Phil's PSS Jet Provost - Build Blog

[Phil Cooke]

Ailerons tack glued to the wing so they can be sanded accurately to accommodate the washout before I glue the balsa/ply/balsa laminate wingtips on. Each aileron is made from 1/2" soft balsa with a very hard balsa trailing edge, which I've cut back just a tad so my resultant T/E thickness is approx. 1/16th".

This is what it looked like with the raw material tack glued to the wing, you can see how much material is needed to be removed...

And this is what it looked like after it has been planed down, with the hard balsa T/E cut back to match the wings T/E line. These can now be final sanded with the rest of the wing panel which will result in a perfectly tailored aileron section with nicely aligned T/Es... that's the idea, anyway.

[Phil Cooke]

Some good progress today - sanding duty mainly, but the weather was good and I was able to work outdoors

The wing tips have been glued to my wings - aligning the ply laminate accurately with the aileron trailing edge. The wing is now ready for sanding before the ailerons will be removed and hinged.

The fuselage was sanded to shape, complete now only needing a final sand with a fine grade paper. The coloured edged formers 1 and 2 really helped with the shaping around the nose. I did need a tiny bit of filler on my planked section behind the covkpit, as a very small region had become re-entrant with the twist needed on each plank. Anyway a little light weight filler sorted that and it was sanded back with a 10" block across the 2 formers. The fus is now ready for air intakes and tail mount.

I cut the top off a bottle top - 30mm dia and perfect for the job of a dummy jet pipe. My fus walls were too think at the very rearmost section and inserting this tube would enable me to fill in against it once mounted in situ. Heres the top - it comes from a Liz Earle moisturiser (ask the missus - you can tell by my hands that I don't use it!!) I cut the end off - making it a tube, then cut a section out the top which would stop the elevator horn from fouling against it in the fus.

It was glued inside the fus at the rear, I then used a little P38 car body filler to build back up the fus walls where needed - this was then sanded in leaving a neat exhaust port and scale like wall thickness at the edge - equivalent to the bottle top - but a plastic edge - so a more resilient one than balsa! This should look quite realistic once painted a matt black, and it will still allow access to the elevator horn through the pipe.

[Peter Garsden]

Great idea Phil, was worried about the fragility of that tail section. I have only just started building - better idea as one can read all the blogs - even got my IPAD set up in the hobby room - I was going to put some light weight fibreglass cloth over the top but this achieves the same goal.

I was also considering making the whole fuselage using the lost foam method - but have now bought the wood pack. It just seems that with these jets there are so many curves, that they lend themselves more to fibreglass than wood - reading the blogs this certainly seems the case.

Have just made an Alpha Jet th is way, but the weight penalty, if you don't get the thickness right and put too much resin on - as I did - is the result - personally I think it flies better heavier and faster - just not flyable in light winds.

Food for thought - will anyone be making a fibreglass fus and foam wings - I wager not!

[Phil Cooke]

On a quest now to try and get the model flight ready for the 12th April when the PSSA have their first meet of the season on the Orme...

Wing and ailerons are now fully sanded, the ailerons are removed and their L/Es have been rounded ready for hinging. I found sanding the wings T/E stock a bit tricky, and the skins, which were pristine having been fine sanded whilst laid out on the bench before application, took a bit of a hammering! I also found the T/E went to near zero thickness with the angle of the wing profile and I may have to cut it back a 1/16th" or so to make the final T/E robust. A little light weight filler sorted the wing skins and they are now back to their former state, albeit a tad heavier...

I've added the wing location dowel and applied a 2" wide bandage with PVA on top and bottom surfaces - I didn't wrap this around the L/E or T/E as I didn't want to complicate the fit of the wing in the fuselage. Now dry, this has been trimmed for the servo bay and cable exits.

The fin and tailplane have been final sanded to profile and are ready for covering. Still deciding whether to cover them now or wait until they are mounted on the fus.

[Andy Blackburn]

If it's any help, I covered my tail surfaces separately (on the first model) and made sure that there was some bare wood to glue to - that seemed to be a much easier option that trying to get it all done in situ.

BTW, suggest you consider adding a bit more bandage reinforcement around the wing dowel...?

[Phil Cooke]

Thanks Andy, I think I'll follow suit on the covering of the tail parts, got to be easiest doing them separate then assembling it like an ARTF model

As for the location dowel, I don't want to compromise the fit of the wing by having the bandage around the dowel, its already a very tight fit upto F4, the dowel it was 'potted' into a slightly oversized hole in the wing ribs so is well secured and well up to the job I think...

