The Warbirds Replicas Macchi C.202 is Landing!

[Brian Seymour]

The model is progressing with the wings and strip planking in tandem, the wings are taking priority but there is an hour or so between stages waiting for glue to dry.

First off, a picture of the wing with the top skin gluing, weighed and pinned down:

Both wings have got their top skins glued on now, with the exception of one small length, the skins have glued perfectly onto the tops of the ribs and spars etc. The small length where the skin didn't take to the rib was out near the tip but it has been re-glued and clamped and is now almost as neat as the rest.

The lower skins are well on their way and will be glued on in a similar process to the Warbirds Replicas Spitfire with three jigs to support the wing whilst it is glued. The jigs ensure that the correct washout is set into the wing panels and, more importantly, that both panels come out identically - more on that soon(ish).

The strip planking is also underway with a stock of strips cut up ready. The strips are cut with the stripping tool kicked over at angle so that, rather than a square cross section to the strip, it is a regular trapezium. This has a couple of advantages: to some extent the strips inter-lock and the extra surface area on the joins help with gluing/filling.

The first strips are on, glued to the horizontal and vertical keels. I used aliphatic resin to glue them because of the large gluing area, once I'm planking on just the formers I will use aliphatic on the strip joins and CA on the formers as there isn't a lot of former area to pin to.

 

I have used a scarf join where the planks need to be joined. On the 2015 model I butt joined the planks on the formers which worked out ok but I reckon that this will be better.

 

The wing seats need to be completed before I can plank much further down the fuselage sides so the wings are the priority because they need to be joined so that the seats can be made with the wings in situ.

More to follow on the planking with a few pictures clarifying how to make the strips with a regular trapezium cross section. I would have put a link to the web site that has the tutorial on strip planking that I followed but it is no longer available (that or I just can't find it!), I think that it was on "Model Flying News". This is the strip cutter that was recommended and I have been using: **LINK**

Edited By Brian Seymour on 23/03/2017 14:00:21

[Nigel R]

Nice build - following.

One question, I can't see from the pictures - does the main wing sheeting just butt up against the centre section sheeting or does it overlap?

[Brian Seymour]

Cheers Nigel, the main wing sheeting overlaps the centre section:

The step allows the fairing to have 1/16" thickness rather than a delicate feathered edge.

The planking so far, it's speeding up with using CA to glue the strips to the formers.

Getting a neat join where the planks converge isn't too tricky, pin the strip in position lining the edge to the point at which the planks converge and mark the point the depth of the overlap:

Cut the end of the strip from the mark to the corner on the opposite side of the strip and it should fit in place just nicely:

[Colin Leighfield]

Isn't it's great to see how a modern approach to cnc or laser cutting combined with traditional building techniques can produce a super result like this. One of the most attractive and effective WW2 fighters.

Edited By Colin Leighfield on 23/03/2017 22:42:49

[Brian Seymour]

Cheers Colin, there doesn't seem to be a better automated option to strip planking, certainly not a cost effective one.

 

The wings are coming on nicely with the lower skins glued on. The lower skins only go back as far as the flap pocket so the template was modified and the skins made in the same way as the top skins. It didn't all go quite to plan first time, this was traced to skins lifting as I was cutting so the balsa sheets were shuffled and shimmied a bit to overlap again and then they were well and truly pinned down before cutting. I remembered to sand the sheets before gluing and despite the little troubles they came out just nice.

The lower skins are fitted with the wings jigged up in the same manner as the Warbirds Spitfire. Jigs will be included in the kit but I hadn't included them when I sent off the laser cutting for the prototypes so I printed off the profiles and cut them from lite-ply (see, lite-ply does have a use in aeromodelling!) The jigs are positioned over ribs R3, R9 and R14:

 

The servo extension leads are fitted in the wing and then the wing is positioned in the jigs:

Glue is applied to the ribs, spars, flap hinge rail and false leading edge, leaving the tip, which will be glued in the next stage, dry, and the lower skin positioned on top. As with the top skin, weights are used being positioned over the location of the rear spar and jigs, and then a few more in the gaps and then over the main spar. With the skin weighed from the main spar back, the leading edge is pinned to the false leading edge.

 

With the lower skins glued, the tips can be glued. The joins in the skins at the tip were not glued, this is to allow for a little fine trimming. The tips are clamped dry progressing from the leading and trailing edges to the joins in the skin. Once clamped, the skins overlap so using the edge of the overlapping skin as a guide, the clamped skin was trimmed. With the scrap sliver removed, the skins butted up sweetly. The clamps were removed, glue applied and then re-clamped and left to set.

Pads of gripper mat were used to prevent the clamps on the lead edge sliding off.

Edited By Brian Seymour on 26/03/2017 15:26:47

[Brian Seymour]

The wings are on the final straight now, the leading edges went on with no problems which left the flaps.

