WOT, another one?

[Andy Butler]

OK, did a bit more so here's where we're up to. The whole thing was taken outside so I had plenty of room to drill the wing dowel holes. The wing is put into place and then simply drilled throught the holes in F12. The dowels were then epoxied in and left in position while the glue went off. Make sure that no traces of glue are left on the wing or dowels ar you will find you have epoxied the wing in place. I sharpened the dowels using a metal pencil sharpener - the plastic ones don't work - and this helped spear them into the wing. I also took the square edges of the fronts so they locate more easily when mounting the wing.

Once done, the holes were marked up on top of the wing for the wing bolts. The holes in mine were measured 1" back from the trailing edge rear and 7/8" (23mm) out from the centre line on each side. The holes in the mounting plate were opened out to 7mm to take the blind nuts which were then epoxied in.

With this done, I cut the slots for the fin and tailplane. The dimesions are given in the instructions, and need to be 1/4" wide. Again this is easy to do but easy to get wrong so take your time and measure several times before comitting to cutting anything. I used a metal rule to make sure the cuts were straight. It's a lot easier to cut too little and go from there than trying to plug the hole for another go but it is doable so don't stress too much - balsa is easily repaired and re-worked.

At this point, the wire tail skid was made by simply bending the last 1/4" or so of both ends of the piano wire supplied for the purpose. I did this in the vice with a largish hammer. try not to fold it by hand as you will end up with curves rather than bending it. A 3mm hole is drilled 1 1/4" from the tail end and a groove filed into the underside until the wire sits flush with the underside sheeting, then epoxy in place.

All of this is much easier to do while the fuselage is still square, so wait until now to do any shaping. I still haven't, it will be the last thing I do before covering it. Here I departed from the instructions. I've installed the throttle cable at the appropriate point on the firewall to line up with the carb. but as the engine is canted over to almost inverted, the throttle cable is now right at the bottom of the firewall. The cable would bend up to the forward servo position but seemed unhappy to bend that far and would have been a bit stiff. I elected instead to mount a small metal gear servo on hardwood bearers and epoxy these into the fuselage base. I used socket head screws so I can still get the thing out if I need to. These are mounted so that the bottom face of the servo is 2-3mm off the fuelage base to isolate any vibration issues (at least that's the theory). It does mean that the elevator servo can go where the throttle servo should fit and the rudder servo which operates a closed loop can be mounted centrally in the rear position which seems a much more elegant solution. The bowden cable was soldered into an extender and a metal clevis screwed on. I like this arrangement as it gives lots of very fine adjustment .

Throttle servo mounted on a scrap piece of balsa to show the clearance.

Servo in place and hooked up. This way the cable does not interfere with the fuel tank and has a dead straight run. Neat huh?

Back to work tomorrow so may be a bit slow until the weekend but to be honest, there isn't much left to do.

Edited By Andy Butler on 30/07/2013 21:26:09

Edited By Andy Butler on 30/07/2013 21:27:44

[Andy Butler]

Ok, so it's been a few days but the build has been continuing so here's where I'm up to.

I've made some holes in the fuselage, one for the switch and one for the remote glow attachment. I toyed with the idea of having a remote glow driver but discounted it because of the extra weight of the batteries, connectors etc. I'm using a 2.5mm power connector from Maplins which I got yesterday. The socket part is the panel mounting type and fits into a 7mm hole perfectly. The plug end will be fitted with banana plugs that go straight into the power panel. I have used this before on the Puppeteer and it worked really well and is useful when the engine is substantially enclosed.

I've also drilled a larger hole - well drilled and then Dremelled - in the firewall for the fuel tank tubes so that the neck is right up against the firewall and doesn't extend too far back. I'm using a Kavan 10oz (300ml) tank. I was going to use a Slec square tank but then draining the fuel tank would either have meant taking the carb feed off which could be difficult, or inverting the plane which I don't fancy either so this tank has bent brass tubes that go to the bottom of the tank for filling / draining and one goes to the top for the exhaust pressure feed as well as the clunk to carb feed line.

