Official FMS 1400mm P-51D V8 Thread

[curlyculp]

Hello Curly,
The power mods to this bird have been well documented over the years as well as the recent past because of the latest motors to hit the market.
So to put things in a nut shell for you versus perusing hundreds of pages on both the forums looking for those pearls, here ya go.;)


Hope this helps,

SO, I got the stuff recommended, KV650 motor, 85A ESC. I put it all together, put the prop on and bench ran it on a 3200ma 30C 4S battery. In only 3 minutes at medium to high power it drew the battery down to 22%. The back of the motor was pretty darned hot but I've never felt one before after running so maybe this is no thang.

Now, I know bench running it with the prop on puts a bigger load on everything than actual flying loads as the prop is always pulling stationary air. I know I'll get a little longer performance airborne...

but, if I get a 5000ma 4S battery will it do better? I would think so.

Other than max and min power which is programmed easily, is there anything else I'm supposed to program on the ESC?

[Evan D]

The S means series. A 6S battery is 6 cells in series. P means parallel though it's rarely uses anymore in RC. C means capacity, as noted, and is normally used for a discharge rating. a 30C battery can be discharged at 30 times is capacity. A 4000mAh 30 C can be discharged at 30 times 4000mA or 30 times 4 Amps or 120 Amps. It is also used as a charge rating as noted and the same math applies.

[xviper]

I have two 6c batteries (yeah, only two, I'm kind of a newbie) and I'm not convinced I can fit even my smaller one in the V8. I know I can't on the tray.

Depends on what size the "smaller" one is. I use a 4000mah, 6s battery in mine and 1/3 of it sticks out the rear of the tray. It doesn't have to sit entirely on the tray. You move one of the straps to the rear and it works. If you have a 5000mah, 6s battery, it may not work but that's purely because you may not be able to close the canopy unless you cut out the front underside of it but then, that cuts into the cockpit that you can see and it would look weird. The battery needs to go where it needs to go to balance the plane properly.
Re: the nomenclature of LiPo cell numbers. I know it's designated as the # of cells, so one would think that logically, it would be (eg.) written down as 6c but for some strange reason, it's actually called "6s" (meaning 6 cells). "C" is used to designate the charge rate - eg. a charge rate of 2c can be charged at 2X (twice) the mah of the battery ........................... 5000mah can be charged at 10amps. It should be stated on the battery label if this can be done. However, it's far better for battery longevity to charge at 1c no matter what it says. Some batteries, according to the manufacturer can be charged at 5c or more.
"C" is also used to refer to the ability of the battery to release it's energy. You commonly see batteries rated at 20C and as high as 70C or even higher. The higher the "C", the faster and harder the motor can draw from it without getting strained (ie, get hot or puffy, which can also shorten it's life). Usually, once it's puffed (bloaty), it's not going to UNpuff.
"MAH" is like the size of the gas tank in a car. "C", in this case is like the size of the fuel line going from the tank to the engine. The "C" that is the charge rate can be thought of like how you fuel up a gas tank on a car. You can pump it in on the first detent (slowly) or pump it in on the 3rd detent on the handle (fast). Not all cars can take it at the fastest pump rate due to the filler neck and the kinds of bends in it. It could bubble up and pop (stop pumping). A LiPo, if charged at too high a rate, won't stop charging. It could just get hot or blow up and burn your house down.

[curlyculp]

Hello Curly,
The power mods to this bird have been well documented over the years as well as the recent past because of the latest motors to hit the market.

I did those 580 upgrades back in the day and they were so-so, when the 650 and 460 came out now that was the boost.;)

Hope this helps,

I have two 6c batteries (yeah, only two, I'm kind of a newbie) and I'm not convinced I can fit even my smaller one in the V8. I know I can't on the tray.

Finding all the 650 pieces in one place was a challenge. I was looking at the prop shaft via your link to Motion RC and when I looked at it they offered in the "Customers often bought together..." the whole P-51 mod kit. Motor, ESC, mount, prop shaft.

Looking forward to it! It's a way cheaper hobby than cars or motorcycles. Hell my wife and I are serious bicyclists and I barely have as much invested in my airplanes now as I have in only one of my bicycles!

Thanks for the tips.

[OV10]

I maidened my V8 recently and have 8 flights on it now. And I have to say, it's a bit of a dog. I also have the FMS 1400mm F-4U, same motor and ESC, (at least that's what the literature says) and though the Corsair is a bit heavier and "dirtier", it's peppy-er. I'm thinking it's the prop. The scale blades on the P-51 might look right, and they do, but are they efficient?

There definitely looks like there's room for a small 6C battery. Like a 4000ma. Is the motor and ESC changeover that big a deal? I have the Motion RC 1600mm Spitfire with a 6C setup and it ROCKS. It's super powerfu

Can I use the P-51's stock prop if I swich to the bigger motor? Does it just spin it faster?

Hello Curly,
The power mods to this bird have been well documented over the years as well as the recent past because of the latest motors to hit the market.
So to put things in a nut shell for you versus perusing hundreds of pages on both the forums looking for those pearls, here ya go.;)
What I am presenting below is a basic bolt in swap of equipment that doesn't require any frame modifications and can still use the 4 bladed prop.
First the motor mount X brace hole spacing is 30mm at the plastic motor mount.
There are two newer FMS motors that have the same X mount brace spacing as the 4250-540kV stock motor & the 4250-580kV which was the early years upgrade along with the zip tie prop mod and bigger ESC.
For a 4S setup you will use the 4258-650kV from the FMS 1400 P-40B.
For a 6S setup you will use the 4258-460kV from the FMS 1500 P-47.
For either one of these motors you will need to use this prop shaft adapter from the FMS F3A Olympus in order to keep the spacing for the spinner appropriate because both of those motors are 8mm longer than the stock 540.
You will also need to upgrade the ESC from the stock 70A to a minimum of 85A. I used the ZTW 85A with no issue on both my 1400 Stang and Corsair upgrades.

