rcguy2012

I need suggestions on a balancing problem, on my second flight i noticed that when the front landing gear touched down the plane wants to nose over, even when up elevator is given.. I moved the battery pack back over the center CG and was wondering if moving the gas tank back about a 1/4 of an inch would help, Has anyone else had this problem with the Mustang, Hoping to get some answers.

Dash7ATP

You must be flying from grass. A lot of taildraggers have that problem if the grass is a little high. The most important consideration is how it flies. If you get the CG back too far, the plane could become uncontrolable.  Then it won't matter how it lands.

Dash

rcguy2012

well it flew straight and true, and yes you are right we are flying off a grass field, it could be that it needs to be cut, but the plane does seem to be alittlenose heavy.. I will give it another try on the next sunny day.. Fingers crossed.. lol...

spaceworm

Do you have retracts? If not, shim the rear of landing gear plate so that the wheels are more forward. Placing the axles right below the leading edge of the wing when the plane is level has worked well for me. Good luck.

oldtyme

I'm not flying a P51 but I am flying a H9 P47 off a paved runway and I still have to do some elevator management and so does another fellow with a P51. Even on takeoff, the tail wants to fly before the wing is ready so I have to give a slight up-elevator to keep it on the ground until it reaches flying speed. On landing, try a little up-elevator when you land and that will probably solve your problem. A little up-elevator in taxiing is also helpful with these warbirds.

oldtimer4759

I have had several different P-51's over quite a few years, a Model Tech, the H9 Blue nose and now an ESM 51, moving the CofG back can be fatal, the CofG is for flying, not ground handling, I had to tilt the Undercarriage forward as "spaceworm" has said above on all my 51's to improve the ground handling, moving the fuel tank back to the CofG, or as close to it is a good idea as well, I had a small 2oz tank right up front in my H9 51 then another tank almost on the CofG, it was a fair bit of fiddling to get it all to fit, but, the combination of tilting the gear forward and the tank worked, even on grass,
if it flies OK, moving the CofG back to improve ground handling could be fatal. CofG and elevator throws are VERY IMPORTANT on War Birds.

Oldtimer.

da Rock

Funny how things happen, but I spent the morning measuring my H9 Spitfire because it has the same nose over problem. The last time out was the straw that broke the camel's back.

Models the size of the H9 warbirds (60 size) can be safely flown with the CG anywhere in a range that's about 1.5" wide. All you've got to do to stay safe is to know where the CG is in that range and adjust your elevator throw to match. With tricycle gear it's not usually a big deal. With conventional gear, and especially with scale models, it is often very important to how the plane handles on the ground.

It's easy to measure a 60 size model and know for sure what the CG range is.

http://www.geistware.com/rcmodeling/cg_super_calc.htm

I've got a number of H9 60 size warbirds. P-47, Spitfire, Corsair, and Hellcat. Using the H9 recommended CG location has produced taxi challenged planes every time. Moving the CG aft blindly is not smart, just as oldtimer4759 warns. However, it isn't much risk if you do the job right. Find out what your model's CG range is and pay attention to finding where the CG actually is. None of this 'slightly nose down for extra safety' garbage. And if you're moving the CG aft on a model you've flown and trimmed to respond to the elevator comfortably, then realize the elevator will be more sensitive and reduce the throws as you go.

It's not a death defying trick at all.

bigtim

My Feedback: (13)

is this the blue nose or the "Marie" version of the H-9 P-51

rcguy2012

Thanks for all the excellent information, I will try the suggestions that were given hopefully i can get a handle on this, better yet more practice with up elevator when landing lol...

rcguy2012

Its the Marie .60 Mustang version

jamesc43

My Feedback: (2)

H9 P-51D Marie version
OS 91FX engine
MAS 14X8 prop
Tru turn spinner
On board glow system
Robart air up/air down retract system with large air tank

We fly off a dirt runway. The west border of the runway consists of loose soft dirt. I've taken off a few times and the tail comes off the ground.
I have the recommened control throws on the elevator. On the lower limits, it barely keeps the tail down level enough to prevent a nose over.
I have the same problem with my Marie edition P-51 when landing. As long as I can stay on the main part of the hard dirt runway it seams OK
but when it gets in the soft dirt it wants to nose and has done so many times.

da Rock

I'll be test flying the Spit with the added tail weight in a couple of hours. I worked out how much would move the CG back about an inch after running the numbers to see what CG range was safe. The mfg suggested CG was at the very front of the range.

I've already tuned the elevator throws and flown the plane a fair amount like that. It's never impressed me with it's flying, but I've only ever wanted it to be a pretty warbird with a nice look in the air. So moving the CG to help the ground handling makes sense. My expectations are that it'll have a quicker response to the elevator. Since I've done this same thing with conventional geared planes before, I'm not too worried about the elevator response.

We'll see in a couple of hours. (if the weather cooperates... it's acting like it won't)

rcguy2012

hey Da Rock, looking forward to hearing what the results were and how the Spit landed
I'm flying the P-51 Marie .60 Mustang with mechanical retracts, our cllubs runway is a grass runway, hopefully when it gets cut it will help with the landings..

da Rock

So......... the test went good. Adding the tail weight definitely helped the ground handling. Takeoff, landing and taxiing on the grass on the runway is definitely better. Unfortunately the grass in the taxi ways and pit area is still too deep. Guys were carrying tricycle geared electrics out to the runway because taxiing in that grass ate up too much capacity. So I'm going to shim the retracts to angle forward some more to deal with that grass.

As for the shift in the CG affect on the flying..........

Good results there too. The new CG is aft... very aft. And the Spit flies great. MOF it got a couple of extra flights just because it looks so good beating up the runway.

I expected the pitch sensitivity to increase, for the elevator to get a bit nervous. Didn't happen. It's one of the most positive and accurate models I've ever had. If the rudder wasn't like most are on scale models, coupled to everything and almost worthless as a rudder, it'd be a good aerobatic plane. Moving the CG aft turned out to be a real yawner. And it was already behind the mfg recommendation significantly.

But MAN DOES IT LOOK GOOD doing what it does.