PSS A-4E 'Top Gun' Skyhawk

[Phil Cooke]

great day for the post man today! - my Aggressor A-4 acrylic paints have arrived, so has a big bag of foam Jenny brushes so I can finally commence my glass covering!

No building to talk of today though, not yet...

[Phil Cooke]

A bit more fettling and sanding tonight prior to the start of glassing this weekend.

I've added the tailplane doublers to the fin and cut out the wing wheel bay 'pontoons' ready for final sanding.

The elevators are now fully sanded and hinged, I've decided in an attempt to keep the edges and angles 'sharp' I'm going to solartex the elevators and the ailerons - the inner mating faces of the tailplane and wing will just get the flow coat of resin, no glass.

One strange thing I've noticed different to the prototype - the elevators on my build stick out a few mm beyond the T/E of the fin - they should all be co-planar as per the full size - I've either made my 'home brew' rudder a few mm too thin (but I'm sure it was the same size as the supplied kit rudder) or the tailplane slot isn't deep enough - I could relieve this further but then the tailplane doublers would foul the elevators.

Anyone else's fin T/E not co-planar with the elevator T/E??

[Harry Twist]

Hi Phil ... burning late oil.. just checked my elevator - mine looks same as yours- measured the extension as just shy of 4mm beyond rear of rudder!

 

Edited By Harry Twist on 04/08/2016 00:32:13

[Phil Cooke]

Thanks for the tail check Harry - I'm not sure whats happened there, very odd. Anyway with me having glued the fin doublers on now I cant move them forward so it will have to stay as it is. Ooops!?

I made the ailerons up tonight and despite having seen Steve Houghtons superbly hand crafted ailerons where the washout twist was sanded in, I couldn't resist another lung full of the ammonia so tried a different approach (to be fair my aileron section wasn't deep enough to allow the sanding method otherwise I would have gone that route!)

Just like when I added the wings top skins and set the washout - I made 2 little balsa wedges from 1/4" sheet, running in from zero thickness to 3mm over the length of each aileron. The aileron stock was then painted with ammonia, left to settle, then pinned down over the board with the leading edges battened down flat across the entire span, the T/E were 'formed' over the wedges - ensuring of course a left hand and right handed pair was made.

The photo shows 3mm 'form' at the tip end and zero at the root. Hopefully this should all dry up overnight and we will be left with perfectly formed ailerons with just the right amount of 'twist' to match the wash out. Ill report tomorrow, I'm just a tiny bit worried about shrinkage and also the ammonia has raised the grain significantly so the surface finish now needs more work that it should.

[John A H]

Just checked my elevator - rudder and they line up OK. I angled the slot in the tailplane to match the fin post layback and that means the top of the slot is approx. 3mm further back than the bottom (if that makes sense). Could that be it ? I can't remember if I specifically checked that they lined up before gluing the tailplane doublers , maybe I did.

[Peter Garsden]

Yes indeed - good thinking Phil. Don't do what I did, and will have to undo I think:-

1. Built in the wash out at the tip.
2. Didn't build it into the ailerons.
3. Taped up the ailerons to be level with the washout tips and applied the fibreglass cloth.
4. This effectively removed the washout from the tips.
5. When I flew it, it tip stalled, so somehow I will have to pin the wings down and twist in some washout with some steam methinks.

Doh!

[John A H]

As Pete has already got paint on the wings it might act as a barrier and prevent the steam doing its job, or depending on the paint cause the finish to crack.

You could make a new set of Ailerons with washout in them. It will mean they won't match up with the tip trailing edge (will be a bit higher) but might give you enough washout. Bit easier than messing with the whole of the wing and you could see if it stops the tip stalls ......... or fly faster - easier said than done when you're attempting to stay up in marginal lift.

[Peter Garsden]

Thanks John - great ideas. I think I will fly it again and see how it goes - fly faster seems a good idea. Not sure I can bothered to re-engineer now it is all assembled. If it proves a nightmare to fly I will consider it. After all marginal lift does seem the PSSA norm these days. We will see how it goes at the Lleyn next week.

More exciting is the fact that my fuel probe has arrived in the post from Andy - brilliant job matey. Will just have to nip out for a burger today and we are sorted. Probably an Egg Muffin for breakfast actually - anyone want anything?

[Phil Cooke]

I'm really getting quite fed up of modelling sessions being dominated by sanding now... it seems to have gone on for an age - but I'm so close to completion in that bar a final surface finish and ding check on the fuselage I think all components are ready for some glass.

