Roger 2 Posted July 16, 2009 Share Posted July 16, 2009 About 3 years ago after a major heart op I bought the above kit. (I am an average pilot, I started in the 70's and fly a couple of days a week with my club.) I have always liked the actual real RF4 and having seen the adverts for the model expected a relaxing Sunday type powered glider. The plane turned out to "hate" flying slow and if you looked at it side ways it would tip stall. Lots of adjustments were made from members suggestions but it remained a very wary plane to fly. On the first flight a stall was recovered at grass height In the end it ended up decorating the garage. You are having to make flat turns so as to not dig the wings in, and the club field is not the longest when making a reasonably fast approach. I have now decided to have another go; I have spent time on the net and have read that many people have experienced exactly the same thing. I have read it described as a pylon racer in disguise and other less complimentary things. Here at last is the question. I have always thought that with differential ailerons, the surface goes up more than down; so at low speed the downward surface does not create too much drag. On the plans the ailerons have +5mm and -12mm movement.Does this seem ok to you all? Have any of you experts out there any ideas or suggestions to tame the beast????? Thanking you all in advance. Roger Quote Link to comment Share on other sites More sharing options...
Former Member Posted July 16, 2009 Share Posted July 16, 2009 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Roger 2 Posted July 16, 2009 Author Share Posted July 16, 2009 Hello Eric Thanks for the reply. No ! This is the odd thing, in the plans was a sheet with drawings of the ailerons, elevator and rudder throws. I have it in front of me now, the up movement is shown as 5mm and the down as 12mm. There is no mistake, that was and is still a worry. The wings have as you say a high aspect ratio and appear fairly symmetrical. The last outboard 180mm have a moulded "slat" , which is the nearest thing you will get to washout ( I suspect) on a plastic/ foam wing. The rest of the leading edge is I would say round. The only thing heart- stopping Eric is the stall....... one funny story to this is..... When I built it, I was post op and going to the gym 3 times a week. Whilst at the gym doing exercise, I had to wear a monitor to check the max heart rate (like a wrist watch and a plastic belt around your chest. I was limited at that time to 130 BPM. One comedian at the club suggested wearing the monitor whilst flying the Fournier, I did ...... and recorded 145 BPM coming in to land. Who says model flying isn't dangerous. Roger Quote Link to comment Share on other sites More sharing options...
Former Member Posted July 17, 2009 Share Posted July 17, 2009 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Stephen Grigg Posted July 17, 2009 Share Posted July 17, 2009 Do you wear a crash helmet pollyprotected Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted July 17, 2009 Share Posted July 17, 2009 Crash helmets are for girls Stephen - and you are now on my hit list too - I read your comments on the wing cutting thread Quote Link to comment Share on other sites More sharing options...
Bert Posted July 17, 2009 Share Posted July 17, 2009 Roger have you tried setting the ailerons so that they are about 2mm up when the stick is at neutral to give some wash-out - this has helped to tame some of mine in the past. I do think the differential given in the instructions may be wrong. Bert Edited By Bert on 17/07/2009 10:42:09 Quote Link to comment Share on other sites More sharing options...
Pete B Posted July 17, 2009 Share Posted July 17, 2009 Roger, There are some comments on RCG about the ARC Fournier being more of a pylon racer than a glider and that it does like to fly fast. I've got the recently updated West Wings kit and, whilst I appreciate it will have its own flying qualities, the aileron throws on the plan are shown as 6mm up/3mm down, so if you aim for 50% less down than up on your model - and Bert's suggestion of 2mm up at neutral - that's a start. Pete Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted July 17, 2009 Share Posted July 17, 2009 Roger If as you say in your post above you have 12mm down & 5mm up then you have negative differential aileron and it does not surprise me at all that it is not particularly nice to fly! It should surely be the other way round, more up than down. Quote Link to comment Share on other sites More sharing options...
Roger 2 Posted July 17, 2009 Author Share Posted July 17, 2009 Hello gentlemen. Well I have gone the middle road , I have set the ailerons 2mm up to give me washout, and set the movement to 12mm up and 6mm down. The movements seem odd but I am not used to the differential settings, I have left in my original setting of 20% rudder /aileron to help with the turns.Is it worth putting the C of G slightly forward to help with the sensitivity??? I have other planes to fly including a 30 yr old biplane that loves to fly, but I hate being defeated. I will now wait for the weather and the scheduled flying days . Cheers Roger Quote Link to comment Share on other sites More sharing options...