The flaps need the trailing edge feathering which, due to them being made from poplar ply, requires a little elbow grease but soon gets done.

The flaps need a slight twist to be set into them to match the washout, I was at a loss but Richard and Vic related the following technique. The required twist is little more than 1/16", following a couple of trials, propping a corner up at 1/8" left the flap springing back to the perfect amount of twist.

So, a wedge, the length of the flap and 1/8" wide at the thick end, was cut from one of the laser cutting scrap ladders.

The wedge was laid on the board, the flap was wetted and pinned to the building board over the wedge to set a 1/8" twist into it.

The filming iron was set to 150°C and the flap was ironed until it had completely dried. The twist sprung back slightly to leave the flap perfectly matched to the washout - Vic & Richard, I guess that means that I owe you a drink!

Next is hinging the flap to the wing, I had a practise on some of the scrap poplar ply. It took a few goes to get the hang of cutting a hinge slot in the ply so it was just as well that I didn't dive straight into hinging the flap. A shallow flat, the width of the hinge, is filed into the edge to be hinged.

Using a scalpel and a bucket of patience, a slot is cut into the shallow flat to accommodate the hinge, the slot then needs a narrow strip of sand-paper feeding through and slot sanded out marginally thicker than the scalpel blade. The hinge needs the all of the edges sanded off before fitting. It's a faff for sure but comes out nicely being tight enough to grip the hinge but not so tight that the plywood splits.

The hinge positions were marked off onto the hinge rail in the wing and slots made in pretty much the same way. One little lack of foresight was that one of the hinge slots crossed a plywood rib, this took a fair bit of patience but the slot was eventually cut. The hinging has come out just right.

 

The aileron was a walk in the park having prepped the hinging before skinning and having got to grips with sanding and adjusting the shrouding on the elevators and rudder.

The apertures for the servo boxes were cut next. This was done with a bit of trepidation, the wing is at a pretty advanced stage and chopping a big hole in the wrong position would have required a call to the Samaritans. I used the template from making the skins to get a starting point and gradually opened out the apertures out, the strips that line the mounting plates in the wing made it pretty simple to get the openings the right size. The servo boxes were put in place and the soft balsa facings easily sanded to match the profile of the wing.

The wing shown is ready for covering and the other wing isn't far behind - you never know, I might get her flown in time for the club concurs.

 

Edited By Brian Seymour on 26/03/2017 20:17:39

Edited By Brian Seymour on 26/03/2017 20:21:58

[Brian Seymour]

In between jobs on the wings, the strip planking has been coming on and got to the stage where the exit for elevator push rod exits and the guide tubes for the rudder closed loop cables can be installed. The planks have come out a bit gappy in a few places so the gaps were given a lick of Poly-C and filled with lightweight filler and given a little abuse with the Permagrit to get them tidied. Slots were cut for the elevator spars and the rudder spars and the tail components dry assembled so that holes/slots could be made for the control linkages.

Elevator push rod exit:

 

Guide tubes for the rudder cables:

 

The concentration of my efforts is on the wings as they need to be joined so that the wing seat can be made in the fuselage which is necessary before the strip planking can progress much further. Believe it or not I haven't got much space for building, little more than the 18" x 48" building board so I'm reluctant to join the wings until the latest possible stage. With both wings ready for covering, I decided to go with Richards tip of brown paper. I googled for brown paper covering a model and found several series of forum posts where experts explained that it results in very heavy models - they may be experts in something but it certainly isn't in brown paper covering! A couple my club-mates took the plunge on our group build last year and their results were truly stunning with seemingly little effort and weight gain.

Despite covering with brown paper being a simple process I still made a hash of it on my first go, watering the glue down too much and applying too thin a coat, this resulted in several areas where it lacked adhesion and bubbled up. On my 2nd attempt I used two coats of the overly thinned glue and got away with it. To rescue my first effort, I asked Richard, and I'm jolly glad I did! On Richard's advise, the bubbled areas have crosses cut into them, the leaves peeled back and simply re-glued and ironed flat, it's not as neat as getting right first time but you won't know it's any different once a coat of primer has gone on.

Subsequent applications of brown paper have been a walk in the park. The 2015 model was covered using glass cloth and epoxy so I was keen to compare the weight difference. Using glass cloth, the weight gain was ~50g per wing, with the brown paper it has been 15g per wing. Prior to covering, the right wing weighed 177g, after covering the weight was 195g and after it had been left over night and dried out it weighed 192g - I don't think that I'll be going back to glass and epoxy.

It's apparent which wing was done first but I reckon that I'll be the only one who can tell once they are finished:

If you are at the covering stage then consider brown paper, it is very cheap, I found easier than film covering and glassing, dead easy to recover from disaster and I doubt that you'll find a lighter alternative.

