steve-richards Posted July 14, 2013 Share Posted July 14, 2013 Hi guy i have a bit of a dilema I balanced my yak with a saito 125a and 7-8 centermeteres from leading edge and it needed nearly 5lb of lead in the buisness end to get the nose to just tip is this right?. This was done with a empty tank and the cowl off And if it is any sujestion on how to attach it woul be great Steve Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted July 14, 2013 Share Posted July 14, 2013 hello steve...i have read your post correct(5lb)....that seems an awfull large amount to add to the model.....i would have a go at moving everthing forward.....check out this ...... ken anderson ne..1 ..everything forward dept... Quote Link to comment Share on other sites More sharing options...
steve-richards Posted July 14, 2013 Author Share Posted July 14, 2013 Thanks ken yes 5lb at 7.5 centeremetres from leading edge, it says the c of g is wrong in the book does not say clearly where it shoul be Steve Quote Link to comment Share on other sites More sharing options...
NigelH Posted July 14, 2013 Share Posted July 14, 2013 Look here and here for the correct info. Quote Link to comment Share on other sites More sharing options...
steve-richards Posted July 14, 2013 Author Share Posted July 14, 2013 Iv looked up on the horizon reviews and they say about 5.25 in from the leading edge, any views on this Steve Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted July 14, 2013 Share Posted July 14, 2013 Wow - that's quite a difference - 7.5cm is mearly 3 inches, a way away from 5.25 inches! What's the root chord Steve? BEB Quote Link to comment Share on other sites More sharing options...
steve-richards Posted July 14, 2013 Author Share Posted July 14, 2013 root cord? they say the book you get with it is wrong very wrong i have added one and a half pound to get it level at 5.25 Steve Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted July 14, 2013 Share Posted July 14, 2013 I've just checked mine and I marked it between 5 and 6 cm from the front of the canopy aperture ...when I put a string across the wings from the quoted position of 7 to 8 cm from the leading edge AT THE TIPS. Mine is the yellow/blue/red version but I think its airframe is identical to the yellow and black version - span, area AUW etc. identical. When I set the C of G at this position, far from adding noseweight, I had to position the batteries as far back towards the tail as they would go - although I have gone over the top engine-wise with a 180 FS It flies very well at this setting... Edited By Martin Harris on 14/07/2013 19:58:17 Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted July 14, 2013 Share Posted July 14, 2013 Ah, that would explain a lot! They are measuring back at the tips not the root? BEB PS Root chord = width of the wing at the root. Knowing this we can estimate value for the CoG. Accurate enough to know which version is right. But Martin seems to has solved it - probably both are right, it all depends where you measure from! Quote Link to comment Share on other sites More sharing options...
karl grey Posted July 14, 2013 Share Posted July 14, 2013 When i finished building mine i ran all the measurements through a Cof G calculator and it gave the Cof G position at 120mm from leading edge at the root chord. With a moki 135 up front i had to place the battery pack just forward off the pull pull wire guides on a tray i built in. The all up weight came in at 81/2lbs less fuel and inverted flight needs a small amount of down elevator. Flies well at this setting but the stall is something to be aware of. When it goes, it goes, so be cautious on the landing. My last landing was a close call when it suddenly went from straight and level to knife edge about 5 feet from touching down. A colleague in the pilot box with me thought for sure i had lost a wing at least but it made a safe touchdown and came home in one piece Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted July 14, 2013 Share Posted July 14, 2013 WHOOPS! Although the marks are where I said they were, Karl's C of G didn't seem to make sense so I just popped the wings on to check - and my C of G is at 120 mm from the leading edge at the fuselage which is about 20mm forward of my marks. Please disregard my earlier recommendation!!! Thinking back, I remember erring on the forward side due to having the batteries as far back as possible and since then I've added a supplementary firewall to accomodate an anti-vibration engine mount in my quest to get it through our club's noise test. I (almost) agree with Karl's assessment - the only way mine differs is that I haven't found the stall to hold any terrors. The only nasty moment I've had was when attempting a "silly" knife edge approach from a great height when it suddenly flicked over the top into a spin but this was far from its normal stall behaviour in level flight. There is a considerable weight difference with my whopping great lump of engine at the front and dual batteries at the rear - it weighs 10.8 lbs so the wing loading is a fair bit higher... Edited By Martin Harris on 14/07/2013 23:32:43 Quote Link to comment Share on other sites More sharing options...
Lee Smalley Posted July 14, 2013 Share Posted July 14, 2013 it prob should be 7-8 centimeters from leading edge at the wingtip, it should balance just in fron of wing spar if you need 5 lbs of lead then you have it wrong Edited By Lee Smalley on 14/07/2013 23:40:43 Quote Link to comment Share on other sites More sharing options...
Lee Smalley Posted July 14, 2013 Share Posted July 14, 2013 the model has no such nasty stall, she stalls properly mind and if your yanking the elevator at low speed then expect her to snap, thats what she was designed to do!!1 duh!! Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted July 14, 2013 Share Posted July 14, 2013 Might be worth checking the lateral balance, Karl? I don't think there was any reference to a flick entry - just a stall during the landing flare? We've had some fairly brisk wind lately - any chance of turbulence from an upwind obstruction having caused your "moment"? Quote Link to comment Share on other sites More sharing options...
karl grey Posted July 15, 2013 Share Posted July 15, 2013 It may well have been just a bit of turbulence catching it out. The stall test was done in its maiden flight at hieght and it seemed to go with out a mush, it dropped its starboard wing and just headed straight down. Lateral balance was checked before its maiden and needed 10g on the port wing. Still a good flying model though Quote Link to comment Share on other sites More sharing options...
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