build 2022 Mass build MK Joker 25.

[kevin b]

Turnigy SK3 35/42.

It will be bolted in from the battery box with a full hatch cover making easy access.

It might be a little overpowered, but I can always put a smaller prop on and have longer flight times.  

 

 

[kevin b]

With the fuselage is in the jig I can fit the rear formers.

While the glue is drying time to look at the tail feathers.

I am going to join the elevator halves to make the linkage easier, so I won't be fitting S6 at the tail end.

The rudder linkage can then exit at the other side of the fuselage opposite the elevator linkage.

 

Edited March 6, 2022 by kevin b

[Keith Billinge]

Oh I'd Love one of these Kits. Looks like a great fun build.

 

Keith B

[kevin b]

Thanks for the interest Keith, I have sent you a reply.

This is proving to be a popular aeroplane !

Quite a few people have asked me to supply full wood kits.

I would love to, but it will be about 3 months before my balsa order arrives.

If anybody wants a kit, or even just some laser cut parts let me know and I will add you to the list.

[kevin b]

I decided to simplify the tail controls, so instead of 2 linkages to the elevators I have joined the elevator halves with a piece of dowel.

This should also slightly reduce the weight at the tail end. The rudder control will now exit at the opposite side instead of out of the top.

The fuselage is now ready to check the motor fit.

[kc]

It's looking good Kevin.   I like the idea of the dowel elevator joiner - better than wire in 5mm balsa.  On this model it's handy that it avoids the rudder and just needs a notch in the fuselage.  Closed loop could be used for the rudder and save even more weight if the only clevis are at the servo.

 

I have to say those tips on the tailplane look vulnerable - I wonder if they are made from hard balsa or perhaps liteply?   If balsa I would favour putting some 1/64 ply into them to reinforce. 

 

I cannot quite see how Kevin is going to get the motor in there and still get to the bolts - no doubt all will be revealed soon......

[kevin b]

Here you are !

 

4 long 3mm bolts.

4 tubes.

2 motor mounts.

4 plain nuts.

4 flat washers

4 nylock nuts.

 

Bolt the motor mounts to the motor using the long bolts, with the nut in the countersunk side of the mount (they fit in nicely).

Slot the unit into position in the model (just enough room to get the bolts through F2).

Secure with washers and nylock nuts. 

 

Simples.   

 

Now to sort out the ESC in the original tuned pipe position.

Should give plenty of cooling without being obvious.

[kc]

Well Kevin certainly got the motor in there in quite an ingenious way.   Is there a commercial source for the tube standoffs or is it necessary to make them?  Most of us would find it difficult to make them accurately square at each and and all the same length!

 

A couple of things that came to mind whilst studying the plan and Kevin's build.....

 

it seems as though the fuselage is built with the rear section flat on the board and F3 up in the air.  As it would be disastrous to get any sort of twist in the fuselage it might be a good idea to have a jigging piece attached to F3 temporarily to go flat on the board ( perhaps 20mm ?) to ensure both fuselage sides are parallel.  Maybe spot glue a bit on or attach with bolts thro the dowel holes.  It's possible the notches into the doubler do this automatically and I am worrying unneccesarily!  But any error in attaching the doubler or 5mm stringers might also cause an error and a twist.  

 

The plan shows a plastic wing bolt fitting.   A week or two ago a forum member was looking for these and couldn't buy any.   So perhaps a ply crosspiece and normal captive nut instead?

 

Looking at the underwing housing I wonder if this should be filled in on electric models - it looks like just a tunnel for the tuned pipe glow version -perhaps it needs streamlining, or maybe not?  Perhaps the covering film is enough.  Whichever it is I would always only glue this onto the wing AFTER covering as its so much easier covering a flat wing.

 

I am interested to see if Kevin puts a fuselage mounted u/c on his model and if so whether its the torque rod piano wire type or a commercial alloy or carbon type.  

 

 

 

[kevin b]

Sorry Keith, it was a lathe job. Standard size are too long.

Another way would be to make several MDF packings with holes in the middle.

I don't think that weight will be a problem.

Undercarriage will be wing mounted as per original.

 

I have now installed the snakes and servo mounts.

Next job is to fit the fuselage underside and sort out the ESC box.

