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Author Topic: VMC Blue Spitfire Build  (Read 5362 times)
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abl
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« Reply #50 on: October 05, 2017, 10:22:07 AM »

... And I doubt yours will need much rebalancing will it, with the added gubbins all being so near the centre?

Actually, you're quite right - it seems to still be in balance. On the other hand, I've not tacked the spinner in place yet but even though I marked the "no wobble" position, it now wobbles a bit...  Angry I forsee much bad language and fiddling with tiny bits of masking tape before I can summon up the courage to glue it in position.

There has been some progress, but not as much as hoped. It took absolutely ages to shape the inside face of the exhaust stubs to match the cowl shape, and then a bit longer to get them attached in more-or-less the right place, and as symmetrically as possible. It's not perfect but it's not too bad.

The tailwheel wasn't too much bother, but it took several goes to get an acceptable bit of tissued paper to represent the castoring bit, and then a couple of goes to get it in the right place. It's not perfect (and so on and so forth).

The canopy (which took forever to trim) was attached with the usual masking tape handle using Canopy glue, and now I daren't move it 'till it's dried. I hope the while blobs dry clear...

I don't know why this is all taking longer than it used to; maybe I have some variant of fear of finishing. Or maybe there's some variant/corollary of Parkinson's law that will cover this situation.
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Jack Plane
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« Reply #51 on: October 05, 2017, 11:32:47 PM »


I don't know why this is all taking longer than it used to...


Everything takes longer than it used to!

I find that in order to get whatever the current model is made, I have to neglect work, household chores, the family, social interaction, etc.  Every fibre of one's being and all spare mental capacity needs to be dedicated to the task in hand.

There's also Jackplane's Rule: the final 20% of accuracy and finesse takes 80% of the time and effort.

In other words... it looks pretty damned good, just get it done mate!  Grin
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« Reply #52 on: October 06, 2017, 05:06:06 AM »

If your modelling works on an 80:20 Pareto basis you are doing pretty well, tbh.
In full size aviation, homebuilding and restoration, we sometimes refer to the "90:90 rule" of project scheduling.

The first 90% of the visible work takes 90% of the time schedule.
And the last 10% takes another 90%.
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abl
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« Reply #53 on: October 06, 2017, 05:37:42 AM »

...

The first 90% of the visible work takes 90% of the time schedule.
And the last 10% takes another 90%.

Hah! That, I can well believe.

I've attached a very important and useful general purpose progress graph that was kindly sent to me by the proprietor of Lurker Industries. I'm going to tidy it up, get it framed and hang it up in the modelling room as a reminder that eventually, everything will be finished.

Andy
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abl
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« Reply #54 on: October 08, 2017, 12:40:12 PM »

Time for the wing fairings - my least favourite job because it's so easy to make a c*ck-up, but on the other hand it does begin to make the airframe look like a proper Spitfire...

Andrew D said something in an earlier thread about using brown tax envelopes to give tissued paper the best colour match for tissued balsa, so I turned the house upside down looking for one, unfortunately without success. I did manage to find a large yellowish-brown A4 envelope that the Minister for Home Affairs is unlikely to miss (she keeps a very tight rein on household stationary), so it's been pressed into service (picture #1); it seems to be slightly heavier than the usual 80 grams/sq metre printer paper, but it's not too far behind the c.g. so I'm refusing to worry about it.

Parts WF have to be chamfered quite heavily to get them to fit (#2 & #3), but they do fit OK with a bit of persuasion.

The wing fairings were eventually persuaded to fit (one of those times when three hands might be an advantage), I found with the second one that it was a lot easier if the inside is given a coat of non-shrinking dope so that it can be stuck by running thinners along the edge, and it's easier if the front is taped in place first. Medium cyano helps to stick the fairing to the bottom stringer at the front (#4)

After that, the under-wing fairing was dead easy (#5).

