An Eleccy WOT4XL - with a twist!

[Kim Taylor]

No foam wings on an XL, like its normal sized artf sibling, it's a built up wing.

Kim

[Geoff S]

That IS a thick piece of balsa but, presumably, fairly soft balsa? That's LOT easier than removing the wing each flight for 'refuelling'.

I know I'm obsessed with getting batteries as far forward as possible but couldn't you neaten up the hole in the firewall so you could push battery through if needed to get the CoG right?

Geoff

[Biggles' Elder Brother - Moderator]

I have looked Geoff, believe me I'd like to get the battery up there as well. But the frontal area on the WOTTY is surprisingly small, this means the standoffs are very close together - at motor spider pitch - and there isn't really much opportunity to build a two stage mount with a wider forst stage because of the small area. I think we are stuck with what we have. I don't think the battery will be far enough forward to eliinate all the lead, we may still end up with at least a little.We'll see.

One thung about this model is it's built for IC and its an old design, so it's massively over engineered for electric power. The wood in the structure is thick and heavy. More modern IC models are made of CNC cut interlocking ply. This gives them the strength to withstand the vibration of IC without the bulk and weight. Compared to them this aeroplane is rather "agricultural" in design!

BEB

Edited By Biggles' Elder Brother - Moderator on 19/09/2018 21:15:37

Edited By Biggles' Elder Brother - Moderator on 19/09/2018 21:16:49

[McG 6969]

Just very probably a totally daft 'novice' question again, BEB.

... but that fuse is looking huge on your pics, so wouldn't it be possible to enter the Lipo more 'vertically' just behind the firewall???

If that's physically possible, or even being 'tilted' at the maximum available angle, the battery's CoG would be closer to the front than in a full horizontal position.

... I guess I'll just grab my coat now.

Cheers

Chris

[Biggles' Elder Brother - Moderator]

It's a good question/suggestion Chris - but sadly my lipo's are just about10-15mm too tall if placed at the front. They might fit further back, but then there would be no advantage over just laying it flat.

BEB

[McG 6969]

Well, at least, not totally daft then, BEB.

Even if it doesn't help you much further.

Cheers

Chris

[Biggles' Elder Brother - Moderator]

Suggesions are always welcome Chris!! Ideas from members of this forum has saved my bacon on more than one occassion!

BEB

[Bob Cotsford]

Since converting the WotsWot to electric I've started using the tray system from that for all my 6S models. Would that help by a) mounting the battery at an angle effectively bringing it forward a smidgeon and more importantly b) make it easier to fit the battery with no scrabbling around for velcro straps inside the nose? I hate those straps with a vengance, it's like trying to tie knots in live eels using just two fingers. Not that I've tried that you understand, honest!

[Geoff S]

Posted by Biggles' Elder Brother - Moderator on 19/09/2018 21:15:10:

I have looked Geoff, believe me I'd like to get the battery up there as well. But the frontal area on the WOTTY is surprisingly small, this means the standoffs are very close together - at motor spider pitch - and there isn't really much opportunity to build a two stage mount with a wider forst stage because of the small area. I think we are stuck with what we have. I don't think the battery will be far enough forward to eliinate all the lead, we may still end up with at least a little.We'll see.

One thung about this model is it's built for IC and its an old design, so it's massively over engineered for electric power. The wood in the structure is thick and heavy. More modern IC models are made of CNC cut interlocking ply. This gives them the strength to withstand the vibration of IC without the bulk and weight. Compared to them this aeroplane is rather "agricultural" in design!

BEB

So, do away with the stand-offs and build a smaller ply mount with a bigger 'firewall' at the end to suit the motor?

Just thinking aloud without the benefit of actually seeing problem in real life. I know I'm teaching my Granny to suck eggs (not that I ever saw her doing that).

Geoff

[Shaun Walsh]

I know it involves extra expense but could you fit 2 lower capacity 6s batteries in parallel or 2 3s batteries in series vertically right up against the firewall it looks like you have enough room for 2 batteries side by side they just need to be short enough to fit under the hatch?

[Biggles' Elder Brother - Moderator]

Thanks for all the ideas chaps - brilliant stuff.

Bob - yes I did the sloping battery tray trick with my Chipmunk conversion, so that might well help and I'll certainly have a look. As you say the impact on the CoG would be very small, but the convienience, in terms of getting the battery in/out and snuggled down securely, is potentially considerable.

Geoff - the fundemental problem is even if I could open the space by re-designing the mount and just about get the battery in betwen the actual firewall and a back plate to the motor it would have to be vertical - I've recently done exactly that on a BlackHorse Sea Fury. But in this case the battery is taller than the depth of the cowl so it wouldn't fit! I never really realised hown much the front of a WOTTY tapers. The bottom of the fuselage comes up quite sharply and that line is continued by the cowl itself and so you end up with a surprisingly small cowl and frontal area for what is a fairly "chunky" model!

