Wot 4 Squared

[Concorde Speedbird]

In the family we have had many Wot 4s over the year, all MK 2s. One of which was an original kit one which flew for 30 years across three generations. So I quite like it.

I have two Wot 4s on the go now:

• The ARTF Wot 4 Pro, the super-light one, but I am modifying it to fit a Saito four stroke. Should be the ultimate flying Wot 4 I have done.
• The Chris Foss Classic kit, a mark of Wot 4 I have never done and I have always wanted to build one after the success of the old MK 2 kit. Saito 62 for this one- small but this lightweight combination has worked brilliantly on the original Wot 4, and you can mount the 82 on the same mount. Modifications will be the wide aileron option Mr Foss offers in the instructions and MK 2 wingtips.

So anyway, to business:

This is the new engine bulkhead on the Pro to fit the four stroke. Servos are going in the tail because it is horrendously nose heavy due to the fuselage being incredibly light.

Only a 45S on this one but it is a very very light airframe and this is a pokey engine.

And over to the Classic. Almost forgotten with the ARTFs these days- this is a really nice high quality kit that should build into a very strong yet capable airframe. Steve Webb got me the decals for the scheme below:

Fuselage sides, more shapely than the MK 2 that I am used to

I am going to change the wing tips to MK 2 spec because the swept MK 3 style wingtips have never appealed to me. This is how the kit comes:

And this is the MK 2 tip on the pro:

So I chopped the end of the wings off square ready for MK 2 tips

Finally, these are the 1" spacers to set the bulkhead back for the four stroke (there are several spacer options, a clever design).

I hope you like wot you see... (sorry)

Jacob

[Rich too]

nice, sub'd

[Ace]

Watching with interest as I have a Mk 3 to start shortly

[Tim Flyer]

Agreed Wots are fun. I built a Mark 3 a year ago and put a Laser 80 in it plus air brakes as per Chris Foss’s plans. Definitely an all weather plane ! The 80 only just fits with the bulkhead as far back as possible. Obviously it has lots of vertical and is a great “playing around plane”. The great thing with these kits is that they can be made to fly well with almost any engine as you said. A light build on a sporty .30 will work as will the bigger engines and heavy duty builds

[Concorde Speedbird]

Thank you.

Classic work comprised of cutting the mounting holes for the engine mount. I am using an adjustable engine mount should I want to change the engine in the future.

I couldn't glue the bolts in because I didn't have any suitable washers, which I will get tomorrow. I glued the firewall in on one side instead.

And with the pro, the dremel was used to let the engine sit in position:

And I hinged the tail controls.

I think I might put diagonal struts on the fin and tailplane to improve rigidity and strength.

Jacob

[Concorde Speedbird]

Apologies I have had a busy few weeks.

On the Pro I have installed the tail servo mountings:

Thrilling. Slightly more interesting is the fuselage build on the Classic. This kit goes together very nicely, it is easy to build and high quality.

Undercarriage mounting:

Servo tray, with modification for the smaller HS225 servos which I use extensively (standard servo for the throttle unless I change my mind).

Engine bulkhead- note I have trusted Mr Foss with his use of 1/8" ply for the bulkhead (I normally use 1/4" ) but I will deviate from the kit by adding triangle stock.

A jig isn't necessary to build this aeroplane but I have used mine anyway to ensure a straight fuselage, and I am pleased with the result thus far. Looks like a Wot 4 and there is nothing wrong with that.

I have also cut 1/2" off the trailing edge of the wing for the super wide ailerons (interestingly they will now be the same size as those on the Pro ARTF, which are also enlarged) and glued the leading and trailing edge pieces onto the wing. Pictures of that would be even more dull than the servo mounting pictures.

More soon

Jacob

Edited By Concorde Speedbird on 03/06/2018 19:59:32

[trebor]

Watching with interest, I had a Wot trainer but never got a Wot 4. It would be nice to see the different Wot 4s together. Are they all the same size with subtle differences ?

[Concorde Speedbird]

All the standard ones are the same size. The MK 1 was a plan set with foam wings, and it had a different wing section to the later Wot 4s. 52" span and very rare.

The MK 2 looks similar to the MK 1 and was a kit. It had the now standard Chris Foss wing section and mildly modified fuselage design. It has now become ubiquitous thanks to the ARTF Wot 4s using this design. Standard size is the same 52" wing span, but of course Ripmax have released several different sized ones.

The MK 3 has a much modified fuselage with an enlarged tailplane, a rudder which is angled slightly backwards and extended below the fuselage (I believe to improve knife edge) and a more subtly curved fuselage in the undercarriage area. I've noticed my one is slightly wider than the ARTF MK 2 fuselage too. It also has a 56" tapered wing with new wingtips, but the fuselage is the same size as the other two marks.

The Classic is a MK 3 fuselage with basically the same 52" parallel chord wing as the MK 2, especially on mine because I am putting MK 2 wing tips on.

[Former Member]

[This posting has been removed]

[Concorde Speedbird]

Plenty done on the Classic today

Snakes for the tail controls inserted

Note the angle of the rudder snake for the angled rudder.

Top deck

I then decided to sand and glue the wing together

And the underside cross grain sheeting.

Very strong fuselage!

[Neil67]

I am building the same mark 3 kit and just behind you in the process so your photos are a great help! I have read the debate on the engine firewall and I am also going to add some re-enforcement as I would also have used 1/4 ply.

Thanks for putting up the photos.

Neil

[Nigel R]

1/8" ply does sound a bit light for this size model.

What about a layer of glass behind the ply?

[Concorde Speedbird]

I think it will be fine, it's very solid even without any triangle reinforcement.