And luckily, I've just avoided gluing the radiator to the wrong wing...  Smiley
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abl
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« Reply #55 on: October 09, 2017, 10:22:05 AM »

Right, so it's sort-of done - by which I mean that it's flyable, but isn't quite finished because it hasn't quite got to toh bu**er it that'll do (with due deference to the staff of Lurker Industries).

It's missing some detail:
  • White reference mark on port wing for the oblique camera - I forgot to do it when spraying white markings.
  • A few panel lines - my Letraset pantone 11F cool grey marker has dried up.
  • The rear-view side blisters on the canopy - I haven't yet worked out how to attach then without making a right mess.

There are also numerous errors and deficiencies (one of which two of which are glaringly obvious) over which I think we should draw a discreet veil.

However, on balance I think it looks quite Spitfire-esque.

The important numbers are:
  • Bare airframe = 28.7 grams
  • Airframe + 4 strands 0.100" rubber 14" long = 32.8 grams
  • Airframe + rubber + nose ballast = 38.1 grams

So, tentatively, that looks quite flyable. Might have gone a little bit overboard with the rubber size but I have half an eye on gate crashing Jon's secret proving ground "somewhere in Oxfordshire" the next time he has a trimming session...  Smiley
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danmellor
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« Reply #56 on: October 09, 2017, 12:44:27 PM »

Very nice indeed!

Dan.
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« Reply #57 on: October 09, 2017, 01:09:05 PM »

It is very pretty, a credit to kit and builder both. Well done!
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Jack Plane
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« Reply #58 on: October 09, 2017, 01:47:32 PM »

Well done Andy - that looks really cracking!

I'm considering taking mine to Newbury on Saturday, maybe even with the completed Camel?!

Outdoor weather not looking great this week, except perhaps first thing Thursday morning?
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« Reply #59 on: October 09, 2017, 02:35:18 PM »

The rear-view side blisters on the canopy - I haven't yet worked out how to attach then without making a right mess

Really nice build.  Don't yet know if I will vote for the pink'un or the blue one. Smiley

I like this glue for small stuff.  http://www.cjbeaders.com/g-s-hypo-cement-684

It has a very small dia., applicator, sticks well and is transparent.  Worth trying.

Ralph
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Jack Plane
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« Reply #60 on: October 09, 2017, 03:05:40 PM »

Err... the pink 'un of course!   Wink

Thanks for the heads-up on that adhesive - just ordered a tube for the supplies box.
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« Reply #61 on: October 09, 2017, 03:06:19 PM »

First of all a very lovely example of KS.  Total honesty when you're not daubing paint all over them like I do!

As for your blisters I go back to the RC56.  All you do is gently tape the blister in position with a thin trip of Tamiya tape and then get some RC56 thinned with a drop or 2 of water and apply it to the seam with a small paintbrush.  The RC56 will wick its way right around the join with a bit of encouragement from your brush.  You'll find that the surface tension of the glue will fill any gaps.  Best of all the glue will draw itself into a neat line as it dries.  Try it - you won't be disappointed
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« Reply #62 on: October 09, 2017, 03:09:44 PM »

First of all a very lovely example of KS.  Total honesty when you're not daubing paint all over them like I do!

As for your blisters I go back to the RC56.  All you do is gently tape the blister in position with a thin trip of Tamiya tape and then get some RC56 thinned with a drop or 2 of water and apply it to the seam with a small paintbrush.  The RC56 will wick its way right around the join with a bit of encouragement from your brush.  You'll find that the surface tension of the glue will fill any gaps.  Best of all the glue will draw itself into a neat line as it dries.  Try it - you won't be disappointed

I bought a bottle of RC56.  Not all that impressed with it.  It may be me of course.   :'(
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« Reply #63 on: October 09, 2017, 03:16:39 PM »

You do need to thin it and I generally apply it with a brush or toothpick as described.  Over on my Morane Borel thread in outdoor F/F Scale there's a picture of how I did the windscreen , in reply#103.  In that case the windscreen is inset into the surrounding cockpit coaming with about a 1-2 thou gap all around,  which is filled with the RC56.  Just an application technique,  but I find the product itself is ideal   
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abl
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« Reply #64 on: October 09, 2017, 04:42:58 PM »

Thanks for the kind words, gents...

