Steve Houghton 1 Posted June 2, 2014 Share Posted June 2, 2014 I've recently purchased a 2nd hand thermal glider with a 2.66m wing span which has both aileron and flaps and I have coupled the flaps to the ailerons so giving me full span ailerons as well as crow braking, launch and speed settings. I maidened this on Saturday and the plane had a tendency to want to turn to the left all the time and really struggles to want to turn to the right. No amount of tweaking the trims improved the situation, even on rudder. All of the wing control servo's are centred and have the same amount of movement both up and down. I have set aileron differential and tried increasing the amount of down movement in case it wasn't enough. I've looked at the wing and can see no sign of warp. The wing servo's do need replacing as they are somewhat juddery and don't always return back to centre. Even so, I can't see that this would stop the plane from turning to the right. Has anyone experienced this before or have any thoughts as to why this should be? Steve A470Soaring.blogspot.co.uk Quote Link to comment Share on other sites More sharing options...
Ben B Posted June 2, 2014 Share Posted June 2, 2014 One wing heavier than the other? What's the lateral balance like? Quote Link to comment Share on other sites More sharing options...
Lindsay Todd Posted June 2, 2014 Share Posted June 2, 2014 Hi Steve, you say you have increased the amount of down aileron, if you are suffering some adverse yaw, and I belive this to be quite common with gliders then this will only make things worse, go for more up aileron rather than down. I would also check the wing weights by doing a lateral balance check even a crude balance might show something up. Replace the wing servo's or give them a service - no point in risking a model with know dodgy gear. Linds Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted June 2, 2014 Share Posted June 2, 2014 I agree with Lynds - if its not a typo then you are applying the differential in the wrong direction! The down movement should be decreased - not increased. Having said that it doesn't sound like an adverse yaw problem as you are having much more difficulty turning one way only, which might be the case for a powered model but I can't particularly see a reason why a glider with straigh wings should exhibit strong adverse yaw in one direction only. BEBEdited By Biggles' Elder Brother - Moderator on 02/06/2014 09:09:38 Quote Link to comment Share on other sites More sharing options...
Steve Houghton 1 Posted June 2, 2014 Author Share Posted June 2, 2014 A lateral test is probably a good idea . On aileron I had no idea what movement there should be so I set movement to about 14mm up and down to about 5mm. When I adjusted, I increased the down movement to about 7mm but there was no difference. Even with full right aileron trim applied, and some right rudder trim, there was no difference. I had to give it full right stick to turn, and then it was really sluggish whereas left is great and as it should be. Maybe I could try disabling the aileron to flap coupling also and see if that makes a difference? Quote Link to comment Share on other sites More sharing options...
Gary Binnie Posted June 2, 2014 Share Posted June 2, 2014 Are the wings two separate halves? I had this problem when I accidentally left the incidence pin out of a 100" glider, each wing was at a different angle of incidence making it roll! It could just be that one wing is heavier than the other, gliders are quite sensitive to this. A few of mine have lead taped under the tip of the light wing, sit the model on a table and let it rock on the fuselage. Cheers Gary Quote Link to comment Share on other sites More sharing options...
Steve Houghton 1 Posted June 2, 2014 Author Share Posted June 2, 2014 Yes Gary, the wing is in two halves, with a steel joiner going through the fuz and two locating pins at the leading and trailing edges. The fuz is moulded and wings built up, but with a rounded fuz, surely one wing or the other is going to tip, but I guess that I need to rock it and see if it keeps going to one particular side, then try adding weight on the light side. Quote Link to comment Share on other sites More sharing options...
Rich too Posted June 2, 2014 Share Posted June 2, 2014 weigh each wing panel individually? Rich Quote Link to comment Share on other sites More sharing options...
Gary Binnie Posted June 2, 2014 Share Posted June 2, 2014 Should not be a problem with incidence then. What glider is it, sounds like my cup of tea?! One wing will always fall, it's whether it is random or always to one side as you say. You could weigh the wing panels individually on a kitchen scale, they should be within 20 or 30 grammes of each other, if not there could be a hidden repair. If it does need weight on one side you can hide it in the aileron servo box if it has one, the weight on my non-aileron gliders is just sellotaped under the tip. Quote Link to comment Share on other sites More sharing options...
Steve Houghton 1 Posted June 2, 2014 Author Share Posted June 2, 2014 Well, the guy I bought it from called it the Elegance, but I could find no reference to this with a Google search but I did find the RCM Pelikan Elegent, which looked identical. However, this model came with ailerons and flaps fitted but the guy I purchased from told me it had originally been a rudder & elevator model only and the ailerons and flaps were fitted later. This is mine. Quote Link to comment Share on other sites More sharing options...
Ben B Posted June 2, 2014 Share Posted June 2, 2014 Is there any way the steel joiner could be going further into one wing than the other? No point ensuring the wings weigh the same only to find out the wing joiner is mucking things up. Also remember that the weight distribution of the wing is also important- if one wing tip was massively heavier whereas the other root was heavy they might weigh the same but the plane will fly with a distinct deviation... Quote Link to comment Share on other sites More sharing options...
Steve Houghton 1 Posted June 2, 2014 Author Share Posted June 2, 2014 Well if one wing tip was heavier than another, or the root, there's no way I can tell because I can only weigh the entire wing. I haven't measured each side of the joiner once it is in position, but visually they look the same. It is something I can check however. Quote Link to comment Share on other sites More sharing options...