Shaun - I don't have any higher capacity 3s batteries, but I do have a number of 6s 3000mAh batteries and two of them in parallel to make a 6s 6000mAh might well be a possibility as they may be short enough to go vertical against the firewall - thus reprising Chris's idea above. I could also slightly stagger them in the stack - as I say the floor slopes upward to the front in a taper. I shall look at that as well.

Thanks again chaps - all ideas much appreciated.

BEB

[Martin Roberts]

Hi BEB, very interesting so far....pick up price - very enticing

[Nigel R]

" even if I could open the space by re-designing the mount and just about get the battery in betwen the actual firewall and a back plate to the motor it would have to be vertica"

how about,

ditch the standoffs; build a ply motor box - larger than the lipo - sides of this box to extend back to wing LE if needed for strength

cut a big hole in the existing firewall, the size of the motor box

the lipo can slide forward into the motor box, almost up to the motor then, while laying horizontally

ESC can be strapped to underside of the box, in the cowl

Excuse the quality of my top view diagram:

[Biggles' Elder Brother - Moderator]

I have been spending some of this morning fiddling with different battery arrangements and combinations.

The two 6s 3000mAh solution won't go, basically I can't get two packs through the hatch and even if I could, while they are each slightly narrower than a 5000mAh they are not much shorter.

I thought I'd include a few photos of the battery in context so you can see the issues better. Sorry these are not wonderful quality but they were taken on my phone held and operated in one hand while my other hand held the battery in place!

The first picture shows why the battery can't go vertical in the cowl:

And the next photo shows that it can't go upright in the fuel tank bay either:

Now it could go on a slope - as Bob suggests:

So far that looks my best option.

Your suggestion is good Nigel, I have done something very similar to that previously - see the photos below. I started with a motor box:

Then cut a big hole!

And installed a "poke through into the cowl" sloping battery chute:

The problem is,...call me lazy,....but it is a lot of extra work for a winter hack!

If I end up with the CoG too far back and need too much lead I can revisit this and do it if I have to. But for now I'll hold that in reserve!

BEB

Edited By Biggles' Elder Brother - Moderator on 20/09/2018 12:50:28

[Kim Taylor]

I did something similar to your 'sloping' option on mine

As you can probably see, I also positioned the esc on the motor stand offs to get the weight forwards and it pretty much balanced (complete fluke).

I did my top hatch the same as the 'normal' size Wot4 artf, i.e. I sliced the whole 'windscreen' area off after carefully cutting down the relevant bulkheads, but your way is doubtless stronger.

Still watching with interest - I'm beginning to wish I'd persevered with mine now, rather than going over to petrol.

At least the battery hatch made it easy for me to place the cdi unit and battery.

Kim

[Bruce Collinson]

BEB,

Are you familiar with an electric Acrowot/Crowrat/Raw Coot? The latter pics look remarkably similar but inverted, battery as far forward as the firewall etc will permit, sloping at about 30 deg through the smallest hatch practical = minimal loss of integrity; ESC on the standoffs but without the ply plate, keep air circulation to the heat sink.

I recall that Ripmax show the build notes online. Batteries tape to a thin ply plate which slides over the fitted battery plate, engages a simple tongue fixing at the rear and fastens with a nylon bolt into a T nut right at the front. No more velcro.

BTC

[Biggles' Elder Brother - Moderator]

Hi Bruce,

yes I had an electric version WotsWot (until I stuffed it coming out of the reversal! I swear the ground moved up 20 feet!)

I liked the "plate" idea and may well use it here - or I might just put in a ramp, a non-slip mat and a big Velcro strip.

[Glenn Philbrick]

Hi BeB

I have been following your thread as I modified an Acro Wot in a similar way to your Wot 4. As you can see from the photo I made a plate to mount the motor using the original IC mounting holes as I would go back to IC if not happy with the performance. You could use a similar method and open up the firewall to get your battery pack further forward. I did not do this but mounted the ESC on the stand off so it would get maximum cooling within the cowl.

I have left it electric powered as I also have an Acro with an OS 90 FS. They both fly well but there is a slight difference even though the CG is the same. The electric one will flat spin but the IC will not flatten out.

[Biggles' Elder Brother - Moderator]

Hi Glen,

Thanks for that suggestion, I've done exactly that in a Sea Fury,...

But its not possible here because the cowl isn't tall enough for the battery,...

So that image is with the cowl off and you can see there is no way the cowl would fit over that battery. I also doubt I could get the stand-offs far enough apart. It really is surprising how much the WOT4 tapers at the front end. The main fuse is deep - but the front/firewall is very shallow.

BEB

[Former Member]

[This posting has been removed]

[Biggles' Elder Brother - Moderator]

Nice one Percy. I used to fix batteries with velcro on the bottom but it's sometimes very difficult to get the battery out - and occasionally completely impossible! The battery I'll use here is, as you all know, a 6s 5000mAh, big chunk of weight. Any velcro strong enough to hold that down just by contact is not going to be easy to part! As we shall see, while my hatch allows me to get my fingers in there, to position a battery and lift it out, I can't get my hand in there, so I can't exert much grip. If we had velcro on the bottom I'd never get it out!

