MS Spitfire CG ?

[Sparky45]

So I’ve finished my MS Spitfire and somehow the suggested cg of 2 inches behind the le just doesn’t seem correct. Normally I would expect the cg to be somewhere around 25% of the wing chord which would make it 2 7/8 inches . With a 2200 3S battery pushed all the way forward it does balance ok at 2 7/8 inches so what are other folks using for the cg ?

 

[BadBowtie12]

So I’ve finished my MS Spitfire and somehow the suggested cg of 2 inches behind the le just doesn’t seem correct. Normally I would expect the cg to be somewhere around 25% of the wing chord which would make it 2 7/8 inches . With a 2200 3S battery pushed all the way forward it does balance ok at 2 7/8 inches so what are other folks using for the cg ?

I had to add almost 1.4 lbs of lead to the nose, even with the battery shoved all the way forward, to get the CG to balance out at 2". At 2 7/8, it would have still taken quite a bit of nose weight on my build. I set it at 2" and never tried to move it back so not sure if the flight characteristics would be any different.

 

[Sparky45]

Thanks Bad Bow tie !
I haven’t flown mine yet but based on your answer you’ve had to add 1.4 lbs to the airframe that according to FT should weigh 1.6 lbs !
My interpretation of a forward CG is that it provides a highly stable airframe so maybe that’s the point on this model. I know that the spit can be pitch sensitive on other models I’ve flown.
How did yours fly at 2 inch forward of the LE ?

 

[BadBowtie12]

I had to add almost 1.4 lbs of lead to the nose, even with the battery shoved all the way forward, to get the CG to balance out at 2". At 2 7/8, it would have still taken quite a bit of nose weight on my build. I set it at 2" and never tried to move it back so not sure if the flight characteristics would be any different.

 

[BadBowtie12]

Thanks Bad Bow tie !
I haven’t flown mine yet but based on your answer you’ve had to add 1.4 lbs to the airframe that according to FT should weigh 1.6 lbs !
My interpretation of a forward CG is that it provides a highly stable airframe so maybe that’s the point on this model. I know that the spit can be pitch sensitive on other models I’ve flown.
How did yours fly at 2 inch forward of the LE ?

I have flown it a few times since finishing it up. The way I built it took zero consideration for total weight as there are several coats of Polly on it, lightweight filler, and and then the top color coats. It also has a double full wood spar in the wings as well as carbon rods in the fuselage, rudder and stabilizer. Mine ways in at 4.25lbs including the 3300 Mah battery. So all things considered, it flies well but it has to be flown at higher speeds. The 2” CG seems to be fine. It is stable and flies way better than I ever expected. I hand launch it, requires full throttle, but once it is up to speed, it’s great.

 

[Sparky45]

Thanks !

 

[CrshNBrn]

Those MS planes seem to crave nose weight, don't they? My Spit balances with a 4S 3000 right at the CG.