Rich too Posted June 2, 2014 Share Posted June 2, 2014 it doesn't have to be scientific - judging by the symptoms, I think the weight differential would be pretty obvious? Rich Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted June 2, 2014 Share Posted June 2, 2014 hello Steve......you get one end of the fuz and support the beak and someone at the tail end doing the same----see which side the model leans......un scientific but it will give you a rough idea......if it falls towards the side you say is causing you the prob-put a tiny bit of lead on the opposite side-I would also give the servo's a going over in case they aren't going back to neutral straight away/ish.... ken Anderson...ne...1........beak/tail dept. Quote Link to comment Share on other sites More sharing options...
reg shaw Posted June 2, 2014 Share Posted June 2, 2014 If there are no warps and the fin is on straight, then lateral balance is most likely the cause. Weigh each wing, but also balance each wing on a rolling pin to see if they rock at the same rib position. Ian. Quote Link to comment Share on other sites More sharing options...
Steve Houghton 1 Posted June 2, 2014 Author Share Posted June 2, 2014 Ok guys, lateral balance seems to be general opinion so I will take a look at that this evening. Steve A470soaring.blogspot.co.uk Quote Link to comment Share on other sites More sharing options...
Gary Binnie Posted June 2, 2014 Share Posted June 2, 2014 Very nice Steve. Unlikely but I suppose it could have different weight servos side-to side, I've got one like that!! Hope you get it sorted. Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted June 2, 2014 Share Posted June 2, 2014 How has the model been stored.....could one wing be warped slightly? Quote Link to comment Share on other sites More sharing options...
Steve Houghton 1 Posted June 2, 2014 Author Share Posted June 2, 2014 Well I am going to change the servo's as soon as I can Gary. I have just weighed each wing and there is just 4 grams difference between them. I've assembled the model and checked the lateral balance and the right wing definitely goes down, which is the opposite of what I expected as the plane wants to go left all the time. So I added weight over the left aileron position as the servo hatch is probably the best place for me to place extra weight, and it takes 20 grams to balance. Opinions welcome please before I go fitting the weight. Quote Link to comment Share on other sites More sharing options...
Steve Houghton 1 Posted June 2, 2014 Author Share Posted June 2, 2014 I have no idea how the model has been stored Steve. When I place each wing on a flat surface there is no sign of any warping. Quote Link to comment Share on other sites More sharing options...
Steve Houghton 1 Posted June 2, 2014 Author Share Posted June 2, 2014 Well there isn't enough room under the servo cover to fit 20 grams of weight, so it's looking like I'm going to have to remove a little film from the very end of the wing tip and then recover. Not ideal, but I can't see that there is an alternative other than surgery. Quote Link to comment Share on other sites More sharing options...
Gary Binnie Posted June 3, 2014 Share Posted June 3, 2014 Very bizarre?!!! Don't cut the covering, just tape thin lead sheet to the lower surface, I have two like this. Can't understand why it is always falling on one side if the wings weigh the same, it doesn't look like it's been repaired at all. One glider I built (so I know it hasn't been repaired) fell to one side and needed weight when it was finished, the only thing I could put it down to was using different grades of balsa for the 'D' box sheeting. Not something I've tried but you could hang it upside down from the towhook and see if it still does the same. That kind of weight difference (4 g) between wings is typical for a modern moulded glider and would need no aileron trim at all. Did someone suggest checking the rudder neutral already? Are you anywhere near me (Brackley, Northants)? GB (glider trimming dept!) Edited By Gary Binnie on 03/06/2014 00:33:40 Quote Link to comment Share on other sites More sharing options...
Gary Binnie Posted June 3, 2014 Share Posted June 3, 2014 Just a completely random thought but when I first read the thread title (unresponsive controls) I thought it may be being flown at too low an airspeed (one of the symptoms demonstrated to student full-size glider pilots of the approaching stall). Is it a problem that gets worse or better with speed? GB Quote Link to comment Share on other sites More sharing options...
Rich too Posted June 3, 2014 Share Posted June 3, 2014 I wouldn't worry about 4g, I would check the controls - change the old servos and make sure there is no slop in the controls. What does it use, snakes? Rich Quote Link to comment Share on other sites More sharing options...
Steve Houghton 1 Posted June 3, 2014 Author Share Posted June 3, 2014 Gary I managed to make a small incision at the very tip of the wing and slide in a sticky backed tyre weight of 10 grams and then put a solartrim patch over the incision and now it seems to balance perfectly. I did look more closely at the wings and the last 8" or so at the tips, (the last part of the polyhedral) the trailing edge does seem to warp upwards somewhat, but then it seems to be the same on both sides. Now, when I centred the ailerons I used that part of the TE to line up the ailerons. I think that was my mistake and I should have lined it up with the flaps and the underside of the wing using a straight edge as the aileron was definitely up when compared to the right one. So I have adjusted that and now need some reasonable flying weather at the weekend to test it. I had to smile at your remark about the plane flying at too low an airspeed as I had launched the plane over a slope in very light conditions and as I couldn't turn to the right, I was somewhat quietly bricking myself, so I really didn't want it to pick up any more speed, and hence I couldn't test speed flap or crow. The wing servo's are Npower and don't seem very good, so I think I will change them for Hitecs at the earliest opportunity. I also adjusted the flap linkage to give me as much down as possible for crow landings whilst I was at it. No, I'm nowhere near Northants, I'm in that slope soaring heaven called South Wales. Steve Quote Link to comment Share on other sites More sharing options...
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