Next it was on with the fuselage and the 1/4 X 5/8" strips were cut to suit and glued on the front edges. This stock is left over from the wing trailing edge. You only get two pieces left over which are plenty long enough but you won't get two out of one so make them a little over long. They can always be sanded back but if too short bring a whole host of pain.

The eagle eyed will spot that a pad of foam has been fitted to the tank bay floor.

While that was drying, I made a sortie into the garden and sat for some time happily sanding away shaping the tail feathers. Now I have to admit that I didn't sand the rudder and elevators to a perfect airfoil section but rather rounded them off, quite a sharp round admittedly, but not the perfect shape in the instructions. I am more than certain that this is not going to matter overmuch, it's not going to be a contest or 3D model after all.

This post is quite long and we've a way to go yet so more in a minute. Now where did I put my tea?

Edited By Andy Butler on 04/08/2013 19:53:33

[Andy Butler]

Right, found my tea and Mrs B is watching Country File so I'll scribe some more if I haven't bored you all silly.

Next on was the fuselage top sheet that encloses the tank bay. This has to be sanded to fit the angle and simply sits on top of the two lengths added previously with the back up against F12.

While that was drying, I fitted the hinges to the rudder and elevators. I used four for the elevators and only two were shown for the rudder but I fitted a third midway between the two in the instructions. The bottom hinge is fitted into the fuselage rear and I'm using furry CA hinges. These will be pinned in place and metal clevises used, as an SC.52 is being used, performance could be 'spirited'.

Once thias was done, the fuselage rear was marked up for the control exits. A hole was drilled 1" down from elevator slot and 3" from the rear for the closed loop rudder exit on both sides. Then a slot for the snake exit was cut in 1" in front of the rudder line exit hole and 3/4" down from the tailplane, the ends rounded off and the snake trial fitted. I'm using a snake I had already rather than a solid control rod as with a closed loop set-up it could get a little crowded back there.

The slot for the tailplane is straight, the camera angle makes it look a little off.

So then with my trusty David plane - if you haven't got one yet, get one, they save so much time - I started shaping the fuselage. First the top of the front was sanded back to the edges and the last former, F14 was epoxied in place on the front and then the fuselage top was planed and sanded to shape. Don't forget to add a little filler piece on top of the bottom sheeting behind F14 or you'll have a lovely little depression where all sorts of goo will accumulate.

Then the edges were taken off the underside to match the curve on F14, and then the upper sheeting rear of the wing seat was shaped. I used the plane again and from about 2" behind the wing seat, took the sheet at a 45° angle down to the glue line then sanded it all smooth.

When sanding I use 120 grit garnet paper on a sanding block for rough sanding and shaping, going down to a flexible 180 grit sponge thing that goes round corrners nicely, follwed by 800 grit wet and dry then a final polish with 1500 grit wet and dry both used freehand. This gives a lovely silky finish that covering really sticks to and gives a good smooth finish. So some pictures of the finished fuselage and one with the fin and rudder in place - well you have to don't you?

It's definately a WOT 4, there's no mistaking that characteristic tail, it's big too.

Now the snake was epoxied in and the fuselage and tail feathers are ready for covering. I'm going to fit the tail into position before covering. It does make it more difficult but I want to fair in the fin and tailplane plus I think it looks nicer.

Next the wing was sanded a little to make the edges of the glass cloth bandage blend in a bit and then a smear of light weight filler was added to the bandaged area and the servo recesses. Make sure when doing this that you don't sand into the wing's veneer skin. There are dire warnings about this in the instructions regarding structural failure and believe me, it happens.

This needs a quick rub down with some fine glasspaper and the wing too will be ready to cover. Just the ailerons to cut and shape and the build is finished. So next is fitting the ailerons, the tail group and covering.

More soon.

Edited By Andy Butler on 04/08/2013 20:47:56

[Steve Hargreaves - Moderator]

Looking really good Andy....

