Hi Guys, I'm just about finished putting together my Skymaster F-16, I'm still a bit confused with placing the CG on it, guys are flying this Jet with CG from 140 to 175 and all have very successful flights? does this style of jet have a very forgiving cg placement? is it flying styles/prefrences? I know this one has been discussed many times, just looking for some friendly updated suggestions

It has a Wren SS and dry weight has come in at 17.12lbs

That really looks awesome Angus!! Please let me know how the maiden goes.

Pete

the more forward you have the CG the harder it is to slow down, it takes much more stab travel (and you'll run out of stab) and more turbine power to get the AOA up so it'll slow down on landing. I've had just about every F-16 out there and what worked best for me was to get 'in the ball park' with the CG based on the recommendations then adjust it so it's hands off when inverted or up right, then they hold a high AOA easily, slow up nicely, don't use as much stab on landing and aren't pitchy. either way for landing you need all the stab travel you can get. on the skymaster i think i ended up around 150-155mm

Thanks Guys, appreciate the feedback, I'm pretty sure I will be starting at 155 as suggested and work with that.

Angus

Angus,

Be very careful early in the flight, particularly with your c of g at 155. Three pilots here (Perth) found that even at 165, with tanks full at the start of the flight, if you bank steeply and pull on the elevator she would roll further and dive for the ground. More elevator makes it worse. Only solution is to roll out level and then apply elevator. Guys on the east coast in Aus have adopted our c of g (175mm) and have not looked back (and others in Adelaide have done the same with their FEJ F16's). Inverted flight still requires a little down elevator but that is normal. Flare is gentle and predictable but you will not need more than 40-45 mm elevator at that c of g.

Try it at 155 if you like but be prepared for the above. It really wants to tuck into the turn....very alarming and quick when it happens. Roll her inverted and see how much down elevator you need!

Then put an incidence meter on the stabs when you have trimmed it for hands off flight and see how much up trim you are carrying....alarming but indicative of where the c of g should be!

There are four of these flying at my field, all at 175mm measured very accurately, and still carrying around 3 degrees positive on the wing relative to the stab at neutral. 100% confident in my recommendation. I con only assume that there are alot of guys that like hanging on the elevator the whole flight or that they are carrying a heap of up-trim....not good for flight performance.

Good luck with yours!

Regards,

Craig.

I am not sure if the F-16 is very forgiving or what. My old Skymaster F-16 1/8 which I don't have with me anymore had the CG at 140mm and the jet flew spectacular, had none of the bad habits Craig talks about. I never had the chance to test the CG further back since I sold it but I flew a lot this jet and I never had any problems with it. Landings where vere smooth and easy, without using too much elevator. Stalling this jet had no problems as it will not even drop a wing. One of the easiest jets I have flown.
But again I didn't test the CG further back so I do not know how it handles first hand, I can only tell you that at 140mm it worked great.

Check the video:
http://www.jetsrc.com/videos/F-16_Tiger_JetsRC.wmv

Michel

Michel:

Where did your old F-16 have the turbine installed? In the center or in the tail?

Mine had the turbine in the center and had all the bad behavior described by that Craig until due to this behavior it crashed.

I am planning to set the CG of my new F-16 in 175 mm as he reccomends.

According to Craig's experience, it seems that those F-16 with the turbine in the tail, are not affected by the CG set at 135 -145 mm, but those F-16 with the turbine in the center, has the bad tendencies described by him. Sounds crazy but it is my conclusion after reading another thread regarding this issue.

Please confirm where was your turbine installed (in the tail or in the center)

Hi

I am building a SM F16 and don't understand why there is a difference between these 2 kinds of install. After all a CG is a CG, whether you have a turbine mounted in the tail or center mounted. I believe Michel had a Super Bee installed in the tail and I already had a FEJ 1/8 F16 with a P60 in the tail. I used to had a CG of 140 and in the turns it used to pull down and flair was kind of hard, so I took of some lead from the nose until it flew great. I guess I should have end with 150-155mm

I am planning to build mine with a CG of 150mm this time to start with.

Good luck

Nuno

all mine were center mounted and I've never had any of those issues. the only time it would tuck and dive is when way too much stab was pulled in a tight turn (was pulling too many Gs to start with), this was due to stalling from all the drag of the fuselage/wing due to the extreme exposure in the tight turn.

I had a Super Bee on the tail, but we also have another 1/8 with a Falcon on the center, same CG and it fly's perfectly.

Michel