Just Possible Jet Provost by Steve

[Steve Houghton]

Having not undertaken a major build for about twenty years, due to various family commitments, my New Year's Resolution is to spur myself on by setting a target. Having learnt to fly with single channel slopers, I thought the PSSA mass build would be a good opportunity to return to my roots in soaring.

I have built a few gliders in the past but have never built any PSS before, or anything near-scale, so this will be an interesting venture.

I received a very warm on-line welcome from Phil Cooke upon joining the PSSA and have now taken delivery of my Traplet plan pack and purchased most of the supporting accessories and extra wood from Barnstormers.

Work started this week, so I am a little behind schedule. I have several non-modelling activities and a young family to juggle alongside the build, so I am just hoping I can complete it before the 1st June - time will tell, hence the thread title.

[Phil Cooke]

Hiya Steve - great to see you on here with your own build blog.

There's still plenty of time and I'm sure you'll find it all goes together quite quickly with the aid of the Traplet parts. There's loads of good advice on the build in this section of the forum now, a few 'lessons learnt' and alternative ways of doing certain jobs - so well worth a good read in the evenings when you are not building and you'll find it all goes together right first time!

Enjoy your first scale build, we will be watching

[Steve Houghton]

Thanks for your welcome, Phil. I'm following all the other blogs, and find Andy's design notes particularly useful.

I have been trying for 40 minutes to upload some photos, but the website keeps timing out, even if I only upload one. I shall persevere, but don't want to lose too much building time.

Meanwhile, initial impressions of the plan pack:

• The liteply sheet containing F3 is a little twisted, as others have reported, but I think the formers are useable.
• F1 has the correct cut-outs at the sides.
• Tip tanks have the correct cut-outs in all sections.
• Quality of die-cutting is excellent.
• One fuselage side is very hard, but I'm too skinflint to discard it.
• I paid the extra £2 for the construction notes and got a complete copy of the magazine as well

My idea is to finish the model in a military scheme if time permits, so probably a T52 variant. I considered a T5 or Strikemaster but didn't fancy fiddling with the nose and canopy shapes.

I hope to fit a rudder and to incorporate magnet-attached tip tanks, similar to RedBaron but with the whole tank able to knock off, complete with wing tip.

Now to try those photos again......

[Steve Houghton]

Finally some photos....

I found a rather nice Art-Tech pilot who weighs in at 12g, although he'll need to lose a bit of height from the lower body. No scale is marked on the packaging, but I think its around 1/12. I'm hoping to get away with just one - does anyone know if the JP was ever flown by a single pilot?

 

Here he is in his future home, which he seems to fit well.

 

 

Edited By Steve Houghton on 09/03/2014 02:05:32

[Phil Cooke]

It's good that the later kits from Traplet have been modified with all the feedback we've provided on the laser cutting issues like F1 and the tip tanks, but like you, my light ply parts were warped and needed a little work to get the useable. Water will help you with the hard fuselage side when you get to pulling the nose in.

Yes the JP was commonly flown by a single pilot, both 'normal' ops and the display teams of course. Students had to fly solo training missions as part of their basic flying training in jets. The instructor would sit with the students to drill them through tougher tasks like low level, formation, navigation.

[Steve Houghton]

Phil, thanks for the information about the pilots. no need to rush out and buy another, then.

Also noted the tip for bending the fuselage side in. I have used steam in the past, but this tends to burn your fingers, and the kettle keeps switching itself off! Could use a pan of boiling water, I suppose, or the water as you suggested. I have a new SLEC building jig that I shall be using for the first time, which should help.

Servos

I plan to use these New Power XL-9HM metal gear servos - 10g and 2.5kg.cm torque, as the budget wouldn't stretch to a set of Hitecs. I haven't used 'budget' brand servos before, and if these don't come up to scratch I may never again! They may lack the precision of more expensive ones, but I'm hoping they'll be adequate.

[Steve Houghton]

Finally, the build commences.....

Wing Skins

I have used 4inch med-hard sheet for the bottom surface, for ding-proofing, and lighter 3inch med sheet for the top. Using different sheet widths means the edge joints on the top and bottom will be staggered, which may possibly help to spread the loads, at least in a hard landing rather than in the flying. The panels are only rough cut for now, to be trimmed after fitting ribs etc..