OK, so I too have been playing battery trays/chutes today. Here is what I made:

I don't know about you but, though I say so myself, that is a slight improvement on the "quarter inch plank of hairy balsa" it replaces!

It's a basic tray, non-slip matting on the base and fat Velcro strip to hold the battery to the matting - that I can reach to undo as it isn't underneath! There is "back stop" with a bit of foam just to make the battery comfy! The triangular pieces and the block beneath it are just braces - the battery weighs over 2lb this needs to be reasonably tough and strong, but light. Most of the material is 2mm ply with a bit of soft balsa block thrown in.

Here is the view from below:

If you look carefully those spots on the right-hand side are blood! My blood to be precise! I managed to cut myself removing a broken scalpel blade from the handle - idiot! Well, it's said that they fly better if you bleed on them - its always worked for me in the past!

So this is the battery in place, it can't go all the way to the front of the tray - much as I'd like it to - as if its there it will poke out of the hatch!

And here is the tray fixed into the model. It is supported by a piece of triangular stock glued to the firewall at the front and a block glued to the ply former at the rear:

Last but not least here are two shots of the battery in the model, on the tray, having been inserted and removed via the hatch:

So, that's probably the single most important and difficult task done. It may seem, if you're new to electric conversions, that we faffed about a lot dithering about where to put the battery. But this is vital decision, you have to consider it very carefully. I'd have loved to have put the battery into the cowl, but I believe that only Nigel's proposed solution could do that (battery lying down poking through the firewall). But while I have done similar I also know that is an immense about of work - and I can't justify that for what is in the end a low cost winter hack.

There is still more to do: we need to re-install the motor and the speed controller. Then we need to patch up the holes and repair the covering. We need to do the aileron servos and push rods. We can then have a balance up and see how we stand - or not as the case may be. If all is well we install the radio gear and go flying - if not we return to the drawing board!

BEB

[Ron Gray]

Nice work BEB, I copied the ARTF WOT4 leccy for mine but sized to suit my 5s and 6s batts.

[Biggles' Elder Brother - Moderator]

Thanks Ron.

OK, nothing done really over the weekend and Monday. Went flying in a "weather window" on Saturday and was busy else where the other two days. Anyway - back at it today!

I intend installing an arming plug on this model, so we need to do a bit of soldering. I know most for you will be very familar with this, but just incase anyone finds it useful I'll cover how I did that.

First we solder two connectors together like this:

The broken red wire will go via the arming plug, which is just a shorted out XT60. I find it helps to do a circuit diagram here - not because the circuit is complicated - it isn't its simple - but you need to be very conficdent about the gender of each connector. It would be a pain to assemble all this only to find you can't connect it! Also double and triple check the polarity of each connection - its surprising easy to get this wrong - ask how I know! I was putting together an FPV UAV at work a few years ago, OK it was much more complex than this - but when I connected the battery, big bang, about £300 quids worth of posh flight contoller "went west" and it nearly set the whole model on fire! Opps!

We install this inside the aircraft between the ESC and the battery, So, as space is very tight upfront, I connected it to my ESC:

I then fed the wires in from the front, and connected the broken red lead to the back of the arming plug socket:

We are really shoe horning stuff in here! You can also see I managed to touch the model with the iron!

The front of the arming socket (the other side) looks like this:

So now I just make up a XT60 to fit in there and bridge across the two terminals.

Next up I installed the new ESC in the cowl space and reinstalled the motor wthout the upthrust it had before.

I found all the screws on the motor and the standoffs were lose when I was striping things down, this time they are all tighten firmly up with blue lock-tite.

Finally I put cowl back - yes I have installed the receiver and checked that the motor is spinning in the right direction - I've been caught out by that one too many times!

Finally here is a side-on view of the spinner location:

As you can see there is a gaping great gap at the top! This has happened of course because I have taken the motor up thrust out, so now the cowl is in slightly the wrong place. It just clears the spinner at the bottom, so I'll leave it like that for now and see how it flys without the upthrust. If (crazily!) I have to reinstate it I don't want to have changed the cowl screw locations only to have to change them back again!

So what stands between us and flying this beast? Well, I still have to put the servos in the wing, and I need to fit catches to the hatch. I still haven't repaired the holes! But they can wait until after the "maiden"

What's the balance situation looking like? A quick, very rough, look tells me that the fuselage, on its own, now balances fairly close to the right point. But of course we have to add the wing - and I suspect that will will push the CoG back a little, not much though. So, this going to be close. If I was a betting man I'd give 3 to 1 against it balances as it is, but evens that it is within less than 10mm! If the later then a little bit of lead may be needed - but nothing like the over 1.3lb I took out!

BEB

 

 

Edited By Biggles' Elder Brother - Moderator on 25/09/2018 16:24:54

[Colin Carpenter]

BEB . I use those HK panel connectors as an arming plug on many models where I can get them to fit . Simples !!😁 Colin

[Bruce Collinson]

Great build log. What's the arming socket plate made from?

BTC