What WOT 4 (ARTF electric)?

[Jonathan M]

I'm thinking about an electric sports-aerobatic for clean, low-fuss winter and lunch-break flying on our often windy hilltop site - both for enjoyment and to help work up eventually to my B. Have had the Acrowot ARTF with a 70 FS for a couple of years now and would like something a tad smaller to fit assembled into the car but with a similar wing-loading (the AW is about 21oz/sqft). I'm not after all-out power or mad aeros, and would like to be getting 9-10 minute  flights with moderately-paced aerobatics at various throttle settings rather than 5 mins at all-out welly - so I'd fit the largest capacity battery in the suggested range. I don't currently have the time to do any proper kit building.

The 53" WOT 4 MkII balsa ARTF seems the closest to my IC Acrowot in terms of size and weight for penetration, and the volume of sky I usually fly in (and can see!), and shouldn't take too long to put together, but the total cost (including 4x 4s 4500mAh batts) is just over £500.

The 43" WOT 4 E balsa MkII ARTF is 80% of the size with a loading of 18oz/sqft, and would involve a similar fit-out time Total cost (with 4x 3s 2600mAh batts) about £325.

The 48" WOT4 Foam-E MkII appears to use exactly the same electrical components etc as the E balsa but, whilst marginally bigger (easier for my eyesight), is much lighter - its loading comes out at about 11-12oz/sqft. This would make it very similar to the Riot I originally trained on - too light for satisfying flying in all but calmer conditions, and I really don't like foam. But it would be much the quickest to go from box to air, and the total cost (with 4x 3s 2600mAh batts) about £230.

I'm inclining towards the 43" balsa ARTF (which would usefully fit the car without having to put the back seats down), but there's little by way of reviews etc online, and I wonder whether it would be too fast for its small size?

Any suggestions or prejudices on which way to go?

Cheers

Jon

Edited By Jonathan M on 07/10/2018 07:52:20

[Old Geezer]

As revued in RCM&E a while ago, the smaller wood built Wot4E would seem to be exactly what you're looking for, not sure exactly when but a quick search through the digital archive should find it for you.

[Jonathan M]

Thanks OG - found it **LINK**

[Biggles' Elder Brother - Moderator]

Well as you probably know I'm a bit of a fan of the old WOTTY, I actually think that when Foss designed it it really was the last word in sports aeroplanes. Consider the fact that many of the most successful competitors are actually just WOT4 clones - the Riot being a case in point I believe.

Anyway, which one to get? I would suggest the larger one - 53" span. I have had one of these for some time now and it is a "go-to" model for me. Whatever else I take to the strip I always take that and settle my hand in by flying it first. It has the weight and presence to cope with all but the very worst conditions. Its inertia also helps with its aerobatics - it as more "follow through" due to its momentum, so the tops of even very large loops become more easily round and with full control, rolls are more constant speed and can more easily be flown slower.

In terms of performance: with the recommended set up - or equivalent - verticals are unlimited, every mainstream aerobatic manueouvre is possible - even on a large scale. Endurance is a little over 8 mins if you hammer it continuously, easy 10 mins for mixed aeros (B-test style). It cruises on under half throttle!

Does it fit in the car? Well that depends how big your car is! I have a Mondeo estate (the ultimate aeromodeller's car!) and it will fit in that fully rigged. But even if you do have to break it down - it's only two aileron connections and two wing bolts, so hardly a major "set up".

So,that's my tenpenneth worth - based on owning one of these for good few years in form or another!

BEB

[Shaun Walsh]

Have you looked at the Max Thrust Ruckus or Riot?

[Rich too]

If you want a hack to throw in the car assembled you can’t go wrong with the foam-e. It will fly in any weather and the foam construction will take a lot of abuse.

[Jonathan M]

Posted by Biggles' Elder Brother - Moderator on 07/10/2018 10:05:08:

I would suggest the larger one - 53" span. It has the weight and presence to cope with all but the very worst conditions. Its inertia also helps with its aerobatics - it as more "follow through" due to its momentum, so the tops of even very large loops become more easily round and with full control, rolls are more constant speed and can more easily be flown slower.

In terms of performance: with the recommended set up - or equivalent - verticals are unlimited, every mainstream aerobatic maneouvre is possible - even on a large scale. Endurance is a little over 8 mins if you hammer it continuously, easy 10 mins for mixed aeros (B-test style). It cruises on under half throttle!

BEB, thanks for that valuable heads-up for the 53" version. It should be my obvious choice for electric, more or less matching my IC Acrowot in terms of size, presence and momentum. I can just fit the 58" Acrowot diagonally in the car boot assembled with both back seats down, the 53" Wot 4 should fit easily, possibly seats-up. Also, being used to 15 mins with IC, I'd be very happy with 10 mins for mixed aeros!

