Correx built PSS models

[Phil May]

Evening Mark.

It's 1350 mm span which if my calculations are correct it's approx 1/8 scale....I think.

I've still a fair bit to do on it yet ( Andy Meade is printing up a spinner, a couple of manifolds and a super charger intake ) but hope for it to come in at less than 1200g all up. The problem I'm finding with these correx builds is that they start off tail heavy and need a fair bit of lead up front to balance.

The plan is for a conventional balsa build that I was sent from a guy off RC Groups.

[Harry Twist]

Hi Phil, Looking like it's coming together nicely now!

Did you do anything to prepare the correx before painting? Also did you prime then topcoat ?

This one will look great beating up the slopes!

Regards Harry

PS I've still not maidened my Impala!

[Mark Kettle 1]

Thanks Phil, will look the business with Andy's printed plastic parts.

[Andy Meade]

Parts are in-print today. Here are the 3D models from SolidWorks for your viewing pleasure.

Carb-scoop thingy :

Exhaust Stack :

Spinner with big 'ole :

[Phil May]

Brilliant, Thank you matey 👍

Edited By Phil May on 19/02/2016 10:19:33

[Andy Meade]

All done, and a quick coat of primer. Ready for despatch!

[Phil Cooke]

Nice work Andy they look great!

[Phil May]

Thanks mate, they'll look brill 👍

[Phil May]

Well, these 2 have been keeping me busy the last few weeks.

The Mig is for a mate and my 109 is near completion and may be ready to chuck off something big this weekend.

[Harry Twist]

Brilliant as ever Phil, I am sure they will fly a treat off those big hills you have to choose from!

Regards Harry

[john stones 1 - Moderator]

109 looks a bit good Phil

John

[Harry Twist]

Hi All, thought I would share some images of a correx model I have been working on recently. Its a Horten 229 flying wing- it's virtually finished - but not yet flown. Built from blowing up plan view images and drawing on to cheap paper before making the correx wing fold "plan". Printed several Ho229 images as well to help with engine intakes/cockpit and general proportions.

Conventional correx folded wing - built with significant washout and some dihedral, hopefully to aid some stability.

Flying weight has come out at 2 pounds wingspan approx 58inches.

I may add a lateral fin - not sure yet.

Colours are ghost white and slate grey upper with sky blue underside.

Regards H

[KiwiKid]

Awesome build Harry - very scale looking. I did a similar kit bash on a HK X-8 - makes a great sloper.

How have you got on with B&V 215? Really looking forward to seeing that finished - it's one of my favourite designs.

[Mark Kettle 1]

Printed parts Andy look brill.

Looks like your've nailed it Harry and KiwiKid on those fine models

[Phil May]

Excellent looking models guys.

Harry, how do you 'finish' the exposed flutes of the correx when you paint the model?

Thank you for the P.M, that would be great thank you.....looking forward to seeing the Horten at the Bwlch next month, should have my new build finished by then ( P 51-D )

Still dithering over War bird or Renno?? 😕

May wait and see what it's flight charictristics are like before I decide....

[Harry Twist]

Thanks for the comments.

Phil - ref the flutes -I dont do anything- the wingtip area is glued closed but the wing trailing edges are left open( have a look at the third picture above). Once paint added top and bottom they are not overly noticeable- I reckon probably the way to go is to cover them with a paintable covering material but you may see a lines where this ends on the upper and lower training edges. I did add a little lightweight filler to the forward facing flutes just in front of the two engines - where I fitted an upper doubler. Where the nose was cut away I infilled with balsa - sanded in to shape.

For your P-51 - definitely Reno racer style!

Kiwikid - like the HK X8 how much modification did you do to make it a sloper? MY B&V215 nearly done - had a little issue with painting - two surfaces reacting together - so am rubbing back and repreparing but ready soon hopefully - hey ho!

Regards H

Edited By Harry Twist on 24/04/2016 14:00:41

[KiwiKid]

Hi Harry, the X-8 has a large load carrying capacity for FPV work, so I used some of that to strengthen it for slopin'. Glassed all over and internally also on the fuse with some cf strips embedded in the wings - goes great

B&V 219 from KiwiKid on Vimeo.

 

Edited By KiwiKid on 24/04/2016 15:00:34

Edited By KiwiKid on 24/04/2016 15:01:13

[Saint 1]

I’m more than a bit late to this party I know but I discovered this Correx build thread the other day and seeing as I can’t seem to stop building in Correx myself I thought I’d post up some photos of my previous builds along with the one I’m on with currently (build number 16!)

