Thomas Nilsen Posted September 3 Share Posted September 3 A while back my son acquired a YAK 55m. It's been standing in the corner for 2 years now and it's time to get it in the air. One thing we don't have was any info on CG and recommended control throws. I could of course use maths to a suggested CD, but I'm hoping someone on the forum might have the old manual for this kit available and perhaps take a snapshot of such details. It would be even better if someone who is still flying this model (might be a long shot... 🙂 ) could provide some hands details. Regards, Thomas Quote Link to comment Share on other sites More sharing options...
MattyB Posted September 3 Share Posted September 3 (edited) I would have thought TLAR was plenty accurate enough for a first flight on one of these, barring that just use an onlinecg calculator then refine with std tirimming practices from there https://rcplanes.online/cg_calc.htm Edited September 3 by MattyB Quote Link to comment Share on other sites More sharing options...
Philip Lewis 3 Posted September 3 Share Posted September 3 Just start on the wingtube an adjust to suit from there. Quote Link to comment Share on other sites More sharing options...
Robert Welford Posted September 6 Share Posted September 6 I have an unbuilt Flair Yak 55M kit in the loft with plan and instructions included. If you need further info. I could dig them out. Quote Link to comment Share on other sites More sharing options...
Thomas Nilsen Posted September 7 Author Share Posted September 7 Robert, if you don't mind it would be highly appreciated. I'm not confident in the CG I've found using the usual online calcs, which differs between 105 and 160 mm for LE at root. Phillip, The wingtube is on about 130 mm. It looks a bit to far forward when using the TLAR principle as MattyB suggsted 🙂 Quote Link to comment Share on other sites More sharing options...
Cuban8 Posted September 7 Share Posted September 7 I use the methods shown in Gordon Whitehead's scale bible and have found them to be pretty much bang on. This site gives the methods used in the book https://www.rc-airplanes-simplified.com/scale-model-rc-airplane.html#google_vignette I have a couple of Yaks and there are quite a few in my clubs - they are tollerant of a fairly variable CG to suite pilot taste (up to a point of course) but my feeling is that your model will be fine for its first flights if it balances at about 30% of its root chord measured from the LE. Don't have too much elevator movement (set rates ) and I wouldn't dial in any expo at this point. Too far forward a CG will give you a machine that will fly safely but will be very unresponsive in pitch so you could go to a 25% point or somewhere in between if you prefer. Hope this is of some use. Quote Link to comment Share on other sites More sharing options...
Robert Welford Posted September 7 Share Posted September 7 Thomas, I will seek out the instructions in the next few days - ok? Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted September 8 Share Posted September 8 (edited) If the wing tube appears too far forward then start there . Some CG and control throw given in kit instructions were way off the mark . Old Confucius Ploverb say . Plane wiv forward CG fly badly . Plane wiv rearward cg fly once . Edited September 8 by Engine Doctor Quote Link to comment Share on other sites More sharing options...
Jim Hearnden 1 Posted September 8 Share Posted September 8 What ED says above. But I've designed loads & excluding the really odd ones then 20-25% has always served for the first few flights. As for throws typically around 10-12 Degrees with 50% more on full rates. In the absence of better ideas this is a good starter for 10. Quote Link to comment Share on other sites More sharing options...
Thomas Nilsen Posted September 8 Author Share Posted September 8 On 07/09/2024 at 22:55, Robert Welford said: Thomas, I will seek out the instructions in the next few days - ok? Much appreciated Robert! @Cuban8 - The method you described is the same that's used for this online calc: http://rc-plans.com/articles/cg-calc.html Using this I get a CG at 116 mm for 25% MAC, which is about 10 mm in front of the wing tube. At 30% I get 130 mm. The weight needed to get this balanced at 20%-25% is a worry. I'm up to about 800 grams now and that's just about balancing at 30%. The model currently comes in at 6.8 kg before fuel. When using this calc https://rcplanes.online/cg_calc.htm which takes the tail into considerations, the CG varies from 106 mm (5% static margin) and 142 (15%). I'd like the latter one to be the needed spot but it's probably unlikely to be the case. Looking forward to find out what the Flair manual actually says. Thanks, Thomas Quote Link to comment Share on other sites More sharing options...
Thomas Nilsen Posted September 9 Author Share Posted September 9 @Robert Welford You can skip your dig in the attic. One of my fellow Norwegian fliers sent me this picture from the manual today. The CG indicated here is just on the backside of the wing beam, at around the 130 mm mark. So I'm good to go for now with the current weights. Will post some updates once the model has flown. Regards, Thomas 1 Quote Link to comment Share on other sites More sharing options...
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