aquila Posted June 18, 2015 Share Posted June 18, 2015 Hi, Just maidened above model which went into a dive and would not pull out. Seems pushrod outers are not secured at all, has anyone else experienced this? Peter Quote Link to comment Share on other sites More sharing options...
simon barr Posted June 18, 2015 Share Posted June 18, 2015 I found the long lengths of unsupported push rod where they exit the fuselage were too flexible for my liking, so I cut down some old servo arms to make push rod guides and glued them into the side of the fuse after first removing the clevises and sliding them over the push rods. Positioned about half way between the push rod exit and the control horn supports them perfectly. Also, make sure the c of g is correct... It should be a lot further forward that indicated in the instructions. Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted June 18, 2015 Share Posted June 18, 2015 Mine has been fine over the last 12 months or so, but I did move the c of g forward as the quoted c of g is too rearward, which can make it hard to pull out of a dive. Quote Link to comment Share on other sites More sharing options...
aquila Posted June 20, 2015 Author Share Posted June 20, 2015 Thanks for that but I'm quite new to rc gliding and don't understand how the c of g could make it difficult to pull out of a dive with full up. Can you tell me how far forward please and what elevator throws you were all using as I'm contemplating a rebuild. One thing I noticed during the flight was how much the wings flexed at times during the flight even when in level flight, the wind was 8-19 gusting to 13mph on the hill. I have also now realised the outers are fixed inside the fuselage. Quote Link to comment Share on other sites More sharing options...
simon barr Posted June 20, 2015 Share Posted June 20, 2015 Hello Peter. A reward c of g will make any aircraft unstable, and pretty much impossible to fly if it is too far back. When you say you had full up to pull out of the dive, then you had probably stalled the model, and unless you release the elevator to un-stall the model, it will never pull out. The stated c of g for the K8 is 75mm.... I think mine has ended up around 65mm (back from the leading edge at the wing route). Start at around 60mm and go from there. My elevator throw is as it comes out of the box... Not sure what it is to be honest., but with the c of g further forward, it won't be as violent as you have probably experienced. Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted June 20, 2015 Share Posted June 20, 2015 The wings do flex a lot and even with the c of g set forward the Ka8 can be unstable in pitch, we aerotow ours and if you go to fast they start to porpoise along (you can see that in the video here https://www.youtube.com/watch?v=-LiwHMkGYn4) It's a standard test for slope soarers to do a 45 deg dive test, they should just pull out as the speed increases, if the dive steepens then the c of g is too far back (but you'd need to consult the aerodynamic text books to understand why) which means you need more elevator force to right the aircraft, note I'm talking about the turning moment the elevator applies when the control surface is deflected not the force applied by the servo to move the control surface. It may also be that as speed increases the main wings could twist making the restoring force even greater. Quote Link to comment Share on other sites More sharing options...
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