Edited By Brian Seymour on 30/03/2017 19:28:39

Edited By Brian Seymour on 30/03/2017 19:31:03

[Paul Johnson 4]

I love the stuff.... looking good Brian.

[Dwain Dibley.]

You've done a good job there Brian, I think we on the 110 thread will be taking notes from this point on Matey.

D.D.

[Brian Seymour]

Cheers, your 110's are taking shape sweetly too, the thread is ace with excellent building tips - shame I didn't see the greaseproof paper tip before I bought the standard brown paper.

[Paul Johnson 4]

Brian

Shhh I didn't even have to go buy mine.... I borrowed what was in the kitchen..... shhhhhh

[Brian Seymour]

That's got to tip the top of the top tips table!

The brown paper covering went so well that I allowed myself to get distracted and cover the tailplanes, fin, flaps and exhaust fairings. The flaps were an interesting little case, I used the same wedge to set the washout twist only to find that with the brown paper on there were was no spring-back - that made setting the twist even easier! I hinged the flaps, wetted them, clamped them to the wing trailing edge and ironed them in situ and set the twist perfectly.

With the wings progressed far enough I joined them. There are two dihedral braces which fit in between the spars similar to the webs, epoxy was used to glue them in position.

The strip planking has also been coming on, the planks are cut using the following process.

A 1/4"sq. block is used to kick the stripping tool up to cut an angle:

In order to minimise waste, a 1/4" wide strip is used space the blade away from the edge of the sheet and cut little more then a sliver:

Once the sliver has been cut, the sheet is flipped over (bottom right to top left in the picture above) and the first full strip is cut:

The sheet is flipped between cutting the strips so that the cross section of the strips is a regular trapezium.

Before fitting the wing seat a few bits for the leading and trailing edge fairings need to be fitted which requires the lower half of the nose to be strip planked and sanded. The picture shows one half sanded and the other just planked:

The planking looks pretty rough before sanding, also noteworthy is that the planking is progressed with a plank down from the horizontal keel and then a plank up from the lower vertical keel:

With the planking sanded (both sides) the fairing components can be installed:

[Nigel R]

a couple of questions, if I may;

1) the planking looks unfinished at one end - does it get sanded back to the nearest former?

2) brown paper...

50/50 PVA/water?

shiny side in or out?

any special precautions to prevent parts from warping?

compounds - slice / overlap / sand back after its dry, like back in the day with tissue & dope?

after it is on, does it need further PVA/water to seal before paint?

poly C as a final stage?

what sort of paint?

blimey - sorry- quite a few questions as it turned out!

[Brian Seymour]

Hello Nigel, the questions are no problem, I'm glad that you are taking an interest.

The planking is in a mixed state, I need to get the wing seat done to progress the wing fairing which blends into the planking so I have gone up to the most convenient point in the strip planking. I couldn't resist the urge to tidy up the areas where the planks have converged so some of the planking has been sanded.

Sanding the nice compound curve smoothly requires a little experimentation with abrasives as some are harsh on the balsa and gentle on the glue. I have found my rough Permagrit block (and 80 grit aluminium oxide paper) used lightly removes the glue at the same rate as the balsa so the curve on the underside of the nose has come out very nicely.

For the brown paper, it didn't need much water adding to the PVA ~15%-20% seemed to do the trick (my first effort was ~ 50/50 but it was too thin), it needs to be the consistency of single cream.

The matt side of the paper is glued so shiny side out.

None of the parts have warped except for where I deliberately ironed the washout twist into the flaps.

The paper forms around compound curves without the need for slicing, I used a dry paint brush to tease the paper around the curves before setting it with the iron. I have overlapped the leading edge and the paper is so thin where the iron has run over it that I reckon the edge will disappear with a coat of primer.

The next stage on the covering (re: Richard's instructions as I have never done it before) is to seal it with non-shrinking dope thinned 1:1, then it is given a coat of primer and then it can be painted.

I guess that Poly-C could be used instead of thinned non-shrinking dope, (feel free to chip in if you have used Poly-C instead of dope on brown paper).

I'll be using acrylic paints finished with 50/50 mix of Poly-C and matting agent as that little recipe has worked a treat on my other models.

[gillyg1]

Brian do you find that finishing mix with poly c and acrylic is glow fuel proof. having used ploy c in the past. I find it not totally fuel proof to glow?
tip: if you can't get non shrinking dope, a few drops of banana oil to normal dope prevents it shrinking, have used this method in the past (LA7)and it works a treat.
my preferred method for finishing. am going too try dulux touch up pots on the 110 as per Richards technique.

[Nigel R]

brilliant, thanks brian

 

more questions!