The rear-view side blisters on the canopy - I haven't yet worked out how to attach then without making a right mess

Really nice build.  Don't yet know if I will vote for the pink'un or the blue one. Smiley

I like this glue for small stuff.  http://www.cjbeaders.com/g-s-hypo-cement-684

It has a very small dia., applicator, sticks well and is transparent.  Worth trying.

Ralph

I think the blue one might be very slightly lighter, in case that sways your judgement...

And thanks for the glue link, that looks like useful stuff. Have just ordered some.

...

I'm considering taking mine to Newbury on Saturday, maybe even with the completed Camel?!

I think I might have to at least get the glide trimmed outside before it sees Newbury (it's only a normal-sized school hall, and I don't want to fly it into a wall before Nijmegen), but the weather isn't looking that promising this week.

(wait a minute - "completed Camel"?! You can't have finished it already?)


As for your blisters I go back to the RC56.  All you do is gently tape the blister in position with a thin trip of Tamiya tape and then get some RC56 thinned with a drop or 2 of water and apply it to the seam with a small paintbrush.  The RC56 will wick its way right around the join with a bit of encouragement from your brush.  You'll find that the surface tension of the glue will fill any gaps.  Best of all the glue will draw itself into a neat line as it dries.  Try it - you won't be disappointed

I like that idea because the blisters are positioned first so there's a much reduced chance of making a mess; I'm going to try that - I assume that Pacer "Formula 560" canopy glue is the same stuff? Smells like a cross between PVA and latex adhesive?

Andy
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« Reply #65 on: October 09, 2017, 05:18:36 PM »

Yup.  That's what I use
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« Reply #66 on: October 10, 2017, 02:08:26 PM »

Very nice indeed.  However I'm not going to vote for the Pink vs the Blue because you've both done very well indeed and everyone shall have prizes. Smiley

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Jack Plane
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« Reply #67 on: October 10, 2017, 02:46:48 PM »

Very nice indeed.  However I'm not going to vote for the Pink vs the Blue because you've both done very well indeed and everyone shall have prizes. Smiley


Give that man an award!!  Grin
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« Reply #68 on: October 30, 2017, 01:09:24 PM »

So Andy popped over today for a bit very calm weather outdoor trimming.

Took him about an hour with no more than a few glides and half a dozen powered flights to get his Spit significantly trimmed.

Early footage shows him bare-headed (at his request): https://photos.app.goo.gl/q6zMOG8weRXVL0yG3

Later footage, with Spit in better state of trim, shows him wearing regulation hat: https://photos.app.goo.gl/SlCN4Od4aWgK791m1

He'll turn up later to explain his tweaks (including a bit more nose-weight), but he certainly left sunny Oxfordshire a very happy aero-modeller!
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« Reply #69 on: October 30, 2017, 02:31:06 PM »


Early footage shows him bare-headed (at his request): https://photos.app.goo.gl/q6zMOG8weRXVL0yG3


I'd just like to point out that this was only because I felt guilty about committing outdoor aviation without a hat.

For those contemplating a build, here's the current state of trim;

  • Balance point is roughly as on the plan - I'd taken out some nose weight after some hand glides at Newbury, but put some back after additional flights today.
  • There's no gurney flap fitted, the left wing has the standard washout of 0.5mm but the right wing has about double the washout of the left wing. So far, this appears to be enough to control the initial power burst, at least from a hand launch
  • The fin leading edge is offset to the right by just over 1mm, and there's an additional 1.5 mm of left rudder offset steamed in.
  • There's about 0.4 grams of weight on the left wing; this (and the fin/rudder offset) isn't quite enough to get enough of a left turn when the power runs down.
  • Down thrust is as on the plan, right thrust is approx 5 degrees; this produces a nice turn under power, but may need to be increased a bit when the glide turn is sorted out
  • Power is 4 strands (2 loops) of 100 thou (~2.5mm) 14" long, so about 2x hook-to-peg distance. This is probably good for about 800 safe turns and seems to provide enough power for a shallow climb from a hand launch. This might be a bit much for indoors on max turns, in which case I'll try some 90 thou (~2.3mm) rubber.