Might be worth pointing out to anyone who isn't used to wing joining & fibreglass bandages etc that epoxy resins are best for this sort of job. Polyester resins (the sort often used to repair car bodies in days gone by) can be used provided you avoid all contact with the foam wing core...being polystyrene, polyester resin will melt the foam core whilst you look on in horror...

[Andy Butler]

Thanks Steve and a good point about the epoxy. And yes I have used polyester resin in the past, horrible stuff, stinks and it's really messy too. You have to make sure your wing veneer is 100% or it will melt the foam.

It's about a week since the last post so a look at what I've been up to. First off the fin was glued in place using aliphatic glue and left to dry. Then I had a look at the front end and realised that because the fire wall is set back from the front edge, the top is not in contact with the top sheet as it angles away from it up to the wing seat leading edge. I had a piece of 1/4" square that fitted perfectly once cut to length so this was epoxied into position. By then the fin was weel on the way so then tailplane was added. Aliphatic was used around the edges and epoxy where it met the fin. The tailplane was pefectly square with the wings and the string test was carried out. By this I mean that the centre point on F12 was marked and then a piece of string (well fine cotton) was used to measure the distance between one tailplane tip and the centre point then the other tip is compared. When the same the tailplane was marked so when it came to gluing it up, it went back in the same place. Simple but effective. The epoxy held the fin and tailplane all square while the aliphatic dried and will add a great deal of strength from little weight. S some photographs;

While that was setting, I cut and shaped the ends of the ailerons and hinged them. The ailerons have to be chamfered at the tip end to match the shape of the trailing edge. make sure that you get these the right way up so that they line up with the pieces added to the centre section previously. The wole thing has a slight reflex angle which I thought about and wondered whether this is effectively adding wash out which would explain the excellent slow speed handling of the design. Probably not but it was all I could come up with.

Once all this was dry, I added a small amount of light weight filler to the angle between the fin and fuselage, the tailplane and fuselage and the wing bandage edges.

Finally after some last very fine sanding, the 1/4" square haerdwood cowl supports were added. A 3/4" piece on to the top and a 3" piece on the bottom like so;

These were sanded to match the curves of the fuselage then I used some Balsaloc around the ply parts and other areas where i needed the solarfilm to stick really well. Then it was on to the great cover up.

[Andy Butler]

I can't really tell you how to solarfilm, it's only practice that will give a half decent result. Preparation is the real key here and the better the surface finsh, the better result you will get. I'm not an expert by any stretch of the imagination but have solarfilmed a fair few models in my time. I usually find I've really got the hang of it just as I finish. And I'm still not greta with wingtips. I opted to do the wings first and the fuselage last as I thought that I may have a slightly better chance of getting a decent finish on a tricky structure. The good thing about white is that the joins all but disappear but it does look a bit stark. The graphics should tone it down but that will have to wait for now as there is still some to do yet. As it happens, I am really pleased with it.

And one shot with it's nose on as I couldn't resist it.

The rudder has to be slotted for the closed loop horn and this epoxied in. Make sure that this is in line with the closed loop wire exits made before covering.

Once covered, it was on with the servo installation and lat night I fuel proofed the whole front end so it could dry overnight. I used JP gloss as it's what I had. Remember that it needs about a week to become totally fuel proof. I don't think there's much danger of flying it in a week - two maybe.

More as it nears the finishing line.

[Andy Butler]

I haven't posted recently as there wasn't much to show here but a little more has been done and it's almost finished. Here's where we're up to;

The engine has been fitted and the throttle connection made with a screw link on the engine end. The elevator connection has been made at both ends with metal clevises and the closed loop connection for the rudder is also complete. The receiver has been fitted and the wiring installed. The only thing left now is the flight battery but until the whole thing is finished ready to fly, I might have to adjust that to get the centre of gravity right.

I also need to make a small block to epoxy the elevator snake to at the servo end.

