Electric Sea Fury

[Danny Fenton]

Well Shaun started a build thread for the seagull Sea Fury, and I must say the Fury is one of my favorites, funny nearly all of my favorites come from the drawing board of Sydney Camm.

Anyway the challenge is to converts said Seagull Sea Fury to electric safely but as cheaply as I can to see just how easily and cheaply a 90 sized model can be converted to electric.

We have all seen articles where something like a Castle Creation ESC is used and AXI motors, not to mention expensive FlightPower battery packs. Well that is great if you can afford it, I cannot. This I am hoping will show what can be done

Here is my conversion. I will not shy away from using China as my source of parts. (I just bought some servos the other day from a UK shop only to find somebody ahd rifled through the accesories and nicked the large output horns).

The kit itself has come from Leeds Model Shop and is I must say of really good quality, colors are pants mind but there we go. The fit of the parts is excellent, the amount that has already been done is far more than I have ever seen. Even the canopy is already cut for you!

The wing is not sheeted but open structure covered in film, ripe for electrifying as it is light.

Seagull Sea Fury £99.

50A Super Simple ESC from Hong Kong $11.95

900 watt motor from HK  $29.99

3 Hextronic 5010 Servos $5.95 from HK 

3 Futaba 3003 £5.99 from Steve Webb (not the ones missing bits these were fine)

8 cells A123, cannobilised from new De Walt power tool battery pack purchased on Ebay, £56

Thats the story so far, I do not intend to do much in the way of modifying, though I will no doubt change the odd bit here and there. I would love to change the color scheme, maybe later after this experimant.

[Danny Fenton]

Centre section done, and yes I am using the cheap retracts that came with it, they are a little wobbly but we will see, I have increased the size of the wheels to 72mm to cater for our grass field. I have also made some glassfibre board horns for the control surfaces, as I hate to see the horn backing plates on the tops of the flying surfaces.

The wheel wells would not allow the undercarriage to retract full and lock, so they have been binned. Though I would say they fitted perfectly, just too shallow.

I am using the cheap Hextronic servos $5.95 each on the flaps, and the rudder. The better (?) Futabas on the ailerons and elevator.

[David Ashby - Moderator]

Very interesting Danny, that's pretty cheap too     

[Tim Mackey]

Looking on with interest Danny - I think this has the potential to be a really good thread!

For those not familiar with buying stuff from H/K I would add that the service is usually pretty darn quick ( often within a week ) and with current exchange rates around almost $2 to the £ - even the most keenly priced UK suppliers are hard pushed to beat the equivalent GBP price; I mean a 50A + brushless ESC for around 6 pounds!

[Tim Mackey]

OK can I chip in a bit here Danny, having had a little time to play with the numbers .

You said over in the other thread you were aiming to keep the Amps down to around 40, and would be trying to "push" the chosen motor to 1200 watts on the 8 x M1 cells. As they usually hold around 2.95v under load that will be only 23.6V. 23.6V X 40A is only 944 Watts input. This 'plane is, I believe, designed around a 90 size IC engine, and likely to weigh in at around a fairly hefty 9lb. Using the 100 watts per lb rule, your 944 watts seems OK, but using the other yardstick often quoted when doing IC conversions "double add zero" gives a wattage requirement of nearer 1800 ( 90 doubled = 180, add a zero = 1800)

Even compromising between the two suggests around 12 - 1300 watts or so ( the other target you mentioned ) and as this is a pretty big and probably quite draggy model, I suggest that 900 watts may be a little low.

One problem with using high volts rather than high Amps, is of course, that the prop speed increases a lot, so Kv selection is crucial. What motor is it you are considering using? I presume you have aimed for a very low Kv so the pitch speed can be kept in keeping with the model on such a high voltage. I know you are fan of M1s, but as you know, there are some real cheap decent LiPos out there today and using maybe 8 LiPo instead would shed a little weight. I still reckon you are going to need closer to the 1200 watt mark, so with A123s its over 50A, yet with 8 LiPo its only 43 A.