 

Fuselage

Joined the four pieces for each fuselage side over the plan with PVA, letting the first one dry before assembling the second on top of the first, to ensure symmetry. I shall be using PVA for everything, as I can never get CA to stick properly (it must be an age thing). Here are the two sides overlaid. I pre-glued the end-grain in the main join, for better stiction.

 

Edited By Steve Houghton on 09/03/2014 22:42:20

[Steve Houghton]

Ribs Added

R1 angled against the template whilst drying (PVA, remember - no CA here!)

 

Washout Wedges

In a change from Andy's sequence, I fitted the washout wedges after fitting the ribs but before adding spars and webs. I'm sure most of the washout gets locked in when the top skins are added, but I prefer to 'glue in' as much as possible as I go, rather than just twisting the panel later. Here's one, showing the 0.8mm gap under R10.

 

Webs and Aileron Spars

No great problems here. I ran the grain of the webs spanwise, as per plan. The plan doesn't show the size of the aileron spars, but I assumed they were from cut from med hard 1/8 sheet.

Do remember to fit R1A before adding the spars. I didn't, and it was a tricky wiggle to squeeze them in afterwards.

I had removed the scrap LE jig after the ribs had dried, in case anyone wonders why it's not visible.

 

Root In-fill

I used a different shape of in-fill at the root, to spread the wing bolt load a little wider (I hope). I used pre-shaped TE stock, slid forwards from the TE so that it needed no shaping at all. That left a small gap at the back to be filled with scrap 1/16" sheet. The blocks are angled to avoid the torque rod positions.

 

Edited By Steve Houghton on 16/03/2014 19:27:50

Edited By Steve Houghton on 16/03/2014 19:29:37

[Steve Houghton]

Black Fingers!

While the wings were drying I decided to push out the laser cut fuselage formers from their sheets. In doing so I ended up with fingers covered in carbon. I haven't used laser cut parts before, so maybe this is normal, but the plywood shapes seem to have been char-grilled rather than laser cut! Here are the waste sections from F1 to F4, showing the amount of burnt charcoal on the wood and on the kitchen towel underneath. The balsa parts were fine; this was only a problem with the ply. The cut edges had to be sanded vigorously to clean them up before I dare to start assembly. Just finished cleaning the black off my fingers.

Next job will be to sand the black finger prints off the surfaces of the formers.

Edited By Steve Houghton on 16/03/2014 19:38:46

[Steve McLaren]

Hi Steve,

I hadn't used laser cut parts before either and I too was surprised by how much carbon came off the burnt edges. But I wouldn't worry about it. - Nobody's going to see the inside and there's so much sanding to do on the outside that any fingerprints will be a distant memory!

Regards

Steve

[Steve Houghton]

Hi Steve,

I know what you mean about the black being out of sight, but believe me, it was going everywhere as I was sanding it off. It was like a crime scene investigation, with the fingerprints over the formers, building board, and even my clothes. Needless to say, the sanding block is a write-off!

Technically, I was concerned that the black would stop the glue sticking properly, which is why I have been so keen to remove as much as possible.

I'm enjoying your blog, by the way, and hoping to catch up soon.

KR's

Steve H.

[Steve Houghton]

Minor progress tonight, after completing a few domestic chores.

Sticking lower LE sheeting

To glue the front of the lower LE sheeting I left the wing pinned down flat at the rear (with washout wedges) and packed under the LE sheet with a 1cm wide scrap strip of 1/16. Using the trusty eyeball I then pushed this under the LE until I could see the PVA being squeezed - more push needed at the root end where the gap is a little larger. I needed a slightly thicker wedge of 3/32 under R1 and R2 for a good fit.

The packing sticks out more at the tip, where the gap is smaller.

Battery Box

I was unsure how to assemble the battery box, so this was my method. I assembled the box 'in the hand' glueing one side at a time, with a couple of pins to locate it roughly against the previous side. With all four sides added, a little wobbly and sticky, I slid F1 and F4 (no glue) over the box to jig it. I then loosened the pins and used light finger pressure to expand the box one side at a time to be a snug fit within the formers, and re-pinned it with more pins. Finally I added a few pins at each end to stop the dry formers falling off.

