Thoughts from the workbench of Radical RC. The online retailer of electronics and kits for radio control aircraft. Dave Thacker shares his thoughts and knowledge of electronics, batteries, kit design and overall enjoyment of the hobby.
More info from Keith Shaw who you’ll remember has done some extensive scale detailing to one of our kits. Keith is an AMA Hall of Fame member. He’s tuning and trimming his bird and offers the following.
Now have 8 more flights on the Wright. Two improvements have GREATLY helped the directional control.
1) I found that the aileron cross pushrod was buckling. Increased wire thickness to 1/16th, helped a little. Rolled masking tape around pushrod ends and middle to get it up to the ID of 1/8th aluminum tube. Coated the tape with 5 minute epoxy and slipped the tube on. Wing warping is now very solid and uniform over flight speed range.
2) Mine had the few hertz rudder oscillation like yours. Carefully flexed everything back there and found that the vertical wire was wobbling all over the place at the bottom. The rudder pushrod was very solid in comparison, so side loads on the fins cause large distortion of the bottom inch of wire. Drilled out the boom bearings and plywood fin cross braces to use a 3/32″ wire instead. Rudder control is nice and solid and the oscillation is gone. Might have been able to get away with 1/16″ wire, but went for the 3/23″. Besides, I needed to move the CG back. 🙂
Now flying with CG about 7/8″ behind leading edge, still need to do some small tweaks on the motor thrust line. The plane now has a very solid feeling, with only a slight pitch bobble when it hits some turbulence. Flew it twice yesterday at an airshow in Detroit in 10 mph breeze with some minor turbulence. No problems. Before the mods this would not have been wise.
BTW, the crowd at the airshow LOVED it. More photos taken and questions asked than any other plane there.
Steve’s built a beautiful 1905. He has added some scale detail including flying wires and pilot.
We can clearly see a pilot capable of flying this model right in it’s sweetest spot, low and slow.
I was at our local field last week, and one of the guys took 60 some jpg’s of the Flyer. Some turned out excellent…! I did a low and slow fly by (didn’t think it was quite that low!) and he caught the whole sequence. I also really like the turn down wind… Use any that you might like.
Last two. Attempt to show Orville “flying”. Last photo is from pre-detailing to show rib and spar details. Done with a light brown Prismacolor marker available from craft stores like Michael’s. Put on the bare foam before over-painting with the High-Heat Almond paint. Gives a nice muted look as if real ribs and spars are underneath fabric covering. Looks great in the air.
Also thought I took a few shots of the launch dolly, but I guess not. It works well, both flights off the dolly. Will be sure to take some shots if the weather holds this weekend.
Dave, this has been a fun project to do, it let me do a lot of “adaptive” engineering that I so enjoy.
Love the Faux ribs and spars idea. It adds an extra dimension of scale detail and sounds really simple. I am thinking the next one I do will use your method. I might do the carbon rods and trailing edge as well??? Might be too much of a good thing if I did.
At the field. Note the “cross-country fuel tanks”. Each tank contains two A123 cells inline, housing made of 1/64 ply and card stock. The 4 cells and holders weigh about the same as a 4 amp-hr 3s LiPo pack, but produce a little higher voltage. I pull 32 amp at full throttle, but the two flights so have been a half throttle. 6-7 minutes consumes about 1 amp-hr out of the 2.2 amp-hr available.>
Keith, an astounding amount of detail. I love the fantasy tanks. You mention flying it. I’m going through the emails one at a time as I’m posting them in the schedule.
I have noticed that although this model should be very energy hungry, when cruising around at slow speeds, it seems almost magical how little energy is used. Think about all that weight, you have to be around 60 ounces, all those struts, two props, two motors and two no-load currents (something worth a whole blog post to explore), both those wings and your only using about 150mah a minute.
I’ve never seen a mah per minute chart based on weight or style or anything else for that mater. However it seems if there were such a guideline out there, something is wrong. This model in my mind should not fly as long as it does on so little energy and so little battery mass relative to machine weight.
A little quick math shows cruise current should be about 9 amps (150ma per minute x 60 minutes). However, when you deduct the no load current (not sure what it is for those motors) we’re talking maybe only 7 amps at cruise for the pair of motors. Figuring a at load depressed voltage of 3.3v x 7 amps _ only 23.1 watts. Further, it would imply that two 14 watt brushed IPS gearbox’s would be able to keep this machine aloft and still have an excess 4.9 watts for climb. It seems impossible, yet, I know it is true.
You’ll notice a detail here. Keith modified the kit so he could remove the front frame and canard assembly for easier transport. Also notice the rib detail on the foam. Keith told me he purchased a marker intended for furniture finish repair. The marker was just a slight shade darker than the paint recommended to paint the wings. He carefully traced onto the foam all the rib locations and a spar. The idea being that when the wing was painted the marks would show through the pain enhancing the illusion of fabric over ribs. Great Idea! If I build another one, I’ll certainly copy this great idea. Dave
Photos of pilot and dummy engine mounted, along with vertical radiator. Note how easy it is to work on the plane with the “head” removed.
The dummy radiator is 3/32 ply with 1/8th balsa on both sides to make it look like a strut with rear-mounted radiator. Cooling tubes are cheap 16 gauge insulated wire. Additional benefit is that it helps stabilize the center ribs by keeping them from tilting sideways. Note also the 0.1″ carbon rod going between the top three center ribs. It serves several purposes, as it helps stabilize the center rib, gives a convenient CG locator (located 1/2″ behind the leading edge), and serves as a hard point for hanging that is not dependent on rubber bands or foam. I’ll later include a photo of the hanger in my living room, where the Wright now lives.
The removable head took some brainstorming, as I needed to come up with a way to do it so that I could take at least another big plane in my minivan to air shows. Once the head is off, the plane sits front down and occupies only as much space as a normal large plane fuselage. It is still tight, but I can fit my big Bearcat or Stomo or Bugatti or Goon or UT-1 in with the Wright. I’m sure another round of photos will be needed to show everything that had to be modified, but perhaps a Mark II of this kit will include this feature. There are total of eight 4-40 allen cap head bolts that are removed, but are screwed into blind T-nuts instead of the nylon inset capture nuts. I didn’t want to fiddle with a nut driver and the chance of dropping the nuts in the grass. The bottom four connect the sled frame members with a kind of a knuckle joint with the blind nut on the inside. The top four allow the various support struts for the front canard to be disconnected, again with blind nuts on the inside of the inner most strut. The two center vertical struts are kept in place with a short length of aluminum tube to act as a kind of bushing. The mounting holes for those struts and ribs need to be slightly drilled out to accommodate the 1/4 long pieces of tube. I lightly tacked the tubes and struts together with a dot of Loctite Stick N’ Seal, a flexible water-based product similar to RTV silicone rubber. Even though this all may sound complicated, I can remove or reinstall the head in less than 5 minutes. It does have the added bonus of making the plane MUCH easier to work on in my very small shop. All of my big giant scale electric planes that everyone has seen over the years have been built in my tiny 9′ x 9′ shop.