2 x 4s 50A capable packs can be had in the UK for just £40 total at the moment ( special offer ) I relaise that the ESC wold need changing to handle the higher volts, but these are available cheaply too.

Also, why did you not go for the very powerful metal geared HK £4 servos for the ailerons and elevator ?

These have a whopping 11.2kg of torque! - far more than the futaba 3003 at only 3.2Kg.

PS none of this is criticism - just wondering thats all

[Chris Bott - Moderator]

I recon Danny will prop for 50A but only use it very breifly.

We've been doing a lot of eagle tree testing lately and its amazing how little power you use at straight and level cruise.
So maybe 1200W just in case and probably less than half to cruise.

100W/lb was an old rule of thumb, generally applied to smaller models using inefficient brushed motors. With a bigger model and efficient brushless motors this can be relaxed substantially.

With A123's we can prop for large currents, they will take it. Then maybe use this for takeoff only or the odd impressive vertical, and fly around scale fashion on much less power.

Danny you'll be fine, especially on our nice new manicured lawn.

You'll find out if the spec of that ESC is correct!

[Tim Mackey]

The issue is not one of the capability of the M1s, 50A is nothing. Substantial relaxation of the 100 watts per pound rule is not particularly applicable in a model such as this. As for it being an old rule, you will find if anything these days people tend to err more on 100wplb being modest! Sure props unload in the air, and current drops, but you still have to get it up there in the first place, overcoming the drag of takeoff, small wheels on grass strips etc - and having plenty of power to execute decent manoeuvres and see quick and ready response to throttle inputs is important too. Dont get me wrong.... I am enthusiastic about this project, and the whole concept of it, but I just feel that this is pretty borderline and for the sake of a few extra pounds, it could be safer and more rewarding.

If it is indeed propped for 50A ( assuming the correct motor choice is made that will provide a suitable pitch speed and prop size for the model on those volts ) you may get away with it - but it was stated 40A was the target

[Danny Fenton]

Hi Timbo,

Kinda thought this thread might cause a few enthusiastic debates lol

Sorry didn't reply sooner, been engrossed in getting Hurricane ready for 2nd flight in the morning.

I know the Fury is fairly marginal on this motor and cell count. The original plan was to go for 12 A123, a HV ESC and a different motor entirely. But If the model does come out light. (I am waiting for Shaun to hopefully come up with his IC all up weight) then it may well work. It is all to do with how much momentum I can carry between bursts of power  as you say if the airframe is just too draggy then the 8 cell route wont work, provided it survives I will up the power.

I am familiar with sports and 3D power requirements where you are up and down the throttle constantly, but never a warbird, so this is a whole new arena for me.

The YT Hurricane at 13.5 lbs flew on 12 A123 at about 2700 watts. But thats just an estimate as mentioned elsewhere the Eagle Tree I was using was way off the money as far as callibration. I will have a better idea after the flight tomorrow. I am propping for MUCH less power more like 1500 -1700 watts, which will be just over the 100 watt per lb. So fingers crossed.

These things are here to challenge us, the bits I am using motor, ESC, servos etc, I have lying around. As I say I did order a larger power solution but it hasn't arrived yet from HK

And as for going down the lipo route......... comments like that and I will have to withdraw my ice cream offer at the funfly  

[Tim Mackey]

Hi Danny, as I say, I am not knocking it all, quite the contrary. I doubt very much that Shaun got his model under 9lbs - and remember he has a 120 IC in that thing I think! It all depends of course on what you expect it to do. At this sort of power input levels, and depending a lot on the prop choice ( which will be a bit limited in order to achieve your current draw limits ) it will not exactly be sprightly - and a long way from lightweight aerobatic sports and 3d stuff! Best of luck,and I will keep watching your progress.

Get the ice cream ready...and I like a flake in mine too

[winchweight]

Mine's nowhere near 9lbs I would say. Probably nearer 12lbs, especially with the engine (ASP1.08), on board glow (from you know who ), big metal spinner, retracts and air tank etc.

