FW P-51 Old Crow

[deadbug]

Wow...that is a ton of weight!
To be quite honest, I'm not surprised it's balancing properly with the weights removed. My CG is just a bit forward of yours...not significantly. Is your battery identical to my Admiral 4000–and is it all the way forward touching the front of the battery bay? If it is, I would set up yours using my setup exactly and set that 3.78mm down neutral deflection on the elevators.
To put your mind at ease, back in the beginning for me in 2018, I remember looking at the old MRC promo video of Old Crow flown by Pilot Ryan. I looked specifically for his elevator deflection when he taxied in with flaps up—and it looked identically like where mine is now. I think it is just the way this model was designed.
I'd also recommend checking your flap alignments with the fuselage lines also; from what I could tell with your photo, your wing looks like its seated properly.
DB

[Jorgcama]

Thanks Jorgcama!
There are quite a few things that you are doing differently in your Old Crow that will most likely change CG and flying performance compared to my setup--and if CG is different, then using my setup (particularly the zero-flap elevator neutral setting) won't be proper for your airplane. However, if you check your CG with all the sound system components in, battery in position and ready to fly--and the CG somehow comes out to the same place I described on mine (see pics above) then it should work well for a starting point. I guess its possible as you are adding components forward of and aft of the empty/loaded CG (aft speaker and board, front speaker, etc...and will likely be using a different battery weight). I just have no idea how it will come out for you until you actually measure it.
Lol--I didn't like the 2-blade for scale...but it performs so much better than the 4-bladed prop--and heck, when the motor's running, you can't tell the difference anyway. I've tried the 4-blade twice. Once right after I got it new...didn't like it; tried it again about a year and a half later, did one circuit around the pattern with it and had to land it right away because it seemed so anemic compared to the 2-blade. Oh well, I thought I was a purist also--then gave it up.

My setup at the CG (gear retracted) shown in post #177 above, with no sound system and the Admiral 4000mah battery all the way forward is:
1. Neutral TX zero with flaps up is 3.78mm downward deflection measured from the center of the trailing edge of the fuselage elevator fairing mold to the center of the trailing edge of the elevator.
2. AILERON - LOW: 35%; MID: 50%; HIGH: 66% - 30% EXPO on all; ELEVATOR - LOW: 59%; MID: 70%; HIGH:82% - 30% EXPO; RUDDER - 100% ALL RATES EXPO 18%
3. FLAP/ELE MIX: FLAP POS 0=100% (full up) no mix. For takeoff flaps (40%) I have a mix of -12. For landing flaps (10%) I have a mix of -19 with a speed delay of 6.0 seconds.
4. The elevator neutral zero-flap position pic is here: https://www.hobbysquawk.com/forum/rc...061#post218061
5. A couple of takeoff/landing tips for Old Crow: https://www.hobbysquawk.com/forum/rc-airplanes/rc-warbirds/1727-fw-p-51-old-crow?p=218691#post218691

Finally, there is a big dedicated RCGroup forum on the Freewing P-51 both for those that have a sound system, and those that don't. Chances are if you do a thread search for your question, somebody's asked and answered it before: https://www.rcgroups.com/forums/show...-sound-unit%29
Good luck with your maiden--let us know how it goes. If you have any questions before you take it up shoot me a pm and I'll do my best to help you out.
DB

You are right but, for now, I have programmed your same rates, not sure how to program youR recommended flap/elevator mixes (your percentages in parenthesis?), For the figures, are those millimeters down on your elevator?. I was able to prgrs
the Sergi delay 6 seconds to
march your set up there😜
I honestly has still a lot of landings training to do with my sky trainer and the warbird simulator before I dare to take off with my Old Crow by you guys will be the first ones to know right before I finally fly it 😎

[Jet Fixer]

Wow...that is a ton of weight!
To be quite honest, I'm not surprised it's balancing properly with the weights removed. My CG is just a bit forward of yours...not significantly. Is your battery identical to my Admiral 4000–and is it all the way forward touching the front of the battery bay? If it is, I would set up yours using my setup exactly and set that 3.78mm down neutral deflection on the elevators.
To put your mind at ease, back in the beginning for me in 2018, I remember looking at the old MRC promo video of Old Crow flown by Pilot Ryan. I looked specifically for his elevator deflection when he taxied in with flaps up—and it looked identically like where mine is now. I think it is just the way this model was designed.
I'd also recommend checking your flap alignments with the fuselage lines also; from what I could tell with your photo, your wing looks like its seated properly.
DB

Same battery. That's why I'm concerned that it balanced and flew with all that weight in it, and now it balances without it. I'm afraid it's going to stand on its tail again when I get in the air. I am going to set the fixed down deflection, also, I'm thinking of doing an elevator mix to give me max down throws but keep the up throw at the recommended settings. That way if it does do a tail stand I'll have the best chance of catching it. Currently surface deflections are as spec in the manual. I hate starting all over again and not knowing what it will do.