 

I started off in early 2019, like many by building the much tried and tested Mig, followed by the A10, Reno Racer Super Corsair, Red Arrows Hawk and then another Mig to replace my first one which suffered one too many heavy ‘landings’. I then went on to modify some balsa plans to make a Mosquito followed by three L39s (part of a group of six in total), a Silver Falcons Pilatus PC-7, a pair of Hawks in the 2010 colour scheme, the Rolls-Royce Spitfire and then most recently 2 more Hawks for a fellow flier.

 

 

 

 

 

 

 

 

 

 

 

 

Of all the builds it has been my Red Arrows Hawk and the Super Corsair that have seen most action, some of you may well have seen them and indeed some of the others at the Orme over the last couple of years. I’ve always loved the look of my Super Corsair and it was one that flew well right from its maiden. It’s had a few bumps and scrapes since and there are a few improvements I wanted to make too so I decided this Winter was the time to build myself a new one, still in the same Reno Racer colour scheme of aircraft NX5577N but BIGGER and hopefully better.

 

Initially my intention had been to build something more scale in balsa this Winter but I’m still relatively new to rc flying so I thought I’d give it another year before doing that and hopefully allow my flying skills to improve a bit more in the meantime.

 

My new Super Corsair will be a 120% version of my current one, making it close to 1/8 scale with a clipped wingspan of 62”. At this size it is just possible to cut the wings and fuselage from 4’x2’ Correx sheets. Finished weight is going to be in the region of 3kg (with around 500g of that being nose ballast).

 

For strength the wings will be made from 3mm Correx rather than the usual 2mm.

 

The ailerons are double thickness rather than the usual single piece of 3mm Correx, both for strength and to blend more smoothly with the wing.

 

I’m introducing a rudder in addition to the standard aileron/elevator set-up.

 

All exposed flutes will be sealed with either balsa, 1mm ply or filler to improve the look and hopefully performance too.

 

The wing will be secured with wing bolts rather than rubber bands.

 

All the tail surfaces will be made from two thicknesses of 3mm Correx rather than one and additional bracing and formers will be introduced to increase rigidity of the tail – a weak point of my current Super Corsair as one or two noted on its last flight from the South slope of the Orme, admittedly when the wind speed was well over 40mph!

I’ll add as much extra scale (ish) detail as I’m able along the way.

 

This isn’t a full photographic record of a Correx build since much of that has been covered many times already so I’ll concentrate on the things I’ve chosen to do a little differently, for better or worse!

 

Firstly though, some notes on sourcing Correx. Like everything it seems to be getting more and more expensive and tricky to source. Ideally you want to find somewhere local to you where you can pick it up directly because delivery can be both tricky and expensive. If you can get hold of 8’x4’ sheets then that allows you more scope to build bigger but generally 4’x2’ or 4’x3’ sheets work well provided the flute direction runs along the 4’ length, plus they should hopefully then also fit in your car. If you’re having it delivered then make sure it will be delivered flat as many places will either roll or fold it rendering it useless, particularly so with the thinner 2mm sheets. Standard Correx builds generally use 2mm thickness for the wings and then 3mm for everything else. Some time ago I also sourced some non-Correx brand 2.5mm thickness sheet which I have used on many of my wings in lieu of the 2mm and will be using again on this build for my ailerons. The suppliers I have used most recently are:-

 

2mm Correx:- Kite Packaging

 

2.5mm Non-Correx brand sheet:- The Plastic Shop

 

3mm Correx:- K&M Wholesale Suppliers

 

And so to the build itself:-

 

Due to the number of photos I'll spread this over a few separate posts...

 

For greater strength I opted to make the wing from 3mm Correx rather than 2mm. Standard practice is for the aileron to be produced from a single piece of 3mm Correx as well with one flute cut away to make the hinge. This results in a step between the aileron and both the upper and lower surfaces of the wing as per the diagram below.

 

 

Over time I have also found the aileron is prone to distorting so for my build I have chosen to effectively cut most of the 3mm aileron away leaving just a stub which I have then sandwiched between a folded length of 2.5mm sheet forming a new and more robust aileron. This aileron then transitions more smoothly from the upper and lower wing surfaces. In theory 3mm Correx should have provided a fully flush transition between the wing and aileron surfaces but I opted to use 2.5mm instead, favouring a slight waterfall effect rather than running the potential risk of an into wind step.

 

 

I glued a few balsa webs within the aileron for support, one of which also serves to strengthen the control horn mounting area. Once folded, I closed the exposed ends off with 1mm ply or balsa as felt appropriate.

 

 

 

 

The wing spar is made from 9mm ply pinned and glued at the crank points and I have then glued and screwed a block of wood in place to support the front wing mounting tab.