The first picture shows the finished ailerons fitted and hinged. The ammonia twist has set in very nicely, but some sanding top and bottom was needed to correctly profile the ailerons to the wing - so in hindsight I think the 'sanding only' method as very well described by Steve Houghton in his blog wins out.

The wheel bay pods are sanded to shape (dry fitted here) and the fuselage blend has received a little filler to finish it off.

Although it won't be fitted until after the fuselage and tail are glassed, my attention turned to the jet pipe shroud under the tailplane.

The plan shows a 1/16" rolled balsa tube and very little description, the reason being this feature was never added to the prototype. I spent some time making the right shape - but kept failing. I found balsa split (as you needed to join 2 pieces to get the required width then cut most of the join away to clear the snake!) 1/64" ply was fine at the rear but would not generate a curve at the front either side of the split - so I've been on the hunt for a 55mm dia plastic tube for a little while.

I found this plastic cup in a water dispenser at the leisure centre - its O/D was 50mm at the base and 60mm at the lip, so 'bang on' size - it was also smooth with no surface ribbing etc - ideal. I used the form I had created from balsa to mark it up and cut it out. As a vac form the curves remained in place even when you cut the central slot away. Success! Note I've relieved the leading edge of the slot so it just slips over the fin post.

Trial fitted to the model. It looks a tiny bit 'deep' but that's because I'm mounting it to the underside of the fin doublers - for true scale it should fall 1/4" under them. But I want the tube to adhere to those to stiffen everything up and visually close the gap that would be evident.

I'll give the plastic a very light sanding with wet and dry paper to key it for spray paint later and glue it with canopy glue once the glass is on the fuselage and the fin and tail are glued up square.

[Phil Cooke]

I couldn't put the glassing off any longer. I've not done a lot of this to be honest, so there is a bit of a learner curve here, but I'm keen to produce a robust, stable finish that doesn't need the constant attention that solarfilm does on my other models...

I'm using pukka epoxy resins and 25g cloth from Fighter Aces, so no excuses regarding the quality of materials

Following John Hey's lead I stuck some balsa strip to the wheel bays for ease of handling, they were glassed first as a confidence booster - with no problems!

Then followed one side of the tailplane and the fin. The fin was a little more complex due to the fin doublers and the rudder, which I had masked (I don't want glass cloth on the rudder diluting the detail in the fluting so that will get a flow coat of resin only prior to paint.)

[Andy Meade]

Pegs hanging off the free edges helps keep everything in place here Phil. I have found that if the cloth is cut neatly around the subject, it will tend to lift. Pegs (preferably plastic) help keep the edges pulled "down" and the glass in position. I've found it essential to do this around sharp edges (TE's etc.) to ensure a straight, defined, edge.

[Andy Meade]

Just had a second look, and saw those pegs on the u/c housings. Sorry - I shan't teach you to suck eggs any more, Granny!

[Phil Cooke]

Trying to get all the basic glassing done this week before we head off for a few days flying and holiday on the Lleyn Peninsula...

Fin, Tailplane and wheel pods are fully glassed, sanded, and tonight have had a thin flow coat added using the Jenny brush method. The rudder detail did not receive glass cloth, so this area is just stippled with resin to give a surface ready for primer.

The wing I'm applying glass in a slightly different method to the other sub-assemblies as a comparator. Tonight I've simply added a little resin to the wood and smeared/scraped it all over with a credit card - thus sealing the wood surface with a very fine sheen of epoxy. Tomorrow this will be glassed again using the credit card to minimise the amount of resin left in the weave.

According to Messrs Jones and Meade, this is a superior method of epoxy application considering weight management.

[Peter Garsden]

Well you're very brave using real 2 part epoxy. I used water based Eeze Kote from Deluxe Materials which is so much easier to work with and, I think, lighter

[Phil Cooke]

Yeah - time will tell on the weight delta - I'm applying the resin as thin as I can, its going ok - maybe not as quick to apply as the Eze-coat or Poly-C as the drying times are longer - but I do think the final finish will be tougher. Lets see - its all an experiment and trial prior to the A-10 for me...

[Bob Jennings 1]

Nice one Phil,

you've certainly got the hang of it. I had an all glass glider, not much bigger than the Squawk and it was a tad on the beefy side but really moved with the extra mass in a 20mph blow.

I might epoxy the replacement JP wing when I get around to it!

September is looming large!

[Phil Cooke]

Had a few days off the A-4 build what with the Lleyn PSSA meet last weekend followed by a few days family holiday in sunny Wales... back now and in desperate need to stay focussed on the task if this is to be finished in good time...its only 3.5 weeks to the fly in!!

The main wing and fuselage are still in the glassing stage and this work tends to get done at night so it dries whilst I rest.

