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Author Topic: Lee's Hobbies Halberstadt D.II Kit  (Read 967 times)
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Newbie_John
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« Reply #25 on: May 06, 2019, 05:34:34 PM »

Hi John
Its Tamiya, comes in various narrow widths.
Cheers
Jon

Many thanks, Jon - I'll get shopping!
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Jack Plane
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« Reply #26 on: May 07, 2019, 03:05:16 AM »

Top tip, Crabby, thanks!  Smiley
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Jack Plane
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« Reply #27 on: May 07, 2019, 03:10:50 PM »

Curly-Wurly time...

Covering the fuselage with pre-printed (but not pre-shrunk) tissue.  Because of the disorderly order of things, I had to resort to best-guessing the curve of the upper longerons for the side-pieces, but this worked out fine in the end!  Smiley

Somewhere along the line I darkened the Merc and added the exhaust, made from very small shrink-wrap tubing daubed brown, and held the blackened Spandau along side it for my viewing pleasure.
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Jack Plane
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« Reply #28 on: May 07, 2019, 03:27:51 PM »

Tails and wing surfaces...

... top wings of this sort take ages to shrink and dope because each of the three panels has to be done and pinned separately!

I don't know how long normal people leave things, but I reckon overnight or a long half-day's worth of pinning should be enough for wing structures to settle after steaming or doping tissue.

Talking of which, I used to bang on a single coat of non-shrinking thinned 50:50 with cellulose, but on the Halb I went 25:75 for each of two coats (the second after tissue markings applied) and think the result is a much finer blend overall.

Tick-tock, tick-tock... but at least there was other work to do!
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Jack Plane
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« Reply #29 on: May 07, 2019, 03:46:05 PM »

While wings were slowly curing...

Windscreen (ex Tunnocks Teacakes packaging cellophane) went on.

Spandau cooling jacket got its slots with a little help from a pin heated red-hot with a candle flame... a bit sketchy but that's this Halb for you!

Turned wheels from white Depron foam with bamboo skewer centres.  Not entirely successful as (i) I had to later drill out the centres (which weren't properly in the centre) and glue in aluminium tubing; and (ii) the whole foam thing just isn't as robust as balsa... as I discovered after a dozen or more landings!  Shocked  So making proper balsa wheels is one of the first jobs I've got to do before the Halb flies again.
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Jack Plane
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« Reply #30 on: May 08, 2019, 10:13:43 AM »

The idea was to meld actual physical details (engine, pilot, etc) with markings in tissue and other details (especially on flying surfaces) with ink.

So the upper-wing radiator was a prime candidate for the ink, along with fuselage step, hand-hold, wing walkways, control wires exiting the fuselage, etc.

The crosses were cut from black Esaki using pin-pricks in tracing paper templates to first prick through reference marks before cutting with scalpel using random lids which seemed to fit (e.g. Coleman's English Mustard) for a clean arc.  White backgrounds were chalked Esaki and doped on first, then the crosses.

Engine access panels were just an extra layer of blue tissue, later picked out with ink borders.
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« Last Edit: May 08, 2019, 10:24:37 AM by Jack Plane » Logged
Jack Plane
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« Reply #31 on: May 08, 2019, 10:38:58 AM »

Then the undercarriage and miscellaneous struttery.

I'm not a fan of bent piano-wire where it isn't necessary, so made up the U/C stuts from hard balsa and the mini-wing between them from soft stuff.  In retrospect could have reduced the section of the struts a bit, but was trying to speed up as my deadline for the Nats was imminent!  The axle itself is piano wire.

The all-moving rudder is actually an all-moving rudder:  the balsa upright notches into the rear fuselage, then two 1/32" basswood struts CA'd together at the top hold the rudder in place courtesy of a pin-head with a few mm of shaft penetrating down into the balsa LE.  This actually a lot more robust than it looks!

Wing struts are 1/32" basswood faced onto 1/24" balsa which is then sanded flush.

Sealed all bare balsa parts then mixed arcylic blue, white and grey to get to the approximate colour for hand-painting.

Working out the geometry for the (scale) U/C struts was a bit of a faff, but sting taken out of the problem by making them over-long according to the drawing and then trimming to fit on the model itself.
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Jack Plane
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« Reply #32 on: May 08, 2019, 10:58:06 AM »

Next the moment of truth... glueing on the wings!

First the upper wing onto the inverted V-struts.

Then the lower wings into the fuse, with the inter-plane struts transposing the correct dihedral from the upper wing.

I ought really to get into the habit of using card templates for this job, but reckoned correctly sized struts (the rear four being 1mm shorter to ensure at least the correct difference in incidence) then tripple re-checking with a clear ruler would do the job well enough.

I like to use CA for these parts, so that if I've got it wrong the joints can be taken apart with de-bonder.

Also, somewhere along the line, Fritzy-Boy got painted.  He's got what's supposed to be a pencil-line tash and his eyes are a bit too high into his forehead, but he looks dangerous enough in black leather with a fur collar!
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Jack Plane
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« Reply #33 on: May 08, 2019, 11:14:16 AM »

The final bits...