 

 

 

I allowed for a spacer under the mounting tab in order to provide some adjustment on final assembly with the fuselage.

 

 

Ply servo mounts were glued to the spar and wing lower surface followed by a bead of hot glue for extra security before fitting the servos.

 

 

 

The four sections of upper wing were folded in the normal manner.

 

 

The exposed flutes on the wing tip leading edges were then cut away and some balsa strip introduced and sanded to shape, followed by some 3mm ply for the wing tip itself and 1mm ply for the trailing edge part.

 

 

 

 

 

 

A balsa strip was also introduced to close off the exposed flutes of the wing upper surface along the aileron hinge line as shown in the last photo above.

 

With the wing nearing completion I felt a photo comparison with the standard wing was in order. Although it IS only 20% bigger it somehow looks more like 50% in the photo! Note that I also chose to reduce the aileron length this time in order to make them look a little more scale in appearance. No flaps though – they looked like being way too complicated!

 

 

I closed the rest of the wing trailing edge flutes off with 1mm ply, I’m not expecting any aerodynamic gains here but to my eyes it will at least look better.

 

 

And then to tidy things up I then glued a couple more pieces of Correx over the previously open upper surfaces of the wing, leaving a small slot for the servo wires to exit from.

 

 

Continued in next post...

 

 

[Saint 1]

The tail surfaces of my current Super Corsair have always been a little wobbly, partly down to their 3mm thickness but also the limited strength of the fuselage location so this is something I wanted to address here. To that end I have made all the tail surfaces from 2 layers of 3mm Correx with one or two 2.5mm carbon rods inserted too for good measure. They are just about visible in the second photo below.

 

 

 

I then closed off all the exposed flutes in much the same way as the wing. I have used Evo-Stik to do this which generally seems to work well but I have found that at times when Evo-Stik gets inside the Correx flutes it can react and cause the Correx skins to ripple a little as can be seen at the top of the rudder. I don’t know a solution for this but a little filler applied subsequently can help to mask the effect.

 

For the fuselage formers I have stuck with the traditional 2 thicknesses of 3mm Correx with the flutes at 90 degrees to one another except at the very front and the two formers which abut the wing leading and trailing edges where for strength I have used 3mm ply glued to a single piece of 3mm Correx.

For the 3mm Correx fuselage skin I de-fluted every other flute to allow it to be formed whilst still maintaining a degree of strength. It won’t be immediately obvious in the subsequent build photos but wherever possible I have also applied heavy duty clear tape to the inside of the fuselage skins in attempt to reinstate some of the strength sacrificed in the de-fluting process. As with the majority of my builds I also incorporated a square Correx battery tube through the foremost formers to enable fine tuning of the CG by positioning the 4 cell square NiMH battery pack within it.

 

 

 

Generally Correx fuselages are built up using a wooden dowel to locate the formers and help maintain a straight fuselage but I have not used one on this build. The foremost formers are located on the square battery tube anyway and with care it is possible to add the remainder accurately. Once the top half of the fuselage skin forward of the wing had been glued to the formers I moved to the tail, gluing the two undersides together followed by the former immediately rear of the wing, taking care to ensure it was positioned correctly to match the wing chord dimension at that point.

 

 

Having already glued the tailplane and fin together I was then able to glue the tail assembly into the fuselage. I temporarily inserted a carbon rod into one of the formers to act as a vertical reference and so ensuring everything was nice and square.

 

 

From a previous similar Corsair build on the RCgroups.com forum I reckoned I’d be needing around 500g of ballast in the nose so I secured the requisite amount of wheel balance weights in place using hot glue and glass fibre tape prior to fully closing off the forward fuselage skin. Hopefully any fine adjustment of the CG should subsequently be possible by repositioning the battery within its location tube without the need for any additional ballast.

 

 

I then introduced the remaining formers and started thinking about the required cut-out for the cockpit.

 

 

With the forward fuselage skin fully closed I was then able to taper the nose down at the front and start roughing out the cut-out for the wing.

 

 

Before final fitting of the wing though I always hot glue a supporting layer of 3mm Correx on the inside edges of the fuselage skin with the flutes aligned 90 degrees to those of the fuselage. This not only adds strength but also makes final trimming of the fuselage sides much more precise; it is far easier and more controllable to carve across the flute channels with a scalpel rather than along them as would be the case with the fuselage skins alone.

 

 

Once the tapered nose sections were glued in place I cut away the excess flush with the ply former and then turned up a fairing piece from ply using a lathe (Well not really, please don’t try this at home! 😀). With the fairing piece glued in place there would then just be a little filler required to smooth things out.

