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Author Topic: VMC Blue Spitfire Build  (Read 2398 times)
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Crabby
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« Reply #25 on: June 22, 2017, 10:24:50 AM »

Looking good! Did you get a canopy in the kit or are you gonna be vac-forming?
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« Reply #26 on: June 22, 2017, 05:26:03 PM »

The kit has the standard canopy for an early Spitfire V with an external armoured screen, but since this is a PR version it has a curved windscreen (no armour) and a large side bulge on each side of the sliding canopy. I might be able to use the fixed rear part of the kit canopy, but will have to mould a new canopy and windscreen; might have to mould the rear part as well, actually. Will also have to mould the side bulges separately and stick them to the main canopy with clear dope. I haven't got a vac-form machine so It'll have to be plunge-moulded, and I haven't done that for, um... well, a very long time. I forsee many, many attempts and several spare canopies...

Pretty sure the new canopy will count as a "significant" deviation under kit scale rules, but I think I've racked up so many penalty points already that I've given up worrying about it.  Smiley
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abl
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« Reply #27 on: July 17, 2017, 09:03:24 AM »

I've had to get on with the non-standard spinner arrangement because I want to do a "bare structure" photo of the type usually seen in the better model magazines ("Aeromodeller", etc.) many years ago, so the spinner and prop have to fit.

Couldn't think of a reliable way of sanding the back plate to match the spinner, so tack glued it in place and did the sanding by eye.

Finding a way of assembling the rest of the components required a lot of considered and thorough consideration procrastination, in the end I thought that the most reliable way of producing something that was almost centered and had minimal wobble was probably to make a small jig (photo 2) from three 2" square bits of 1/16" sheet, 3/64" wire, and a few scrap bits of ply and masking tape to get it as centred as possible - this was done using a drill press to keep everything square; it should enable the prop and backplate to be assembled with minimal axial run-out.

The back plate is a push fit onto the jig, and the prop is just dropped on and fits in a 3mm hole on the backplate. Cut parts SP3 are subverted to hold the prop in the right position, although there's a small amount of play so it'll have to be glued in the jig. I think the best stuff to use for glueing is probably 5 minute epoxy and microballoons, used sparingly.

Also think I'm going to have to temporarily tape everything (spinner, prop, backplate) together and spin it on the shaft to find out where the prop should be glued on the back-plate to give minimal radial run-out.
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Jack Plane
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« Reply #28 on: July 18, 2017, 07:16:39 AM »

Excellent 'well-considered' job.  Grin

My own shenanigans with the spinner fell into the bodge-it-as-well-as-I-could category!
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abl
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« Reply #29 on: July 19, 2017, 04:02:40 AM »

Thanks for the kind words, but whether it works in practice is another matter entirely!  Smiley

I managed to get all the various bits and pieces to a reasonable state yesterday evening, so thought I might as well have a go at a trial assembly so that I could try for some "Aeromodeller" type structural photos; it's all assembled with a combination of masking tape, sellotape, double-sided sellotape, tiny dots of balsa cement and a little bit of blu-tack in the spinner. In this state, it weighs 22 1/4 grams...  Cry

It's going to require about 300 tons of nose weight and the only crumb of comfort I have at this stage is that it's slightly nose-heavy (by about 5mm).

I haven't got a proper dark background for photography so had to use what was to hand, the pictures were taken with an iPhone 6 and if I'd used the "proper" camera they might have been a bit better, but they're not too bad, I think.

Next job is to carefully take everything apart again and make a plug (or plugs) for the canopy.
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OZPAF
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« Reply #30 on: July 19, 2017, 04:54:46 AM »

I think it looks pretty good. Your efforts in jigging the prop / spinner seem to have paid off.
The holey centre spar web looks neat.
Andrew did a nice job on the design of this model.

