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Warbirds Replicas P51 Mustang


RICHARD WILLS

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Motor selection...

Although thoroughly covered elsewhere in these threads, to save you looking, the standard motor for the FMS 1400 P51 is a KV540.

The first 'mod' for a little more speed was to put a 1mm section of a zip tie under the leading edge of the prop between the backplate and prop. The next upgrade was to change to the KV580 motor.

I have tried both these 'upgrades' and found the KV580 a better option.

Downside is flight time, I like to fly 'scale isn't and very rarely am full throttle. On the 540 could get a good 8 mins out of a 4000mah 4 cell.

Lost 2 mins with the zip tie mod and down to 5 with the 580

All using the 14x8x4 fms prop.

Hope you find it useful.

 

 

Edited By Paul Johnson 4 on 14/11/2020 17:53:07

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Hi Geoff,

I think you will find even on 4 cell the current draw will be too high.

Don't know what the motor specs are.

I use a 13x7.5x3 on a 650kv with a 4 cell that pulls nearly 50 amps full throttle. This is in my Yak3. Like a rat up a drain pipe but with a 4 cell 3300mah 4 mins is your limit and that's being careful with the throttle, usually 60 to 75 percent.

If you have a ammeter/power meter try some static tests. This can be a little misleading as the motor usually unloads somewhat in flight so okay for a initial try.

Using a 5 cell with a 660kv could be over stressing the blades.

There has occasional blade separation where the 'speed' freaks push them too far.

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Ok so lets take a rational approach to this . My blue nose P51 being "the control " It has a 580KV motor with no shims . ie standard flat set up . It will go 5 minutes on a 3300 mah 4s pack and do huge loops . So its the best compromise .

If you are going to fit a higher KV motor , you are pushing your luck in terms of blade integrity , amp draw etc .

However if you have such a motor it is understandable that you want to use it .

But before you try it , consider the "control " .

A 650 Kv is perhaps ok if if you are aware of what you are doing and dont open the throttle right up unless its either in full level flight or going down hill . The 700kv , even more so as you will have 20% more revs which is a lot for such a big coarse prop . 5S batteries would be way over the top unless you back off to a 500KV motor .

The other tweak available is to add the shim to the trailing edge of the prop blades in order to reduce the pitch slightly . That would be a good idea for the 650 -700KV motors.

The aim is to get 5mins of full on P51 performance with frying anything of breaking it .

Please remember that I am taking no responsibility for the integrity of FMS prop blades . Their quality and structural integrity is completely outside of my control so I can only suggest that you always stand behind the model and assume it will shed a blade .

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Posted by Nigel Dell on 14/11/2020 17:43:45:

Well Chaps hospital food is no too bad and I have only a couple of breakages but not too bad I guess, she did say I am going to solve your flying site problem and has given me 2 acres to start me off😳🙄🤪😂

So now you have a small holding just over two acres

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Posted by Paul Johnson 4 on 14/11/2020 19:37:23:
Posted by Graham R on 14/11/2020 19:35:32:

I have a spare Ripmax Quantum 55 700kv which I am planning to use in mine.

On a 14x8x4...?

Ooops I didn't give it a thought. You and Richard are absolutely right. I just looked through my collection of motors saw it was rated at around 1300w and thought that will do nicely.

Reminder to myself Consider all of the motor parameters not just power output.

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Posted by Eric Robson on 14/11/2020 20:24:57:
Posted by Nigel Dell on 14/11/2020 17:43:45:

Well Chaps hospital food is no too bad and I have only a couple of breakages but not too bad I guess, she did say I am going to solve your flying site problem and has given me 2 acres to start me off😳🙄🤪😂

So now you have a small holding just over two acres

It’s as if you were there Eric, she said the same. ITS COLD OK 🤭😂

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I know all I have done is dropped by with some inane nonsense on this thread and nothing to do with the model in question, I can attest to the quality of Richards designs and kits, they are well thought out and the kits excellently produced, the P51 is one of my personal favourites and if I were doing one it would either be the A 36 Apache based on the P 51B or the Kermit Weeks P 51B in Tuskegee colours in Fantasy of flight Polk City Florida, I was lucky enough to be shown around it and in it many moons ago and the Tuskegee airman have been a point of interest for years.

Alas I would love to join you in this project especially having just read through the whole thread ( I had missed quite a bit) but the last good while has seen problems with my mobility, ageing parents and their failing health and a milliard of other things to conspire against me but I do have plenty of projects to be getting on with, the La7, 109 and 110 to name but a few, the 109 is up first.

So I will be looking in to see your progress with a bit of a lump, Missus has an excellent right hook, and see how you are getting on, enjoy this excellent of kits.

I will know you will inspire me to get my finger out! 😂

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Always nice to have you pop into the virtual Club House Nige ,.Help your self to a hypothetical Bacon roll .

Graham R has just made them .

 

We all admire your balls .......... (from a distance)

I never under estimate the perceptive powers of "The Memsahib".

It's like she is perpetually behind me .

Isn't that right dear ?

Edited By RICHARD WILLS on 15/11/2020 08:03:49

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