Awesome! I have one question. Does anybody know any forum/forums with scratch build a/c planes at any scale? Thank you in advance
Yeah I bet that Dornier will get pulled out at most a few times, then hung up as a display somewhere. It really should take off and land from the water at least once though Looked pretty squirrly in the air, a lot like my much smaller PBY. Need to really keep the speed up in turns or it will tip stall like a *****. Nur: rcgroups.com has forums for all kinds of scratch built; balsa, foam, fiberglass, etc.
Which PBY do you have? I am wanting to pick up one of those for days when it's too windy/rough for the tiny little A5. You're right. That Dornier looked like a real handful. It looked like maybe it could have been tail-heavy. Or maybe the wind was just really gusty during that clip? I would think a model that large and of relatively conventional configuration (straight, high wing, lots of wing area) would be pretty stable.
Dynam 1470mm: Dynam PBY Catalina Grey 1470mm (57") Wingspan - PNP DY8943-GREY Really nice plane but a handful in choppy water or winds over ~10mph. I programmed in differential thrust linked to the rudder that could be flipped off once airborn, otherwise it weathervanes terribly in the water. Makes a great camera platform! [ame]http://www.youtube.com/watch?v=dNDXevcdWQc&index=6&list=UU-i32YPW7WSt5OSEUvGOaAQ[/ame]
Very cool! I guess for differential thrust you have to have two separate ESC's, right? Are there two separate throttle channels used? Does it come from the factory that way or did you wire it up yourself?
That IS impressive. Beautifully built but a handful in the air, I'll bet. The lack of dihedral and minimal vertical tail area would make it tougher.
Bob, you have more knowledge about this stuff in your little toe than I do in my whole body, so please forgive if this is a dumb question. Would building some washout into that wing make up at all for the lack of dihedral? Also, in your opinion, was the "squirrelly" flight performance more due to lack of dihedral of lack of tail area? I can think of other models I have flown with little or no dihedral (ducted fan jets, low wing sport planes) that still had good directional stability. They did not want to self-level like a high wing plane with a lot of dihedral, but they weren't yawing and slipping all over the place like that Dornier.
I'm no expert, Nathan. I have been messing with this airplane stuff for a long time plus working for 50 years next to a bunch of real experts at Boeing. I have flown several airplanes that suffered from the same shortages as the DO-X; plank wing with no dihedral and low tail volume. Inherent instability requires constant " herding" to stay straight and level, especially in rough air. The DO-X model was constantly slipping and skidding and the ailerons were very busy . Dihedral would have helped to tone down the constant work to stay upright. Washout would not help and could possibly have aggravated the rolling jitters. Washout is usually used to cushion the stall by letting the inboard wing stall before the tips. Ample vertical fin area is necessary to halt the yaw when in rough air and with the jet type and swept wings, the swept wing acts the same as dihedral and maintains stability. The 707 suffered from dutch roll because it had both swept wing and dihedral, 7 degrees, so it was over stabilizing. Hope that this helped.
The real PBY also lacked yaw stability and authority, they kept enlarging the vert stab in each subsequent version. That giant Dornier has what looks like half the fuselage in front of the CG... probably could use a vert stab with double the area. It's hard to say how windy it was for that flight, but even with no dihedral to speak of my little PBY is more stable in roll that that appeared to be. But it also doesn't have 12 gas motors propped up on stilts above the wing either.... Nathan - you'll always need one ESC per motor but the "stock" configuration has one channel (throttle) Y-ed to both ESCs so both motors get the same input signal. The only difference in wiring for DT it to get rid of the Y for the throttles and run each ESC wire to it's own channel. So to run differential thrust you need a free channel (I used the 5th output channel on my 6-ch receiver, typically used for flaps), then create 3 "mixes". MIX 1 sets the throttle as master and "flaps" (or whatever channel you're using for the second motor) as slave. With no rudder input (or with DT switched off) they both follow your left thumb at the same rate. MIX 2 has rudder as master, throttle for left engine as slave (in a negative direction). MIX 3 has rudder as master, throttle for right engine as slave (again, in negative direction), Then you set a master on/off command for MIX 2 and 3 controlled by the flap switch since you don't want to fly with differential thrust. At least this is how I did it on a Spektrum DX8, which isn't the most intuitive to program... even with examples online it took me at least an hour to get the sub-trims lined up and everything working as it should. But it's really nice to have on the PBY since the tiny water rudder barely touches the waterline, and I'll probably do the same thing on the F-82 but will need to swap in a 7-ch RX since that's got flaps and retracts unlike the 4-ch PBY. If you get one let me know and I'll take photos of the various Mix screens on my DX8.
Your comment re fuselage area ahead of the wing on the Dornier are right on. The Boeing 314 flying boat had the same problem with that and low tail volume and as we could see in subsequent revisions they had to add two more vertical fins to attain directional control and stability. Same trouble with Model 247 and Model 299 when initial versions had to have the vertical tails enlarged.
I'll not get into the depths of the tail volume equation but in brief, it compares the wing span, tail moment arm, and lateral areas. Modern inputs I believe enter power inputs. It's been a while but essentially it sets standard for sizing the tail. Nowadays vertical fin area and height are critical to maintain directional control in an engine out on take off. The 707 had fin extensions, KC-135 also until full hydraulic power became standard on everything.
Bob - interesting stuff. I'd been thinking about this topic for a while since I'm building a tail-less plane modelled after the X-Wing from Star Wars. Looking at it from the side there is a long nose but fairly large "vertical area" in the large X-wings. The smaller one I've put over 50 flights on has very good yaw stability and a similar relationship between side area in front of and behind the center of yaw rotation (is that what it's called?), so hopefully the larger one will also. How does the wingspan affect yaw stability?