[Danny Fenton]

Thanks Shaun, half the time these manufacturers AUW claims are hogwash. We will see what the basic kit comes out at and take it from there. 2 packs of six cells fits where tank would go just as well as 1 pack of 8. C of G may be an issue with only 8 cells and a lighter motor.........

I was looking back through some stuff and the leccy Wot 4 flew perfectly adequate aerobatics when running at 400 watts, model weighs 5.5lbs. But that model carries speed really well through manouvres, sharp trailing edges etc. However much better at closer to 800 watts LOL

[Tim Mackey]

Hmmm, sort of thought 9.5lbs was optimistic - 12lbs ! Yikes

'Course with that great big smelly oily thing up front and other modding ( which look great incidentally ) it will be heavier than the leccy version. Personally I think 1kw is the sensible target in the context of this whole project, and should be achievable quite cheaply. You didnt say what motor it is you intend using?...and what about the point on the servos ?

[Chris Bott - Moderator]

I guess proof will be in the pudding as they say. Thats why this is such an interesting experiment.
At least with keeping the cost down, they are not expensive mistakes if an upgrade is necessary.

[Danny Fenton]

Hi smoke tamers, will give more info later as a bit tied up with family. Just flew YT Hurricane 13.5 lbs and it cruised around for three minutes on between 450 and 650 watts at about 1/3 throttle. 2.2kw was on tap but didn't use it, apart from burst at takeoff. Landed after a 3:30 flight having used just 553mah. So that appears to blow the 100 per lb theory for scale flying a warbird, note i said scale flying not Reno racing one lolol. Anyway as you rightly say some where in between would be a good target.

If the fury comes out more than 10 then as you say we will have to think again.

 Will post Hurricane Eagle Tree figures if interested.

Servos were all I had, (trouble with United Hobs is they never have stock LOL, guess we shouldn't have told everybody

The motor is a higer KV than ideal at 500 the motor is the Turnigy C4260-500 if you want to look it up.

[Chris Bott - Moderator]

Not sure if he'll thank me for this or not, but theres a video of todays flight at http://www.greenacresmac.com/Videos/Hurricane%202nd%20Flight.wmv 

Sorry I didnt properly capture the huge grin afterwards Danny.

[Bruce Richards]

Nice 3 point landing

[Danny Fenton]

In my defence thats my first landing with that model. I have never flown one with retracts, flaps, nor a model bigger than 56" wingspan...... got it on the airstrip, if you look closely the port leg buckled and it went over. (Thats excuse no 64 in Chris's book of excuses  )

Anyway onwards with the Fury......... wings finished - onto fus

[winchweight]

Timbo - forum moderator wrote (see)

Hmmm, sort of thought 9.5lbs was optimistic - 12lbs ! Yikes

'Course with that great big smelly oily thing up front and other modding ( which look great incidentally ) it will be heavier than the leccy version. Personally I think 1kw is the sensible target in the context of this whole project, and should be achievable quite cheaply. You didnt say what motor it is you intend using?...and what about the point on the servos ?

I haven't weighed it yet, but I'd be surprised if it was wildly different.

[Former Member]

[This posting has been removed]

[Tim Mackey]

Yeh well done Danny - nice site too! It certainly seems to show that 75Watt per pound is ample for this scale /semi scale type warbird....and I do usually suggest that this sort of figure should be ample, for scale like speeds of scale like models ( see this short extract from my recent article

"Factor in the effect of drag which will differ across model types, wind speed and flying style and you can see why this 100 wplb is a rule of thumb only! Slower flying scale models will probably be happy at around 75 - 80 WPP. Having said that, if during your planning stage you aim for 100 WPP then you'll not be far wrong and even if it proves more than you need, you do have a throttle "

I have an 8.5lb Hangar 9 Camel on the board , and am aiming for just 70 watts per lb, using a £20 turnigy 50-55A outrunner of 400Kv - had a 600 version but revs + watts were too high for what I wanted ...see below

I am fitting a big 16 X 10 prop spinning at 5500 RPM @ just 40A on a 4s LiPo - nice slow scale like revs, for nice slow scale like flight of what is, after all, only a WW1 'plane.