Now the Motion product page for both versions(Redtail & Petie) they show an optional upgrade to the 580kV that I mentioned earlier.
The documentation is somewhat misleading.
" FMS 4250-580kV motor which will pull 62A (static) and yield a significant boost in performance. The 580Kv motor is 2mm longer so there will be a slight gap between spinner and cowl"
First it does not provide a "significant" boost in performance and secondly the 580 is not longer than the 540.
Also the 62A static draw is over the 56A max rating of the motor. This is why the 580 was not a long lived upgrade.
They also recommend the 100A Castle ESC which is an overkill for power demand needs and $40 more than the ZTW.
I did those 580 upgrades back in the day and they were so-so, when the 650 and 460 came out now that was the boost.;)

Hope this helps,

[curlyculp]

I maidened my V8 recently and have 8 flights on it now. And I have to say, it's a bit of a dog.

I saw the post to use the 650kva motor from the P-40. Sounds like an incremental change. It's on backorder but I think I'll try it. Does the stock propeller shaft for the P-51 work?

[curlyculp]

I maidened my V8 recently and have 8 flights on it now. And I have to say, it's a bit of a dog. I also have the FMS 1400mm F-4U, same motor and ESC, (at least that's what the literature says) and though the Corsair is a bit heavier and "dirtier", it's peppy-er. I'm thinking it's the prop. The scale blades on the P-51 might look right, and they do, but are they efficient?

There definitely looks like there's room for a small 6C battery. Like a 4000ma. Is the motor and ESC changeover that big a deal? I have the Motion RC 1600mm Spitfire with a 6C setup and it ROCKS. It's super powerfu

Can I use the P-51's stock prop if I swich to the bigger motor? Does it just spin it faster?

[Ron1950]

flew my v7 with the 6s 3300ma batts today darn thing is sooooo much faster then it was with 4s set up... might have a guy that can make alum spinner back plates so the prop wont explode with high rpms ill post if he comes through...

when this plane was stock it was the only plane I have ever had that could take a bird strike from the rear...now the buzzards are scared

[Grossman56]

Yep, definitely the way to go for 4s.

Grossman56

[xviper]

Mine are running 4s 3600s and 4000s. See, post 1111, I also did the zip tie mod as we're at 5000 feet, it helps a lot too.

Grossman56

A 4000mah, 4s balances this plane just fine.

[Grossman56]

Grossman56 Hi! I setup my p51 just like yours. I have a 6s 640g 4500 battery from admiral I stuck in there. It feels VERY nose heavy. I’d like to know your thoughts on this before I put her up. Thanks!

Mine are running 4s 3600s and 4000s. See, post 1111, I also did the zip tie mod as we're at 5000 feet, it helps a lot too.

Grossman56

[xviper]

I fly mine with an Admiral 4000mah, 6s. The battery sits hanging off the tray to the rear by about 1/3 the length of the battery. I had to change the position of the straps so that it held the battery securely. It balances within the recommended CG range. If yours is that nose heavy, it will likely require quite a bit of UP elevator to trim but it will fly OK, with the exception of inverted flight, in which case, it may be difficult to keep level with what elevator travel there is. However, to balance it at the proper CG, you may have to add another strap aft of the tray so the battery can reside further back. There's room under the canopy for some adjustment in battery position, but too far back and the canopy may not close without some foam removal.

[Fishflyer]

Grossman56 Hi! I setup my p51 just like yours. I have a 6s 640g 4500 battery from admiral I stuck in there. It feels VERY nose heavy. I’d like to know your thoughts on this before I put her up. Thanks!

[Dewey H Lee]

Great advice. I forgot about that GMan.

[Grossman56]

The prop shaft is a little long for scale as well, so you could change that out too.

https://www.motionrc.com/products/fms-1400mm-f3a-propeller-shaft

This is the prop shaft. Now, you have to drill new pilot holes for the motor mount to the firewall, which isn't hard, just use the motor mount as a template and make sure it is centered to the firewall. Its easiest if you can put the fuselage in a vertical position and not have to fight gravity, ask me how I know....

Grossman56

[Dewey H Lee]

You will need the x motor mount for the 650. Its the FMS P40 setup.

[Fishflyer]

Thanks! Would I need any adapters or a new mount for the 650 motor?

[Grossman56]

I have all my P-51's Freewing and FMS running 650 kvs (the motor that comes stock with the FMS 1400mm P-40) and 85A ESC's with stock props. They all fly great!

Grossman56

[xviper]

Going to the 580 motor and a 2-blade may give you a slight improvement in performance but it's still a 4-cell system. If you really want speed, you need to do the complete mod - go with the 6-cell motor from the FMS P-47 and keep the stock prop. Change the connector to EC5.
However, if you are going to stay with the 4-cell and want the 2-blade, you'd need to go with about a 16X8X2 or 14X10X2.

[Fishflyer]

Maidened my 51 today! All went well. Feels slower than my apprentice though. I’m going to upgrade to 580 motor. Can anyone link me what prop I should use? It seems like a 2 blade setup yields more speed. Thanks!