John-Frederick Davie Posted March 4, 2015 Share Posted March 4, 2015 I have acquired a 2nd hand SW2 and would relish some advice concerning a reasonable C of G position. Its fitted with a TT54 4s which provides adequate power for me. I used a (I guess sort of standard) C of G calculator which gives me a range of 81 to 107 mm from the LE. I chose a median position of 94 mm and, as they say gave it a whirl. Bearing in mind I am an inexperienced flyer having only just mastered the 'A' Cert I found it not much fun at all. The gurus took over and a vintage adjustable spanner (!) was attached to the engine mount, this equated to some 8.5 oz added to the pointed end. Its wayward characteristics seemed to have been tamed with this addition. I have just rechecked the C of G with this ballast and found it to be some 50 mm aft of the LE. The question is what is the advised C of G position? I don't want it to be all over the sky - conversely I wouldn't mind it being just a little bit lively! JayDee - Ramsey Mac. Quote Link to comment Share on other sites More sharing options...
AVC Posted March 4, 2015 Share Posted March 4, 2015 Hi JayDee According to the manual (available here), the CoG should be between 75-80 mm back from the leading edge (the manual says measured at the wing tip, but in a plane like this with a straight wing, you could measure it at the root as well). In any case, the rule of thumb is, as you know, around 1/3 of the average wing chord (in your case, simply the chord), so I would suggest that these values given in the manual are on or around your own measures (It's a bit concerning that your measures gave you between 81 and 107 mm). Being a new model, I would recommend to start with the CoG at around 28%, even if that means that the landing will be a bit faster, but you also ensure that the model will be a bit less responsive to elevator inputs. As you get familiar with it, you can move it backwards, but I would never go beyond 30-31%, this is not a 3d plane. In any case, If you define yourself as inexperienced flyer, and considering that it is a new model which you are not familiar with, I would strongly recommend that you seek for help, and ask someone experienced to fly it for the first time, to trim it properly and ensure that the plane is correctly balanced. A final comment, although you may already know; just remember that low wing planes must be balanced upside down.. Good luck, and enjoy it!! Quote Link to comment Share on other sites More sharing options...
John-Frederick Davie Posted March 4, 2015 Author Share Posted March 4, 2015 Alex - many thanks! The 'adjustable spanner' gave a C of G at 50 mm from the LE. I have compromised and ballasted to achieve the 75 mm position. We will give that a go and see how it goes. Thanks again.....................JayDee Quote Link to comment Share on other sites More sharing options...
AVC Posted March 4, 2015 Share Posted March 4, 2015 That's good Jay, just check that the value is around 28-30% of the chord, or in other words, that the chord is around 268-270 mm. Enjoy! Quote Link to comment Share on other sites More sharing options...
john melia 1 Posted March 5, 2015 Share Posted March 5, 2015 i have two sets of spacwalker 2 wings you can have free if you want them , depends on where you live though Quote Link to comment Share on other sites More sharing options...
John-Frederick Davie Posted March 5, 2015 Author Share Posted March 5, 2015 Hi John -thanks for the offer - Im in Huntingdon Cambs.......................... Quote Link to comment Share on other sites More sharing options...
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