Decided to work on the Pro with the view of test flying on Saturday. Engine is on now, can't be bothered with the cowl at the moment.

Inside, awaiting battery, receiver and switch (as well as a backstop for the fuel tank)

Tail servos

Aileron servos

There's always time to put the big bits together

It is so very lightweight, about 4lbs with just the battery, switch and receiver left. Should be hovering into the wind easily.

Jacob

[Concorde Speedbird]

The Wot 4 Pro with a Saito is now flying!

First flying session was on Saturday, in very light winds. In all honesty it flies pretty much as I anticipated- like a Wot 4 but better. The 20% weight reduction compared to a standard one (roughly) makes a huge difference in manoeuvrability and control feel. It is even more benign at low speeds too. I have got large control throws on it and it is fantastic fun, not as precise an aerobatic machine as the Wots Wot and knife edge has lots of coupling but it is still brilliant. The 45S is an excellent engine for this airframe, vertical straight from take off is easily achieved should you wish and I wouldn't want more power simply to keep the speed down on this weaker airframe. Flew it 5 times!

Today I took it out in breezy conditions which it handled easily, like all Wot 4s. I did lots of simulated dead sticks and you do notice the lower inertia with this light airframe- it just stopped when you turn into wind with no power- and in a way it is more difficult to land in a breeze than a heavier one because the darn thing just keeps flying! Easy to get the hang of though. This is the best Wot 4 I have flown and definitely worth the extra cost over the heavier standard one (but I strongly recommend modifying it for four stroke power!). This aeroplane is so forgiving that it can give you a false sense of security when switching to other aeroplanes- I've done crazy things at ridiculous angles of attack with this aeroplane and it just lets you do so.

So back to the Classic build. Strangely despite the Pro being so good, it has made me more excited for the Classic now, even though it will be heavier. It will be advantageous in some areas, such as in windy conditions, ruggedness and potentially knife edge with Foss' modifications in the Rudder area. I always enjoy flying ones I have built a bit more too.

Using this for the wing band. Good practice before the Mustang which will be entirely skinned in GRP. The Jenny brushes from East Coast Fibreglass are really good.

The weights aren't really necessary, just for confidence that it is flat. Top and bottom done now.

Jacob

[TartanMac]

Good to hear your report on the Wot 4 Pro. I have one new in box got it with the Irvine 39. I was gonna use it with a West mini pipe (speed pipe) with a 10x4 and just scream the nuts off it. I think I will do the mod with the servos in the tail like yours. Looking forward to hearing what you think of the kit version in comparison.

[Masher]

Good thread, always good to read about Wot's. I maiden'd a Wot 4 Pro for a club mate the other day, fitted with the Irvine 39. He had to put a (too) big prop on to meet the noise test but the model was very impressive in slight wind - landing is easy to control. I would guess that with the correct prop, the 39 is the perfect match with plenty of power but I would go Saito 4 stoke like you!

[Rich too]

excellent news on the maiden, well done

[Nigel R]

The Pro looks great fun

You absolutely sure it doesn't need a bigger engine?

[Tim Flyer]

On My Wot 4 mk3 kit build with the Laser 80 , I just added an oil drain hole and small tube to stop oil accumulation just in front of the firewall on the bottom shelf ( this was because using the big engine the firewall had to be moved further back). Before doing that oil would pour into the fuselage when inverted via the upper holes in the firewall for fuel tubes etc.

Edited By Timothy Harris 1 on 13/06/2018 10:03:11

[Neil67]

I am knew to building but just about to put the controls in to my Wot 4. I noticed you have put in direct snakes for the elevator and the rudder rather than the pull push system for the rudder and balsa trip approach for the elevator as suggested in the instructions, any particular reason - it does look at lot simpler and neater.

Neil

[trebor]

How do you think a Laser 70 would go in a wot4 mk 3. Would it be a bit small ?

[ken anderson.]

Posted by trebor on 12/07/2018 17:16:55:

How do you think a Laser 70 would go in a wot4 mk 3. Would it be a bit small ?

……………………………………………………………………………………………..

I would say-Spot on...

ken anderson...ne..1.... wot dept.

[trebor]

I think that's wot I'm going to do no more Artf for me.

[Denis Watkins]

Posted by Neil67 on 12/07/2018 11:31:18:

I am knew to building but just about to put the controls in to my Wot 4. I noticed you have put in direct snakes for the elevator and the rudder rather than the pull push system for the rudder and balsa trip approach for the elevator as suggested in the instructions, any particular reason - it does look at lot simpler and neater.

Neil

I think because push pull in a narrow fuselage is a faff Neil. It is quite difficult to set up in a small space. And a nuisance too if you don't assemble the crimps too well and the cable slips.

Direct snakes can be quick and easy to install and are reliable.

Push pull, done correctly is just as positive and reliable and can be gentler on the servos, for example, where a steerable tailwheel is used.

[Concorde Speedbird]

Good evening,

Apologies for the silence but I have been on holiday and I am currently at RIAT. Back building next week.

Neil, I've used snakes simply because it is what I normally use and I had some spare. From my experience snakes work very well. I've also used pushrods and closed loop/push pull systems which also work well, so it is a case of personal preference. The stuff provided in the kit will be adequate (although I would reccomend metal clevices- I can't remember but I think the kit comes with plastic ones).

Trevor, a Laser 70 would be excellent. I'm only putting a Saito 62 in! Feel free to post your progress, it can always become Wot 4 Cubed.

I have flown the Wot 4 Pro many times including in very heavy winds and it has been sublime. Plenty of power with the 45S! I think the kit built one will be a bit smoother though.

Jacob