Piper Cub

[Piper Cub]

Hi all.

Im seriously thinking of going down the electric flight path(!) since lugging all the associate IC gear around is just too much. I just love Piper Cubs and have spotted a few models \ kits on the market.

Ones Im thinking of are the DB Scale 84" Cub, Hangar 9 Power 46 Arf 80" and SIG 84".  Any thoughts on which would be best for leccie? Obviously the Hangar 9 Power is designed for electric while the others would need to be build as electric flyers.

It seems a brushless motor along the lines of the EFlight Power 46 or bigger (60?) would be suitable. Any other suitable suggestions as the EFlight motors look a tad expensive (I get a bit confused over the brushless motor ratings. Is there an easy way to find what size motor would suit a model based on weight \ wingspan??)

Lipo's look too expensive at the moment IMO so would look to go down the NiMh route but using as ESC that could take both NiMh or Lipos. Are Lipos & Li Ion the same?

Thanks for any advice & happy New Year!

[David Ashby - Moderator]

Hi Piper

Looks like you have a choice between building and ARTF there, only you can decide....

Use the watts per lb method of estimating the motor you need. Aim for at least 100 watts/lb and you wont go too far wrong. Nigel Hawes wrote a long article in our recent special issue on the very subject. Go with Li-Po's though, they're not much more expensive and their power to weight ratio means you get more for your money in flying terms. Li-Po's will be of more use going forward too.  

[Piper Cub]

Thanks for the info.

Im starting to think I should go along the Hangar 9 route for my foray into electrics (I've flown ic before) since this is 'made' for electric rather than ic and just lob a few electric bits into it. Once I've got more experience of electrics then, I think I'll be better placed to selected say a DB Piper Cub kit and build that specifically for electric.

For the Hangar 9 Cub (approx one fifth scale, flight weight approx 7lbs, this comes with a E Flite 46 so would assume the manufacturer knows its neither under or overpowered. Recommended Lipo configuration is 4S2P or 5SX (what does this mean?).

Is it better to get two 4S2P packs, cost approx £132 each!

A Pheonix 60amp ESC would cost approx £80.

Is all this a good combination? Recommendations for an alternative ESC would be welcome.

Thanks!

[Tim Mackey]

Piper...some of the answers are given in your other thread which i have just rerponded too.

 If you are looking for budget motors etc, then here is a typical replacement of similar spec to the eflite 46 you mention. it is the one I am going to be using in my Hangar 9 Sopwith camel.

Motor ...approx £20

The 4s batteries I am using cost me £ 30 each ( I am using 2 in parallel )

batteries

[Tim Mackey]

The ESC I am going to be using is here....

approx £22 60Amp with good BEC

[Piper Cub]

Hi Timbo.

Many thanks for the info! Are you UK or US based as Im wondering about the UK availability of the items mentioned.

The cost of those items is a real eye opener! Im assuming they can be bought in the UK, probably for around the sterling \ dollar equivalent cost. Even so this would represent a fantastic saving.

What sort of flying time would you expect on that size lipo? Assuming you're not racing about the sky with a Camel, of course.

Once again, thanks for your patience with a newby.

[Tim Mackey]

Hi Piper.

I am UK based, but do buy a lot of my stuff from abroad ( and UK too if I can get what I want, although my nearest model shop is a 2 hour round trip, so almost all my purchases are WWW based )

There are a few UK specialists about that may well be able to supply similar spec'd gear at prices close to those I linked to, and I only showed you those as examples of budget gear which is available these days, rather than a direct endorsement of the supplier / product. BRC hobbies, Robot birds, Giantcod and so on...again apologies to those I didnt mention. We all have our favourites I guess, and those items linked are from a personal favourite of mine, and I was ordering other items at the time, so made up an economical shipping order.