Then some sanding (did I tell you I don't like sanding).

Edited March 13, 2022 by kevin b

[kc]

Making motor standoffs is not for me and in fact I think it's much better to be able to move the Lipo right up behind the motor bulkhead to make the CG come right without lead.   Therefore I will move the bulkhead F2 forward a little (by 35mm )and reduce it's width slightly (by 4mm)  to enable the nose to be shaped nicely.  Means the ply doubler will need to be a bit longer to meet the bulkhead.

 

I realised that the motor bolts could be made captive even if not using the standoffs and an extra mount, by simply putting a nut on and countersinking the bulkhead slightly to clear the nut.   Should make easier fitting and save all the time I wasted in the past trying to insert bolts when screwdriver access is near impossible

Edited March 13, 2022 by kc

[kc]

Nobody likes sanding!   However I  find that Permagrit blocks remove wood fast and the 'sawdust' seems larger and therefore less messy.   Much better than glasspaper and well worth the cost - I find I only need the wedge block to do most things.

I am looking forward to the razor plane shaping on this model - it's a bit of art more than craft and very satisfying when finished.   Nowadays a lost art!

[GrumpyGnome]

@kc you can get standoffs in various sizes, lengths, colours off ebay.  I got some for my SFM SE5, 25mm, for about £5...... E.G. https://www.ebay.co.uk/itm/402452486918?hash=item5db4099b06:g:gg8AAOSwd39fasJh

[kevin b]

The original model had a plastic wing bolt bracket that screwed to F5.

I have fitted a piece of 6mm ply with some trailing edge behind it to take a T nut.

A, because I think it will be stronger and B, because it is cheaper !

The ESC box is now sorted out, but I have not fitted the bottom hatch yet.

That way it will be easier to fit the wing dowels in the wing.

I have fitted the top rear sheeting and also done some "rough" shaping.

It is beginning to look like a fuselage !

The tail parts are ready to sand and fit, so it is now on with the wing.

[kc]

Kevin it's coming along well!

As this will be a Mass Build I will ask some questions about items not actually explained by the photos for the benefit of newer builders.....

 

Is F20 - fus lower sheet- grain along the fuselage or crossgrain?

 

Stringers under F19 - fus top- are they shaped or are they planed down after sheeting? 

 

Is the motor to be enclosed or will there be an air outlet underneath?

 

What glues did you use for balsa and what for the ply doubler?

[kevin b]

F20's grain is along the fuselage. I forgot to mention that you have to fit 5mm sq cross pieces, though they are shown on the plan.

The stringers under F19 need to be planed, or sanded flat after the upper planking (no part number) is fitted.

Then F19 is glued flat on top.

The ducting for the motor will exit underneath (will be shown later).

Aliphatic is my glue of choice for all uses on this type of model (except canopies and vac formings !).

 

More photos tomorrow.

[kevin b]

Ok. On with the wing.

As the dihedral is dictated by the wing ribs the wing must be built upside down on the plan, so that the top of the wing is flat and the wing ribs are vertical.

Therefore, as the wing ribs taper as well as the wing then the first job is to secure the bottom spar to the board and build from that.

First the ribs and then the top spar. Making sure all the ribs are vertical.

Once the glue has dried the webbings are added, still keeping everything vertical.

In the second photo the upper trailing edge sheeting is pinned to the board, but not glued.

Once the glue has dried the spar is released from the building board.

The trailing edge is then glued to the sheeting so that the ribs can be glued into their notches and the trailing edge bottom sheet fitted.

This can all be pinned down solid to keep the trailing edge straight, but the main spar must be packed up to take the weight or a twist will set in.

Note the packings are not all the same to allow for the wing rib thickness.

 

 

Edited March 19, 2022 by kevin b

[kc]

Quite good progress there Kevin.   

I am going to ask some more questions - I can probably guess the answers but just to clarify for everyone ....

1.  is one of those a reverse printed half wing plan?

2.  what is the webbing material - on the plan it is shown as W18 which I expected to be ply.  Does it extend beyond W7?

3. have you used balsa spars and are they notched?

4.  will you use a fibreglass bandage?  Or add any ply doublers instead? 

[kevin b]

I printed out a reverse copy for building on. I usually do this.

