sharpy1071 Posted January 30, 2012 Share Posted January 30, 2012 Hi there I need some advice, please. I am about to start on a Practical Scale Jodel Regent by Roy Scott. The full size uses an all flying tailplane, the model uses a conventional tailplane and elevator. In the instructions, which are very sparse, it says in their experience all flying tailplanes should be avoided, bearing in mind this was written in the early seventies when radio was not as sophisticated as it is now what do the readers of this forum think? I have a Arriba motor glider by Multiplex with an all flying tail and never have experienced any problems. All flying tailplanes over comes any problems with angles of attack between the mainplane and tailplane so I am thinking of going down this route. Thank you for your responses in advance. Quote Link to comment Share on other sites More sharing options...
Erfolg Posted January 30, 2012 Share Posted January 30, 2012 I find it hard to think why an all flying tailpane should not be used, that is on the grounds of aerodynamics. The only issue is building a system with no lost movement (slop), ensuring that it is pivoted so that it is aerodynamically stable and that the servo cannot be overloaded. Many gliders use all flying tailplanes, some of which are required to achieve speeds over 100mph. I have seen many IC fast jet types in addition. Pretty common items, more you think about it, the more examples come to mind. Quote Link to comment Share on other sites More sharing options...
sharpy1071 Posted January 31, 2012 Author Share Posted January 31, 2012 Thank you Erfolg for your input, yes from my experience with the Arriba it has to be tight and slop free, the next thing to find out is where to put the fulcrum point to save loading the servo to much. thanks again Sharpy Quote Link to comment Share on other sites More sharing options...
PatMc Posted January 31, 2012 Share Posted January 31, 2012 Assuming a symmetrical section is used, if the pivot is 25% chord from LE there will be no servo load except friction. If the pivot is behind this point then it will be overbalanced, unstable & liable to flutter. Forward of 25% will be stable but the load will increase. Quote Link to comment Share on other sites More sharing options...
Erfolg Posted January 31, 2012 Share Posted January 31, 2012 George Stringwell in his book Thermal Soarers recommended no more than 20%, so Patmacs 25% is a good pointer. The only other bit of design philosophy i would adopt is to pull on the servo, to provide up elevator. The other way round, I have seen control issues at high speeds where push rods or the bell crank can bend, with less than satisfying effects. Quote Link to comment Share on other sites More sharing options...
sharpy1071 Posted January 31, 2012 Author Share Posted January 31, 2012 Thanks to both off the above for your help, I did think of pull-pull for operation of the actuating arm, any thoughts on stress on servo in this mode? thanks sharpy Quote Link to comment Share on other sites More sharing options...
Erfolg Posted January 31, 2012 Share Posted January 31, 2012 If pull-pull is closed loop, then, it needs to be well designed. I have fastened each wire to the servo arm,with the same spacing as on the AFT, then tightened to remove all slack, unless the servo has a proper ball race on the output shaft, there will be wear. If left with little tension, it will be prone to flutter. It is the same with a worn output shaft. The well engineered solution is to have a arm centrally pivoted near the servo, with the same centres as the arm on the control service. These can then can have good tension on the fishing trace. The arm is driven by a short push rod from the servo. You will probably never reach the speed of a pushed glider with a scale model, yet flutter can be catastrophic, in either case. Quote Link to comment Share on other sites More sharing options...
sharpy1071 Posted January 31, 2012 Author Share Posted January 31, 2012 Ah! this forum never fails to come up with an answer, although i have used this system before i didn't think of it this time thank you for jogging my memory, I still have a Flair tension wheel where the wire goes twice around a circle with a spring loaded tensioner, i guess i will use this device,. thank you Quote Link to comment Share on other sites More sharing options...
PatMc Posted January 31, 2012 Share Posted January 31, 2012 The only issue with pull-pull is that the tension of the wires put stress on the servo, the clevises & control surface pivot (or hinges) at all times, even when not in use. That said I've used it for years in a lot of models without much problem in practice.Edited By PatMc on 31/01/2012 20:37:07 Quote Link to comment Share on other sites More sharing options...
RedBaron Posted March 24, 2012 Share Posted March 24, 2012 You might want to look at and photograph the tailplane details on a real Regent near you. Search the CAA database GINFO {google GINFO to find it} using the search term "Regent" or "DR400" in the "aircraft type" box and you should find many variants on the UK register and their location. Most owners are very helpful to researchers and modellers. A number of Regents are kitted out as glider tugs Also the database will allow you to access photos of many of the registered aircraft and gliders giving a wealth of ideas for the final finish. I do know that one of the real Regent owners has built the PS kit - unflown yet Best wishes der.baron Quote Link to comment Share on other sites More sharing options...
sharpy1071 Posted March 26, 2012 Author Share Posted March 26, 2012 Hi there Der Baron thank , thanks again Brianyou for that, I will go on the site and try to find a 'pretty one' close to home, I live and fly (models) near Bournemouth airport but have never seen a Regent like the ps kit, so hopefully I will be able to get to one in the flesh as to speak, thanks again Brian Quote Link to comment Share on other sites More sharing options...
Former Member Posted April 1, 2012 Share Posted April 1, 2012 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
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