I dont intend to be racing around with the Camel and will be striving to keep her light as possible within the constraints of the kit of course - I am only aiming for around 75 - 80 watts per pound on this type of model - which I admit is a little low for me ! My home made spreadsheet indicates that at my target weight of 7.5lbs I need just a shade over 600 Watts, which on a 4S pack will require around 44Amps static, and with unloading of the prop in the air... thats about 40A WOT. This then  calculates the duration by dividing the packs capacity ( 3200m/ah ) by the estimated WOT current draw ( 4000m/a ) multiplying by 60 ( for minutes ) and then adding 50% to allow for low throttle settings and calm flight manners   and It estimates flight times of around 6 -7 minutes or so with the single 3200ma pack, and maybe around 10 - 11 mins with twin packs in parallel. The spreadsheet has proved pretty accurate on past and current models. I have also ordered a 5s pack of slightly lower capacity, and will be experimenting with that too. Thats the thing with electric flight, there is quite a degree of flexibility, and experimenting with different batteries and props ( monitoring things closely of course with a wattmeter ) is part of the fun for me

[Malcolm Blows]

Hi Piper

I have been flying a Hangar 9 Cub for a while using a Dual Sky 4250 and 5S pack. This provides an embarrassing amount of power and will take off in a scale - like manner on 1/3 throttle. It is not an aeroplane to tear up the sky and will reward careful flying on much less power. The reason for my power choice was to enable the quiet towing of my 1/4 scale Minimoa. Enjoy!

Malcolm 

[Piper Cub]

Hi Malcolm.

The slower flying capability of the cub is one of the things that appeals to me, besides thinking they are just such a good scale subject.

Did you not get the Hangar 9 electric ready version of the cub or did you ditch the kit motor or is the dual sky 4250 and ESC (google doesnt find anything for this!)

What sort of flying times do you get on your set up?

I used to fly gliders and would liked to have had an aero tow with a cub!

 Thanks

[Tim Mackey]

here.

The claimed 900 Watt power input is really only for short bursts, and it is more likely to be most efficient at around the 40A mark. Assuming correct propping to get this amperage, then on a 4 cell pack this will provide around 560 Watts, which should still be sufficient for your Cub providing the weight does not pass the 7lb mark or so.

Obviously, keeping the same prop and moving to a 5s like Malcolm has done will increase that to around 700watts, still well within the motor's maximum limits.

[Reno Racer]

Malcolm,

Dualsky motors can be bought in the UK through Als Hobbies.  www.alshobbies.co.uk I have used a 0.21 class for ages and they are very good motors, and much cheaper than the E-Flite ones, although the dualsky ones are slightly less powerful for the same IC rating. The motor mentioned available in the US looks good, certainly for the cash, although I'm not sure how long the post would take, or more importantly how much it would cost - of course, this could make the cheap option actually more expensive (although Timbo would be better placed to comment on that).

The other good thing about Dualsky motors is that they specify its IC equivilent, power output (although this is the max power for short durations), number of lipos required and ESC Amp rating required.

I have also used a HIMAX (JPerkins) C3520-0700 motor which is a 400watt motor - although not the size you require, these motor do come complete with all mountings, prop spinners and much more. They are quite powerfull outrunners and they are pretty cheap. I have one mounted on a Seagull Innovator (1.6Kgs), which should require at 3.6Lbs should require a 350 watt motor (according to my excel homemade EP database). This HIMAX motor is rated at 400watts, but pulls the innovator into the sky like an aerobat!!

[Reno Racer]

Malcolm, forgot to mention,

In terms of cheapish ESCs; I have been using a Duramax 60A ESC (80A burst) for sometime now. Its an excellent little ESC, I've had no real problems, it can be programmed either by card (about £12) or by using the instructions and the throttle stick. It too has a switching BEC caple of a 5V/3A output to power a few more servos, without resorting to a seperate Rx battery pack or UBEC. It also allows from 2-6 Lipo, or 5-18 NiMH/NiCad if you prefer.

It cost be about £35.

Chris

[Tim Mackey]

Christian -The link I gave Malcolm in my post WAS to Als hobbies

[Reno Racer]

Timbo,

Apologies, I only noticed that after I'd posted mine. I would add one of those smiley things but don't know how.