The web is 2mm (3/32ins) balsa as per original.

The original had 5mm x 7mm balsa spars notched, but I replaced them with 5mm sq spruce as it was easier than notching the wood and in my opinion stronger.

Remember that when these kits were new they were trying to make them as light as possible because of the available engine power.

I am not intending to use a fibreglass bandage, as will be seen during the wing build.

I did forget to mention in the last post that the trailing edges were made of 5mm x 5mm balsa (as per plan) and that I had notched them to take the ends of the ribs as in the original kit.

 

Having glued the trailing edge sheeting on I decided to fit the undercarriage reinforcement ribs and the mounting plates before fitting the leading edge.

This made them a lot easier to fit. After which the leading edge strips were fitted.

Interestingly the mounts appear to incorporate some toe in as they are not in line. I checked this on the plan and found it to be correct.

 

I need to get on with this now as I have just turned my Mignon back into a kit, only with more pieces !

It had been a nice day until then.

[kc]

Thanks for the info Kevin.    Spruce spars are so much better than balsa and very little heavier.   

 

I await with interest to see if there will be any extra bracing instead of the fibreglass.   Looking at the plan I considered that inserting a ply doubler straight across from W6 to W6 on underside might be worthwhile, with another on top side from W5 to W5.  At about the servo area it might help form the servo box centrally or outboard for 2 wing servos for those who prefer.   Perhaps another small ply dihedral  brace in the TE/wing bolt area?

I see that the wing sheeting is specified as 2mm while the commonly available 1/16th is of course a bit thinner.  Someone here on the forum said some months ago that 2mm can be a lot stronger than 1/16th for sheeting so I wonder if 2mm is available in England.

 

Edited March 21, 2022 by kc

[Nigel R]

A layer of glass tissue (or the thinnest of cloth) makes for strong sheeting at the middle section. Plus, it doubles up as a good wing joiner - two jobs for one. I know not everyone likes glass though.

[kevin b]

kc. For 2mm balsa read 3/32ins, which is available over here when it is available, if you understand what I mean !  

As the top of the wing is flat I will be sheeting the centre section in one piece to increase strength. Photos will follow soon.

[kc]

Well choosing 3/32 or 1/16 for the sheeting is a bit like buying trousers - they only come too big or too small!    I always  opt for comfort-  it could be easier to persuade 1/16 to go around the curves. 

It looks like 7 sheets of 4inch by 36 for the sheeting alone, although there could be less wastage from 48 inch stock.

It would appear that light is out of stock while medium seems available from Balsa Cabin just now. Maybe I would opt to go up a grade and down a size - 1/16 medium instead of 3/32 light.

 

[kc]

Kevin, could you show a photo of the elevator and rudder servo mounting?  Have you moved the servos to the retract servo position?

 

Whilst studying the plan for servo positions I realised why they used a plastic central wing bolt fitting - maybe it helps clear the horns on the aileron torque rods.   Replacing that fitting with a piece of ply might mean clearance problems.   Of course the horns could project down into the underwing housing but if so any raking of the torque rods would need to be the opposite of that normally used in a low wing model and be the same as a high wing model.   

[kevin b]

Wing sheeting should take 5 sheets of 3/32ins x 3ins x 36ins long and 1 sheet of 3/32ins x 4ins x 36ins long.

You will not get 2 lengths out of a 48ins sheet (wingspan is 52ins).

I am still not sure about the wing mount, as to whether it will be 1, or 2 bolt fixing. That is why I fitted a substantial piece of ply backed with trailing edge section.

Also the 2 WC3 trailing edge pieces shown on the plan will be replaced with a single piece of thicker wood to improve strength.

[Nigel R]

10 hours ago, kc said:

aileron torque rods.   Replacing that fitting with a piece of ply might mean clearance problems

 

Torque rods are my preferred solution for strip ailerons. The clearance angle is why I use two 1/2 x 1/2 x 1-1/12 blocks, glued to the fuselage side, then tap them for M5 nylon bolts.

 

11 hours ago, kc said:

It would appear that light is out of stock while medium seems available from Balsa Cabin just now.

 

SLEC show stock of light 1/16 sheet.

 

Edited March 22, 2022 by Nigel R