Wing span itself doesn't affect yaw stability. The combination of wing span and tail position and tail size would affect yaw stability. To me there are several examples of proper wing span / tail size, the ME-109 and B-17E . One glaring bad example would be the Curtiss SB2C, short coupled tail and huge surfaces to compensate and a long nose to add to the problem. Lousy airplane to boot.
Funny how in many cases if it looks right it will fly right And then there's the A380.... which somehow managed to stay in the air despite it's ugliness.
Relatively cool and calm morning so velcroed the keychain cam to the tail of Blond Dynamite for some very enjoyable flights. Love the new 3300mAh battery that allows 6 minutes+ flight [ame=http://www.youtube.com/watch?v=AkzR7T34lpo&list=UU-i32YPW7WSt5OSEUvGOaAQ]P-38 Lightning Aug 2014 Scobee Field TX - YouTube[/ame] Also put a couple more flights on the F-16, playing more with the thrust vectoring. I need more practice coordinating throttle and throttle, thrust angle, elevator and aileron at the same time but a fun challenge! Image Unavailable, Please Login
Very nice chatting with fellow F-Chatter Barry at Scobee field yesterday. Barry is part owner of ultimatejets.com, and was out giving one of his modern (all electric retracts and self-starting gas turbine) demo jets a check flight before a big jet rally in Waco. How about a few pics of your RC workshop/man-cave/airplane shrine? Please let me know if you're involved in any future charity events with Bomberfield like the one you did teaching Wounded Warriors how to fly and giving them their own planes. I'd be happy to donate my time to help out. Barry's company also sells these sleek machines: [ame=http://www.youtube.com/watch?v=MHMbBFiWXnc]RC Jet Jetpower 2013 - Aviation Design Diamond - YouTube[/ame] Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
Took the boy out to the airfield today for his first lesson. Here I'm explaining why one of the prop blades is white (they nicked one on a landing and could only find a white replacement) on the F2G Bendix racer. Have to get some planes to hang in his room Image Unavailable, Please Login
Put the GoPro on a Slow Stick today. Not a great video, due to the lack of stabilization, but I'm still happy with it. Had to pull the gear off in order to get better video, hence the "catch" for the landing. [ame]http://www.youtube.com/watch?v=s2TR0U16CR4&list=UUQMtvtuTvEqJGz7YMELesJg[/ame] Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
Lou, I really liked that video AND THE MUSIC. What was that and who? I can't believe the stuff that you can do now with RC models and cameras. I keep going back to my days of flying free flights, rubber and gas, in the late 30's and early 40's. I would still like to do it but I'm also intrigued with the models that you can fly now.Thanks for posting.
Song is, "Help Me Lose My Mind" by Disclosure. Yeah, that plane is $43, motor and all. Another $100 (maybe less) for a radio and 30 for a battery and charger and off you go. Amazing really. That plane has landing gear, but I pulled it off for the video. Takeoff is about 3 feet, and that's with the GoPro on it. I typically fly it right in front of the house although the wind has to be light. Good XMas present for someone I'm sure.
Cool vid! Which model GoPro is that with? Since I misplaced my 808#16 Keychain cam (the one I used for the P-38, PBY and F-82 on-plane vids above) I recently bought an $80 Mobius action cam with wide angle lens. Slightly better vid quality than the 808 (1080p vs 720p and a bit better contrast&color) but at 40g too heavy to stick on the tail of my little foamies. And with the lens too wide a FOV as a hat cam (planes get too small to see too quick) so I won't be using it too much until getting the big X-Wing done and putting it in the cockpit. Interesting that you fly a four engine jet and a high performance bipe in real life, and a slow, light cruiser RC Plane Also interesting that this thread and your 747-8 one are within a few hundred views of each other. Almost exactly equal interest in the biggest and smallest planes! cheers Kurt
Was a GoPro Hero 3 Black. I usually shoot it in 2.7K/30, and then compress it to 1080. That comes out looking awesome. This time, I tried something different and shot 1080/60. I was told you could then take the 60fps back down to 30fps effectively slowing down the video without quality loss and making it less shaky. I used that in just one part of this video. The rest was at full speed. Next time I'll just go back to 2.7K I think. For some reason this video looks a little pixelated to me. I tried quite a few different compressions too. Oh well, it was just a fun quick flight. While the Slow Stick can easily carry this camera (with the housing), it's 3 channel rudder/elevator doesn't work well for smoothness and the wing has too much dihedral. Yeah, big differences in flying. I feel very lucky to fly the 747. It's such a great airplane. Of course the fuel tanks are too big, and flying in a straight line for 10 hrs isn't all that fun. But pushing the throttles up for takeoff and also trying to grease it on is a lot of fun. The Christian Eagle is a mixed bag. It's a whole lot of fun, but honestly I get a little nervous before stepping into it. Once the engine is running, I feel a lot better. But it truly feels like you're sitting in an RC plane. The wings are so small. The glide ratio is aweful, and landings can be interesting. But as long as the engines running, it's a blast. It's the "what if" that has me concerned. Solo is OK, but with a passenger there's a bit of pressure. Don't get me wrong, I have a blast flying it. The Slow Stick is everything these 2 aren't. So slow, so relaxing. I like to fly as low as I can and will just circle the field at 3 feet. The wind bounces it everywhere, and I like that. You can really feel the wing flying. Yeah, strange how the views are almost the same between the threads.
