Ki61 Combat Warbird
Building and Construction Tips for the Ki61 Warbird (a.k.a Kawafoamie)
This is my first shot at building a foamie warbird. I chose the Daves Aircraft Works Ki61 because the guy at the hobby shop said it was one of the best. Besides, it was the only one they had! Its taken me quite a while to get this thing together, learning as I went and getting used to heat shrink covering again (tape is so much easier). Its pretty heavy now, but I wanted something that I would fly in the 20-30 mph wind conditions So, ready? Here we go!.
As a preliminary matter, I chose to use standard servos in the elevator and ailerons. I did not install a rudder, I don't really have much use for one on this application. I used two servos in the wing so I could enable flapperons and allow for tighter loops and turns. I could also (I think) camber the wing a little bit to improve on the lighter lift flights. Also, if the servos strip its easier to pull them out of the wing rather than have to tear the entire wing off to get at the one servo mounted inside the fuse cavity. Its really up to you, but the standard servo setup in the wings doesn't leave much foam underneath the servo, so just be careful.
General Building Tips
1. READ THE INSTRUCTIONS THREE TIMES! This is very important. If your new to this type of construction, you need to read through the instructions before you start building. Reading all the way through them will prepare you for the next step in the process. Trust me, I should have learned this by now!
2. I first began by sanding down the leading edge of the wing panels. Make sure you use 100 grit sandpaper, it really makes quick work of the foam. I then installed the main spars (they are longer than the wing, but just let the extra hang over the wing tip). I used hot melt glue squirted into the routes and then pressed the spars in snuggly on a flat surface. DON'T USE HMG THAT IS TOO HOT OR IT WILL MELT THE FOAM!
3. Next I measured and attached the subtrailing edge stock on each wing panel. I used HMG on this as well (that stuff is great). Then you have to measure and cut (depending on whether your using a 1 or 2 servo wing setup) the trailing edge stock away from the aileron portion and glue that to the subtrailing edge.
4. Finally, you have to cut a small route out behind the main spar on each wing panel near the root. This is for the dihedral brace that is glued in to maintain the recommended dihedral angle of three inches. I glued this in with PFM brand adhesive (goop clone) for more strenght than HMG provides. Set the dihedral to three inches, then glue that brace in. One note here. Because the brace is just a length of wood, you have to dig deeper into the wing foam near then end of the brace so that it lays flush. I didnt do this as much but just cut a groove into the fuse to accomodate the higher areas. Email me if you have questions about this.
5. Whew! Now that the wing is together, you have to make it look pretty. You have to cut out the template that is on a page of the instruction, trace that onto your wingtips, and then using a sharp exacto knife, trim off the excess foam. I then took my Dremel with a sanding drum on it to sand down the excess spar, subtrailing and trailing edges to fit the contour of the tip. I also used the Dremel to taper the top and bottom of the wing tips to a nice shape.
6. Now, because I love to work on the fun parts, I began positioning the gear on the fuse where I wanted it to be. I just trace around the parts on the fuse with a marker. I put the batter in the nose (one of those flat packs) near the spinner from the top down. I put the switch area right behind that, and the reciever behind that near the canopy. I installed the elevator servo sideways and dug out an area to allow free movement of the servo horn. Finally, you have to put in the control rod housing (golden rod) along the length of the fuse toward the tail. Don't put it all the way to the end, you have to shorten it by about two inches from the tail so your control rod will be able to flex without binding to the elevator control horn. To dig out the gear compartments, I just use an old soldering iron I have. It works amazingly well. I also used it to dig a route for the control horn. All the gear was glue gunned in with HMG as was the control rod. I put a foam cap over the battery bay so it would be smooth and look good. Finally, because I used two servos in the wing, I had to melt a hole in the wing saddle for the servo wires to reach the receiver. Don't forget to do that.
One note. I had a hard time determining whether to put the servo arm outside the finished fuse, or bury it deep inside. I decided just to mount the servo bottom flush with the other side of the fuse and bury the moving parts inside the fuse. I am going to just cover over the open servo area with shrink covering and it will look invisible (I hope).
7. OK, now the fun part. Get a sharp blade on your knife, and get ready to shape the fuse. Do as the instructions say, and cut the sharp corners off the fuse at a 45 degree (or more) angle. Do this all the way around, except for the wing saddle of course. Then, once that is done, you can actually carve it down to a more fine shape, much like carving wood. Then take some new 100 grit sandpaper, and a sanding block, and sand down the carved areas moving in one direction. Do this lightly, it can easiliy chunk out the foam. After this is done, its pretty much rounded and nice looking. Also, dont round off the scoop area just behind the wing saddle. Its supposed to be square like that.