[Phil Cooke]

With the wing assembly complete its all been given a final sand ready for covering.

I found sanding the tiny ailerons was a little tricky, but the resultant 'matched' fit is well worth the effort, the hardwood T/E makes them very stiff and straight.

The wingtips need a little more refinement to enable the tip tanks to slip on and off, they are all a bit tight at the mo, and covering will make this worse.

Edited By Phil Cooke on 03/04/2014 00:42:05

[Phil Cooke]

The build now turns to some of the JP's scale details, wing fillets, air intakes etc.

I followed Andy Blackburns lead and cut out a pair of wing fillet plan guides from some 1mm ply, shaped to fit upto the fuselage former F6. I included the Trailing Edge extension, scoring along a line formed by the wing T/E allows this part to be 'folded' to the required angle and aids alignment/symmetry on the finished job.

The fus sides were gently relieved by 1mm where required (on the wing saddle) the wing was bolted in position and the ply fillet guides were slipped accurately into position. They were then tack glued using medium cyano on the outside against the fuselage side.

Once the cyano was dry, I removed the wing, the ply plates are angled by the wing skins dihedral, resultant in only a line contact between these little bits of ply and the wing saddle - hence this needed reinforcing with some 5 minute epoxy (again, following Andy's written method)

Here they are in position. That's the underside finished, now we just need to add some soft balsa on top and sand that back concave to form the fillet.

Edited By Phil Cooke on 03/04/2014 00:55:50

[Phil Cooke]

So tonight I've got the wing fillets finished and have made and sanded the air intakes...

For the fillets I cut two 3/16" balsa formers which were sanded to the shape of the fus and glued between the fuselage wall and the ply fillet 'saddle' with cyano, I then blocked in with small pieces of 1/2" soft balsa sheet, cutting them to rough shape as much as possible in all planes before gluing in place fore and aft of the tiny formers. These were then carefully sanded using a cylindrical form block to get the re-entrant feature required. They're only cartoon scale but fit for purpose and I think enhance the look of the fuselage significantly. I'm not looking forward to covering them though!!

The air intakes were cut from 1/2" balsa sheet and laminated. To aid creating a matching pair I tack glued the pair together prior to rough shaping and sanding.

Once they were roughly shaped I broke the tack bonds and finished them off individually with a fine grade paper.

There's certainly a lot of sanding needed on this little model - when will it all end!??

[Danny Fenton]

Looking good Phil, wish I could have joined in and built one of these. Excellent blog I might add, really clear pics

Cheers

Danny

[Andy Blackburn]

I've thought a bit about covering the fillets; I think it might just be possible to use a couple of pieces of film (front half & back half) and the rounded edge of the iron, but if that's not possible then I was going to use some self-adhesive trim (silver ProTrim, in my case), again two pieces a side. In either case, there'd be a shaped bit of film covering the overlaps.

Edited By Andy Blackburn on 04/04/2014 13:45:59

[Phil Cooke]

Tried to complete the build today in an attempt to have the model ready for covering by end of play tomorrow...

The underwing fairing and air intakes were the main focus, a lot of fitting, sanding, filling and re-sanding, I had to use a bit of thought at the trailing edge where the fairing runs out to zero thickness, P38 saved me again here near the centre around the wing bolt - Ive also sanded down my wing bolt head so it doesn't stick out too proud.

Here's the basic wing fairing in place and sanded to match the fuselage profiles at the front and rear...

I then temporarily mounted the air intakes to enable the underside intake extensions to be made and fitted/sanded accurately...I tacked my intakes in position with 3 small blobs of medium cyano. The intakes needed a little refinement on the wing top side, due I think to the dihedral.

Back to the underside the intakes were extended rearward with 1/2" balsa and sanded so they matched the fuselage mounted parts... again, only cartoon scale. Sanding to final profile was a little tricky near the edges, a bit of sanding damage on the wing skins was later filled with light weight filler, a small blending radius of filler was added to all the edges too which will look great once its all sanded with a very fine grade paper...

The wing was put to one side and a bit more work was done on the underside of the fuselage air intakes, Ill cover these before I glue them permanently to the fuselage. Finally in an attempt to progress the job and allow drying time whilst I sleep, I gave the cockpit and the ejector seats their first coat of primer paint.