The other bits were glassed and flow coated prior to my holiday. These have now been sanded, filler primed, and sanded again ready for the final primer and final sand prior to paint. Do you see the repetitive cycle there? Is there enough days? There must be...

[Phil Cooke]

I should be outside sanding back primer but foul weather here in Derbyshire has put an end to that plan... instead I've been focussing on a little detail modelling - features that will be glued onto the fuselage once it is glassed.

First, the ejector seat was made from scraps of balsa, plasticard and a paperclip.

Jester looks comfy enough in that... probably because its a little oversize for scale (?) but it will do!

Edited By Phil Cooke on 19/08/2016 17:15:01

[Andy Meade]

Looks good chief! My mistake with seats is that after I have made them the cockpit doesn't fit on...hehe. I always have to resize them to miss the glassware.

[Phil Cooke]

The seat is too big isn't it. I think I might run the band saw down the middle of it and take out 1/4" width...then reglue it.

[Phil Cooke]

This photo shows how the head rest part of the A-4 ejector seat necks in at the top to approx. 2 fist widths...now unless this guy was a pro goalkeeper or WWE wrestler with massive hands I'm going to say that's a 4" fist meaning an 8" headrest. At 1/12th scale my 1" wide headrest needs to come down to ~5/8"... back to the bandsaw!

It also shows evidence that all A-4 pilots had boss moustaches

Edited By Phil Cooke on 19/08/2016 19:53:43

[Phil Cooke]

I got sufficient ribbing on the phone last night regarding my 'comedy' scale ejector seat that the first job this morning was to down size its width on the bandsaw. Unfortunately the rework proved more complex than expected and in gluing the two thinned halves back together I ended up with a non-symmetrical seat, so I took a step back and made another. Now just 18mm wide and looking much more representative.

[Phil Cooke]

Glassing, priming, sanding, priming & sanding all goes on... with a few other detail jobs in between to keep my interest in each session.

The wing is now fully glassed and filler primed ready for sanding back.

The fuselage is being glassed in 5 or 6 panels following advice from Harry Twist who has recently done the same. Tonight the under side nose and tail have been glassed. I drew lines on the model to give an indication how far round to bring the wetted cloth with the Jenny brush. All overlaps should sand in but its nice to place them on a radius if possible which will aid the process.

With that all drying I set about making an arrestor hook - an important feature on any Skyhawk! The prototype proved this to survive landings just fine as the rear fuselage slopes up, although it's important to peg/bond it well to make it robust. This also dictated the materials.

First up the hook - it's only representative, too blocky by far for scale but this will allow a peg and secure bond to the fuselage. I cut out a template from plasticard and then cut 3 copies, one from 1/4" ply and two 'cheeks' from 1/16" ply. I recessed the 1/4" ply core to allow a 1/4" dowel to be inserted, then glued the 3 together with epoxy. Once trimmed and filed it looked like this.

A hard balsa block was shaped and drilled to accept the dowelling at the front. This too will be pegged and glued firm to the fuselage. The dowelling doesn't actually touch the fuselage it bridges between the 2 mounts front and rear. Ill give this all a coat of epoxy resin and then it will be ready for paint.

[Phil Cooke]

More sanding after work before dark today, but nothing worthy of a photo. Once the dust settled I did do a little more detail work on the hook - I covered the dowel in white solarfilm then added a number of 7mm wide black stripes made from trim.

Having fully sanded the tailplane ready for final primer and paint I covered the elevators in vintage Solartex and these are now hinged and dry fitted, I'll glue them up AFTER they've been painted to ensure all internal faces get some top coat.

Finally there was a treat for me in the post when I got in from work tonight, my spray masks and decals (a mix of self adhesive vinyl and waterslide transfer) had arrived from Tim and ModelMarkings. More on these later - but big thanks to Tim for his usual quick service and on time delivery

[Phil Cooke]

Put a good few hours in on the airframe today, more sanding, more priming, sanding some more - everything I own is covered in a fine mist of Halfords Primer yellow - but we are getting there!

The fuselage has received the last but one 'panels' of glass cloth - glassing will be completed tomorrow!

I've trimmed and test fitted the finished tailplane to the fin, which itself is now final sanded.

The only new bit of building to show is a number of 'lumps and bumps' I've made to glue onto the airframe prior to final primer.

The fairing which goes under the port wing, a pair of little air scoops that sit mid ships on the air intakes, a warning beacon for the spine etc - there are some others not shown too - all these little bits have now been painted with a coat of epoxy resin and will be sanded up and primed prior to fitting to the main airframe.

Edited By Phil Cooke on 26/08/2016 00:00:36