John
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malc
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« Reply #31 on: July 19, 2017, 06:32:48 AM »

Thats looks really nicely finished, esp the nose infill and the shape of the exhausts, the weight seems reasonable. How are you going to do the upper wing fillets?

Malc.
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abl
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« Reply #32 on: July 19, 2017, 04:54:56 PM »

Thanks for the kind remarks.  Smiley

...

The holey centre spar web looks neat.
...


I enlarged them slightly with a Permagrit file.

Um... perhaps I shouldn't have admitted that because I suspect Kit Scale judges do occasionally look in to see what's going on, but I've racked up a fair number of penalty points already so a few more won't make much difference...  Smiley

...

Andrew did a nice job on the design of this model.


He did indeed.

Thats looks really nicely finished, esp the nose infill and the shape of the exhausts, the weight seems reasonable. How are you going to do the upper wing fillets?

Malc.

I worry about the weight because Jon's Pinko PR Spitfire had lighter components and still required a significant amount of nose weight; on the other hand, I suppose that my tissue is probably a bit lighter than the pink stuff that Jon used. I'm going to do the upper wing fillets exactly as it says on the plan - paper pattern, covered with tissue, curved to fit and stuck in place - looks as though it ought to work OK.

Andy
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abl
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« Reply #33 on: September 08, 2017, 08:32:20 AM »

Time is rolling on and I really should try and get this finished, and if I'm honest I've been putting off the next bit (the canopy). I'm still planning to plunge-mould it, so we'll see how that goes - it'll be a lot easier if I can persuade one of my fellow aeroplane nuts to assist, the last time I hand-moulded a canopy was in front of a gas fire (probably 30+ years ago) and from memory it usually requires about three hands to do reliably. Might be easier with a heat gun, though.

The canopy side view came from a combination of "Spitfire in Action", the photo further up this thread and the dim memory of seeing the Old Warden PR.XI, also quite a long time ago. As it is now it's about ready for sanding, then it can be split off and faced with 1/8" sheet and a dowel stuck in the bottom.

Still need to make a mould for the side blisters, of course...
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MKelly
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« Reply #34 on: September 08, 2017, 09:04:45 AM »

Great idea with the masking tape- I'm going to be using that frequently.
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abl
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« Reply #35 on: September 14, 2017, 12:33:25 PM »

Great idea with the masking tape- I'm going to be using that frequently.


Thanks - I only do it because I'm too much of a klutz to get away without it.

In other news, I wish to report a degree of success with the plunge-moulding - see pictures.

The canopy mould turned out OK, it's just bare balsa finished with very fine wet & dry - about 600 or 800 - so that the surface acquires a mild polish, the former plate was made from liteply. I made a separate mould and former for the side blisters, the plan is that they'll be attached afterwards with clear dope. I'm painfully aware that this will be a one-shot operation. But that's a problem for another day, thankfully.

One of my clubmates came over and we had a few goes at plunge-moulding, with varying degrees of success; I thought a heat gun (for covering with plastic film) might work, but it just wasn't hot enough. Neither was the gas fire. However, turning the electric oven grill up to full worked really well; unfortunately, SWMBO came home part-way through the process as we were both crouched in front of the cooker, stopped at the kitchen door, opened and shut her mouth a few times and eventually managed to say "WHAT are you doing?"...

We had several goes at moulding canopies and side blisters from 10 thou acetate sheet, and managed to get 1 1/2 acceptable canopies and two good side blisters, so I'm counting that as a win.

On with the covering, then...
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Jack Plane
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« Reply #36 on: September 14, 2017, 01:37:14 PM »

Top job Blackburn!

...AND best SWMBO story I've heard in absolute ages!   Grin
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abl
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« Reply #37 on: September 18, 2017, 01:36:49 PM »

I've focused on the covering over the past few days and it's not looking too bad...