The wings were completed by adding the servos but this took a little while. The servo wires were too short but not by much. I decided to cut the wires and solder on a short extension. this is not as difficult as you might imagine, it just needs a little practice, a good soldering iron, some correct size heatshrink and some flux cored solder. I heatshrink each wire seperately and then put some larger diameter over the wires all together to make a good solid joint. Do make sure you test the servo when this is done just to make sure that everything is in order. At this point, the servo wire has to be threaded through and with this one, it just wasn't going to happen, so a length of thread with a nut tied to it was dropped from the centre into the servo bay. This was then attached to long extension and pulled back through. Now the servo wire was plugged in and taped and then gently pulled through into position. I made up the pushrods using the threaded rods supplied, but using my preferred horns and metal clevises again with z bends at the servo end. I had to put a slight bend in the pushrods due to the angle between the servo and the control horn on the ailerons but it works well.

Just the cowl to cut to fit the engine now and the graphics, which I always find satisfying as it marks the end of the build.

[cymaz]

Super build mate.......may I suggest a couple of things.

1.fuel tube on all the clevises

2.the wing pushrods should be close to the spline centre om the sevo and further out on the aileron horns. And the other surfaces.

[karl grey]

Any update on the wottie Andy. Have you flown the maiden yet?

Mangaged to get my build completed a few weeks ago and it had its maiden today. Needed a tiny bit off right thrust and a bit of down but flew lovely. After 3 flights today it went on to win our club novice aerobatic comp .

Looking forward to many more happy flights with the model.

[Andy Butler]

Cymaz, thanks for the reminder about the fuel tube on the clevises. The pushrods are adjusted to give about the right throws and then fine tuned at the Tx,

Karl, She's all finished but haven't flown it yet. Threw my shoulder out a few days ago so no flying until that's sorted. Then I'll hopefully get some more flying done and do the maiden. Glad you got yours sorted.

[IanR]

Karl, when you refer to "...a bit of right thrust and a bit of down..." do you mean the engine mounting thrust angles or trim changes to rudder and elevator?

I haven't taken the bits out of my Mk 3 kit box, yet, but reading through the build instructions I can't see any reference to engine thrust angles, either so many degrees right or so many degrees down or confirmation that they should be zero/zero.

Should there be any positive engine thrust angles or are they both zero?

Ian

[Alan Dorrell]

Hi Andy,

Just found and read your blog. Extremely good. An early post gave a link to elecrtrifying a Wot 4 which I promptly downloaded as you will now see why.

I am an avid builder but a real rabbit as a flyer, I have to use my wheelchair and be on buddybox. Anyway, this past June, having spent weeks, maybe months trying to decide between a Riot or a Wot 4 foam-E, I decided on the Foam-E as my birthday present to myself. Reasons for choosing ? I just wanted to drop in the Rx and lipo and be ready to go. A visit to my LMS, a very good establishment, surprised me with a total lack of the model desired, however, they were on order. Well, as far as I know, they are still waiting !! Anyway, when I went a couple of weeks ago, I bought their last remaining ARTF Orange one, as the speed of getting into the air is no longer a criteria, but I am still going electric.

So, I know that I do not actually need your very informative blog for building assistance. On the other hand, one of my winter build projects is a kit for the Galaxy "Gazelle" which is of similar foam wing and balsa fuselage construction. I could do a blog on that perhaps.

Now I do have an immediate problem that maybe one of the followers of this forum could solve for me. The motor I have for the Wot is a JP EnErG brushless600 O/R 1100(C35-14). It was bought for another model but not used. It is the recommended motor for the Seagull E-Pioneer leccy trainer. My problem is that the shaft sticks out at the end where the X-mount is. Now I know that this can be loosened and pushed through but I would rather not. Like most motors I have seen, there a holes drilled and tapped in this opposite end which indicate a stub prop shaft can be fitted. However this not included, unlike other motors I have bought. AND, there are only three holes rather than the usual four. Can anyone recommend a leccy specialist who could supply the appropriate item, because Perkins apparently do not.

