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62 inch WS RCME plan Spitfire

Power system suggestions, please

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Clive Jones 412/06/2020 15:22:04
47 forum posts
11 photos

Looking for electric motor power ststem suggestions for my Spitfire. I was given the airframe and as you can see it needs covering etc, so a way to go.

I would like to use 4S if at all possible as that is what I use in my other Spit, but if deemed unsuitable, I have friends who I can borrow 6S batteries off for test flights etc.

It is about 62" wingspan and will probably be about 8lbs "wet" when finished. Currently it is 4 and three quarter pounds. I will try to post a photo in subsequent posts, because I lost all my last message whilst trying to do just that!

Thanks,

Clive.

Clive Jones 412/06/2020 15:24:52
47 forum posts
11 photos

20200612_145857.jpg

Bob Cotsford12/06/2020 15:37:18
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8628 forum posts
483 photos

You could link two of your 4 cell packs for 8S on something like a 320-380kv motor, that would keep the current down but would need a high voltage ESC as most only go up to 6S. You really want to be aiming for 800W+ for fighter type performance, 1000W would be better at 8lb. 800W on 4S is asking for nearly 60A, are your 4S packs big enough to give decent flight times at that? If so I'd look at motors around 600kv with an 80A ESC. I must admit I'm guessing there as I use 6S for this size model. 6S, 60A+ ESC, 4258 500kv motor, 14*7-14*8 prop, 800W easy. For more performance 5055 motor, 80A ESC, 15*8-15*10 prop 1100-1300W iirc.

Trevor Crook12/06/2020 15:49:24
982 forum posts
71 photos

Clive, I'd suggest a 6s setup will be needed to fly that size of Spitfire. It's a little bigger than the Avios MkV (1450mm) and a little smaller than the Flightline MkIX (1600mm), and both of these are designed for 6s. I don't know what the AUW of yours will be, but my Avios is 6lb with a 6s 3300 Turnigy on board. These are not too expensive - I paid about £30 for mine. My model is fitted with a 380kV motor to turn the scale 15x10 3-blade prop, and has an 80A esc.

I haven't done any power measurements on the Avios, but we did with my son's Flightline when he was thinking of using a 5s pack. It read 1200W with the 6s, and 950W with the 5s. The 5s flew it acceptably.

Hope this data helps, feel free to ask any further questions. I know the models I've got access to are foam ARTFs, but they are not super light, and are of similar sixe to your project.

Trevor Crook12/06/2020 15:51:45
982 forum posts
71 photos

Btw, Bob beat me to it with his response!

Clive Jones 412/06/2020 16:00:56
47 forum posts
11 photos

Thank you gents, two great suggestions in the time it took me to walk the dog!

6S looks attractive as clubmates would lend me theirs to test but I also have enough 4S to double up with a series lead into the ESC.

With the info above, I will scan the internet to see what is out there in terms of ESC and Motor combo.

Thank you.

Clive.

Clive Jones 415/06/2020 15:55:35
47 forum posts
11 photos

Bob - which kV of 5055 motor?

430, 380 or 580?

Clive.

Bob Cotsford15/06/2020 17:34:45
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8628 forum posts
483 photos

I use the 430kv motors on 6S with 15" props, the 580 would need to go down to somewhere near 12*8, I have 590kv motors in my WotsWot and Bolero and iirc they are on 12*7 or 12*8. I'd imagine the 380kv on 6S would take you up to 16 or 17" props. I like the 15" as a happy compromise between ground clearance and scale-ish size on warbirds and the similar model types. I used 590kv on the two quoted models as the Bolero came with it fitted and the WW I'd got the motor and it fitted the cowl/mount.

If it were me I'd go for the 430 for your Spitfire.

eflightray15/06/2020 19:50:33
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624 forum posts
132 photos

My 72" Spitfire ( 7 Lb - 2 oz), uses an Emax 4030 385kv on 6s, flown with 14 x 7, 15 x 8, and 16 x 10 during testing. Chose the 15 x 8 as a good compromise of power and duration.

spitfire22.jpg

Ray.

Clive Jones 415/06/2020 19:59:02
47 forum posts
11 photos

Thanks guys. Ray, your depron beauty is a lot lighter than mine will be - I take it the weight you quoted is "wet" (incl. Battery). I am sure I will need the extra torque/power that a 50 size can would give on my porky example.

Bob, I was leaning towards the 430 myself, just needed a second opinion. I have a 70A ESC coming, that should cover the current needs I hope as I do not do 3D etc, just scale flight. Might have to experiment with pitch of prop as well.

