Official FMS 1400mm P-51D V8 Thread

[mavdriver]

Hi guys i`m going to maiden the red tail tomorrow just want it to be sure according to the manual the cg is supposed to be 100 mm from the leading edge it feels like it needs to go back more what you guys think ? also I`m running a 3300 4s 60c pack for those that want to know TIA

[OV10]

Hi guys i`m going to maiden the red tail tomorrow just want it to be sure according to the manual the cg is supposed to be 100 mm from the leading edge it feels like it needs to go back more what you guys think ? also I`m running a 3300 4s 60c pack for those that want to know TIA

Hello mavdriver,
Not sure if your manual is incorrect or you have a typo of 100 in your question but the manual of the v8 Marie I have says 110 and it is spot on.
This is also widely confirmed/ratified over on the RCG thread for the FMS v8 Mustang.
This airframe also has a rather wide and forgiving CG window to work with.
Here's a link to Wrongroad's(respected contributor) acknowledgement on the 110 over on that RCG thread.

https://www.rcgroups.com/forums/showpost.php?p=34810577&postcount=7701

Best regards,

[mavdriver]

Hello mavdriver,
Not sure if your manual is incorrect or you have a typo of 100 in your question but the manual of the v8 Marie I have says 110 and it is spot on.
This is also widely confirmed/ratified over on the RCG thread for the FMS v8 Mustang.
This airframe also has a rather wide and forgiving CG window to work with.
Here's a link to Wrongroad's(respected contributor) acknowledgement on the 110 over on that RCG thread.

https://www.rcgroups.com/forums/showpost.php?p=34810577&postcount=7701

Best regards,

OV 10 that`s what i thought 110 feels right , my manual says 100 , also is ironic that the throws were off , but i figure that on my own me being a 3 D pilot like allot throws on the surfaces with about 30 expo thanks again for the quick response will let you guys know how maiden went .

[Shirty]

If you're used to 3D throws, you'll find the mustang easy as. I'm the same, and all my warbirds are set up for as much throw as I can get. Good luck on the maiden mate.

[mavdriver]

If you're used to 3D throws, you'll find the mustang easy as. I'm the same, and all my warbirds are set up for as much throw as I can get. Good luck on the maiden mate.

Thanks Shirty

[mavdriver]

Successful maiden report everything went well no bad habits 110 mm CG was spot on , but i got to say this bird is way to slow for me i`m use to flying fast my friend was the one that bought this plane , now his talking about upgrading the power system LOLall well here we go again , going try a 6s set up :)now that`s more like it i`ll be sure he adds reinforcement where needed :Cool:stay tune will be another maiden on the fast motor set up .

[Shirty]

Cool, grats on the maiden mate. It took me two flights to figure out that it was a bit slow for my personal preferences and order a new motor. Though I'd agree she's more than fine for scale flying with the stock setup. I'm getting about 115km/hr out of 6s keeping with the stock prop, but chuck a two blade on and you'll be just over 100mph according to others that have done it.

[AkumaZeto]

Does anyone feel that this frame is squirrely in the air. My Cg has always been spot on and I fly with a Hobby eagle dead nuts on teh cg and I never feel SAFE in the air with this frame. It just feels off to me and always has. I love the way it looks but it is my least flown plain because of these issues.

[AkumaZeto]

Here it is balanced perfect at 110. I have tried moving it further forward a tad and no diffrence. Its like its dragging its rear around fish tailing everywhere if that makes sense. It does not feel locked in at all.

[rifleman_btx]

Try to bring the CG forward about a half inch. If the tail is pointed down in level flight, she's definitely tail heavy, and with a p51 that's exceptionally dangerous with it's tendency to tip stall. Only other thing I can see is might be alittle slow for some reason causing it to fight you. If that's the case might try alittle hotter motor?

[Shirty]

I have noticed with both my D and B she gets a bit of a tail slide in knife edge or just over the top of a loop, but that's about it - certainly not fishtailing everywhere like you describe. I just control it with rudder. (I'm so used to it now I just automatically add a little left rudder out of the top of a loop). As rifleman said, try moving it forward a bit further and see how you go.

One thing i will mention though, is setting your cg on the ground with a balancer is no guarantee it's correct for flying. Of course, it will be very close if balanced this way, but flight testing your cg is your best bet to get a plane dialled in. A lot of things can differ in the air, even a slight warp in the foam can cause a plane to behave as if it's not balanced correctly. Experiment with your batt position in flight to see what you like best is my advice. I've owned three of these mustangs, my mates have another four at my club, and they all need a little left rudder for straight loops and the tail slides a bit in knife edge. None of them drag the tail like you describe though so I'd suggest something is up with your model, and worth checking everything is straight and aligned.

if all your flight surfaces are aligned properly with their respective leading edge and zero trim, then first check it flies straight upright, hands off sticks about 65% throttle. Then repeat inverted. This will be your best indicator (imho), as to whether your cg is off, or it's something else like incidence out slightly or foam warping etc.

[Shirty]

Ok, did some work on my new one today and just thought about a couple of things when I was doing it that might help you as well mate.

First, check the elevator/horizontal stab for any side to side movement. One thing that all my mates and my mustangs show is they have a bit of side to side movement here. As part of my build on these I glue this stab in along the joins to reduce any flex or just loose fitting movement. All my mates with these have done this as well. It varies model to model, this one wasnt too bad but my mate Alan's redtail was terrible until we glued it. If it flexes or moves side to side, it'll make your tail wobble all over the place (esp at speed), and maybe this will help.

