Clive Jones 4 Posted June 12, 2020 Share Posted June 12, 2020 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. Quote Link to comment Share on other sites More sharing options...
Clive Jones 4 Posted June 12, 2020 Author Share Posted June 12, 2020 Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted June 12, 2020 Share Posted June 12, 2020 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. Quote Link to comment Share on other sites More sharing options...
Trevor Crook Posted June 12, 2020 Share Posted June 12, 2020 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. Quote Link to comment Share on other sites More sharing options...
Trevor Crook Posted June 12, 2020 Share Posted June 12, 2020 Btw, Bob beat me to it with his response! Quote Link to comment Share on other sites More sharing options...
Clive Jones 4 Posted June 12, 2020 Author Share Posted June 12, 2020 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. Quote Link to comment Share on other sites More sharing options...
Clive Jones 4 Posted June 15, 2020 Author Share Posted June 15, 2020 Bob - which kV of 5055 motor? 430, 380 or 580? Clive. Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted June 15, 2020 Share Posted June 15, 2020 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. Quote Link to comment Share on other sites More sharing options...
eflightray Posted June 15, 2020 Share Posted June 15, 2020 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. Ray. Quote Link to comment Share on other sites More sharing options...
Clive Jones 4 Posted June 15, 2020 Author Share Posted June 15, 2020 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. Quote Link to comment Share on other sites More sharing options...
Clive Jones 4 Posted June 23, 2020 Author Share Posted June 23, 2020 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? Quote Link to comment Share on other sites More sharing options...
Clive Jones 4 Posted June 23, 2020 Author Share Posted June 23, 2020 Quote Link to comment Share on other sites More sharing options...
Martin McIntosh Posted June 23, 2020 Share Posted June 23, 2020 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. Quote Link to comment Share on other sites More sharing options...
Clive Jones 4 Posted June 24, 2020 Author Share Posted June 24, 2020 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. Quote Link to comment Share on other sites More sharing options...
Martin McIntosh Posted June 24, 2020 Share Posted June 24, 2020 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. Quote Link to comment Share on other sites More sharing options...
Clive Jones 4 Posted June 24, 2020 Author Share Posted June 24, 2020 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 Quote Link to comment Share on other sites More sharing options...
Clive Jones 4 Posted June 27, 2020 Author Share Posted June 27, 2020 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. Quote Link to comment Share on other sites More sharing options...
Clive Jones 4 Posted June 27, 2020 Author Share Posted June 27, 2020 30 - 40C pack - My fat fingers.. Quote Link to comment Share on other sites More sharing options...
Martin McIntosh Posted June 27, 2020 Share Posted June 27, 2020 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. Quote Link to comment Share on other sites More sharing options...
Clive Jones 4 Posted June 27, 2020 Author Share Posted June 27, 2020 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. Quote Link to comment Share on other sites More sharing options...
Clive Jones 4 Posted June 27, 2020 Author Share Posted June 27, 2020 Just weighed all the bits, less covering and paint, 3531g. 7.7lbs. I am pretty sure she will need ballast so will try to source a brass weight that will thread on to and butt up to the propellor nut. Does anyone know of a source for a 95mm spinner? The one that came with the model is a soft plastic, possibly vac formed, which is gonna be a bu**er to get on concentrically. Quote Link to comment Share on other sites More sharing options...
Clive Jones 4 Posted June 27, 2020 Author Share Posted June 27, 2020 I have weighed the components and presently it is 7.7lbs with battery. I still have to cover, paint and balance but I will try to keep the weight down especially around the tail. I am now looking for a 95mm spinner as the one that came with the Spit looks like a light plastic moulding and is a bit of a bear to get straight on the motor. Clive. Quote Link to comment Share on other sites More sharing options...
Martin McIntosh Posted June 27, 2020 Share Posted June 27, 2020 Chuck the spinner. HK do a normal plastic 3 3/4" one but you could wait months for it. Traplet used to sell a pressed alloy one but they were flimsy and c**p, at least they were the right shape for a Spit. It would be unusual for a model Spitfire not to need lots of lead up front, especially a leccy one. Quote Link to comment Share on other sites More sharing options...
Clive Jones 4 Posted June 27, 2020 Author Share Posted June 27, 2020 Sorry for the triple post, operator error. Quote Link to comment Share on other sites More sharing options...
JAMES KEMBLE Posted June 28, 2020 Share Posted June 28, 2020 I'm building #6 (of 6). I started #1 and flew it that year. I'm not a fan of foam and I designed a built-up structure to copy the foam shape. On number 3 I re-designed the wing to follow a scale section and adjusted it to be at the same scale as the fuse. It flew well. However it was heavy, 9lbs 6 ozs.. I bought a lot of 4-6 lbs balsa and lightened as much as possible everything on the model. around the nose area it's easy to lose an oz by using a foam tailwheel and# 4 tipped the scales at 7 lbs 3 ozs and it flew like a bird and like a bird it ended in a tree top Finis. All this doesn't help you too much. To finishing. I used heavy weight tissue and no shrink dope on all the solid surfaces and Humbral model paints to finish, followed by a thin coat of satin polyurethane, The up front power is a K&B 60 from 1992, and it's going strong. Hope it is of interest. Quote Link to comment Share on other sites More sharing options...
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