Clive.

Clive Jones 423/06/2020 19:38:42
47 forum posts
11 photos

Hi Guys, I am just sbout to install the motor "box" to the firewall. Do I give the "x" shaped motor mount some down and right thrust or straight ahead and level?

Clive Jones 423/06/2020 21:17:50
47 forum posts
11 photos

20200623_203750.jpg

Martin McIntosh23/06/2020 21:53:35
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3471 forum posts
1216 photos

No down or side thrust is generally used on a model Spit. for some reason; there is none of any of my 44", 62" or 72" TN ones. My 62" TN Hurricane is very lively on a Propdrive 50/50 and 5s 5000 packs. 6s was too much. I think that it is on a 14x7 APC electric prop. but could check on that.

Clive Jones 424/06/2020 11:15:20
47 forum posts
11 photos

Hi Martin, thanks for your input.

I will try dead ahead and if I find it ballooning under power or diving for the LH hedge on takeoff I will adjust the thrust angle with washers.

Can you give me the weight of the Hurri, please. That would give me some idea of how my similar Spit might fly.

I have stuck mine together with tape/wingbolts and sacrificial balsa to estimate the C of G. I used 2x2200 3S LiPos to mimic 6S but after looking up weights on the internet I find that the 2x3S was about 250g under the weight of one 6S 3300. Good job too - the CofG indicated was 130mm rear of LE whilst the similar sized Freewing Spitfire quotes 90mm.

As you can see on the photo, I could cut away the centre part of the original IC firewall and extend the battery compartment (Old IC tank bay) to possibly move the batteries forward if they are not too wide.

Clive.

Martin McIntosh24/06/2020 11:48:17
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3471 forum posts
1216 photos

Hi, it is 128oz (8lb)/3.625kg including 0.65kg of batteries.

I don`t think that you stand much chance of success with only 2200`s. To develop sufficient thrust from those would be highly unlikely and even if they did you would be lucky to get a minute or two. My Hurri needs the 5s 5000 as far forward as possible.

Do not try to fly a Spit with a rearward cg; I speak from experience. The 90mm mark is almost certainly the one to go for.

Clive Jones 424/06/2020 12:46:51
47 forum posts
11 photos

Hi Martin, Thanks for the information. Mine might be a bit north of 8lbs, but I am trying to not add too much weight at the rear. The model as I received it has built up/solartex elevators and rudder but I will have to source some superlight balsa for the missing trim tabs.

I will not be flying with the 2200s linked, I just wanted an approxomation of the weight of a 6S battery to see where the C of G was currently. I then found by looking at online sources that my dummy 6S ballast was 250g lighter than a genuine 3300 6S. Even with this added weight (I will just tape another 3S 2200 to the two others to again approxomate the weght of a 3300 6S) I bet I will have to cut the IC firewall to enable the 6S flight battery (when I get it) to be positioned forward an extra couple of inches.

Clive,

 

Edited By Clive Jones 4 on 24/06/2020 12:47:30

Clive Jones 427/06/2020 13:53:43
47 forum posts
11 photos

Well I have whattmetered it and I get 949W with a draw of 42A.

System is Turnigy 30-49C 4000 mAh 6S pack, Jeti Advance pro Opti 70A ESC, Leopard 430kV 5505 motor APC - E grey prop 15 x 10.

What are your thoughts on those figures, bearing in mind the model will be probably 10lbs when finished in flying trim.

Clive Jones 427/06/2020 13:54:51
47 forum posts
11 photos

30 - 40C pack - My fat fingers..

Martin McIntosh27/06/2020 14:50:22
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3471 forum posts
1216 photos

Sorry but that sounds very heavy to me considering that the target weight is around 7lbs. Where does it all come from? Cannot remember what mine is and a mate has it at the moment with a view to purchase. I used a YS 53 on a two blader then a 63S on three to cut down the power and reduce the landing speed by dropping the pitch by 1", but on electric you can obviously cut to zero for the last three feet. Probably about the same power as you have at a guess.

Clive Jones 427/06/2020 15:06:34
47 forum posts
11 photos

Hi Martin, yes, I was hoping for about 8lbs ish myself. This is an airframe that was given to me and looks like it was meant originally for an IC power unit of about .61 size. As I fly exclusively electric, I needed ideas for an electric power unit, hence the original post. I will have to weigh the various component parts to get a better idea ofthe current weight but I then have to factor in finishing and balancing .

Nobody said it was gonna be easy...

Clive.

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