Second, check your wings are aligned. As I've noted before, it's my experience that these mustangs are still a great plane to own and fly, but there's a lot more qc issues slipping through of late with FMS I've noticed on all the different threads and forums - and my new one is a good example. You can see my wings don't fit properly, one side hangs out a bit more than the other, and doesn't run evenly with the fuse for its width either. The other side isn't too bad, but still not a nice aerodynamic fit. Wind passing over these will create a lot of little vortices, and I might get a little yaw like feel from it again, more so in the high speed stuff. (Especially since this will be a 5s/6s setup). Anyway, worth looking at yours mate hope it helps.

Other little qc things Ive noted about my new one before in this thread: wing screws wouldn't fit, end of the tail isn't painted, I've got a big dent in the fuse and they put the sticker over it anyway, missing a prop nut etc. All little things that aren't deal breakers, but a little frustrating all the same. Did a bit of final painting and detailing today, silver stacks (a must for a blue nose imho), and silver radio mast, painted the servo horn plate thingys black and silver to match the wing and elevator so they don't stick out like dogs balls, and a coat of minwax gloss for a nice finish and to help protect the foam from transport and finger marks in the foam etc when I carry it. Shiny! Lol. :)

[AkumaZeto]

My wings do stick out from the fuse like that on both sides and I have never been able to correct the issue. I did just glue my stab down as it was loose as well.

[gooniac33]

I have had lots of Mustangs... but never a B model... Just ordered the Snoots Sniper version and will be making it into a Red Tail... Can not wait!!!

[Shirty]

Nice, don't forget to post pics. :)

[Grossman56]

It's a great plane Gooniac,have had mine for years and they fly beautifully,but a little different than my D model. They're slightly lighter although the difference is minimal, so it could be the airflow just as it was with the full scale ones. You guys already know that they're underpowered as well and about the metal retract sides so I won't get into that. Alot of my 'concerns' went away when I upgraded the motors to 580's. Had some spares sitting around from the Freewing P-51's after I upgraded them to 650's, works like a charm! We're sitting here at 5000 feet so the zip tie prop mod helps as well, and flaps at 15 and 30 degrees rocks with these planes!!
Again, I know you guys know all this, but in case someone new is reading, never hurts to mention it again.

Grossman56

[gooniac33]

It's a great plane Gooniac,have had mine for years and they fly beautifully,but a little different than my D model. They're slightly lighter although the difference is minimal, so it could be the airflow just as it was with the full scale ones. You guys already know that they're underpowered as well and about the metal retract sides so I won't get into that. Alot of my 'concerns' went away when I upgraded the motors to 580's. Had some spares sitting around from the Freewing P-51's after I upgraded them to 650's, works like a charm! We're sitting here at 5000 feet so the zip tie prop mod helps as well, and flaps at 15 and 30 degrees rocks with these planes!!
Again, I know you guys know all this, but in case someone new is reading, never hurts to mention it again.

Grossman56

I will fly this stock to begin with and then maybe add the new 650kv motor a little later on. My buddy has done that with his and it made a big difference!

Here are my 2 possible red tail schemes

[Grossman56]

She's going to look sharp Gooniac! Wiped out My Little Gal II today, kind of figured it was going to happen, but she had a 650kv with the 85A ESC in her so now it's in Shangrila, that should make for a pretty great plane, not that she wasn't before!
I was running a 4250 580 kv in her before so it's not a huge upgrade, but since the motor was available, might just as well use it. Only drag is the ESC doesn't have very long motor leads and I didn't have a spare set, so I have to run the battery with the plug facing forward until I score a set of extensions.
Other than that, she should be great. It might just be my old guy eyes or wishful thinking, but the B model always seemed faster than the D model, so this should rock!!

Grossman56

[wrongroad]

G'day AZ,
I know I am a bit late with this but check the security of the rudder push rod at the servo end.
I had my BBD go ape one day with the model yawing badly and then wagging the tail like a dog looking for a cookie!
I called that I had control issues and set up to land. All of a sudden, she started to behave herself and the landing was a cracker.
So, yes, I was dumb enough to go up again because the problem had 'gone away'. Yeah, riiiiiiggggghhhhhht!!
On the first circuit she was all over the place like a palm tree in a cyclone. However, as I set for landing, the problem went away.
This time I was not stupid enough to go up without finding and correcting the problem. I quickly discovered that the grub screw in servo arm was not done up tight enough. Out with the Allen key set, find the right size and do the rotten thing up. A bit of contact glue over the top and there has never been an issue with the screws backing out since.
Now, why the problem went away while landing and taking off, I have never been able to work out.
It is also worth your time to check the integrity of the two screws holding the vertical stabiliser on. These can and do work there way loose over a period of time and this, in turn, allows the fin to flutter.
Earlier models, the V7 comes to mind, only had a foam tongue to secure the vert stab to the fuselage [along with the screws] while later versions have a hard point and is much, much better.
I have three P-51's [four if you count the first BBD that was cut in half by another model while waiting for her maiden flight] and the tail does need attention from time to time. Do not forget to do your checks and that goes for everyone.:)
I have not been doing all that much flying in the last few months but it is all looking good from here in.
I hope you have already found the problem but if not, at least you have another thing to check!
Regards and respect
Daryl

[Grossman56]

Had Shangrila with the 650kv in her, up last evening. It's a bit better than the 580kv, but nothing to write home about. One of the guys mentioned a whole back, that if you go from the stock 540 to the 580 and then to the 650 as I have done, it doesn't seem like all that much of an improvement. But if you go directly from the 540 to the 650, it looks like a big improvement.
I'd agree with that, and she flies great with the 650.
I also changed out the connectors to ball links on both my FMS P-51s, just for added peace of mind.

Grossman56