[deadbug]

Same battery. That's why I'm concerned that it balanced and flew with all that weight in it, and now it balances without it. I'm afraid it's going to stand on its tail again when I get in the air. I am going to set the fixed down deflection, also, I'm thinking of doing an elevator mix to give me max down throws but keep the up throw at the recommended settings. That way if it does do a tail stand I'll have the best chance of catching it. Currently surface deflections are as spec in the manual. I hate starting all over again and not knowing what it will do.

I think you'll be pleasantly surprised at what that 3.78mm down elevator neutral setting will do to fix your issue. Remember, that deflection is at the end of the length of the fuse, as far almost as you can get from the CG (long arm on a fulcrum) and a little does a lot to fix it. I would absolutely make sure you do the FLAP/ELE mixes I gave you. You'll need it to rotate and not nose over, and for the airplane to climb after takeoff with a slight amount of back pressure on the stick. I wouldn't overthink things here--you can read posts from folks on this and the RCG forum who had first flights like you describe. Mine climbed like a bat outta hell until I trimmed that elevator down and flight tested various mixes and settings to "dial her in".
DB

[deadbug]

...so I was wondering...where exactly did you have all those weights?
If you added them ALL in the forward section of the battery bay--then yes, you have a big problem, but then it would not have balanced properly with your battery full-forward in the bay. If you placed them approximately where you guessed all the sound system components would have gone (some in the rear speaker compartment and some forward) then I could see how it may have come close to proper balance (just a ton heavier lol), but you would still need that downward bias (mechanical trim) in the elevators I gave you.
DB

[Jet Fixer]

...so I was wondering...where exactly did you have all those weights?

Lower speaker bay on the forward and side bulkheads. Even had some on the forward bulkhead above the battery. It was a mess.....

[deadbug]

Lower speaker bay on the forward and side bulkheads. Even had some on the forward bulkhead above the battery. It was a mess.....

Whoops, I was editing my post when you replied--check again. Did you put any weight in the aft speaker bay or anyplace aft of the wing squares?

[Jet Fixer]

Whoops, I was editing my post when you replied--check again. Did you put any weight in the aft speaker bay or anyplace aft of the wing squares?

nope. Everything as far forward as I could get it.

[deadbug]

nope. Everything as far forward as I could get it.

This may seem like a dumb question--but I cannot see how it could have balanced within the wing square with all that weight AND your battery in place...you did have the battery in place full forward when you balanced with the weights still in?

[Jet Fixer]

This may seem like a dumb question--but I cannot see how it could have balanced within the wing square with all that weight AND your battery in place...you did have the battery in place full forward when you balanced with the weights still in?

Those are my exact concerns also. Cannot explain it. I guess I'll find out when I fly it.

[deadbug]

Those are my exact concerns also. Cannot explain it. I guess I'll find out when I fly it.

LOL you absolutely must've had a sweater or TX lanyard hanging from the tail back then when you checked CG that time and didn't see it... ;-))

Okay--these are the only other things you could check--wings and empennage for proper installation/incidence...if yours checks out identical to these AND you've checked your flaps "up" position alignment with fuse wing filets/form. Then you are good to go. Just program everything as I've given you, if you want to change anything, you could maybe use HIGH elevator rates for takeoff just to ease your mind that you'll have enough...but overcontrolling right at liftoff could be a consideration--obviously your call. Again, with my settings, I use low rates for takeoffs (I've tried MID but prefer low) and LOW RATES for landings. After you re-maiden, adjust to your preference--but at least you'll be safe to fly.

EMPENNAGE: IMPORTANT: Check the circled areas for flush/proper installation so that stab incidence is proper--screws all the way in.


BOTTOM WING: check center leading edge and center trailing edge flush with snug screws.


Just a look at the other side--mid to check flush installation.

[Jet Fixer]

I'll be giving everything the twice over before it leaves the hangar......

[Jet Fixer]

The only other thought I have is that the tail section is the only original fuselage part still flying. The main fuselage and wings have been replaced due to crashes in the past. There may be something not right with it. It isn't obvious right now though.

[deadbug]

You are right but, for now, I have programmed your same rates, not sure how to program youR recommended flap/elevator mixes (your percentages in parenthesis?), For the figures, are those millimeters down on your elevator?. I was able to prgrs
the Sergi delay 6 seconds to
march your set up there😜
I honestly has still a lot of landings training to do with my sky trainer and the warbird simulator before I dare to take off with my Old Crow by you guys will be the first ones to know right before I finally fly it 😎

PM Sent...