Personally I hate seeing warbirds of that type ( indeed also spitfires etc ) careering around ike a pylon racer

To get the flight characteristics I want, I am using the big prop, turned slowly, which will give me a pitch speed of around 50 mph flat out ( therotetically of course, not allowing for airframe drag or prop inefficiency ) Obviously, allowing for the draggy nature of the big bipe with huge radial cowl, rigging wiires etc, I expect that speed to reduce to a more suitable speed for the model.

So maybe this partcicular flight was a bit slow, but Danny did say that he was only at 1/3rd throttle most of the time, so it would obviously be a lot quicker opening up the go lever!

What prop you planning on Danny ? Obviously with 23V on tap, your RPM will be quite a bit higher than the Camel - but then thats no bad thing on a Sea Fury - as long as it doesnt get too high of course!

Due to the loading of the 16" prop, my 400Kv motor on 15V spins at 5500, pretty close actually to the theoretical unloaded rpm of 6000! You may well find that your 500Kv motor gets close to its theoretical RPM too with the M1 cells holding good voltage under load - 23.5 X 500 = 11750...so even knocking 10% off for loading, thats still over 10500.....pretty high for a big propped warbird.... you may even get away with LESS cells rather than more.....providing you fit the correct prop

[Chris Bott - Moderator]

Danny, get that motor mounted and run some tests, I'm dieing to see some results.Timbo, not on your scale obviously, but I flew a DB Sprot and scale 56" Tiger Moth first flight yesterday on a 670KV Motor on 6M1's and a 12x6. (had the motor, cells esc spare and it made the cg spot on). Was so good I had 4 flights, last one must have been over 10 mins and I only put 1000mAh back in. I was very pleasantly surprised how slow and sedate the flying was. Having never ventured into scale or bipes before. Took more rudder than aileron to fly, but everyone had warned me about that.If you like the look of the field, I'm hoping to be there this afternoon with a live webcam.
This is another practice for our funflys. Mind you on a day like today, I can't see anyone looking at a website this afternoon lol. If yr interested see greenacresmac.co.uk

[Tim Mackey]

Whats a "sprot and scale" then Chris

[Danny Fenton]

Its a Midland thing

[Chris Bott - Moderator]

 you may have to get used to my spellling!

[Danny Fenton]

Here are the motor and ESC the motor was $29 and the ESC $11.95 (note US dollars)

The sexy mount is not going to be used as it was a whopping $11 and this is a budget build so we will do it the Screwfix way

The Screwfix components, A 1/4 ply (real ply not funny lite stuff) drill a hole to centre the mount More later (thanks Mr Redshaw great tip) holes to mount the "mount" assy to bulkhead of model and obviously countersunk holes to allow the 50mm long 4mm steel bolts

And here it is ready to go, infinitely adjustable but I rarely alter mine once made. Note the nuts directly behind motor are NYLOCS this stops them spinning at random lol and makes setting up the distances from the bulkhead to motor easy.
Using a short 4mm bolt and wing nut, lossely mount this assembly on the model using the hole for the fuel tank in the models bulkhead. loosely fit the cowl and then slide the motor mount assembly around until centred. Once happy, pinch up wing nut to clamp it all together, drill through the 4 unused holes straight through model bulkhead, fit blind nuts at the back and mount entire motor asembly to model bulkhead as though it were a normal IC mount. I will include more pics when I come to it for those that haven't a clue what I am on about lol

Centreing the motor in a radial cowl is easy when you know how, I am afraid I owe this one to Phil Clarke of Fighter aces (thx Phil) simply make a card or stiff paper disk the size of the cowl opening. Mount this on the motor and use the above procedure.

everybody still with us