Keith Sharples Posted June 20, 2017 Share Posted June 20, 2017 Advice please from seasoned scratch builders. I'm fine scratch building from plans when all is there on the plan to work to. Adding something new I have not done before. I have an old, very old, 2 channel slope glider that I am giving a revamp/update. I am fitting an electric motor and folding prop up front, ESC etc. I am also thinking of altering the wings to include ailerons making it a 4 channel (inc motor control). Its 1800mm span with the wing in 2 halves, joined with bent rods inside close fitting tubes. The rods are fixed in one wing and slide into the tubes in the other. I was intending to permanently join the wings leaving the rods in and use some fibre glass wing joining tape etc to give more strength. The wings are already solarfilm covered. For the ailerons. 1, Do I fit 2 x 9g servos (1 in each wing) and run the cables to the center to drop out of the wing for the RC. 2, Fit 1 std central servo and run snakes through the wing to each aileron. Either way I have to run something along the wing, putting a hole in each of the wing formers in situ is not a problem. Which would you do or is there another way. Thanks in advance Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted June 20, 2017 Share Posted June 20, 2017 You can fit the two 9 gram servos but getting the leads through the wing can be interesting. You could fit a central servo with 16 SWG wire pushrods out to bellcranks and then 2 mm clevis rods to the aileron. See any of my full size plans. Personally I do not like snakes, if the bend is a bit tight they can bind and make extra work for the servo and also play havoc with centrering the ailerons. Quote Link to comment Share on other sites More sharing options...
Dave Hopkin Posted June 20, 2017 Share Posted June 20, 2017 Personally I would go with 2 servos but does the wing have suitable holes in the ribs for the servo lead? If not you could use some brass tube with the end roughed up and serrated as a drill/corer to create a small hole then thread some servo wire (without plugs) through the tube to the servo bay, then gripping the wire withdraw the tube leaving the wire through the holes ready to have plugs fitted Quote Link to comment Share on other sites More sharing options...
TIM Shaw Posted June 20, 2017 Share Posted June 20, 2017 No Brainer for me, separate servo in each wing is the way to go. Yes, routing the wires can be a bit fiddly, but then so is routing pushrods and bellcranks. I'd suggest using a sharpened brass tube to cut a route to the servo wells from the root, run a string or cable down the inside of the tube before you remove it, and use that to pull the cables through. Bear in mind you can put the servos at the extreme inboard end of the ailerons of you want, so a long cable run is not necessarily needed. I agree with Peter re snakes, I'd avoid them like the plague for this job. Quote Link to comment Share on other sites More sharing options...
Keith Sharples Posted June 20, 2017 Author Share Posted June 20, 2017 Thanks guys. my problem is solved with the usual fount of knowledge on this forum. 9g servos it is, I had already thought of the idea of using a sharpened brass tube to carefully get holes in the wing ribs and run the cable down the tube (without plugs on) then remove the tube. 9g servos arriving tomorrow! Job on!! Thanks all. Keith Quote Link to comment Share on other sites More sharing options...
J D 8 Posted June 20, 2017 Share Posted June 20, 2017 You may find that as the model was designed for rudder elevator control it may have to much dihedral for the new ailerons to have much effect . I made this mistake with my first full house model [ a Rojair Cadet ] which could be built as a three or four channel model and later had to saw through the foam wing to reduce the dihedral angle for the ailerons to work. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted June 20, 2017 Share Posted June 20, 2017 May be easy to reduce the dihedral if the old joiners can be removed and replaced with slightly less bent ones.... Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted June 21, 2017 Share Posted June 21, 2017 +1 for what J D 8 has pointed out.. A wing with a degree of dihedral may be perfectly well behaved with rudder/elevator only but that same dihedral reduces the effect of the ailerons so they have to deflect to a greater degree for a given effect creating more adverse aileron yaw which can promote a 'tip stall' spiral dive.. Reduce the dihedral the aileron effectiveness increases so less deflection is required. This in turn may allow differential aileron movement to be used which further reduces any tendency to "spiral in" . Unless your glider is particularly heavy and fast flying I doubt you really need the power of 9g servos for each aileron.. Quote Link to comment Share on other sites More sharing options...
Keith Sharples Posted June 21, 2017 Author Share Posted June 21, 2017 Interesting point on the dihedral. The glider wing has a dihedral of 3inch each end. My high wing Cessna with ailerons has 2 inch each end. so is the 3inch an inch to far?? I know some of the old 2 channel designs have a huge dihedral in comparison. Advice please Quote Link to comment Share on other sites More sharing options...
Dave Bran Posted June 21, 2017 Share Posted June 21, 2017 Hi Keith, Can only comment from 45 years within RC flight. While I don't doubt some have experienced terminal adverse yaw, I never actually have! Yes, I have had a number of RET planes I have converted to AERT. (or RE to AER), leaving their dihedral. Are you happy flying rudder on the other stick from elevator? If so just go ahead and I'm sure you will find aileron settings that work with the dihedral you have IF you cannot or do not want to reduce it. 6" IS quite a lot!! Along the way if Aileron does not do immediately what you desire then RE or RET flight will not hazard the plane. One likely to be prone plane, once tested, ended up with upgoing Aileron only, no down at all, but ailerons once explored and tested worked and it flew smoothly. A couple have benefited from linked (mixed) aileron/rudder. It hangs though on being happy able to fly rudder and elevator across two sticks while developing a solution, but a solution is in my experience findable. Quote Link to comment Share on other sites More sharing options...
