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What WOT 4 (ARTF electric)?

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Geoff Sleath21/01/2019 20:16:45
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3300 forum posts
251 photos

I acquired a few wheel balance weights when I took the car in to have a puncture repaired ( a nail right in the middle of the tread!) so I'll try sticking them under the tail plane and move the CoG back a bit (with caution)

I haven't checked the wing incidence but I assume those who have take the datum as the tailplane angle which is what I usually do. So what's the ideal? 1 deg +ve?

Geoff

Jonathan M22/01/2019 07:03:14
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669 forum posts
275 photos

Yes, as I understand it (Dave Scott's Performance Tuning Guide) the tailplane is the datum and one wants between 0.5° and 1° for a fully symmetrical wing.

Jonathan M02/06/2019 12:32:58
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669 forum posts
275 photos

Just an update: since my first Wot4 was destroyed soon after completion earlier in the year (Spektrum TX failure), I've maidened its replacement (flying now with Taranis, yay!). With the lighter 4-Max PO-3547-800 motor it is less grunty than the original, but still more than powerful enough for my needs and flying style, and gives me an easy 12 minutes mix of aeros etc with a 4s 4250 LiPo.

The CG came out at 90mm, even after moving the battery forward a bit plus adding some nose-weight, at which it still needs a few clicks of up-elevator for level flight on 50% revs, plus a harder push on the stick than I feel it should need for cleaner inverted, and was almost impossible to stall. So I'll lose some of the nose-weight to move the CG back by say another 5mm.

Perfect model for the job, flying on mid-rates (half way between the recommended range for each surface), and looking forward to less windy weather! laugh

Jonathan M06/06/2019 08:07:10
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669 forum posts
275 photos

I made a mistake in my previous post: the CG was originally at 85mm (not 90) and needed a heavy lean on the stick for inverted. Its is now 88mm (removed half of the 60g of lead I had in the nose) and inverted needs only a very slight breath.

Now, although single axial rolls at higher speed don't need any corrections, two consecutive slower ones at slightly over half-throttle need a wee jab of down at inverted and a hint of up at each end - just what's needed for the B-Cert manoeuvre.

jeffrey cottrell21/08/2019 15:49:31
71 forum posts
6 photos

Hi Guys, could use some advice.

Similar situation to others in that I'm looking for a winter 'hack'. Not too keen on foamies, seem to get more hangar rash getting in and out of the car than I ever do flying.
Also a fan of Chris Foss designs so down to a Wot 4 of some description.
Trying to choose between Wot 4 E at 43" or Wot 4 Mk2 at 53".
Now comes the complication.
In the fleet I have a Limbo Dancer flying very well on a HK Aerodrive motor at 1185 Kv and 3s spinning 11 x 5.5 prop.
Got a spare same motor so would like to use that ( cheapskate, moi?) but my feeling is it would be a little underpowered for the 53" version, but possibly a little heavy to get the c/g right on the smaller one.
Don't intend doing any fancy aerobatics, loops and rolls are the extent of my talents, but I would like reasonable duration.

So, any thoughts?

Jeff

Bob Cotsford21/08/2019 16:13:44
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7931 forum posts
436 photos

In theory it should be ok for the larger version but e-calc puts it at 490W, I think a bit more poke would help. You really need to look at 4S driving something like a 3548 840kv motor propped for 6-700W. I haven't had a smaller version but weight really depends on what size battery you use.

John Bisset21/08/2019 22:12:36
154 forum posts
Posted by Biggles' Elder Brother - Moderator on 11/10/2018 07:58:46:

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

Your memory sounds fine to me - I checked my rebuilt, electric Wot 4 just now and got 4.4 lbs, with a 4S battery. Mine is rebuilt from a 25 year old style Wot, may not even be a Mk2.

John B

Geoff Sleath22/08/2019 00:24:13
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3300 forum posts
251 photos

I electrified a Mk2 Wot 4 last year. My thread is here.

I used a Foxy C4020/10 755 rpm/volt on 4S with a 12x6 prop which gave 600 watts which flies the model perfectly adequately for me. With a 4AH LiPo I get duration of around 10 minutes but I usually think about landing after around 8 minutes as I prefer not to over discharge my packs. In any case that's enough for me.

I flew it yesterday in quite breezy conditions and it coped very well with several touch and goes thrown in.

I was very impressed with the quality of the model and it's become the one I always take up to the field to get me 'warmed up' before flying something I've built myself and have a bit more of an emotional attachment to.