Here's the resulting 'Sputnik'. All the formers will be glued on after the box has dried.

Bedtime now...

[Steve Houghton]

A modicum of progress this week...

Former F4 onto Battery Box

I did a bit of head scratching to decide how to assemble the battery box onto the formers. I decided to glue it together vertically, based on F4 which I believe needs to be positioned the most accurately of all the formers, as it has to align with the LE of the wing.

I had a similar problem to Phil, in that F4 was warped. I also used a similar solution, gluing a couple of pieces of 6mmx3mm Cyparis across the front. Everything was checked for vertical alignment and pinned and weighted down to dry overnight.

False LE

The 1/16 false LE was added next, with a cut at F2 to accommodate the change in direction.

 

Fuselage sides

The triangular sections have been added to the fus sides. The front 1" pieces were cut from soft block and I made a triangular 'hole' template through which to pass the section, then sanded it down until it fitted.

(The TT46Pro engine is for my next project - a Balsa USA North Star - I enjoy messy planes as well as gliders!)

 

Front Formers

Having checked that F1 to F4 fitted well against the fus sides, after a little sanding as necessary, the battery box assembly progressed. I decided to build the rest from the front up, since Andy has cleverly designed formers F11, F12 and F8 to assist the assembly process. F2 and F3 were threaded onto the box without glue, then the box glued vertically onto F1. Formers F11, 12 and 8 (x4) were added at the same time. Lead weights then placed atop the whole, after checking the verticals again. F2 will be glued next, then finally F3.

Tailplane Seat

I stopped the top 3/4" triangle at F7 then inserted a final piece to align with the top of the tailplane seat. This is similar to Phil's build, although I thought 3/4" would provide a little more body to sand away than 1/2" triangle.

I feel a long way behind the rest of the bloggers, but I am determined to fly on the 1st June!

 

Edited By Steve Houghton on 22/03/2014 00:40:19

[Steve Houghton]

Had rather a busy weekend, so not much progress.

F2 and F3 Added

The loose F2 was slid down onto the F8/F11/F12 formers and glued with PVA.

When dry, the final loose former, F3 was slid into position and glued. I used lengths of Cyparis that will eventually become F13, to ensure the slots in the formers would align correctly. Everything was held with bands while F3 set firmly.

 

Further work on the fuselage will have to wait until I decide on the rudder linkage. If I decide to make it internal, which is my current preference, I may need cut-outs in F7 to clear the internal horn, and will require additional snake holes in F6 and F7.

 

 

Edited By Steve Houghton on 23/03/2014 23:13:56

[Biggles' Elder Brother - Moderator]

Coming along nicely Steve - looking good.

BEB

[Steve Houghton]

Thanks, BEB.

I may have to put major progress on hold for a couple of weeks now, as I have volunteered to build a pirate ship out of cardboard boxes for a forthcoming children's holiday club over Easter. All the modelling skills will now be put to use on a grand scale. I estimate it will be about 2.5m long, 1m wide and 1.5m high, and must be 'modular' so that I can transport it in the car! All without the help of CAD.

I'll try and maintain occasional background progress and updates on the JP.

[Phil Cooke]

hehe good luck with that Steve - Are you going to chuck it off the Orme on 1st June??

[Steve Houghton]

Hi Phil,

The aerodynamics and flight possibilities may depend upon the size of the sail. However, as a boat It may be useful for retrieving any 'dunked' models off the Orme!

Last year I 'built' a 3m high cardboard rocket - it would probably fly with several hundred Jetex motors (or modern equivalent) up the tailpipes . It's no wonder I don't get much real modelling done.

 

 

Edited By Steve Houghton on 25/03/2014 13:04:19

[Andrew Price 2]

Hi Phil, Will it have working cannons??

Build looking very good. Andy.

[Steve Houghton]

Hi Andy. Thanks for the comment.

It's actually my ship - working cannons would be interesting, but will delay my JP build for far too long. So, they will probably just be Pringle tubes. I suppose we could have a functional 'walk the plank' for errant children!

Are you building a JP? I'm curious to know how many non-bloggers are building along.

Cheers, Steve

[Andrew Price 2]

Hi Steve (got the name right this time, sorry!!)

