View Full Version : Roll Technique??
08-16-2005, 02:19 PM
Hi All !!!
I got back into R/C flight about a year ago after a 30 yr. layoff. I built a flying wing last year, then turned it into a brushless performer. This spring I built a Tigermoth 400, all stock except I have now entered into Lipo world. My skills came back rather quickly, and I have no problem with the aerobatics with the wing. My Moth has full house controls, and flies differently from the wing. I can do inside and outside loops with the Moth, however, I'm a little puzzled on roll technique. Hard right or left aerleron with the wing accomplishes the roll. The same input with the Moth sets it into a bank turn. Would the proper technique be to add reverse rudder?
I would like to know the theory now instead of risking a possible crash. Unfortunately there is no one in my area to ask, as all of the other flyers I have met fly heli's.
08-16-2005, 02:56 PM
sounds like the Moth doesnt have enough control.if it just banks with full left or right and doesnt roll.if you give right ailrerons and left Rudder or the other way around if the plane will roll it will do a funky type looking roll.
sounds to me like you need a little more aileron movement...typically I will use a little down elevator at the inverted stage of a roll...
08-16-2005, 10:49 PM
Had to put differential in the ailerons to do good rolls, plus all the aileron you can get. two ways to do it. Take the lower wing off. Take a pair of needle nose pliers at the bottom of the wires where they bend up vertically. Take another pair of pliers and bend the wires forward toward the servo 1/8 to 3/16 of an inch. O yeah, take the servo arm off the servo first:p Shorten up the servo pushrods now so the ailerons are level again. That was the easy way. The other way is to put a servo wheel on the servo. Drill pushrod wire holes about 30 degrees towards the back of the plane from parallel. Shorten the pushrod wires again to get the ailerons level. Hope this makes sense. While the pushrods are off, see how much travel you get before the ailerons bind up. Don't want to stall the servo. Long servo arm or big wheel to get the most throw.
08-17-2005, 01:26 AM
It seems that I have plenty of throw, as the ailerons will travel at least 60* up or down. What perplexes me is the flight dynamic. As soon as the plane goes into a bank, it wants to turn (lazy). This tells me that I could possibly have too much throttle, and I could cut back which will not be conducive to the roll, or I could add some down elevator. I was thinking of opposite rudder to negate the turning effect of the bank, but then wondered whether this was the answer or would I just wind up in a "slip". The other situation is that I may need to fine tune the balance to make the ship slightly nose heavy. Right now it balances perfectly, and with the 3S Lipos, there is plenty of power on the stock motor and prop. Anything above 1/3 throttle, and she wants to climb. At full throttle I have to add a little down elevator to maintain level flight even though it is trimmed to level at slower speeds.
Any advice would be appreciated. I had read numerous other threads that the stock roll ability was more than adequate, so I wanted to pursue this and then inverted flight.
08-17-2005, 01:54 AM
It's the adverse yaw that's not letting it roll caused by the lack of ail. diff. Giving it rudder in the direction of the roll will also make it roll faster. After all snap roll is left ail, left rudder and full up elevator. I also shaved the top, front of the motor mount to put downthrust in it to take out the climb under power. Now when I crank on the throttle it neither climbs or dives, just goes faster straight ahead. :p Needs lots of down elevator to do outside loops because of the flat bottom wing.
08-17-2005, 02:20 AM
I took it up to about 150 ft, put it in a steep power dive, then outside loop, as I didn't know how it would respond. I used the speed and altitude to minimize any lack of power. I've done it only a couple of times while still getting used to the plane. I really don't think of it being totally aerobatic until I switch to a BL maybe next spring.
The downthrust that you added sounds good. How much of an angle change did you make?
I have found my biggest challenge to be consistant scale like landings. Every time I think I'm perfect, I get that little hint of wind that seems to screw me up, then I wind up aborting or ballooning. I will be taking it to the beach this year when vacation starts in Sept. Took the wing last year, but belly landings and sand don't mix. The landings would probably improve with the downthrust addition, as the least amount of power on final can make a huge difference on the smoothness of touchdown.
08-17-2005, 03:00 AM
I'm afraid i'm an eyeball engineer when it comes to tweeking. probably 4 to 6 degrees down, and it would help it not to balloon so much. I made flying, landing wires from dental floss to take the aerodynamic stresses. Wings don't bend so much in a tight turn:D Also beefed up the landing gear with forward struts like the real moth.
08-17-2005, 03:18 AM
I beefed up the landing gear with rearward struts and cross braces ( all silver soldered), along with a lexan plate on fuse bottom. Epoxied leftover pushrod tubing to plate. This captures about 3/4 inch ends of rear struts as well as acting as a spring shock absorber. Upper wing has 2 ea. 1/8" carbon spars to stiffen. Used Firewire fishing line as wing wires. This things like a flyin tank now. I built it with the mods, rather than living with the known weaknesses. I studied the forums for months before building it. The plane flies great !!!! Didn't realize it needed some downforce - easy to fix.
08-17-2005, 01:02 PM
Also had a brushless Himax 2025-4200 in it more than enough power. Tried a cheap BP 21 outrunner, 29 bucks up here:p , Would do all aerobatics from level flight. Bought a speed controller from the same people. It lasted about 4 seconds before it went up in smoke.:( local hobby shop traded it for a better quality one.
08-17-2005, 06:02 PM
My original idea for this ship was to have an aerobatic plane that flew well and at a relaxing pace. I can have all types of "white knuckle time" with the wing, as it will hit speeds approaching 100 mph. I was told by one of the GWS people that an Axi brushless setup was the ticket without wanting to tear any wings off. Number escapes me now (2028 ????). As far as esc's I have had nothing but good luck with Castle Phoenix and Pixie.
I just placed an order to AeroMicro for some 2" spoked foam wheels - still can't find a good looking 3/4" tailwheel. Also ordered an Azarr Micro antenna and a couple of different prop sizes just to see if there is any noteable difference. I like this plane so much, I'm thinking of ordering a slope glider just to have a parts bin.
08-17-2005, 06:11 PM
Just a matter of physics. If I were to bend the aileron control arms forward, thus shortening the rods. wouldn't that also reduce the upward aileron travel, but increase the downward travel?? Since the arms are glued into place as well as the hinges, is there enough room to reach in with 2 pairs of needle nose to make the bend?? (I'm not looking at the plane now)
08-18-2005, 03:25 AM
Sometimes I have to think twice about it too, for instance, on a high or shoulder wing, with the horns on the bottom, it would be the other way around. As it moves forward, and down it would be the same as moving in on the horn on the rudder to get more throw. Moving back would be like moving out on the horn. You pretty well have to take the wing right off the plane to bend them. I have a set of needle nose that have about a 45 degree bend out at the end that makes life easier. Bending them too far forward is not a problem. I like them to go twice as far up as down. The old Ercoupe had 30 degrees up and 10 degrees down.