Geoff

Bruce Collinson22/08/2019 07:30:31
384 forum posts

The larger version will surely make the better hack as it will deal with breeze and indifferent ground conditions better, especially when the wheels are upgraded. Mine (third!) flies similarly to Geoff's, 4S and it is possible to smuggle a 5A LiPo in there.

Reinforce the u/c fixing plate, change the wing bolts to metric, think about extra ventilation holes upstream of the ESC, bin the plastic clevises, Dubro low-bounce wheels and find your own solution to the awful supplied elevator pushrod.

My go-to plane, the nerve and rust settler, don't think I'll ever be without one. They were in short supply although they were back in stock 2-3 weeks ago.

Report back!

BTC

Jonathan M22/08/2019 09:12:05
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669 forum posts
275 photos

Jeff, I agree entirely with Bob, your spare motor at circa 500W will be too puny for the 53" ARTF. Mine (see my last few posts above) weighs 5.25lbs with a 4s 4250mAh, and its 4-Max 3547 puts out approx 680W. This equals 130W/lb and the flying reflects this - circuits and calm aeros for up to 12mins or more aggressive flying for up to 10 - and any less grunt would be pointless. In fact I'm going to try a larger motor in this Autumn, a (spare to me) Overlander that puts out 900W, which will theoretically give 170W/lb... whether my flying would then improve is anyone's guess!!

Your spare motor would probably work fine with the smaller Wot4 balsa ARTF with much cheaper 3s Lipos (£20 versus about £60), work out the output/weight figs yourself. A club mate bought the smaller one (because he has tons of 3s batteries) and it flies fine, but I much prefer the size and weight of the full-size version, which has proved itself over and over again this windy summer, and which still fits fully-assembled in my boot.

Jon

jeffrey cottrell22/08/2019 15:49:51
71 forum posts
6 photos

Hi Guys

Thanks to everyone who ventured an opinion, but I'm not sure if it answers my question.
I originally asked whether a 3s 1185 Kv would be enough to power the 52" Wotty, and the general consensus seems to be 'only just' if at all.
Given the power train will be lighter as well, I'm back to the old problem of a light model with big wing area and limited power struggling in the wind.
So, I'm leaning towards the 43" version, but that's where I opened a can of worms.
Trying to find a wing chord, so I could get approximate wing loading, so I toured the internet looking for a shop that could measure it for me.
Couldn't find one, but I did find differences in the specs according to who I looked at.
One shop said Span of 43.1" and fuz length of 41.5".
Another said span of 47" but same fuz length. The 47", I believe is the foamie.
No more foam for me, explain why in a minute.
So, 4" bigger span but same fuz length sounds wrong to me.
Tried to call Ripmax direct but no-one answered the phone.
On the Ripmax site I did find a picture of the kit contents taken from directly above, so I scaled up the dimensions from that.
Using a span of 43" as a baseline gave me a chord of 8.16" which sounds about right, but scaling up the fuz length came out at only 33" or so.
The Ripmax site also gave the o'all weight as 50.5 oz, or 3.15 lb however given the discrepancy with the fuz length, not sure if I trust this either.
So, did some static tests with my Limbo Dancer using the same prospective power train.
Tethered down WOT consumption measured at 48a.and voltage at 11v. This gives an overall wattage of 528. Bob, I believe you predicted 490, so you win first prize.
Using the quoted weight, that gives 167 w/lb. That should scare the horses.
Not sure how much credence should be given to this. I only use full power for verticals, and most of the flight is spent a 1/3 throttle or less.
Flying for a set time and then measuring how much the charger puts back in gives an average real-time current of 18a or so.
That's a more realistic figure I believe.
Also, using the chord I scaled up from the photo, gives me a wing area of 2.47 sq ft
and a wing loading of 20.44 oz/sq ft.
So, conclusions:
W/lb sounds high to me, but it was based on unrealistic figures, and I can always fly throttled back. Wing loading sounds in the ball park. Maybe a little high, but one of my club members who has one reports it difficult to slow down for a landing, which would tend to support that.
So, I think the smaller one comes out on top, provided I can find one. If anyone has a 43" model and could check the fuz length that would help.
Other than that, your thoughts?
Oh yes, why no more foamies.
Took my WotsWot out for a play this morning. Bit windy for it but flew ok. Hit a wind gust on landing, caused a tip on to the nose. No biggy, everyone's done that.
Not so with mine. Broke the fuz clean in half just under the cabane mountings.
Might get repaired sometime, not sure yet.