I've now found an older thread on the (Mk1) balsa E **LINK** from which this:

Posted by Clifford Stone on 22/10/2013 12:16:24:

... battery has to be a 4s, 3's just does not have the grunt on the 'woodie Wot4'. In my humble opinion the 13x4 has the legs on the 12x6 with better torque conversion for sustained vertical!!! CofG has ever been an issue on the balsa Wot4, with carful radio positioning, a 4s battery and slightly heavier and more powerful (torque) motor, I got it to 90mm, weighs 4lb, works fine for me.

So it seems the Mk2 E balsa might be too tame on the recommended 3s 2200-2650 and slightly heavier (for how much extra duration?) on a 3000-3300 (modification needed but possible). If feasible, I've already got two 3300's so only need two more. But if going up to 4s then weight and loading will really increase - and the total cost would also creep up closer to that of the larger one fully kitted!

Cheers

Jon

PS Re the RIOT and Wot 4 Foamie, I just don't want foam and I DO want a good degree of weight and presence.

[Biggles' Elder Brother - Moderator]

I use 4s 5000mAh in my 53" WOTTY - goes very well on them, no question of any lack of power!

BEB

[Jonathan M]

BEB

I've slept on it, and your spec is my choice!

Cheers

Jon

[Bruce Collinson]

+ 1 for BEB’s powertrain, a 5A LiPo will just fit in and doesn’t need balancing weight to achieve a satisfactory c of g. Be careful with the prop and the power readings, mine tends to run a bit warm. I fitted bigger wheels for a damp winter strip.

On my third.

BTC

[Bob Cotsford]

Mine too has 4S power, in my case I have a Power 50 motor (iirc) and with a 4500mAh pack I recently got over 20 minutes with a mix of aeros and pootling about for a consumption of around 3000mAh. I think it's turning a 12*8 though to be honest I bought it second hand and just flew it as it came.

[Biggles' Elder Brother - Moderator]

I don't think that set up will dissapoinbt you Jonathan. I usually use a 13x8 on mine, that seems to give good balance between thrust/power and endurance.

BEB

[Jonathan M]

All useful info chaps. (Bruce, I'll certainly stick bigger wheels on as I did with my Acrowot - makes life on the ground much easier!)

Bearing in mind that I've never before specced an electric powertrain (my Riot was effectively RTF), 4-Max recommend:

800kv 35mm diameter 47mm long motor **LINK**

60A ESC **LINK**

12x6 prop - Are they being conservative or would this be correct for the motor specified? What effect on the performance/temp/duration would a larger/coarser prop have with this setup? Or are you guys using larger motors?

Jon

[Geoff S]

The bigger the propeller (in either pitch or diameter) the more current and, to first approximation, more power. It depends how you use the power as to the effect on duration and, if the current exceeds the ratings of either the motor or the esc, could result in damage to the power train. In all electric power systems a Wattmeter is you friend.

Geoff

[Biggles' Elder Brother - Moderator]

The motor I use is rated at 60A, 800kV. The recommended prop was 12x8, but as Geoff says the Watt meter is the judge. With a 12x8 I was only pulling about 40A+ - I wanted more than that. A 13x8 takes me to about 50A max about 700W (on a model weighing only 4.5lb or so!)

Don't get too close to the motor max current - you need some headoom for both the motor and the ESC (both rated at 60A in my case). You have a little bit of a safety margin because whatever the Wattmeter shows static on the ground, it will be slightky less in the air. So, by pushing 50A on the ground, I'm comfortably within limits in the air.

BEB

[Ron Gray]

I went a bit silly with mine, only because I had the bits lying around. It runs a 550Kv motor on 5s 4000Mah (or 6!) spinning a 16x8 prop. It’s a bit quick!

[Geoff S]

I seem to be bending to any breeze these days.

I fancy a new winter hack and I've been toying with the idea of a Ruckus but an ARTF Wot 4 is about the same price as a bare Ruckus airframe. I have a suitable motor/esc combo (a Foxy C4020/10 I bought from Puffin a few years back) it's 755 rpm/volt and 50 amp maximum current but for 30 whole seconds. It's rated at 800 watts. I think it would be perfect for a Wot 4 on 4S and a 13x8 or 14x7 prop. It's in a Skyshark Fantasy I built a while back and disappointed so ready to be re-homed.

Tempting ... so tempting. Then all I have to do is decide what 'proper' model I build over the dark days of winter. Life is hard

Geoff

[Geoff S]

I ordered a Wot 4 ARTF from Kings Lynn Models on Monday evening, received a phone call from them the following day checking that I realised I might need one of the optional mounting kits (ic or electric) - I did but prefer to do my own thing, and it arrived this morning (Wednesday) at 10.15. I call that excellent service.