Pete B Posted July 17, 2009 Share Posted July 17, 2009 Sounds much more like it, Roger. C of G at recommended is about right -too far forward and you'll be needing to hold in up elevator for straight and level, which can be a bit frightening! Designers often set a conservative C of G anyway and it can be moved backwards from there if you wish. Look forward to a positive report! Pete Quote Link to comment Share on other sites More sharing options...
Roger 2 Posted July 17, 2009 Author Share Posted July 17, 2009 Pete. I also wish for a positive report, so the C of G stays where it is. Talking about elevator settings I have always found that holding down elevator in a circuit is the more difficult especially on a beginners plane when training/proving a model. Anybody know a good pilot with strong knicker elastic ? !!!!!Cheers Roger Quote Link to comment Share on other sites More sharing options...
Roger 2 Posted August 5, 2009 Author Share Posted August 5, 2009 Hello gentlemen; at long last decorating / painting / commitments and crap weather not withstanding the "glider" has taken to the air; in I must admit very strong gusty winds. Two tank fulls later it is still in one piece, just !!! one aborted landing was in the long grass after the wind picked up a wing and it stalled. Put it down to the wind as I am not sure it was the right day to fly. What seems to be happening is that in a turn the down wing is "digging in" and consequently you can be giving full opposite rudder to pick the nose up. Then the turn seems "smoother". All the time you are flying it is like walking on egg shells. It would make a good pylon racer with a bigger engine, if to days performance is anything to go by . As I have said it is not going to decorate the garage so..... interesting times are ahead! Any other suggestions gratefully received !!! .......one from a club member involved using a big hammer. Roger Quote Link to comment Share on other sites More sharing options...
Roger 2 Posted August 5, 2009 Author Share Posted August 5, 2009 Hi gents one thing, I did take out the coupled rudder, to start as it were from scratch . Just to give the correct story. Roger Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted August 7, 2009 Share Posted August 7, 2009 Hi RogerThe RF4 has a "gliders" wing which means that its inertia tends to keep it turning once you get it going. This means significant rudder to initiate a turn but neutral once it starts turning. Your coordinated rudder may have caused the turn to tighten which gives the impression of the inner wing "digging in". With correctly set differential ailerons a gentle turn should need no rudder although a sharp one still does. Probably not of concern but differential ailerons do make a neutral roll rather more difficult. Quote Link to comment Share on other sites More sharing options...
derek critcher 2 Posted November 19, 2010 Share Posted November 19, 2010 Hi all, I live close to RAF Halton and have watched the fornier derived sailplanes cruising over my house, they looked so elegant I decided I must have the model, elegant it may be, but it flies more like a spit than a glider. Has anyone out there tried fitting small upturned wing tips as on some gliders to stop the wicked wing drops. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted November 19, 2010 Share Posted November 19, 2010 derekThe up turned wing tips are to improve the overall aerodynamic efficiency of the wing not to reduce a stall induced wing drop. The RF4 has a relatively big wing span. Flying near the stall whilst turning means the inner wing tip will going slowest so it is very likely to stall first and remember a 45 degree bank pushes the stall speed up by nearly 20%. Quote Link to comment Share on other sites More sharing options...
Stefan Hafner Posted November 19, 2010 Share Posted November 19, 2010 Posted by Roger Darlington 2 on 05/08/2009 00:32:21:What seems to be happening is that in a turn the down wing is "digging in" and consequently you can be giving full opposite rudder to pick the nose up. Then the turn seems "smoother". This is similar to what used to happen when i was flying full size gliders, and we always had to hold in a small amount of opposite aileron to avoid the turn getting tighter. As its a relatively high aspect ratio wing i would always use some coordinated rudder but personally i would just add it by hand rather than with a mixer, as all high aspect ration wings will suffer from adverse yaw in a turn. my 1/4 scale T1 bulldog has the same problem with turns tightening and using rudder and a bit of opposite aileron works great, even if it take a bit to get used to it. An interesting point, is that when we did an analysis of the stability of a full size K21 that we flew we discovered that it was actually unstable in roll, and seems to be a pattern with a few gliders so this might be a conributing factor Quote Link to comment Share on other sites More sharing options...
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