By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by CML

What WOT 4 (ARTF electric)?

All Topics | Latest Posts

Search for:  in Thread Title in  
Kim Taylor10/10/2018 20:21:41
255 forum posts
53 photos

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!!devil

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 Sleath10/10/2018 23:41:47
avatar
3248 forum posts
247 photos

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!

dscn2157.jpg

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 110/10/2018 23:56:05
78 forum posts
2 photos

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 Sleath11/10/2018 00:02:49
avatar
3248 forum posts
247 photos

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 Geezer11/10/2018 07:47:01
588 forum posts

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.

Biggles' Elder Brother - Moderator11/10/2018 07:58:46
avatar
Moderator
15748 forum posts
1460 photos

The weight question has filled me with curiousity now! It's perfectly possible my memory is at fault - it was some time ago when I put this together.

I'll try to nip out to the shed this afternoon and quickly weigh the WOTTY. I'll report back.

BEB

Kim Taylor11/10/2018 10:54:43
255 forum posts
53 photos
Posted by Kim Taylor on 10/10/2018 20:21:41:

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.

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

Just for comparison purposes, I've weighed my LiPo which comes in at 425g and the catalogue weight of my motor - EMax 4020/09 - is 290g.

As I said above, total weight of mine is pretty much spot on 6lb, so you should be able to work it back from there.

Kim

Jonathan M11/10/2018 11:45:10
avatar
667 forum posts
275 photos

Ordered mine now from SMC who had all the particular bits I wanted and threw in 2/3 different props for watt testing.

Overlander power-train: Tornado Thumper Brushless 4250/06 800KV (about 800W), 60A ESC (max 80A 10 secs), and some 4s 4,250mAh batts - all of which is a little meatier (and heavier) than the 4-Max options.

New Power XL-38HMB servos - metal geared standards.

3" foam wheels

Watt-meter.

Will be interesting to see what it all weighs... and how it eventually flies... and for how long per battery! laugh

Cheers

Jon

Bob Cotsford11/10/2018 12:08:31
avatar
7822 forum posts
433 photos

If I could extract myself from this armchair I'd go and weigh mine but I doubt it weighs as little as 4 1/2 lb even without the battery. The supposedly lightweight Wot 4 Pro is listed as 4.4 lb so I would have thought 6 -6 1/2 lb more likely for the full blooded one.

Jonathan M12/01/2019 17:23:50
avatar
667 forum posts
275 photos

So my Wot4 ARTF, which was assembled and test-flown by a club-mate, is now good to go. I had a single flight at handover this week. It was a bit blustery and was flying on his 'soft' TX which I wasn't used to (my sticks are set to stiff) and 10% expo (I'm normally 15% plus) so it was a bit twitchy... but WOW! Quite different to my comparatively more stately Acrowot with its 70FS. Being back on electric for the first time in the few years since I trained on a foamie, I'm also going to have to get used again to the immediate throttle response!

With a Overlander Tornado 4250 800kv motor, a 60A ESC and a 14x7 prop, the max static draw was 54A with 25N thrust (the 13x8 maxed at 50A and 23N). The model is exactly 2kg plus 0.4kg for the 4S 4250mAh Lipo, so the flying weight is right on spec at 2.4kg (5.25lbs), giving a loading of 20oz/sqft which is almost exactly the same as my IC Acrowot. CG is at 82mm specified.

I was originally going to buy the Wot4 and power-train from 4-Max, but he insisted the flying weight would be 4.75lbs and that the model should take a smaller motor, ESC and Lipo. From the feedback earlier in this thread I wasn't so sure about that, so went down this route - if I don't hooligan it around the sky, I expect to get decent flight times with this setup.

One other thing: despite the coloured trim and decals, white isn't exactly the easiest colour to see against an overcast sky!

Now just the weather...!

Jon laugh

PS my mate is now buying the slightly smaller 43" Balsa ARTF version for himself, as it takes the cheaper 3S 2200mAh Lipos of which he has plenty.

Edited By Jonathan M on 12/01/2019 17:32:44

Jonathan M20/01/2019 19:00:15
avatar
667 forum posts
275 photos

First flights today on my own TX, working through all four 4250mAh 4S Lipos. Aim was to settle the Wot4 nicely down on mid-rates, do a full stick roll no faster than about 1.5 to 2secs, trim out any warps etc (both ailerons certainly have inherent twist), etc.

