Yep, another post here so soon. Actually, the reason I am being able to update so much right now is because I am waiting for glue to dry. Since I use wood glue to build with there are times that I have to sit and wait for a bit while the glue dries. In some circumstances you can do prior planning so that you can work on something else while the glue dries on another part. But right now I've got the wing laid out and I'm doing the starting structure of the wing. This is on the Dynaflite Super Decathlon that I'm building next. The right wing half is 44-1/2”!! Yep, a 89” wingspan. But anyway, because the structure of the wing is just starting and it takes up so much of the building board it's actually hard for me to work on something else. No big deal though, because it gives me a good chance to catch up here on this build thread.
To continue on from our last post, we'll continue putting together the front landing gear. We already have the wheel mounted on the axle, so now we can mount the front landing gear into the gear mount that we previously mounted in the engine compartment. Picture #1 is just a little better picture of what the assembled hardware of the control arm looks like. And in picture #2 you can see that we have removed the set screw from the control arm. You don't actually have to remove the screw, but at least loosen the screw so that it will slip over the landing gear wire. If you notice the landing gear mount you will see that it is made up of an upper and lower “loop” of plastic that the landing gear slips into, and there is an open area in the middle of the mount. This open area is where the control horn will go into. To assemble the gear place the control horn into the middle slot of the mount, and then insert the landing gear from the bottom and push it upwards. Referring to picture #3 there are two things that we want to pay attention to. First is the spring coil of the landing gear, you want this coil on the backside of the landing gear, you want it this way in order for the landing gear to “flex” backwards to give is some spring to absorb shocks and bumps. If this coil isn't facing to the rear you'll run a real good chance of ripping the front gear off with a “less than perfect” landing. The second thing to notice is the gap between coil and the bottom of the fuselage. The amount of the gap will be determined when the plane is fully assembled as this will adjust the height of the front of the plane. You can raise or lower the nose of the plane, but you definitely want to make sure there is a gap there. You want to gap so that the coil doesn't hit the bottom of the fuselage as the gear flexes and bend backwards. Pictures #4 and #5 also show the gap you need between the coil and the bottom of the fuselage.
If you remember from my last post I mentioned that we were going to use an extra wheel collar in the mounting of the front landing gear. Here is where we are going to use it. This wheel collar is a “Murphy Preventer”!! Remember that Murphy says that anything that can go wrong will go wrong. This is especially true for RC aircraft. Here for the front gear that means that if you only have one screw securing something that screw will loosen up and whatever it's holding in will fall off. Looking at pictures #4 and #5 you can probably already see where I'm going with this one. Looking at the landing gear in those pictures you can see that there is only one set screw holding the landing gear in the mount, and if that screw loosens up the gear will simply slip out and fall off the plane, and will more than likely fall in the tallest thickest grass at your field thus ensuring you will never find them again!!
The wheel collar will be used as a second device securing the gear on the plane. Look at pictures #6-#9 and you'll see how this is mounted. It's pretty simple really. There is a bit of the landing gear wire extending above the landing gear mount, and what we are going to do is slip the wheel collar over the gear above the mount and tighten the set screw. Doing this will definitely help to prevent lost landing gear. Ask how I know. I've lost more than one gear because I only had one screw holding it in. Hopefully by passing this on to you I can prevent your being grounded because you lost the gear while in flight. Plus, landing a plane with no front landing gear makes for added gray hair!!!!
The last thing we need to do here is drill out the hole for the landing gear pushrod. This pushrod will extend back up through the fuel tank compartment and attach to the rudder servo. The instructions are a little vague on exactly where to drill this hole. Other sources I have read will tell you to drill the hole directly behind where you will be connecting the pushrod to the control horn. I don't like that advice because it then limits where you can move the connection to if you need to move where the connector on the control horn. You'll need to be able to move the connector in order to adjust the amount of throw you have in the control, in this case it will be the steering of the front wheel. Most of the time you will have too much throw in the wheel, and this pretty much the mistake that beginners make a lot of the time. You don't want to have huge amounts of throw in the steering as this can make for some pretty wild take off runs. Instead you only want the front wheel to turn only about 5°-15°. A little experimentation as you start flying this plane will help you decide how much or little is right for you. This is why you need to allow for adjustments down the road. At this point some will mention that you could just adjust the amount of throw with a computer radio. This is bad advice for two reasons. First, remember that the wheel is attached to the rudder servo and any decrease in wheel throw will also decrease the amount of rudder throw that you have. Second, when setting up a plane you want to make sure that the plane is mechanically correct before you make any adjustments with the radio. Too many times people will try to use the features of a computer radio instead of making the needed mechanical adjustments first, which causes lots of problems. I tell my students to forget about computer radio adjustments on a trainer and learn how to make the adjustments mechanically. The can play with the computer radio on their second plane
. So back to the build.... If you look at picture #10 you can see that the pushrod tube is actually a little to the side of the EZ connector, putting it in the center of the control horn. This will give you some room to make adjustments, meaning you can move where the pushrod attaches to the control horn without causing binding in the rod. The pushrod will run through the firewall, back through the fuel tank compartment underneath the tray that holds the fuel tank, and then into the fuselage where the servo tray is mounted. If you look at former F-2 you will see that there is a little “notch” in the former, this is there as a point to attach the pushrod tube to (picture #11). Mounting the tube is pretty easy. First mark where you want the hole in the firewall at, and then drill a 1/8” hole in the firewall. Then insert the tube through the firewall and back to the servo tray. When you happy with how it is mounted use a little bit of epoxy (or thick CA) to secure the tube to former F-2. At the firewall I prefer that epoxy is used to attach the tube in order the completely seal the hole you drilled and because the epoxy is fuelproof. Looking at picture #12 you will see the I have a little bit of tube extending past the firewall. You want to do this when you attach the tube so that you don't get epoxy into the tube, after the epoxy has set cut the tube off flush with the firewall.
Pictures
1. Assembled steering control arm
2. Steering control arm with set screw removed.
3. Mount the landing gear wire with the spring coil loop to the rear.
4. Front landing gear secured in mount
5. Front landing gear secured in mount
6. Front gear and extra wheel collar.
7. Wheel collar will mount to the top of the landing gear wire.
8. The wheel collar sits above the gear mount in order to help secure the gear.
9. Extra wheel collar will help prevent loosing gear if the set screw loosens up.
10. Pushrod tube exiting firewall
11. Steering pushrod tube will be glued to fuselage former F-2
12. Extra pushrod tube can be cut off
Until next time
Ken