent on putting it together I had a hard time to disassemble it - knowing that I would have to do this again some time far away. With a muffled sigh I did what I had to do and continued on to finish the rudder.
Now, as I am following other builder's blogs and websites, I was aware of two major problem I could have run into. The best (and most entertaining) description of these are from the Schmetterling Aviation blog maintained by Dave. He's quite a bit ahead of me and he seems to interpret Oregonian in the same way as I do which means we both seem to scratch our heads about the same manual instructions and run into the same problems.
Reading ahead in his blog told me that some of the rivets I was supposed to use where a tad too long and tend to bend (in a spot where drilling them out is not so easy) and that putting the shop head on the outside of an assembly can avoid the the thin ribs from separating from the opposite part. Be careful about the rivets that connect the rib to the spar where the spar caps go on (put the shop head outside (so that they're visible after assembly) and take extra care to shorten them to the necessary length as they're a bit too long. Also, when riveting the trimmed rib to the rudder horn, make sure that you put the shop head on the side of the rudder horn back plate although this won't look as pretty. Otherwise the rib will try to separate from the rudder horn back plate and this could be a structural issue (the rib is just a bit too thin to stay straight when the rivet forms the shop head).

I got everything prepared and ready for final assembly and then the day was over. The primer got some time to dry overnight which is good as the inside of the skin won't dry as fast as open parts.

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