Cheers. Alan.

[ken anderson.]

hello Alan...give these a try they may have wot you need or something that will help you out

ken anderson ne..1......Wot dept.......

[karl grey]

Ianr, yes I meant engine mount side and down. Built the model with zero offset as per plan but add the thrust after its maiden when she pulled to the left in vertical and the down was added to reduce climb under throttle. I added 2 washers for each and it helped out nicely. Trim wise she needed a little bit of right aileron for straight and lvl. Inverted needed just a breath of down ele so c of g was close from the book.

[IanR]

Karl, thanks for the info. Can I also ask, did this put the prop off centre at the front of the cowl and do you just put up with it, or did you re-mount your engine to one side so that the prop was central? Would you recommend I build in offset at the building stage or should I build with zero offset and suck it and see?

Cheers, Ian.

PS  I intend to fit an electric motor but I suppose this will make no difference either way.

Edited By IanR on 08/10/2013 15:46:08

[David Tweddle]

Posted by Andy Butler on 05/07/2013 17:16:59:

Right then, specially for Ian, and anyone else looking in, let's have a look in the box and see what we're up against. ?

Eh no, mine came in an A4 envelope, no box, no balsa, no sticky thingy's...

Just a plan and build notes; at least I got the notes and thanks to Steve the link for a reminder.

I am interested Andy, if it stops me from kicking it around the floor and doing something constructive.

So Limbo now on hold and Wot 4 it is for me.

Thanks all...

David

[karl grey]

Ian, I left the cowl off for now but it wasn't much offset so will just put up with it. I'd build it with zero as different engines will have different settings, yours might be ok at zero. As you say 'suck it and see'

[IanR]

Thanks, again, Karl. Will do as you suggest. Ian.

[Roy Mundy]

Hi Andy a great build mate, I have saved this as a bookmark as once my other 3 models are built , I'm keen to build a wot 4. I just need more hours in the day lol

[nigel george]

let hope they have made the u/carridge stonger for the beginers

[Andy Butler]

Thanks for all the comments chaps. This is one model that never fails to get a positive response. I find it hard to believe that a design from that long ago has stood the test of time, and to my eyes, still looks up to date, so well done Mr. Foss. I will try to get to the field soon but the weather is not playing ball at the moment. Being a wage slave I have to wait until the weekends but hopefully this weekend may be possible. We have a glider comp on Sunday so I hope the weather will be kind on Saturday, I really can't wait to see this fly.

[IanR]

Thank you, Andy, for a truly great build blog. Good luck for this Saturday.

Ian

[Redex]

Hi Andy, I know that this is an old thread but at the moment is really useful for me, as I have just started a Wot 4 MKIII build, e-conversion. So just finished the fuse sides but your tip for taping some glasspaper to a kitchen roll inner to give the right radius is great and worked well, thanks.

So next for me is to tackle the motor mount. It looks like I am at 3 and 3/4 inches from F4 using an old ply box mount from a previous model and a KMS 4210/05 looking for a new home.

[Richard Wood]

A Wot 4 Mk3 e-conversion is on my workbench at this moment too, for an oldish
EMP 4260 motor in a cage mount. The bulkhead has been fitted at the most forward
position - flush with the fuselage side front.
The fuselage top has been made into a battery access hatch - it was tack glued on
for shaping & sanding & then removed.
It'll use a 4S 4000mAH Lipo & 70A esc.
Good luck with your Wottie.

[Redex]

Thanks Richard, I'm hoping to squeeze in a Dynamic 5S 4500mA 30C LiPo - about the smallest and lightest that I have come accross and using 70A esc too.

Not sure yet if to follow the CFoss LiPo mounting method on the web site or try to mount the LiPo through the top hatch somehow. Top load is better as I don't need to keep inverting the model when changing the LiPo. As a new builder, though I'm not sure my skills are good enough yet to create a top hatch loading LiPo.