Initially found the whole thing a bit too fast (cruise needed about 65% throttle) with the batt down to 40% (my limit for ensuring longevity) after just 8 minutes flying. Next batt decided to slow it up by adding a few clicks of up-elevator trim, which got us cruising nicely at half-throttle and after a few aeros landing on 8 mins with 55% capacity left, although whenever I did need to open up the taps a bit the climb became too steep a bit too quickly. Next batt tried a couple of 3-turn spins, but the model was a slightly reluctant to stall at first and my impression was that it then went into more of a spiral-dive than a flat spin (it certainly both spun and descended particularly fast!). Initial rolls (without any bump of down-elevator when inverted, or top-rudder which I can't yet sequence in my mind) needed a lot of initial climb to compensate for the subsequent dropping out. Landings tended to float a bit then bounce (but this may be more to do with the light wind and my lack of experience?).

All of this should have prompted me to do an inverted dive-test to check CG (set as per instructions at 82mm), but the patch was becoming a bit busy with members doing 3D and random folk talking to me while I was flying. My brain was by now going mushy after such a long layoff and in the cold, so I just pootled around for the last batt.

Now at home, I've just remembered something from Geoff's Wot4 Mk2 electrification thread:

Posted by Biggles' Elder Brother - Moderator on 13/10/2018 13:58:14:

I would agree with Ron here. When I say mine balances fine - it does - but it isn't set at 82mm from the LE as the instructions say. You will find that nose heavy I believe, I know I did. By all means try it, but I bet you move it back!

Personally I think the wing incidence is fine - personal taste of course - but for the CoG I'd say 85mm back is the beginning of the "good zone"! After that it just depends how sensitive you like the elevator to be.

I assume everything I experienced earlier today points to a CG spec that is really too far forward? I plan to add some lead to the tail to bring it to a static 85mm before taking the Wot4 up again, then dive-test and fine-tune etc.

Otherwise a lovely model for the job!

Jon

Geoff Sleath20/01/2019 20:11:52
avatar
3248 forum posts
247 photos

Yes, I use a similar power set up on mine (though with a different motor/esc) with 4 AH 4S LiPos and get 10 minute flights comfortably which is long enough for me.

Mine's very reluctant to spin and I've pushed the battery back as far as it will go so I guess a little tailweight is the easiest solution. When it does go into a 'proper' spin on elevator and rudder it's very fast but recovers instantly on centring the controls.

I'm sorry to confess I haven't been up to the field yet this year. I've been busy playing with a new bicycle and it's just a bit too cold for my ageing bones to be standing on a draughty airfield for an hour or two.

Geoff

Kim Taylor20/01/2019 22:24:08
255 forum posts
53 photos

I originally had mine balanced at 85mm but found I was still dialling in about 4mm of up trim on the elevator to fly level at half throttle.

After conferring with clubmates, I have added (in stages) 20g to the tail. Still flies with approx 1.5mm of up trim but goes inverted with just a smidge of down and slow rolls are nearly axial without elevator input. When I've next got the gauge out, I'll measure where it's balancing.

Beware of the rudder / pitch coupling - I broke mine last week when on a crosswind approach, I needed to input a lot of rudder at the last minute and the resultant nose drop was enough for me to drop in about a foot short of the mown patch and it did a somersault which broke the fin away from the fuselage.

Kim

Ron Gray20/01/2019 22:53:54
1411 forum posts
358 photos

I’ve flown mine quite a bit now but went back to trimming basics. On the 45 degree inverted half throttle climb she gently drops her nose and that’s with the 5s batt pushed back. Similarly when inverted it just needs a smidge of down to keep it level. So c of g ok, but on upright, level flight it drops its nose, power on or off. So I raised the main plane le to give it more incedence but that didn’t make much difference. After removing that I tried to see if I could get it level by using flapperons that I could dial in with a rotary knob. This made it worse! But if I used spoilerons it got better (the reverse to what I expected). I then took the drastic action of cutting out the tailplane and adding - incidence (raised the te) with about 3mm in place it got rid of the nose down in level flight. I’ve got some more tests to carry out tomorrow, vertical power off dives to confirm my settings and if ok I’ll glue it up like that. One thing I will say is that it spins with no problems now (with the batts back). For landings I use spoilerons which result in bounce free touch downs!

onetenor21/01/2019 03:19:09
avatar
1900 forum posts

Surely moving the CG back increases nose heaviness or did I miss something?

onetenor21/01/2019 03:19:10
avatar
1900 forum posts

Surely moving the CG back increases nose heaviness or did I miss something?