The kit prop was a nice white 4" jobbie which was however too small, so I cut down a 6" black one to about 5", which has slightly increased blade area and overall greater pitch than a standard 5" unit showed alongside.  In practice I could have cut the prop down less as there's plenty of clearance for ROGs.  Also, and of more importance, is that test flights revealed too rapid and inefficient an exhaustion of rubber energy, so one of my post-maiden jobs is in fact to make up a larger prop.

The photo shows a standard hook used for weighing purposes, but I made up my own S-hook after this.

Wheels went on, with a small square of snug-fitting card between the wheel and the tiny plastic collet (stripped from electrical wire) to help prevent CA running down the axle.

Static balancing revealed a need for 5g of nose-weight, which took the place of lead CA'd inside the nose and the inside the nose-block.  Test flights later revealed a need for slightly more lead still!  (Measured against a blunt-nosed beast like a Camel reveals that inline engine powered aircraft of this type had no more nose-moment than rotary-engined aircraft!  In fact the CG of a rotary engine is probably more forward than an inline which runs aft under the wings!)

I was really rather pleased with a complete airframe weight of about 12g.  The prop and accouterments are 3g, rubber about 2.5g, then the 5g of lead to give a total of 22.5g flying.

With a total wing area of 55 sq ins, this gives a loading of 0.41g/sq in  Smiley
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« Last Edit: May 08, 2019, 11:39:07 AM by Jack Plane » Logged
Jack Plane
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« Reply #34 on: May 08, 2019, 11:36:56 AM »

Flying...

This was an early trimming flight at Walsall just before the Nats (15" loop of 1/8" rubber, 3.0x hook to peg):

Halberstadt D.II trimming flight

Clearly the model needs more down-thrust and a larger prop, but 27secs plus 10sec bonus for ROG = 37secs, which ain't bad straight off the board!  Unfortunately however my two best competition flights were only 23secs each plus ROG - because I foolishly started messing about with adding thicker rubber, then more nose-weight etc, etc!

So, aside from increasing prop diameter/pitch and dealing with down-thrust issues, I'm also going to move the rear peg one bay forward to help reduce the amount of extra lead in the nose.

The one thing that I didn't finish in time was putting on any rigging, so this is on my list.

And - as alluded to previously - the innovation that didn't work were my turned Depron wheels.  I took this idea from a Tom Hallman 'start-to-finish' video, but didn't account for the fact that he always lands on long grass whereas we come down on hard gym floors!  Now got one permanent flat tyre and one broken axle, so turning balsa wheels is on the list also!

Jon

« Last Edit: May 08, 2019, 12:23:35 PM by Jack Plane » Logged
Monz
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« Reply #35 on: May 08, 2019, 02:40:03 PM »

Very nice Jon, really enjoyed your retrospective build log.
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Jack Plane
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« Reply #36 on: May 08, 2019, 03:11:58 PM »

Thanks Monz, glad you enjoyed it  Smiley

Building the Halb and previously the Bristol Scout have given me a real taste for Peanut WW1 bipes... maybe time soon to design and make one of my own!  Can't be that difficult, can it...?

Jon
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Monz
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« Reply #37 on: May 08, 2019, 03:40:17 PM »

maybe time soon to design and make one of my own!  Can't be that difficult, can it...?

Jon

Not at all, just follow my mantra and you'll be good: IILRIWFR...M
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Squirrelnet
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« Reply #38 on: May 08, 2019, 03:54:03 PM »

Quote
IILRIWFR

 Huh Huh.... oh sorry penny just dropped - absolutely
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Jack Plane
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« Reply #39 on: May 08, 2019, 04:50:45 PM »

That's it!!  Grin
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Jack Plane
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« Reply #40 on: May 11, 2019, 02:39:50 PM »

A few quick minor repairs post-Nats, nose-block/button assembly refurbished to give a snugger fit with more reliable down- and side-thrust, and a gurney added to the upper left wing to join the one already on the lower wing help keep that side up.

Loop of 150 thou rubber 3x hook to peg, now with a slightly larger diameter prop cut down from a 6" job plus some trailing-edge removed and rounded towards the tip, gave a much more pleasing looking flight today, albeit still in the mid-twenty secs range plus ten secs for ROG:

https://photos.app.goo.gl/wEJo7eGijmS233Rh7

I could conduct a rigorous set of quantified tests with different props (diameter, pitch) and rubber (thickness, length), however my conclusion is that the 23g Halb is unlikely to be competitive for Peanut duration, and will certainly always be limited in static due to its coloured tissue and inked on details.

But it is looking like a rather promising ready-made for KS next year - a realistic looking flight of decent height and adequate duration - so that'll be its likely future role  Smiley
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« Reply #41 on: May 11, 2019, 03:16:02 PM »

Thanks for this thread. I've learned a couple of things from it. For instance, those clamps as adjustable supports for the wing.

Nice looking model!
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« Reply #42 on: May 11, 2019, 03:24:54 PM »

Cute little model Jon  Cool Nice detailing and the pale blue is rather pretty  Smiley
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Jack Plane
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« Reply #43 on: May 11, 2019, 03:32:19 PM »

Thanks chaps, very kind.  She is indeed a pretty little bird in blue... I really ought to take some static photos of her complete.
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