 

 

 

 

 

Using my ‘lathe’ once more I also managed to turn up a piece of aluminium bar to make the nose spinner, I will ultimately polish this up and then lacquer it to protect it from the salty Orme air.

 

 

 

 

With the nose spinner made I then used the top section of a 3 litre pop bottle to make a clear fairing cover for the engine in order to minimise drag from the otherwise flat front end. I will use a suitably sized o-ring on the ally nose spinner to help hold the fairing in place.

 

 

 

To further strengthen the tail surfaces, on this build I have introduced an additional former immediately in front of the tailplane leading edge, along with some carbon rod cross-braces hot-glued into the rearmost compartment. At this point I also installed the carbon control rods for each elevator along with the snake for the rudder. The snake was required so as to pass underneath the cockpit rather than through it.

 

 

 

This particular Super Corsair had no fewer than 14 exhausts (for its 4 bank 28 cylinder radial engine) four on either side of the fuselage and six on the underside. I cut the fuselage sides accordingly and introduced some thin ply pieces to create the outlet ducts on either side.

 

 

The underside of the wing required a fairing piece to blend in with the fuselage so I used a few pieces of ply and Correx in order to achieve this and at the same time glued in a ply support pad for the wing bolt fastenings, followed off by a little more filler.

 

 

 

 

 

With this done I was then just about able to drill six more holes to locate the remaining six exhausts, all of which I am making from aluminium tube.

 

 

I glued in a ply radio tray as far forward as possible, thus keeping all the radio gear forward of the CG point. (With any PSS build of a piston-engine plane it is always imperative to keep weight as far forward as possible in order to keep the amount of subsequent nose ballast to a minimum).

 

 

The wing leading edge air intakes are something of a defining feature of the Corsairs and something not at all easy to recreate on the thin folded leading edge of a Correx wing but I have made an attempt here with the addition of some balsa scoops glued on either side. Once painted up they will hopefully recreate the look to some extent at least.

 

 

 

 

There is a pitot tube on the leading edge of the port wingtip so I have managed to recreate this using the inner from a control rod snake glued into a piece of brass tube with a little brass shark fin soldered to it. The whole thing is removable and is a nice snug fit into a disused biro tube that I have glued into the wingtip leading edge. Hopefully its flexibility will mean it shouldn’t get damaged on landing.

 

 

As with my original Super Corsair I once again fabricated a Correx air scoop for the top of the fuselage but this time chose to blend it out all the way back to the canopy – more filler required here too.

 

 

For a bit of extra detail this time I turned up a ply tailwheel, cut it in half and glued and pinned it through the fuselage into a fuselage former. It feels secure so I hopefully won’t knock it off on landing.

 

 

 

 

[Saint 1]

Once I had finalised construction of the cockpit cut-out I used a bit more filler to close off any exposed flutes and then moved onto the canopy.

 

 

For standard sized Correx builds it’s generally possible to create a canopy from one or sometimes two 2 litre pop bottles. For this scaled-up version that was not going to be possible but fortunately I managed to find some 3 litre lemonade bottles that were just about large enough. I made a few Correx templates for reference and then carved some previously glued together blocks of wood to shape.

 

 

 

 

 

Once I thought I had the shape about right I then tried to mould a single 3 litre bottle over it, which failed miserably.

 

 

 

 

Ultimately the bottle wasn’t long enough plus I was unable to shrink the ends down sufficiently before it overheated and turned white.

 

For the second attempt I chose to make the canopy in two pieces with an overlap joint where the canopy frame would be and this proved to be far more successful.

 

 

With the two halves glued together using canopy glue I then used a series of tiny self-tapping screws to secure it place.

 

 

Having done all this, a few days later I then looked at it afresh and decided the rear section of the canopy was too bulbous so went on to modify my wooden block and mould a more teardrop shaped version in its place. This looked a little more representative of the real thing so I then went on to paint the frame.

 

 

 

 

Finding photographic images of the cockpit detail of this particular aircraft remains a challenge since sadly both the plane and its pilot were lost in a crash in 2012. It seems many features of the cockpit area in particular were unique to this aircraft so I am having to use a bit of licence in guessing what some of those features actually looked like. The rear stays for the pilot seat aren’t too much of a problem so I’ve created those from some offcuts of carbon and aluminium.

 

 

Detail of what’s happening behind the pilots seat is a little more sketchy though so I’ve created my interpretation of it using carbon rod, some plastic sheet, heatshrink, electrical wire, a nylon spacer and some tin.

