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Andy's Partly-Retrospective PSS Jet Provost Build


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I've not done anything on the JP (or any build) for 10 or 12 weeks; I don't know about anyone else but I find it impossible to do anything in the workshop when it's hot - just can't do it, and in any case most free time in summer is spent flying.

However, I've spent the week painting and assembling the cockpit furniture etc. :

cockpit-furniture2.jpg

This isn't the best cockpit I've ever done but it's not too bad. I think, on balance, I'm going to leave off the instrument panel because only a very small part is visible and there's not much detail on the rest of the cockpit, so I think a detailed panel might look out of place. And in any case, you can't see it in flight.

Edited By Andy Blackburn on 16/08/2014 12:20:11

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  • 2 weeks later...

Yep, got a fair bit done, although I did have a day off at the Nats last Sunday. Barring incidents, it'll be done by the 13th - knowing my luck, though, I'll probably have to maiden it on the day smiley.

Canopy is now on:

canopy-installed.jpg

- attached with canopy glue as the original was attached with Solartrim and was forever coming loose. It just needs the framing and I think I still have most of the original frame shapes on tracing paper in my desk drawer...

I've spent the available time this week finishing off the covering (mostly):

wing-covered-btm.jpg

wing-covered-top.jpg

...and I think it looks OK. Not perfect - there's a small mistake on the top surface (not visible in the picture) - but it'll do.

There's just the part of the tailplane that sits between the elevators to do, and then the covering is finished and I can start putting it together.

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This was the last bit of covering that needed to be done:

the-last-bit.jpg

The elevators are probably a little further apart than drawn because of the aerodynamic balances, so there was a larger-than-expected control surface gap - easily fixed with a couple of thin strips of wood. Thinking back to all the trouble I had with Profilm earlier on in the build, I used Solarfilm to cover this last bit - and it was no trouble at all.

This was my solution to the rudder horn issue:

rudder-horn.jpg

- basically, it's a nylon snake that's been sanded to a slight cone so that a clevis can be screwed on and then cyanoed, attached to a CG short control horn (cut down to half size) that has had a corner sliced off so that it fits. It'll be painted silver when the detailing is done, which brings me to:

at-last.jpg

Not quite finished, but not far off; in this condition it weighs 26.6 oz including 1.5 oz of noseweight; let's call it about 27.5 oz when all the decals are on, but I can lose about an ounce of that by replacing the tip tanks with the plug-in wingtips.

Should be able to get the missing decals etc on next week in good time for the PSS event a week on Saturday.

If I was doing it again, I'd think very carefully about lightweight modelspan tissue and sanding sealer, finished with car aerosols or enamels/acrylics applied with a large, high quality brush - I suspect it'd be considerably easier, and possibly no slower in terms of time spent on the model, as opposed to time spent waiting for stuff to dry.

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  • 2 weeks later...

I'm going to call this finished on the basis that I would have flown it today if the ISA PSS event was on:

finished.jpg

There's maybe a bit more I could do with panel lines and the like, but that can be done later; in this condition, it weighs a tad over 27 oz including a 2000 mAh NiMh and an additional 1/2 oz of noseweight - I've meddled with the wing incidence a bit so I'm not 100% certain where the c.g. should be, am hoping that I can remove the extra 1/2 of of lead after test-flying.

I did try and paint the lights on the leading edge of the tip tanks but it didn't go well (turned our to be a right mess, actually) and I had to clean it all off again; I'd be interested in hearing how other people have done theirs.

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"I'd be interested in hearing how other people have done theirs."