It's my aim to have the cockpit fully fitted out and the canopy glued on before I retire tomorrow evening so slapping the primer on tonight was a must.

[Phil Cooke]

Sanded the fillets of lightweight filler back this morning around the underwing fairing and the intake extensions, other than a little work on the tips to ease the fit of the wing tanks, this now sees the wing complete and ready for covering. Incidentally, I found the use of these foam sanding pads really useful for the filler rads, worked well on the wing fillets too - I bought them a while back from B&Q - nice fine grade and the foam enables you to create various radius with your finger much better than paper I found...

[Phil Cooke]

I joined the tailplane to its rear extension, cutting a small running groove in its front face to enable the elevator actuator to run in it as a bearing. A little care is needed when gluing the two pieces together to avoid gluing up the metal rod running within - wax or Vaseline would help, I was too lazy to walk into the house to get some...anyway I got away with it. Once cured, I sanded the top surfaces flush and feathered the back end in a little as per the plan.

Close up shows a small volume of both tailplane and extension piece has to be removed to enable the elevator horn to swing +/- 45º.

A final sand all over with a fine grade paper saw the tailplane, elevator and fin all complete and ready for covering.

I trimmed the canopy carefully - just outside the lines embedded in the vac form - as a word of warning I would leave 1/8" extra along the straight side edges as this will aid fixing, whatever your chosen method. Mine will be glued using canopy glue, but I must admit I wish I had a little more vertical overlap on the sides!! Its important to cut the front and rear curved profiles right to the line, as this enables the canopy to 'drop' fully, but do leave a bit extra on the sides! Anyway, generally a good fit despite the minimum overhangs.

The Traplet canopy shape is about right, a little square at the front in plan view maybe - in comparison to the Vortex one, but good in profile. Unfortunately my canopy as supplied shows a little grain from the mould on the inner surface, it is not 'crystal clear' so any cockpit detailing I decide to employ will only be viewable through this 'hazy' effect. That's a shame, I'm wondering whether its only the first pulls that were effected - Ill have a word with Traplet to see if this has been improved.

[Phil Cooke]

Couldn't resist a quick mock-up...

Nice to see it all together, but in my haste, I forgot to attach the air intakes -

So I've got the rest of the day now to complete the air intake make-up piece, final sand the fus and wing tanks, add the cockpit details and glue the canopy on... then she's ready for the covering. I've gone with the Red Pelican scheme, an all over 'day-glo' Red (or Orange?) so the covering shouldn't take too many hours this week.

[Phil Cooke]

I couldn't quite work the make-up piece method as developed by Andy B (with the sandpaper stuck to the fus to create an accurate intake profile) - I think this was due to the 'low tack' masking tape I was using which meant the sandpaper kept slipping and it became an impossible 3 handed job. So a rethink was needed if I was to finish these air intakes without sticking them to the fuselage (enabling more accurate covering of these parts...)

In the end, I taped a small sheet of cling-film over the fus, pinned the air intakes into position (using the wing as a guide, then removing it, once pinned), I then glued (to the intake) an oversized piece of balsa aileron stock, filling the majority of the void, the rest was then (unceremoniously) filled with P38.

Once dry, the intakes were unpinned and the P38 (not sticking to the cling-film) dropped away, this was then quite easy to sand back to the required intake profile. Placing this back onto the fuselage once done shows this to be a good neat fit, confirming very well. You can see the void is more 'balsa filled' than P38, but this solution is not as weight optimised (or as elegant) as Andy's method.

The wingtips were given another light sanding as the tip tanks were really tight, these would get tighter still once the wing was covered of course, so I've eased this to a point where the covering should make them a nice snug push fit. I tapered and rounded the tips very slightly too.

Looking at the airframe now, I think the only 'wood bashing' left to do are the small scrap infills between the tailplane and the fin. I'm going to dry fit the parts then glue those to the tailplane now, ready for covering before the tailplane and fin are glued square to the fuselage.

[Phil Cooke]

Time to fit the cockpit out and get the canopy glued on before bed...

First, the front console and rear panel behind the seats needs to be painted matt black. Before the paint I covered these areas in some scrap Solartex, I also trimmed a printed copy of the cockpit dash jpeg and fitted this with a few tiny drops of medium cyano. I elected to try and use a bit more of the dash by allowing a few mm to fold over onto the cockpit floor.