 

 

The only photo I’ve managed to find of the cockpit instruments themselves is this 360 degree panoramic one by Moose Peterson, plus there is some in-cockpit video footage too so I have yet to see what I can come up with in the way of a photographic image of the instruments at least…

 

 

I am using a David Banks pilot figure – beautifully modelled by David and super lightweight too. He is only a bust figure so my cockpit is quite shallow in depth to suit. I’ve got him mostly painted now with just a little more detail to add.

 

For the plane my plan is to spray paint the blue and the white chequerboard and stripes, then use white self-adhesive vinyl for the text and numbers but I am holding off from doing that until we have some warmer weather.

 

So for the time being everything is now on hold. Roll on the warmer weather!

 

Phil

 

[Phil Cooke]

Really impressive building Phil, you do make some wonderful shapes with Correx, its mind blowing - I will keep on at you for your first Balsa build but I must admit I cant wait to see your new bigger Super Cosair up close!  Great work on the vac form canopy btw - impressive again!!

[Saint 1]

1 hour ago, Phil Cooke said:

Really impressive building Phil, you do make some wonderful shapes with Correx, its mind blowing - I will keep on at you for your first Balsa build but I must admit I cant wait to see your new bigger Super Cosair up close!  Great work on the vac form canopy btw - impressive again!!

Thanks Phil, I promise I'll build something in balsa over next Winter 🙂

[Ace]

Cleaver, creative, inspirational = stunning results 👏

[Saint 1]

Well my eagerness to make some more progress on my build finally got the better of me. It wasn't particularly warm yesterday (about 10 deg C) and a bit breezy but I decided to have a go at getting some paint on nonetheless. Thankfully it just about all went ok, one or two minor runs on the wing but hopefully I'll be able to minimise those with a bit of polishing in due course. The biggest challenge though was manipulating the wing and fuz whilst spraying them due to their size and in the case of the fuz the weight as well because I had already built in 500g of nose weight! I used aerosol spray paint, four cans worth so a bit more weight added there I should think 😄

I'll give the paint a few days to harden off and then I'll be able to think about masking off to spray the white graphics and get on with everything else too 🙂

[Saint 1]

Well, after another week it’s finally just about finished!
After spraying the blue I then masked off the fuz and wing to spray some white (I didn't spray them in the garage as it might look!)

 

 

I used an assortment of masking tapes but found the Tamiya squared masking sheets particularly useful for creating the chequerboard pattern on the nose.

 

 

It took me four hours to mask the fuz, not helped by me masking half of said chequerboard pattern before I realised I was masking off the white squares instead of the blue!

 

 

With that done I then sprayed a couple of coats of clear gloss sealer over my ally nose spinner and exhausts to protect them from the elements and then went on to fit the exhausts.

 

 

 

I was unable to find a good quality photo of this plane’s instrument panel so used the same one as I had previously in my standard sized Super Corsair. After having painted inside the cockpit I then added the instrument panel photo.

 

 

Similarly with the engine, I also used the same Photo-shopped image as previously. I sealed both photos with a couple of coats of clear satin coat sealer to prevent them fading.

 

 

I had already trial fitted all my radio gear and linkages prior to spraying so it didn’t take too long to re-install all these again so then all that was left was to get the CG point ‘right’ and weigh it.
My standard build Super Corsair has its CG point set in line with the plan at 3.25” or 82.5mm from the root L.E. and it flew well right from its maiden. However this seemingly has a static margin value of 17% according to the rcplanes.online CG calculator so, on the face of it, pretty nose heavy. It weighs just 1437g giving a wing loading of 15oz/sq.ft. It will fly comfortably in wind speeds upwards of around 12mph and with considerable ballast has flown in up to 40mph winds.
Based on all the above I decided to calculate my CG point for this 120% Super Corsair using the same 17% static margin which worked out to be 103mm from root L.E. Achieving this necessitated installing a further 150g of nose ballast inside the battery tube, over and above the 500g I had already built in earlier!

 

 

So with the plane balanced it was time to hit the scales….a tad heavier than anticipated at 3232g or 7lb 2oz.

 

 

This is giving it a wing loading of 24oz/sq.ft. for a plane with a 61.5” wingspan. Does this sound a lot or still ok for a PSS? What sort of wind speed do you guys think it might need for its maiden off the Orme please?

There are still one or two little more bits of detail I may yet add but here are a few photos of the finished build and one or two with its little brother in the background, hope you like them!

 

Nose spinner clear cowl fitted and retained by an O-ring

 

 

Tail wheel painted

 

 

My pilot could do with a little more detail, I'm sure he'd appreciate some sunglasses one day 🙂