Andy,

On the tip tank lights, I dropped the nose of each covered tip tank through a piece of stiff card cut with a 12mm hole in it, checked alignment for square then drew around the card with a medium bullet permanent marker. This created a black 'edge' - thicker than a panel line - upto which I hand painted the gloss red and green using good old Humbrol Enamels... they are a little 'cartoony' but look fine and a good thick coat of enamel permanently seals the covering overlaps on the nose section too!!

dad10.jpg

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Ah! enlightened

Phil, that's brilliant, thanks very much. The lights usually show very dark in daylight so I was going to use a coat of matt black and then a mix of 50:50 gloss red or green enamel : clear lacquer, the intention being to end up with a dark tip with a slight colour tint. Good idea to seal it with clear lacuer afterwards.

Edited By Andy Blackburn on 17/09/2014 14:56:07

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  • 1 month later...
  • 2 weeks later...

I was privileged to see Andy's maiden flight yesterday on the south slope at Ivinghoe. The forecast was 14 to 15 mph, but we measured around 30 gusting to 40 on the edge of the slope. The conditions were rather turbulent, keeping quite a few models on the ground, but Andy was determined to give it a go, and he made the choppy conditions look smooth and easy.

img_9911.jpg

andysjp1.jpg

andysjp2.jpg

andysjp3.jpg

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Actually, I'm very pleased with it.

Scotty kindly agreed to do launch duty, and I'm happy to say that it was one of those occasions where one instantly feels at home with the model; if anything, it was smoother and more stable than the original of 10 years ago!

The only obvious faults were just a hair too too much aileron differential, and very slightly more aileron movement needed; other than that, it felt really well-balanced. It can be steered very nicely with just the rudder (definitely worth fitting), and seems to be able to fly a bit higher than Steve's example so maybe the drag-reduction program (wing fairings, slightly rounded/thinned intakes) has worked. I wouldn't want to move the c.g. any further forward but it still required a fair bit of down trim (but then, most JPs seem to need it) so maybe in future the wing-tail set-up should be zero-zero.

On landing, I managed to execute two perfectly good circuit-and-overshoots but then when it came to the landing proper, dropped it upside down in a thorn bush - basically pilot error. Um...

blush

There was a bit of puncture damage and a dented leading edge, I'm going to repair it this weekend.

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I don't believe I've ever crashed a model on its first flight before smiley

This is the damage being fixed:

repair1.jpg

Not a lot of overlap on this film patch...

repair2.jpg

But it shouldn't be too obtrusive after a few panel lines have been added:

repair3.jpg

I'm not going to touch the dayglo area because it's a bit translucent and a patch would be very obvious.

On balance, could have been worse.

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  • 4 months later...

The problem with something like the JP is that I tend to fly it a lot, so it gets a lot of wear and tear. Or in this case, a mid-air with a foamie... sad

Here's the crease right across the top wing skin:

img_1027.jpg

film removed:

img_1034.jpg

Wing skin removed:

img_1035.jpg

replacement wing skins in place:

img_1040.jpg

...but you need some reinforcement/positioning pieces to carry the wing skin strength through, otherwise it'll be really weak. Blu-tack is useful for holding stuff in position whilst the glue dries:

img_1043.jpg

...ready for the replacement wing skins:

img_1051.jpg

before pinning down, we need to make sure that the washout is preserved so a 1/16" -> 0 washout wedge is taped under the wing in the normal place:

img_1055.jpg

Glued with PVA - for reasons of strength - and pinned in place with loads and loads of pins and a hammer to make sure it stays flat for 24 hours:

img_1054.jpg

...24 hours later:

img_1058.jpg

+ too much filler:

img_1064.jpg

..sanded more-or-less flush:

img_1068.jpg

...and covered:

img_1075.jpg

- there are some minor blemishes but they're not visible is this photo. I'm hoping that it'll be less noticeable after the panel lines are (finally) added.

Edited By Andy Blackburn on 25/03/2015 18:36:53

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  • 10 months later...

Hi Andy,

I am looking for the 1/12 pilots that you had installed in your first Jet Provost.

I checked Pete's Pilots,but only the vizer-down version is available in 1/12.

Can you please tell me where they came from?

They really make the difference in an already magnificent model!

jet provost.jpg

Friendly regards,

Wim.

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