Regards 

[Former Member]

[This posting has been removed]

[Tim Mackey]

Thats OK Christian, I will not throw you to the lions

[Piper Cub]

OK, think I've decided on the model Piper Cub to get as a first leccie.

The J Perkins Piper Cub is 68" span and weighs in at a reasonable 5.5lbs. Its ARF so minimal build, although will need converting for electric and has a good scal appearance. Best bit its available for under £50! At that price, even if it gets a bit of hangar rash I dont think I'll have been robbed.

Probably look to get an HXT 50 55B motor havent decided on ESC yet but thought a Hi Model Fly 60Amp OPTO (no BEC)

Anyone had one of these Perkins Cub's and thoughts on motor ESC combo?

[Tim Mackey]

I have now received and bench run my HXT 50 55B (600kv) motor, and I am very pleased with it's performance. It throttles smoothly and shows no signs at all of being even warm after test runs. Considering it cost the equivalent of just £21 I am well chuffed. I will be using a pretty large diameter prop as the Camel cowl is BIG - tests so far with a 15 X 7 prop show 588 watts on a 4s pack, at 42A and shade over 7000 RPM. Similar set up on your model would give around 100Watts per pound+ , which is, frankly overkill for a Cub.

A 14 x 6 prop gave me 34A and around 476 watt, which I think would be better suited to you.

You may even be able to drop to a 13 x 6 and get even longer run times - when I tried a 13 x 6 on the same pack, I got 29A and 406 watts. This still gives you 70+ Watts per lb, and I estimate run times of around 10 mins at least. 70 watts per pound for this type of model should be fine IMO.

The 60A ESC should be fine

[Piper Cub]

Cheers Timbo. Where are you getting the motor from at that price!? Cheapest in the UK I found was £35!

Would I be better with the Cub going for 2 packs in parallel rather than series? Im assuming parallel gives duration while series gives more speed (which I dont want for this model)?

The model only needs 3 servos so would you recommend a BEC ESC in this case, if so, could you suggest something suitable? (The ESC in the earlier link seems to have changed!)

Ta!

[Tim Mackey]

Hi Piper... I am afraid that the motor ( and rather excellent switch mode BEC 60A ESC also @ 21 quid)

both came from Hong Kong.

Now I dont normally like to endorse a specific product or supplier on forums, but I think most peeps know who my current favourite HK supplier is

If you want more info, then I suggest you PM me, I am likely to be placing another order soon, and we could share postage?

A good BEC should be OK for this model with only 3 servos.

Yes - parallel the batteries for duration....if you series them you would end up with WAY too high a current and wattage. I would try it on a single 4s pack first ( assuming a good capacity such as 3000mahr or so) and if the flight time is long enough for you, then you have a second flight waiting to go with the second pack.

[Piper Cub]

Is this a good spec motor for the cub? Cub weighs between 5lb and 5lb 11oz.

L3520-7 650 KV (45A)

This is a '600W' class motor, equivalent to a .40 or .50 glow engine and is recommended for planes up to 8 lbs (128 oz / 3.6 kg) total weight using 4-5 LiPo cells.  
The motor is capable of packing a serious punch - i.e. 14.8 volts x 45 amps x 93% efficiency means you've got 620 watts of power (short bursts only) - at the prop!  A 20c battery running flat out wont last long, so you're probably better off with a 15c. Ideal battery for this motor would be a 3000 - 4000 mah, 4 cell, 15c. 

Specifications
No. Of cells: 4 x Li-Poly
RPM/V (KV): 650
Efficiency: 93%
Max RPM: 6500
Max loaded current (A/60s): 45
Maximum efficiency current:26A
Voltage: 13.5v
Idle current: 1A
Recommended Prop Direct Drive: 13x8What I dont seem to understand is you can get motors of very similar specs but when some quote Max Load current and Max Efficiency Current and other dont, how do you compare them!?