"The paper forms around compound curves without the need for slicing, I used a dry paint brush to tease the paper around the curves before setting it with the iron. "

regular finishing iron? cold/med/hot? do you just wash off the pva that sticks to it?

the brown paper must stretch when you brush it, I guess I had assumed the paper was too heavy to do this, but it must be quite light grade paper you are using?

 

I have done a few fuselages with tissue/dope/rattle can/fuel proofer, back when rattle cans where hazardous to your health and dope was able to make you go odd in the head for a few minutes. The brown paper / PVA combo seems like it may work as a modern substitute, without going to the lengths of resin & glass (which I dislike). I might also get away with doing paper & PVA in the house where it is warm and dry, as it doesn't smell!

Edited By Nigel R on 06/04/2017 15:20:56

[gillyg1]

Nigel : the brown paper I use is what car body shop / sprayers use for masking up , comes on a roll and is lighter than post office parcel wrap . So pop along to the nearest " bodyshop" and see if your friendly sprayer will let you have what's left at the end of the roll.

[Victor Arcudi]

Personally, I'll be using old fashioned heavyweight tissue & either WBPU paint or regular dope.

[Brian Seymour]

Hello GillyG1, I can't vouch for Poly-C with regard to fuel proofing as, I must confess, I haven't got any ic planes. Great tip on the banana oil and the car body shop brown paper thanks.

Nigel, yes, it's a regular finishing iron set to 125° which is what I set it for with Solartex. The paper I have used is this: **LINK** but folk use all sorts as GillyG1 and Paul have given us tips for. I don't know what the scientific explanation but it has worked well for all of us that have tried it and no two folk seem to use the same brand or weight of paper.

I'm looking forward to seeing your Macchi Vic, tissue covering seems to come out really nicely, we had an excellent modeler (Richard Ginger) flying with Jon who had cover his Tempest with tissue and dope. The finish was outstanding and for a big airframe it was dead light.

No further progress today as I was at the strip with my Warbirds Replicas Yak-9, she's a cracking flyer and I'm surprised that Richard hasn't had many enquiries for the kit.

[Paul Johnson 4]

Flying out in that glorious sunshine whilst i was stuck at work...

Siiiiggghhhh...

Bills they always get in the way of fun....

[Bucksboy]

The Yak-9 isn't offered for sale on the web site, unless you read the Wycombe build thread you wouldn't know about it. I fully understand the difficulties Richard is working under, I've bought both the La 7 and 110 from him, so I can see why he's not added it to the web site.

[Paul Johnson 4]

Brian

I have been avidly following your build, not only fascinated by the design but also keen to learn, new to me, techniques.

Keep posting so I can keep learning....

[Brian Seymour]

Thanks fellas.

Bucksboy, good points on the Yak-9 and the La7 is certainly sweet enough.

Paul, talking of learning, I'll be swotting up on your panel line and weathering tips for sure.

Latest progress on the build will follow soon, not that there has been much with the decent flying (and gardening) weather over the weekend.

[Brian Seymour]

The fuselage is coming on treat with the wing seat on and the strip planking a few planks short of a full skin.

The next job was to fit the wing seats, 2 sets of 4 pieces of 1/16"thk medium balsa were butt joined to form the wing seat. The resulting cross-grain planks were laid in position on top of the wing and slots to fit the formers were cut into them and then they were trimmed to the leading and trailing edges.

The seats were fitted in place in the fuselage.

Polythene sheet was laid on top of the wings to prevent the wing from getting glued to the fuselage.

The fuselage (complete with wing seats) was fitted to the wing and the laser cut front fairing top blocks were glued in place..

Laser cut ribs (for want of a better word) were glued on top of the wing seat to set a curve to match the wing top surface into the wing seat. 20mm wide soft balsa strips were cut and wetted to make them pliable and then glued on top of the wing seats flush with the edge. In order to set the exact curve of the top surface of the wing, the strips were pinned through into the wing skin and then left to set and dry out completely (takes a while so next stop was the flying field!).

Once completely dry, the pins were removed and the whole lot turned upside down and a bead of glue was run into the joins on the underside.

The laser cut lower leading edge blocks were glued in place

With the wing seat reasonably robust, the strip planking on the top of the fuselage was finished off, the cowl fitted and the Permagrit put to good use.

The planking does have few gaps in places and some of the edges haven't adhered together so, once the planking and fairing are somewhere near done, the whole lot will be given a coat of Poly-C and filler worked into any gaps.

At times the strip planking felt like it was going to be my life's work when all of a sudden I was on the last few strips and 10mins with the Permagrit smoothed the uneven joins rather nicely into something almost resembling a fuselage!

Edited By Brian Seymour on 10/04/2017 23:15:41

[Dwain Dibley.]

Blimey Brian,

I bet you were glad to see the back of that planking, but what a superb job you have made of it, I am impressed by your undeniable patience.

It will be a shame to cover all that work up.

D.D.