My GF is a primary school teacher and every year we have to shop around for new pirate "teaching aids". Forget yer actual xbox, the kids still love good old fashion pirates. She would welcome the plank and I suspect, at times, that working cannon.

Sadly I'm not building along with you. Am new to the hobby and haven't either built, or flown a thing - my day will come!!

Andy

[Steve Houghton]

The Pirate Ship is finished and delivered!

If you want to see the culprit for delaying my JP build, please check out my thread on Cardboard Modelling.

Now, just a few backed up household tasks to clear before I resume the build, hopefully within a few days.

[Steve Houghton]

After a longer pause than anticipated, finally I can return to the build.

I made aileron torque rods as per the plan, with Andy's modification of using wooden dowel instead of carbon fibre tube as a filler.

 

However, the drill wandered a little and went through the side walls at the outboard ends.

 

Easily remedied with a bit of brass tube sleeving, but one of those mistakes you feel like kicking yourself for.

 

Aileron servo boxes made, with a slot left in front for the 1/32 dihedral brace up against the rear of the webbing.

 

Aileron servos installed. I left slots for cable exits in front and behind the mounts, to keep my options open. I shall probably use the front exit to avoid fouling the pushrods.

 

Wings were joined with 24hr epoxy. Then the dihedral brace was added, having cut a slot into the bottom sheet first and left enough to project through the top sheet. I also adopted a variation of Andy Blackburn's additional brace of 1/8 balsa behind the servo boxes.

 

 

 

Edited By Steve Houghton on 06/05/2014 00:45:42

[Steve Houghton]

Top wing sheet added

Both wing panels were sheeted on the top, after having joined them together. The only tricky bit was cutting a neat slot for the dihedral brace to poke through the top sheet without leaving a gaping hole.

Here's a close up of the brace in the top sheet.

Similarly a bottom view of the brace.

Joining the fuselage

I pre-bent the nose sections by wetting them and laying them flat on the board with the fronts propped up by 20mm whilst holding the rear flat on the board. This was vital for one side in particular, which is rather hard balsa (from the Traplet kit), and I also had to score the inside with a knife to persuade it to bend. I shall probably fill the scores with glue later.

This made it fairly simple to clamp everything together in my SLEC jig. At this stage, I have only glued F2, F3, F4 and the front part of the F13 stiffener. The sides are held in against F1 but not glued - didn't want to push my luck or the glue strength too far in one jump.

F6 behind the wing is dry positioned to help align the rear fuselage while everything dries.

The tail end is weighted down to keep the bottom of the sides aligned.

The jig supports need some strong bands to hold the tops together and exert enough pressure on the top joints. You may be able to spot that the top of F4 is not straight due to the warped lite ply that came in the kit. There is a gap on the starboard side but I think it won't show when filled. I made sure the bottom edges were aligned to keep the front of the wing seat true.

Rushing against the clock now to complete on time. I just noticed Matt Jones has thrown his hat into the building ring - how does he build so fast??? Well done, Matt.

[Steve Houghton]

Leading and Trailing edges

LE taped into place. TE strips added while wing pinned flat to board. Despite this, I still ended up with a slight TE droop afterwards.

Front Sides Pulled In

I was able to pull in the final part of the fuselage sides at the front with just pins. The jig wasn't necessary.

Rear Fuselage Joined

Back onto the jig for joining the rear fuselage. I marked centre lines on all the formers and ensured they were lined up over a line on the building jig grid. I was worried whether it would hold alignment after removal, due to one side being very hard, so I ensured the rear ends of the triangular longerons were well glued.

Warped F4

As mentioned earlier, my F4 was badly warped. I managed to straighten out the vertical twist with stiffening strips but the horizontal twist remained, as seen here on the starboard side. I later filled the gap with a piece of lite ply, tapered from 2mm at the gap down to zero on the other side. This may or may not matter cosmetically as some people have covered this part of the cockpit with sloping 1/16 sheet, whereas others have left it visible and vertical.

Top Deck Planking

Mine was planked with 1/8 soft sheet. One wide strip in the middle, then strips 3/8 wide at the front and 1/4 wide at the back, until the final lower pieces which were 1/4 wide all the way along.

Nose Top Sheet

Top 3/8 sheet between F2 and F3.