Jeff

Old Geezer22/08/2019 23:03:44
605 forum posts

Jeff, I've been away from this thread for ages, but in the interim I bought a Blue Wottie. I was never really happy with my BW, yes, it flew alright but somehow it wasn't the same as the larger artf airframes, it certainly "felt" heavier when I flew it and was definitely more difficult to get back onto the ground. I have a dreadful confession to make, I tip stalled a Wot4 - yes, the BW, on the downwind leg ( windy, turbulent - honest ) of the landing approach. Just dropped out of the sky like a grand piano. Fuselage beyond repair - well for me anyway - scrapped it. Wotties are funny planes, each one is different. My first built from a kit was brilliant and tough, and pretty lively on a cooking 40 ( Fuji, Enya etc ), my first artf went really well with a big Axi and a 4s 4500 under the wing ( much much easier to take off the wing rather than the later battery hatch set up ). My latest Wottie was a disappointment despite exactly the same motor - battery - prop set up. Eventually I resurrected an Irvine 46 and hung it on the front of Number 3 - apart from a bit of noise and a smudge of (synthetic) oil No.3 then went just like No.2, if you want to be picky the throttle response is a bit lethargic compared with an outrunner, that's all.

Your only problem will be finding an artf Wottie - having flown both the i/c:ep artf and the blue artf ep I would definitely go for the "dual fuel" airframe - and if you go for the ep option, as many watts as you can get, that wing will carry them. If going with a big LiPo you might change the battery mount and load it through the big 'ole under the wing - much easier.

Gurth.

Old Geezer22/08/2019 23:03:45
605 forum posts

Jeff, I've been away from this thread for ages, but in the interim I bought a Blue Wottie. I was never really happy with my BW, yes, it flew alright but somehow it wasn't the same as the larger artf airframes, it certainly "felt" heavier when I flew it and was definitely more difficult to get back onto the ground. I have a dreadful confession to make, I tip stalled a Wot4 - yes, the BW, on the downwind leg ( windy, turbulent - honest ) of the landing approach. Just dropped out of the sky like a grand piano. Fuselage beyond repair - well for me anyway - scrapped it. Wotties are funny planes, each one is different. My first built from a kit was brilliant and tough, and pretty lively on a cooking 40 ( Fuji, Enya etc ), my first artf went really well with a big Axi and a 4s 4500 under the wing ( much much easier to take off the wing rather than the later battery hatch set up ). My latest Wottie was a disappointment despite exactly the same motor - battery - prop set up. Eventually I resurrected an Irvine 46 and hung it on the front of Number 3 - apart from a bit of noise and a smudge of (synthetic) oil No.3 then went just like No.2, if you want to be picky the throttle response is a bit lethargic compared with an outrunner, that's all.

Your only problem will be finding an artf Wottie - having flown both the i/c:ep artf and the blue artf ep I would definitely go for the "dual fuel" airframe - and if you go for the ep option, as many watts as you can get, that wing will carry them. If going with a big LiPo you might change the battery mount and load it through the big 'ole under the wing - much easier.

Gurth.

jeffrey cottrell23/08/2019 08:43:57
71 forum posts
6 photos

Hi Old Geezer

Certainly been a while since we spoke. Great to hear from you again.
Agree with what you are saying. If all things were equal, the full size Wotty would be my choice, probably built from a kit.
However all things are not equal (are the ever?).
First of all, I am recently retired so money is not as free as it used to be. Makes no sense to make the sizeable investment in a 4s set up, and leave brand new equipment in the shed gathering dust.
Also I have recently downsized, so storage space and build area are at a premium.
Mind you the whole discussion might be academic anyway.
As I understand it, Ripmax have recently moved their warehouse and ran down their stocks prior to the move.
Might be a while before any of the artf's are available. One shop is quoting March 2020. Don't want to wait until winter is almost over before I buy a winter hack.
Ho hum.
My next post might be to ask if anyone can suggest an alternative, similar size and layout, that might be more available

We'll see

Jeff

Old Geezer23/08/2019 09:04:21
605 forum posts

Jeff, I know the feeling ( retired, fixed income, asset rich and cash poor!). If you're looking for a sub-40 sized Hack model, i.e. 25-32 i.c. or the e.p. equivalent, you could do worse than look at Pegasus' website - they have quite a few kits which can be either IC or LiPo powered in that size range, and being balsa with ply doublers and foam wings, they're pretty strong. The Wasp is on my list as it has the look of an old Mick Reeves "Gangster" about it! And if you wanted something a bit less demanding there's always a Uno-Wot.