Jonathan M21/01/2019 06:38:10
avatar
667 forum posts
275 photos
Posted by onetenor on 21/01/2019 03:19:10:

Surely moving the CG back increases nose heaviness or did I miss something?

The more nose-heavy a model, the further forward will be its CG.

Adding tail-weight (or moving the battery in the direction of the tail) will therefore "move the CG back".

Jonathan M21/01/2019 08:21:32
avatar
667 forum posts
275 photos

Interesting Ron and Kim...

Last night I carefully re-checked the CG, which is already in fact at 85mm. While I've got stick-on weights to tweak things further when next in the air, in the light of Ron's comments it would seem wise to first check wing-incidence on the bench. On the principle that a symmetrical wing aerobatic model should actually have a smidge (0.5° appx) of positive incidence (and my ARTF Acrowot had similar problems until I discovered it was manufactured with 1° negative incidence), a slight re-seating of the wing may be necessary?

Of course increasing the wing incidence will also increase the nose-down flying attitude, so Ron's method of correcting this by packing up the TE of the tailplane would be a smarter solution... but harder to do given my tail-parts are all now permanently fixed!

The other thing to sort out before I next go flying is the engine thrust line. There's a sharp swing to the left on take-off and a sharp pitch-up on opening the throttle from slower speed, which each indicate that the engine probably needs 2° of right- and 2° of down-thrust.

Edited By Jonathan M on 21/01/2019 08:23:04

Jonathan M21/01/2019 08:22:07
avatar
667 forum posts
275 photos

[oops, double-post]

Edited By Jonathan M on 21/01/2019 08:22:44

Jonathan M21/01/2019 19:24:20
avatar
667 forum posts
275 photos

So I managed to get out again with the Wot4 this afternoon - colder and windier but had the patch all to myself which made concentrating easier!

The CG at 85mm is actually spot on - no pulling to canopy or undercarriage in a long vertical dive - and have decided to leave thrust-lines at neutral for now, using rudder to correct swing to left on take-off etc.

Ran through the B-Test manoeuvres - not very well but it was starting to blow harder with increased turbulence from various tree lines, a tricky variable cross-wind and slope-related lift/sink beyond the main patch on two sides. Tweaked rates a bit (a bit less rudder, a bit more aileron) and, despite wearing padded gloves, suddenly found myself much more in the groove! Got rid of the previous bounce on landing by coming in slower at a less steep initial descent, then levelling out while watching to keep the fuselage horizontal until it settles. Managed two passable consecutive rolls upwind with a bump of down-elevator at each inverted, but bottled out of the second roll downwind due to the rising wind. Stall-turn fine, figure eight circles of roughly equal size and height/bank-angles with crossover in the middle, but need more practice on setting up the stall and three-turn spin - rudder alone won't do it, but full aileron as well turns it into a spiral dive.

Now that I settled down a bit, have increased the timer to 10 minutes, which is just the right length for each flight, and landing with no less than 35% remaining.

All told a lovely bit of kit with loads of potential, and an ideal electric aerobatic model to get me up the patch as frequently as possible to progress my side of the flying! Glad also I went for the normal size balsa ARTF rather than either of the smaller options - it has exactly the right weight and presence (very similar to the FS Acrowot) and I can easily fly using the whole airspace without losing orientation.

Cheers for all the earlier advice.

Jon

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of RCM&E? Use our magazine locator link to find your nearest stockist!

Find RCM&E! 

Latest Forum Posts
Support Our Partners
Revoc
electricwingman 2017
Gliders Distribution
Pepe Aircraft
Slec
Wings & Wheels 2019
CML
Motion RC
Sarik
Advertise With Us
Latest "For Sale" Ads
Does your club have a safety officer?
Q: Does your club have a safety officer, or is the emphasis on individual members to each be their own safety officer?

 Yes we have a SO
 No, it's down to everyone

Latest Reviews
Digital Back Issues

RCM&E Digital Back Issues

Contact us

Contact us