What it needs is a good left turn on the glide, so I'm going to try a trim tab on the rudder, failing that I'll try some more weight on the left wing tip and possibly a small gurney flap on the very tip of the left wing. It remains to be seen whether this will be enough to kill the stall on the glide, I suspect that a small amount of additional nose weight might be required.
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« Reply #70 on: October 30, 2017, 02:43:37 PM »

Looking good.  Is there is a free-wheel on the prop assy?  This complicates things for indoor and the lack of free-wheel spoils the end of flight outdoors. 
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« Reply #71 on: October 30, 2017, 03:22:23 PM »

Quote from: abl
Quote from: Jack Plane
Early footage shows him bare-headed (at his request): https://photos.app.goo.gl/q6zMOG8weRXVL0yG3
I'd just like to point out that this was only because I felt guilty about committing outdoor aviation without a hat.
A gentleman should never go flying bareheaded, apart from anything else aeroplanes always fly better when you are wearing a hat.  Well known fact. Wink

The Spit. flies very nicely indeed.
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« Reply #72 on: October 30, 2017, 03:26:38 PM »

Looking very good indeed ... and we like to hear an autumnal crow!  Smiley
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« Reply #73 on: October 30, 2017, 04:46:20 PM »

Thanks chaps - I'm quite pleased with it, and top marks to Mr Darby for a well-thought-out design.

Quote from: abl
Quote from: Jack Plane
Early footage shows him bare-headed (at his request): https://photos.app.goo.gl/q6zMOG8weRXVL0yG3
I'd just like to point out that this was only because I felt guilty about committing outdoor aviation without a hat.
A gentleman should never go flying bareheaded, apart from anything else aeroplanes always fly better when you are wearing a hat.  Well known fact. Wink


Well, that's all very well, but I'm still not clear whether the overall quality of flight necessarily depends on the type of headgear...?

Looking good.  Is there is a free-wheel on the prop assy?  This complicates things for indoor and the lack of free-wheel spoils the end of flight outdoors. 

Yes, there's a standard plastic prop free-wheel inside the spinner, took some time to get it to operate correctly without binding on the inside of the (balsa) spinner. It's worth it, I think, because it means that it's flyable outdoors as well as large indoor venues.

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« Reply #74 on: January 30, 2019, 07:03:15 AM »

I have to report the sad loss of BR416 following an unfortunate incident when tidying up in preparation for the window-installers. The pilot, wheels and spinner were saved.

It flew pretty well outdoors but I never did get it to behave indoors, for some reason - it flew very fast and the (indoor) flight pattern was quite stall-zoom, timed so that the circle was low at one end and high at the other; I don't know if it was a classical phugoid (i.e. ~constant AOA, airspeed varies) but it certainly looked like it might have been. There's no chance it would fit in a standard-size hall, it flew at Nijmegen but that's a very large venue.

If I were to build another one, I think I might try the following:
  • Replace everything aft of the wing trailing edge (except the motor peg plate) with 6 lb/cu ft balsa, maybe a bit heavier for the stringers.
  • Experiment with more negative incidence on the tailplane (~= -2 degrees) in an effort to get the flying speed down so that the turn might then be more manageable. That'll require the c.g moving forwards, of course.
  • Use heavier wire for the undercarriage because 0.7 mm wire will splinter the oleos when it bends.
  • Use the gurney tab and a little wing-weight to induce a turn because the rudder isn't very effective, the main effect of left rudder is to mess up the power flight and require far too much right thrust.
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