Gurth

jeffrey cottrell23/08/2019 19:43:27
71 forum posts
6 photos

Hi Old Geezer

Thanks for the idea of Pegasus. They certainly do have quite a range, but nothing really floated my boat. especially when you look at how many they actually have in stock.
Did phone them to clarify something, and ended up having a long chat with a very helpful guy. He had a different take on why Ripmax has no stock. Sounded plausible to me.
Anyway, no help to me, guess I'll have to hold my nose and get a Riot.
Ho hum.
Being a 'glass half full' kind of guy I did see one advantage.
The Riot shares most parts with the Ruckus, which means I can buy one, airframe only, and transfer the gear from that rubbish Ruckus lying dead in my shed.
CenturyUK have an E-Bay site, so they can do me the airframe post free.
Turns a £159 mistake into a 'mere' £100 one.
That's my excuse anyway.
Meanwhile, had a look at the Wasp. see your point, definitely Gangster'ish.
Instead, wonder if you might have looked at one of these:
https://www.probuild-uk.co.uk/index.php?route=product/product&product_id=5130&search=bullet
So much prettier, imho.
Certainly when I get a build area sorted, a Mini Kosmo is going on the list:
https://www.pegasusmodels.co.uk/product.asp?type=&maingp=RC+Aircraft&prodid=1011705#.XWAytXt7mzc
That's a real model.

Jeff

Old Geezer24/08/2019 08:51:22
605 forum posts

Shame about the non-availability of the artf Wot4s - had a look at the Bullet, it does appeal but a) when it first re-appeared the revue published in one of the comics was less than enthusiastic, and b) a Bullet with it's u/c hanging out in the breeze just looks wrong except when landing or taking off ( as does any warbird ) and our patch isn't exactly retractable u/c-friendly*. Anyway, I've promised myself a Wasp now as I've managed to pick up a 2nd hand 32 that should fly it very nicely.

* I know some folk will use the retractable u/c to get their pride and joy into the air (like a sailplane's dolly) then pull the wheels up and slide it in dead stick on it's belly, but I get the feeling that eventually it would all end up in tears.

Bruce Collinson24/08/2019 09:45:36
384 forum posts

There are no ARTF Acrowots either. Apart from the one I bought from Just Kits at last weekends Winterton open day (flying the flag for the UKCAA). They had one at the shop and went back for it.

They had a Wot 4 too. Very nice helpful people, in Hull.

BTC

Lima Hotel Foxtrot24/08/2019 17:02:47
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345 forum posts
Posted by Old Geezer on 24/08/2019 08:51:22:

Shame about the non-availability of the artf Wot4s

Addlestone Model Centre have some in.

**LINK**

Shaun Walsh25/08/2019 07:40:40
175 forum posts
12 photos
Posted by jeffrey cottrell on 23/08/2019 19:43:27:

Hi Old Geezer

Thanks for the idea of Pegasus. They certainly do have quite a range, but nothing really floated my boat. especially when you look at how many they actually have in stock.
Did phone them to clarify something, and ended up having a long chat with a very helpful guy. He had a different take on why Ripmax has no stock. Sounded plausible to me.
Anyway, no help to me, guess I'll have to hold my nose and get a Riot.
Ho hum.
Being a 'glass half full' kind of guy I did see one advantage.
The Riot shares most parts with the Ruckus, which means I can buy one, airframe only, and transfer the gear from that rubbish Ruckus lying dead in my shed.
CenturyUK have an E-Bay site, so they can do me the airframe post free.
Turns a £159 mistake into a 'mere' £100 one.
That's my excuse anyway.
Meanwhile, had a look at the Wasp. see your point, definitely Gangster'ish.
Instead, wonder if you might have looked at one of these:
https://www.probuild-uk.co.uk/index.php?route=product/product&product_id=5130&search=bullet
So much prettier, imho.
Certainly when I get a build area sorted, a Mini Kosmo is going on the list:
https://www.pegasusmodels.co.uk/product.asp?type=&maingp=RC+Aircraft&prodid=1011705#.XWAytXt7mzc
That's a real model.

Jeff

I can recommend the Riot, have been flying one for about a year now and it has had a few heavy landings and visited two trees with only minor damage, it's pretty robust. The only niggle I have is that the battery box is pretty small, I had to cut away the bottom to fit a 3S 2200 in and the plastic clips either side of the hatch break easily, I reinforced them with thin piano wire epoxied behind them to act as torque rods.

Recently re-motored with a 4-Max 3541-1070 giving it about 400 watts it will climb vertically .

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