I've not wet-covered a whole fuselage in Jap tissue for, well, for a very long time, so a quick revision of my extremely dog-eared copy of "Flying Scale Models of WWII" was in order. I wanted to use three pieces of tissue for the fuselage because I didn't want a tissue overlap down the middle of the cowl, and it all worked as advertised - almost. There is a very small patch where I accidentally cut through two layers of tissue, but I don't think it's too much of an eyesore. In the end, the fuselage took less than an hour and a half to cover. There were some minor imperfections so I used 50/50 dope to try and shrink some of them out.

The tissue for the tail surfaces was pre-steamed on a balsa frame before covering with the Approved Glue Stick, and I tried to make really certain that the tissue grain went straight down the centre of the piece on both sides. Then it was briefly steamed again and (when dry) doped with 50/50 non-shrinking dope, pinning down at each stage. So far (after 3 or 4 days), it's stayed straight.

The wings were covered with the glue stick and then each panel steam-shrunk and pinned down, then each panel was doped with 50/50 non-shrinking dope and pinned down again. So far, it's also been quite stable, it's only lost a tiny bit of the washout on the port wing, so I can probably steam that back.
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Jack Plane
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« Reply #38 on: September 18, 2017, 01:57:57 PM »

Looking very crisp Andy!

Just a couple of things though...

1.  If you're going to have to take a hit on the laminated tailplane, why not go the whole hog and do similar on the fin?
2.  The wing centre-section seems to have ground a pair of angled riblets - to match the fuselage?

Standing by in-coming!  Grin
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Andrew Darby
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« Reply #39 on: September 18, 2017, 02:06:17 PM »

Nice Job, but as Jon says that laminated tailplane is pretty obvious!  I don't think that the plea of over sanding will really wash with the judges...  John Churchill got done over by simply sanding the surfaces too thin a few years back.  These were punished in the marking under "assorted cheats"  Huh

Yes, what are those extra bits in the wings?

Andrew
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« Reply #40 on: September 18, 2017, 03:17:58 PM »

Great covering job!  RC56 would stick that wing to the fuselage very nicely indeed (see comments in CT4 thread)
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abl
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« Reply #41 on: September 18, 2017, 03:29:47 PM »

1.  If you're going to have to take a hit on the laminated tailplane, why not go the whole hog and do similar on the fin?


Well, I made the fin first, then had the c*ck-up with the stabiliser (over which we should draw a discreet veil) and having gone through the draw/print/cut-out/glue process with the fin, I felt that it was easier to make the laminated outlines than make the outlines from separate pieces.

2.  The wing centre-section seems to have ground a pair of angled riblets - to match the fuselage?

Yes, what are those extra bits in the wings?

Um, well, the thing is that if they're not there then the covering will sag between R1 and R2, so there'll be an unsightly gap between the fuselage and wing because I'm (legally, mind you) in-filling with 1/16" sheet rather than using paper patterns. So I added a couple of riblets to support the covering. I was going to claim that it couldn't really be classified as a "significant" deviation because once it's assembled you have to look hard to see it. And if the tissue was more opaque, you might not see it at all...  Smiley

I don't think that the plea of over sanding will really wash with the judges...  John Churchill got done over by simply sanding the surfaces too thin a few years back.  These were punished in the marking under "assorted cheats"  Huh

Oh, that's harsh! Very harsh!

And in any case, strictly speaking it was incompetence rather than over-sanding; the wood was a bit heavy and what I probably should have done was - before making the stabiliser - make some new parts out of much lighter wood.

...That's not going to work either, is it?...  Smiley

But, to be honest, the chance of me winning anything is remote because a) I can't resist tinkering with and/or changing designs and b) I don't build anything that's too big to circle in my local sports hall. So, I'm just building things to my own satisfaction and if one of them happens to get on a kit scale podium then that's great, but I'm just doing it for the fun of it, really.

So I'll take the penalties on the chin.  Smiley
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Jack Plane
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« Reply #42 on: September 18, 2017, 05:11:53 PM »

Good man!  Cheesy
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