[Jet Fixer]

I think you'll be pleasantly surprised at what that 3.78mm down elevator neutral setting will do to fix your issue. Remember, that deflection is at the end of the length of the fuse, as far almost as you can get from the CG (long arm on a fulcrum) and a little does a lot to fix it. I would absolutely make sure you do the FLAP/ELE mixes I gave you. You'll need it to rotate and not nose over, and for the airplane to climb after takeoff with a slight amount of back pressure on the stick. I wouldn't overthink things here--you can read posts from folks on this and the RCG forum who had first flights like you describe. Mine climbed like a bat outta hell until I trimmed that elevator down and flight tested various mixes and settings to "dial her in".
DB

So, I got it out to fly today. For the most part everything was good, except your flap setup. I set my flaps to the same mix as yours and the plane had a major float up. It was hard to keep it heading down for landing. I moved them back to the manufacturer settings and it flew much better. Trim was good. Aileron authority is very low at the manufacturer settings. I think I'm going to pump them up a bit.

These are my current settings. I'm going to increase the aileron throws though.
Flap mix:
Up - 100% flap, 0% Elevator
Half - 54% flap, -7% Elevator
Full - 35% flap, -11% Elevator

Aileron: 36% low, 61% High
Elevator: -40% Low, -60% High
Rudder: -100% Low and High

With all that weight out of the nose the performance is much better, as expected. The other issue I had was the landing gear only went up about half way again. I took the doors off for the second flight and everything worked normally. This gear is giving me fits.

Happy to say the balance and trim is almost perfect. Thanks for the assist.

[deadbug]

Congratulations on the successful flight!! I knew it would work for you.
I'm sure the difference in trimmed flight with flap extension for you (assuming you used my set positions and mixes) was due to a slight CG difference. Also, the more the flaps are extended on this plane, the more UP elevator is needed to be input (or mixed in); and of course the inverse is true. Also, the speed at which you extend the flaps (or fly with them extended) makes a difference as well. With the positions and mixes I have programmed and recommended (see iX12 screenshots below) I fly down final approach on speed, full flaps having to hold a little back pressure on the stick with about 25-40% power. (see also video posted here: https://www.hobbysquawk.com/forum/rc-airplanes/rc-warbirds/1727-fw-p-51-old-crow?p=267915#post267915)
DB

[deadbug]

....Aileron authority is very low at the manufacturer settings. I think I'm going to pump them up a bit...These are my current settings. I'm going to increase the aileron throws though.
Aileron: 36% low, 61% High
Elevator: -40% Low, -60% High
Rudder: -100% Low and High...

Here are my rates again for comparison--I noticed your aileron HIGH rates were lower than mine; and the big difference was on the elevator...yours was much lower than mine. I usually am in LOW rates--and I wouldn't want any less than where I have it; my HIGH rate elevator is probably excessive, but I can't remember using it much, if at all.
AILERON - LOW: 35%; MID: 50%; HIGH: 66%
ELEVATOR - LOW: 59%; MID: 70%; HIGH:82%
RUDDER - 100% ALL RATES

Now in my programming, I adjust the percentage of elevator different up/down to net the following deflections:
Aileron - 8mm; 11mm; 15mm.
Elevator - 9mm up/8.5mm down; 11mm up/10mm down; 12mm up/11mm down.
Rudder (all measured from the raised dot lower aft rudder) - 23mm right/14mm left; 23mm right/16mm left; 23mm right/17mm left
DB

[Jet Fixer]

Any ideas on the gear issue? On the first flight the main gear stopped about 60 degrees retracted on both sides. On the second flight I removed the main doors from the struts and both retracted normally. I talked to a MRC rep and he said that the sometimes the gear doors will cause the wheels to not retract because of air flow impeding the speed of retraction. I have the new version retract servos he recommended. I try and make sure that I am reasonably slow and start the gear up as soon as I get positive rate of climb, but this airplane just doesn't like to retract. Have you had the same issues?

[deadbug]

Any ideas on the gear issue? On the first flight the main gear stopped about 60 degrees retracted on both sides. ....Have you had the same issues?

Fortunately, my gear retraction and extension have always been flawless.
This probkem was really common on the Iron Ass version...but with a few exceptions, seemed to be corrected on Old Crow when they beefed up the retract servo motors. Check the thread on RCG I mentioned in an earlier post...there were quite a bucketload of posts on your gear issue. The only suggestion that comes to my mind is to delay gear retraction, don’t accelerate too much, but reduce power while retracting the gear. That big 2-blade prop blast may be generating far more air resistance to the servo/door combo than your actual airspeed at that moment, if you’re at full power. Something else to check is not to be pulling up into a climb at retraction...the combination of airload and prop thrust together with “G” loading could overstress your retacts. Just a thought. Maybe someone else can offer a fix...
DB

[Jet Fixer]

That's what is so frustrating about this. It always works on the ground.