Recently I got bit by the building bug. I don’t know why, but I’ve been wanting to build something. There was a thread on RCGroups about building a woodie DLG. I decided that it would be cool to have. It looks like an awesome flying glider. However, I have’t built anything before. A DLG airframe takes a bunch of stress. Building one has to take this into account. You don’t want it to come apart after a few hard throws. I decided that building something cheap like the Sunbird Electric Glider would be best for me to try before I got the DLG kit.
HobbyKing Sunbird Electric Glider
I wanted something that would be an OK challenge but still easy enough to build confidence. I also wanted something inexpensive so that if I built a flying turd I wouldn’t feel too bad. In the end I settled on the HobbyKing Subird Electric Glider Kit. For less than $40 I was able to get the kit to my house.
Upon opening up the box I found a bunch of balsa and three sheets of paper. Where are the plans?! This kit comes with no plans to build on. The three pieces of paper cover building the fuselage, wings, and tail feathers. Each of these pages are have a few pictures and some poorly translated instructions. Each section listed out the parts necessary to build what was in the pictures and instructions. The parts are shown in a photograph with a letter and number identifier. This seems nice until you go look at the balsa and see that there are no corresponding identifiers. This leaves it up to guesswork on the parts to which each step and picture refer.
Fuselage Frame Up
Following the order of steps on the instructions I started with the fuselage. This part off the build is pretty straight forward. There are few parts and there are only a single set of them. The only thing here that took extra time was making sure that the bracing along the sides butted evenly to the bottom of the fuse. Where I goofed was when I was putting the two halves together they shifted a couple of millimeters so that I now have left thrust in the motor mount. The slots for the tail feathers may need to be filed so that I can get them to be exactly perpendicular to the fuselage.
I have not built the canopy yet. I decided to wait and finish that piece along with the wing mount pieces until I have the glider almost completed. There is really no instructions for bolting the wing to the fuselage so I don’t want to wind up with a surprise at the end.
Test fit of the leading edge on the left center section.
The next section in the directions is broken into two parts, the inner wing panel and the outer wing tip. This is where you really see how the instructions are lacking. They list a bunch of ribs and webbing to use for constructing the these panels. However you’ll quickly see that there will end up being a number of different types of ribs that could fit. The webbing for framing up the spar is also cut in a way that suggests a taper, but it isn’t called out in the instructions nor is it very apparent that it is needed when test fitting.
I ran into the real problem when working with the inner piece, where it appears the two center sections will be joined. There are no specific instructions on how this occurs, but it appears that I do have a joiner that will fit here (more on this later). The inner section uses four separated ribs glued together to make about a 2.5cm section for both the leading and trailing sides of the wing. The reason they split them is so that the joiner can pass between the two down the spar, I assume.
I had a lot of trouble getting the fitment correct here. On my first panel they ended up coming out crooked. On the second panel I ended up doing too much sanding and had to come up with some scrap balsa to get the pieces to meet the trailing edge correctly. In the end, if I were to build these two panels again, I would not glue in this section of the wing until I was ready to join the two panels together. This way I could insure that the wing met in a square fashion and that the two sets of four on the leading and trailing could be correctly matched up.
Also regarding these sandwiched pieces, at first glance you don’t realize that they’re a bit narrower than the other ribs. The instructions make no mention of this and do not say anything about placement in the vertical plane of the wing. Should they be set to the bottom, middle, or top of the spar? I accidently set them to the top on one and didn’t realize that I did the bottom on the other! You’re supposed to come back with a balsa sheet to cover this area. I’m thinking that if they were bottom aligned the sheet would fit flush on top as shown in the later pictures. Since this area will meet with the fuselage I want to make sure that there will be wood meeting up with the sides of the fuse so that the covering doesn’t get pulled apart. I’m going to end up having to make sure that the balsa sheeting is flush on top AND bottom with the ribs. Shouldn’t be difficult but it’s going to add a little more weight than I wanted, plus I’m going to have to use a bit of filler on this area already.
Hmm… I wonder if this will work?
While framing up the center panels I started looking at the leading edge. The kit provides 1/8″ balsa strips. I have the Great Planes sanding tool that includes the leading edge curved section. I was going to use this to make the leading edge. While looking at the fit I saw that I had a 3mm piece of carbon rod sitting on the bench. I grabbed it and pinned it in place. It fit perfectly in the grooves in the ribs!
Testing carbon fiber rod leading edge.
I ran out to HobbyTown and got four lengths of 3mm carbon rod. The center sections were a little longer than half of the rod. Dang that sucks! Hopefully the two other complete rods along with my two scraps will finish the wing tips.
Doing this should setup the wing like my Gracia Maxi. It looks great!
Framing Up Second Main Section
It took me two nights to do the center sections. Hopefully everything smooths out now that I have some building time under my belt!