To examine the model I had to resort to my master's degree in unpacking technology but it meant everything seems to be undamaged.

I've found a brand new motor I've had for ages which may suit. I originally bought it for my DB Tiger Moth. It's a HiModel 2820-7 919 rpm/v, with a continuous current rating of 45 amps and, according to the data sheet, draws 37 amps for 460 watts on 4S with an 11x7 prop (530 watts, 40 amps, with a 12x6) which I think should be OK.

How heavy is the model with a 4AH 4S LiPo (I have several I use for other models)? Does anyone know?

I'm going to fit this out and then concentrate on building whatever scale model I plump for over the dark days ahead.

Geoff

[Biggles' Elder Brother - Moderator]

Nice one Geoff.

It's a long time ago now but, to the best of my memory, mine came out at 4.5lb with a 4s on board.

I did my own conversion as well - very straight forward as the most difficult part of any conversion tends to be making a hatch and that's already done for you!

BEB

PS Mine balanced fine with the battery right forward in the fuel tank bay - I found no need to break into the cowl area - which is very small anyway - though I have mounted the ESC in there.

[Bruce Collinson]

Now it’s dark, do you want me to go to the outside Mancave (some people call it a garage) and weigh mine?

Jonathan, some of my club mates fitted litho plate mudguards to theirs after I floated the idea, half hoping a pair would make it to mine but nobody took the bait. We share our strip with sheep .....

BTC

[Kim Taylor]

I don't know if they've got heavier over time, but my one which I recently completed, albeit using a 6s 2700 Lipo, weighs 6 pounds.

I know my power train (which I had 'in stock' ) is a bit ott, but I don't think it's a pound and a half heavier than a 'standard' setup.

Flies fine though, although according to my club mates,on some of my landings the tyres leave scorch marks on the grass!!

I you look at the Wot 4 artf thread, most electrics seem to come out at around 5 and a half pounds, which I would agree with.

Kim

Edited By Kim Taylor on 10/10/2018 20:22:38

Edited By Kim Taylor on 10/10/2018 20:23:17

[Geoff S]

Well, I managed to get the motor fitted after a bit of a faff. Most of the said faff was sorting through my notorious junk drawer seeking a suitable piece of material to mount the motor on. It's probably just as well I didn't buy the electric motor mounting accessory kit because the cross-shaped mount on my motor is bigger than most and probably wouldn't have fitted.

In the end, after an abortive attempt with some 3mm aluminium which ended up with the nuts for the studding fouling the nuts for the motor, I used a piece of 3mm old fibre glass PC board which seems to be sufficiently sturdy. I suspect I rescued it from a scrap bin at work which means I've had it for over 23 years - you see junk does indeed get used eventually. The piece of aluminium definitely came from work because it was originally the front panel of an MC68000 OS9 development system we used to play with!

Kim, not sure if the ARTF Wot4 has become beefier but this one seems to be quite light, though I haven't weighed it. Mine will be 4S 4AH. All the stuff I'm using to get it in the air I have already and this airframe is just a means to an end - a quick build winter hack. I just wanted a rough idea of the final all-up weight to get a feel for the necessary power I needed. It looks like I'll achieve 100 watts/lb which is more than enough. I don't have the talent to be a real hooligan!

Kings Lynn Models wasn't the cheapest source; they are about £5 dearer than some others but I've had good service from them in the past and really a fiver's neither here nor there.

Thanks for the replies gents. I won't bother detailing the actual 'build' except where I deviate slightly from standard. It looks quite well made with triangular stock in the right corners but I'll probably daub some WEST epoxy around inside to make sure things like the u/c plate stay where they should.

Geoff

[Brian Dorricott 1]

Geoff your a man after my own heart , I tell the wife I'll keep that you never know when you want it , she tells me it's junk I throw it and the day after you need the same ! I never say what's all that wool and material in your workroom for because that's a one way ticket to the doghouse !

[Geoff S]

Brian, I'm not sure if it's fortunate or not but my wife and I are of the same mind when it comes to hoarding. I always tell people we live in luxurious squalor Right now there are several models stored 'temporarily' in the lounge because I'll be getting them out at the weekend.

Geoff

[Old Geezer]

I'm with you Geoff on the u/c reinforcement - except that I use thinned epoxy and a some glass cloth off-cuts to spread the load beyond the ply plate fore and aft and a little way up the sides. Oh, and I also use 3 or 4 inch air wheels too - these take some of the sting out of a less than perfect landing and a side benefit is that they roll better if the grass on the patch is a bit long.