The seats had been made up from the Traplet kit of parts, lightly sanded and painted prior to today. These were positioned and epoxied in place, as was the little pilot. He must have short arms as he sits awfully close to the console... but he'll do. I'd made some little ejector seat jettison handles from yellow paper clips, simply bent to shape and pushed into two pin holes in the balsa seats.

With everything dry and cleaned for dust (my garage is awful at the moment with all the sanding I've been doing!) the canopy was washed with soapy water on the inside, a small bead of 'Formula 560' Canopy Glue was applied to the side faces of the fuselage where the canopy would sit and the little vac form was popped into position. Once 'fine tuned' and taped, I ran a bead of glue around the front and rear of the canopy, squeezing it into the gap with my finger from the outside before a damp cloth was used to clean off the excess. This should give an air tight seal once dry.

Job done.

[Phil Cooke]

Not got as much done tonight as planned, I have covered some of the fiddly bits (ailerons and elevators) with film, but with me still having a little wood work and final sanding to do at the back end of the fus, I wanted to make sure the cockpit was fully 'sealed' so no dust found its way in now the vac form canopy was glued down.

I used Solarfilm to cover around the canopy so the Solartrim finishing strips would have a good, shiny surface to adhere to.

I then spent an hour adding the canopy frame with Solartrim, bridging the canopy to fus joint with 1/2" wide strips. Fully weather proof now I hope - certainly I can get the sanding block out again without the risk of dust ingress!

[Phil Cooke]

It's an insignificant build update - only that these little tailplane fillets represent the very last parts of the airframe build - cut from scrap 3/16th balsa, I pinned the tailplane in the correct position on the fus, slotted the fin into place then glued these pieces to the tailplane topside only. The fin and tail were then removed. Once the fillets are sanded to profile, the fin and tail will be covered separately before they are glued square to the fus.

I also filled the topside of the little hole which I'd cut as a relief for the elevator horn right through the tailplane, this was a mistake - the elevator horn only needs this relief on the underside - so a small 'wedge' of 1/16th balsa was stuck into the hole and sanded back flush with the tailplane so this will no longer be visible on the assembled model.

So tonight after a little more sanding, and a good clean up (the model and the workshop!) the covering will begin in anger...

Edited By Phil Cooke on 08/04/2014 19:22:34

[Danny Fenton]

Nice one Phil, I think the covering of this one could be fun with all the lovely curves

Cheers

Danny

[Phil Cooke]

Thanks Danny, yes, nothing like a challenge eh!? It is quite curvy but I'm doing all I can to help myself by breaking it down into sub assemblies to be final fitted after covering... I'll keep you posted on progress...

[Steve McLaren]

Impressive work rate Phil, and you've still got time for reporting!

On Saturday I didn't think you had a hope of completing in time for this weekend, but now it looks like you might make it.

How are you planning to do all the lettering and decals?

[Phil Cooke]

Steve,

I've ordered on of the Jet Provost vinyl decal sets from Pyramid models, if you speak to Lee there he will supply you with the same, and he'll tailor the pack to include any registration you may want for your model, or additional lettering as needed - well worth the money IMO.

Got all the 'fiddly' bits covered tonight, ailerons, elevator, fin, air intakes (these were quite tricky to get right!) so tomorrow we can focus on the main fus and wing... still a bit to do, but still hopeful of a flight this weekend!

[Phil Cooke]

The covering of the fuselage and all the 'fiddly' parts has taken a lot longer than I estimated, its a small model, yes, but a curvy one - the bulbous nose, air intakes and wing fillets in particular took some serious work with the iron and heat gun combined to get the parts covered without any nasty creases... The wing is still being covered this evening, but having burnt the midnight oil (and then some!) this past 2 nights I thought I'd upload a couple of fuselage shots to show progress...

'If Traplet did ARTF PSS models' - straight from the box ready to epoxy together

Close up of the air intake once epoxied to the fuselage - I was glad I covered these separately!

As a break from the covering I've started tonight's work with some panel lines and decal application - still more to apply, and some paint needed around the nose and cockpit too, but she's starting to look the business...

The forecast is looking great for the Orme on Saturday with 17mph SW winds, perfect PSS conditions - so I'm still committed to getting this flight ready tomorrow but its cost me a days leave from work to guarantee this is finished in time...

Right, back to the wing...

[Matt Jones]

Now that looks really, really nicely done.

The Orme event is tomorrow, chop chop!