Dave Bran Posted June 21, 2017 Share Posted June 21, 2017 Posted by Peter Miller on 20/06/2017 21:12:57: Personally I do not like snakes, if the bend is a bit tight they can bind and make extra work for the servo and also play havoc with centrering the ailerons. Snakes, YUK!!!! Seconded. Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted June 21, 2017 Share Posted June 21, 2017 Large amounts of dihedral have a self levelling affect on the wing And personally, have modified a few models and halved the dihedral Quote Link to comment Share on other sites More sharing options...
John Stainforth Posted June 21, 2017 Share Posted June 21, 2017 Threading servo wires and extension leads through wings is not difficult as long as the lightening holes in the ribs are somewhat larger than the connectors. All you have to do is drop a heavy nut on a cotton thread through the holes from either direction. It's just a matter of holding the wing vertical and jiggling a bit. The thread then has to be tied around the lead connector in such a way that the connector is not sticking out sideways, and then gently pulling the connector and lead through the ribs. I find this usually goes surprisingly easily. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted June 21, 2017 Share Posted June 21, 2017 Posted by Simon Chaddock on 21/06/2017 00:12:17: Unless your glider is particularly heavy and fast flying I doubt you really need the power of 9g servos for each aileron.. To me, 9g servos would be the minimum I'd use! Whether or not typical 5g servos are up to the job, 9g ones will be a bit more durable than miniature ones. My experience with even 9g servos is that they are very prone to servo gear stripping if the control surface gets a knock e.g. putting it into the car. I needed to fit metal geared ones to a very small 3D Extra due to repeated damage although this did have rather large control surfaces. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted June 21, 2017 Share Posted June 21, 2017 Feeding servo connectors through the wings? I much prefer to do without intermediate connectors altogether and simply 'extend' the servo's wire as required and only fix the connector on the end (I solder the wire into that as well) after it has been threaded through the wing. Fiddly but a good soldered joint is more secure and has lower resistance than a connector with 'crimped on' wires. As for replacing the servo I just make sure there is sufficient 'spare' wire in the wing to allow the soldered joint to be exposed so the wire from the new servo can be soldered on. Just an aside but my 'light' 1.8 m powered gliders manage quite happily with just 3.7 g aileron servos but i so make sure the hinges are really free moving. Quote Link to comment Share on other sites More sharing options...
Steven S Posted June 21, 2017 Share Posted June 21, 2017 I had to run servo wires down my Wiggo wing and did it by pushing some yarn into the wing root and the using a vacuum cleaner to suck it out of the servo hole, then tied the servo wire on and pulled it back out. Quote Link to comment Share on other sites More sharing options...
Martin McIntosh Posted June 21, 2017 Share Posted June 21, 2017 Depends on what you mean by 9g servos. Some of these have very delicate gears and will strip them. I would go for HS82MG or even 125MG or similar which are made to fit glider wings. If you go with the existing dihedral then you will probably need the ailerons to go up only. Surely no one uses a central servo anymore, especially on a glider. You need to be able to program the movement each way on both. Quote Link to comment Share on other sites More sharing options...
Robert Armstrong 2 Posted June 22, 2017 Share Posted June 22, 2017 Posted by John Stainforth on 21/06/2017 16:18:54: The thread then has to be tied around the lead connector in such a way that the connector is not sticking out sideways, and then gently pulling the connector and lead through the ribs. I find this usually goes surprisingly easily. Tie round the wire then sticky tape the thread to the servo plug face works for me. Servo lead locks or heatshrink wrap if there is an extension join inside the wing. Quote Link to comment Share on other sites More sharing options...
PatMc Posted June 23, 2017 Share Posted June 23, 2017 Posted by Keith Sharples on 21/06/2017 08:00:51: Interesting point on the dihedral. The glider wing has a dihedral of 3inch each end. My high wing Cessna with ailerons has 2 inch each end. so is the 3inch an inch to far?? I know some of the old 2 channel designs have a huge dihedral in comparison. Advice please Back in the '80's I built and flew a 100" John Hall Diamond glider that was designed to meet the 100s comp rules of RE only. After I lost interest in entering comps I retro-fitted it with ailerons without any alteration to the dihedral. I've not flown it from a tow or bungee launch for years now but still fly it as a light - moderate wind sloper. The dihedral is 6º giving 5" each wing. The model weighs 5lb (2.25kg), is moderately aerobatic in a stately sort of way and doesn't display any tip stall or other nasty characteristics though the dihedral does make any inverted flight "challenging". The ailerons have about 2:3 differential ratio to avoid adverse yaw. The ailerons are also used as spoilerons with as much up travel as possible, in this condition there's only "down" movement one side when turning so 50% rudder is coupling is used in the landing phase. The rudder coupling is also used at altitude when it's difficult to judge rudder input for co-ordinated turning. Here's a couple of videos taken a few years ago from the model : Quote Link to comment Share on other sites More sharing options...
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