ajflyer

Hi, can anybody help will the location of c of g on this model i.e. distance from leading edge at wing root ?
What c of g distance is recommended in instructions?

opjose

I do not have the 50 size version of that plane.

I have the 50cc size instead.

You are safe with a C.G. all the way up to 30% of the MAC.

I would recommend that you stick with 25% of the MAC.

ajflyer

Thanks opjose for the info.
The "50" size model has a 1400mm wingspan, and for engine sizes 40-46 2 stroke / 52-63 4 stoke.
I hope somebody may still have the instructions / manual for the model, but if not I will use your recommendations as a guide and starting point.
I assume your plane being for 50cc size engines is the later 2000mm wingspan version.

JohnBuckner

My Feedback: (1)

I very strongly endorse what opjose has suggested here. And definitely for that type of airplane if you are new to them then stick with the 25% MAC. Those new folks who often go with 30% MAC tend to find theirselves just a tad in over their head and that really sucks if you are not working with a mentor. Ya sure so what does that mean?

OK MAC just stands for Mean Aerodynamic Chord and that percentage just means a percentage of the distance from the leading edge to the trailing edge, in other words just a method of finding a distance back from the leading edge. Now lets take that 25% we want to target and yes that is what we want to target in many types of airplane especially first flights and newer pilots. If the wing is more or less rectangular i.e. straight parallel leading edges and trailing edges then its a no brainer to divide that distance between the leading edges and the trailing edges by four. Bingo that is the distance back anywhere along that leading edge that you want make your target point to balance the airplane at. That means moving stuff around inside the fuselage or even adding lead to actually make that the point that the airplane will balance level at (not slightly nose down for mother and country).

Ya I know your wing is not rectangular. It has a swept leading edge or it has a forward swept traiing edge and maybe even both. Well then this too can be very simple for our purposes and no you do not have to go on a mad search for a long lost set of instructions, plans or designer. OK I am going to offer any who care to listen a very simple method agine almost as simple as the rectangular wing. Is it exact? no of course not but agine most of what we do is not but it will work and no computer needed and well serve one well in your hobby for all those airplanes you just don.t have the info on.

All we need to do is simply locate a position that is halfway between the fuselage and the wing tip. Hm simple enough now just measure the distance at this half way point between the leading and trailing edges. Heck all we gotta do now is divide this by four and we have that magic number of 25% MAC, all we have to do is find that point out there at this mid way point between the fuselage and wingtip then project it inwards to the fuselage and mark it. Bingo, done that is where we want the airplane to balance at for those critical first flights.

Is this for every configuration of airplane? agine no of course not and examples it will not work with are Canards, Biplanes with one swept and one straight wing, Any form of tailess, Tandem wings and so on.


John